Replacement for Fluke 700013 IC (quad SPST analog switch) - Page 1
Forum section: electronics / testgear

author: richipedia
author_rank: Contributor
timestamp: May 03, 2018, 03:46:45 pm
content: Hello everybody,I recently bought a broken Fluke 8842A bench multimeter. As it turns out, two Fluke specific ICs with Fluke stock number "700013" are broken. Those are quad SPST analog switches with some integrated logic (latches and NAND gates) to accomplish the input voltage scaling and the current source switching for the resistance measurement - see images below or see the users manual atassets.fluke.com/manuals/8842a___imeng0300.pdf.I tried to find a genuine replacement IC, but was not successful. From the 8842A users manual, I can deduce that Fluke stock number "803478" is a similar device, but I have no success either in finding one of these. After so much frustration, buying another broken Fluke 8842A or Fluke 8840A (both contain said ICs) seems too few of a challenge to me, so why not design a replacement, that can replace any of the five 700013s in use in a 8842A? And why not share it with you? I already figured there are some guys also looking for a suitable replacement.The logic functions can easily be replicated using standard 74xxnnn CMOS logic gates, I believe. As far as I'm aware, I need to consider for those...supply voltagepropagation delaydigital logic level voltages (inputs need to match levels at hand on the PCB, outputs of the (N)AND gates need to match levels required by the analog switches)latch must be transparent while the signal not(L) at pin 3 is lowThe analog switch function can be implemented using analog switch ICs (who would have thought?). Jelly bean ICs like the Intersil DG411 or the Analog Devices ADG411 (better specs) are readily available for hobbyists like me, but I'm not familiar with all the peculiarites of these devices, I believe. Anything to consider for this purpose other than the following?supply voltage: must run off analog voltages -8,2V / +7,5V and -5V / +7,5V and 0V / +15Vcurrent consumptionpropagation delayon-resistanceoff-resistance a.k.a. leakage currentcharge injectionThe values of most of the requirements above need to be extracted from the PCB and from the two working 700013s I have. This is where I'm at so far. Just start screaming at me if there are some horrible mistakesdigital logic levels: using my humble DS1054Z, I measured clean square waves at the digital signals with low levels close to 0,0 V and high levels at 4,0V or above.propagation delay: tbdlatch transparent while not(L) is low: should be easily obtainable using a standard 74xx373 or 74xx573 and an inverter in front of the latch inputcurrent consumption: if I draw more than 4 mA from either the -8,2V rail or the +7,5V rail, the voltage drops dramatically. Haven't tested the +15V rail yet. The +5V rail seems to be very stable - no wonder as it is supplied by a standard 7805 voltage regulator IC.on resistance: plots in the DG411 data sheet show that on-resistance is dependent on the bias voltage at the switch nodes. So I closed a 700013 switch, put a DC voltage on one of the switch pins using a trim pot, and measured DC resistance using a measly multimeter. Is that sufficient? Seems like a very casual, unsophisticated approach to me.off-resistance a.k.a. leakage current: similar to the above, I opened a 700013 switch and measured DC resistance using my measly multimeter. Result: infinite ohms. Bummer, leakage current is too low. Next try: put a high voltage on one of the switch pins, connect the other pin to the multimeter in DC-voltage-mode connected to ground. From the measured voltage and the (not very precisely specified) input impedance of the multimeter, I can calculate that leakage current must be in the order of 10 pAcharge injection: there is a nice Analog Devices appnote showing how to measure charge injection. Put a cap with known capacitance at one of the switch nodes, open and close the analog switch using a function gen at a rate of 10 kHz, and track the capacitor voltage using an oscilloscope. There should be a significant voltage rise when the switch is turned off. Result using a 10 nF cap: there is no voltage rise. Apparently, the capacitance is too large. Using no capacitor at all (so that just the probe input capacitance affects the circuit), I can see and measure the charge injection voltage rise. Any ideas on how to measure probe input impedance?Well... enough ideas and questions for now. Or is it? Ah, wait!Bonus question: what might be the root cause for the 700013s failing in so many Fluke DMMs? Is there a way to prevent my little replacement from suffering the same painful death? I would guess that there might be an unfortunate condition at power up, causing multiple switches which act on the same node to be closed at the same time, resulting in a short circuit.

author: mlefe
author_rank: Regular Contributor
timestamp: July 15, 2019, 07:56:30 am
content: Hi Richipedia,I'm exactly in the same place as you are... did you make any progress?Thanks,Martin.-

author: richipedia
author_rank: Contributor
timestamp: July 15, 2019, 09:20:02 am
content: Hi mlefe,I did build a replacement for the 700013 IC, but have not yet put any effort in testing if the analog switch IC I use (DG411) has similar performance as the originial ASIC.I will provide my schematic later to share with the forum.

author: mlefe
author_rank: Regular Contributor
timestamp: July 15, 2019, 01:28:31 pm
content: Excellent!! Thank you very much

author: Kleinstein
author_rank: Super Contributor
timestamp: July 15, 2019, 04:52:17 pm
content: The DG411 is a relatively low ohms switch, but with relatively high leakage current. In cases where leakage is critical (e.g. ohms circuit), the DG211B should be the more suitable replacement. At least DG211 and DG411 use the same pin-out.

author: mlefe
author_rank: Regular Contributor
timestamp: July 16, 2019, 04:46:05 am
content: Do you know if HEF4066BD could be used as well?Here is the datasheet:https://pdf1.alldatasheet.com/datasheet-pdf/view/17724/PHILIPS/HEF4066BD.htmlI'm sorry for the question, I never played with analog switches before and I'm not sure what to look at...

author: Kleinstein
author_rank: Super Contributor
timestamp: July 16, 2019, 09:20:30 pm
content: HEF4066 and similar would be tricky, as the control voltage likely uses only 5 V logic level. So it would need extra level shifters. In addition the supply at some 15 V is close to the maximum, depending on the exact version.The 4066 CMOS switches can be used for analog functions in principle, but the chips are not well tested - this is more like the very cheap version, many may be OK, but not guarantied.

author: edavid
author_rank: Super Contributor
timestamp: July 16, 2019, 11:06:50 pm
content: I think 74HC4316 would be a better choice than 4066.The question is whether the Fluke IC uses CMOS or JFET switches. Are there any clues in the manual?

author: mlefe
author_rank: Regular Contributor
timestamp: July 18, 2019, 01:13:55 am
content: They're CMOS, this is the description: IC CMOS, QAS, PLASTIC, HIGH, B GRADE

author: mlefe
author_rank: Regular Contributor
timestamp: July 26, 2019, 01:38:55 am
content: After reading and studying a bit, I finally came up with a couple of circuits using HEF4066B on one ocasion and max399 in a different version.Unfortunately, I still can't figure out the 'latch part'.Can you help me understand the purpose of it?When I put a probe on pin 3 looks like it's always low... am I missing something?Thanks!

author: Kleinstein
author_rank: Super Contributor
timestamp: July 26, 2019, 08:00:04 am
content: The latch function is a kind of memory function. A 74HC75 could probably do the job. For U403/402, they seem to no use the extra logic AND function. So one could for these positions get away without that extra functions.A hef4066 would make like more difficult with the logic levels. The 74HC4316 (suggested by EDavid) and similar would make things easier. For higher supply it might take DG201B or similar.

author: softfoot
author_rank: Contributor
timestamp: May 29, 2020, 08:57:06 pm
content: Hi, I'm yet another Fluke user looking for a solution ...Did you make any progress on a replacement for the 700013 ??If you did I'd love to see what you did.BTW is the 700013 normally open (ie if an input is LOW is the switch OPEN)If that is the case then the DG212B (normally open) would be best because the DH211B is normally closed.Best regards,Dave

author: Kjo
author_rank: Regular Contributor
timestamp: August 23, 2020, 02:39:51 am
content: The 700013 and it’s variants are very special devices. First, they are evidently unobtanium.The latching function reduces the number of signals required from the ADC chip and in-guard uprocessor. Some 700013 switches are used in rather static applications, such as the precision current source. Others are VERY dynamic, such as the DC scaling circuit.It would be informative in we knew prop delay for digital to analog. It would also be good to know the on and off capacitance presented by analog switch nodes.The bus between the DC scaling and Sample-hold amp is a very sensitive node. It has like 5 switch nodes in common.Anyone with a 700013 to spare for testing I would be appreciative.PM me if so.I have actually build several prototype 700013 with no success.

author: g0rsq
author_rank: Contributor
timestamp: December 22, 2020, 10:49:49 pm
content: HiI am now at the same position as others here, and looking for a solution to the 700013 issue.I have just made a replacement LCD using a GLCD, only to find one faulty 700013Is anyone willing to share their work so far, before I sart looking into building a 700013, as I dont want to go down a blind alley if someone else has already been there!In the next few days I will be testing the bad 700013 in case it is just one switch that has died (301C).Then I will put a logic alayser on my good 8840A and work out the timing issues through the chip. I dont want to remove any good 700013's to test though.Peter

author: richipedia
author_rank: Contributor
timestamp: December 27, 2020, 02:58:47 pm
content: Oh well... 1 year and 9 months since I started my yet unfinished project. Still, glad to see that there are people interested in seeing how far I've come.The 8842A's manual clearly shows the internal functional blocks of the 700013 IC's:The logic part consists of 4 2-input AND gates, each having one input connected to a latch and the other input connected to the 8842's electronics either directly or through an inverter.Mimicking that part using standard logic gates should be easy.The 700013 is supplied using 3 different voltages:Pin 6: This is connected to +5V for all 5 700013 ICs. Seems to be digital supply VDD.Pin 10: GNDPin 20: +7.5 V for U301, U302, U303 (DC scaling, sampling etc); +15 V for U402 and U403 (precision current source). Seems to be the positive supply voltage V+ for the analog switch.Pin 11: -5V for U301, U302; -8.2 V for U303, GND for U402 and U403. Negative supply voltage V- for the analog part, obviously.For the analog switch, I figured I could use a DG411. Supply voltage is +5V ... +20V for V+ and -5V ... -20V for V-. (Probably made a mistake here, because U402 and U403 use V- = GND, but more on that later.) I do not remember more on why I chose this one, nor do I have a note.I ruled out the 4066 analog switch. If I remember correctly, the supply voltage requirements did not match at all.Be aware that the DG411 is active-low (enabled using a low input signal), contradictory to how the 700013's internals are presented in the manual.For the digital part, I figured I use mostly 74AC logic devices.With the DG411 having active-low inputs, the AND is replaced with a NAND 74HC00.For the latch, I chose a 74AC175D. To ensure all analog switches are turned off when the unit is powered on, a little reset circuit is provided.For the inverter, TI offers the 74LVC2G14 in a handy SOT23-6 package, which is 5V tolerant, so I chose this one.And there's the schematic:Fluke-700013-Replacement_Iteration02-Schematic.pdf(33.77 kB - downloaded 394 times.)

author: richipedia
author_rank: Contributor
timestamp: December 27, 2020, 03:13:22 pm
content: I cobbled together a simple test interface to be controlled by a RasPi. It helped my to get my understanding of the workings of the 700013 right and to see which of my ICs are broken.The RasPi provides the logic control signals. The outputs are connected to just a bunch of resistor dividers, so see if the analog switches can be enabled and disabled. This is basically a DC test, though, not taking care of digital timing or any of the properties I mentioned in my initial post.

author: richipedia
author_rank: Contributor
timestamp: December 27, 2020, 03:23:49 pm
content: Just to feed your interest, here's prototype 0 on a breadboard (while it's in the making), shoved into my test adapter.

author: richipedia
author_rank: Contributor
timestamp: December 27, 2020, 03:25:51 pm
content: Prototype 0 was already built to fit into the original PCB, so that's what I did.With the 8842's PCB populated my working 700013 ICs and the prototype in the right places for the right measuring mode, it kind of works.

author: richipedia
author_rank: Contributor
timestamp: December 27, 2020, 03:29:29 pm
content: For some reason, I built prototype 1 on veroboard. It plugs nicely into the 8842.

author: richipedia
author_rank: Contributor
timestamp: December 27, 2020, 03:56:14 pm
content: The 8842 has 5 700013 ICs. There is one IC in my unit which I believe is fully functional. The remaining 4 are somewhere between "suspiciously high current consumption/input loading" and "completely dead". I didn't quite like the idea of making a total of 5 hand-wired veroboard replacements, so I ordered some PCBs.Eagle files are attached.I tried to recreate the solder mask keep-outs I found on the 8842 PCB on my PCBs, although I am not completely aware of what I am doing here and how to get it rightWith U301, U302 and U303 populated with my replacement PCB and using two of the original 700013 for U402 and U403, the DMM kind of works. I tried calibrating it at work.Some of the higher VDC ranges did calibrate correctly. Success!Some of the lower VDC ranges did not calibrate. Probably it was the 20mV and the 200mV ranges, but would have to check again to be sure.Most Ohms ranges did not calibrate correctly.The ADC ranges did calibrate correctly. Yay!

author: Kleinstein
author_rank: Super Contributor
timestamp: December 27, 2020, 06:27:02 pm
content: The DG411 is low resistance, but also has more leakage. The DG211 should be a lower leakage counterpart - AFAIK with the same pin-out. Leakage can be a problem with the higher resistors.

author: softfoot
author_rank: Contributor
timestamp: December 29, 2020, 10:37:32 am
content: I am following this project with great interest, and look forward to a working solution.Regards,David.

author: Noopy
author_rank: Super Contributor
timestamp: April 17, 2021, 07:28:10 pm
content: Hi all!TiN had sent me a 700013 and I have taken some pictures of the die.Well you know what it does...The die is 2,6mm x 2,3mm.A 1982 Fluke design.QAS-B seems to be the name of the switch. In the servicemanual of the 8842A the chip is named "IC CMOS, QAS, PLASTIC, HIGH, B Grade". Sounds feasible!Fluke used eight masks to manufacture the switch.Some test structures.On the right side there are three different type of the resistors.On the left side it seems like there are complementary MOS transistors. You can see the small spot in the middle of the cross where the thin gate oxide is placed.In the middle perhaps some bipolar transistors?Let the music play!The four switches are easy to spot.You can see that the left control side is supplied with +5V and 0V while the right switching side is supplied with +7,5V and -5V (of course other voltages are possible).Some protection at the input pins.On both sides of the analog switches there are metal lines to isolate the switches. On the left side +5V/0V and on the right side +7,5V/-5V.The inputs without the latches are fed into a kind of a push-pull-stage before reaching the control circuit.The control circuit contains the latch, the AND gate and the chip select.The upper area is connected to +5V, the lower area is connected to 0V.On the right side of the picture there is the transition from +5V/0V to +7,5V/-5V.To control the analog switch quite a big differential push-pull-stage was integrated.It seems like the transistor areas were optimized for ideal switching behaviour.Now that is interesting: There are two small MOSFETs doing the switching of the analog channel. But there are two additional bigger MOSFETs connected to two unused bondpads. It seems like you can choose which transistor you like: a big one with low resistance but with a high leackage current and parasitiv capacitance or a small one with a higher resistance but with lower leackage and capacitance.https://www.richis-lab.de/aswitch01.htm

author: JoergR
author_rank: Contributor
timestamp: May 26, 2021, 06:06:34 pm
content: Hi all,This is my first post on the EEVBlog - pls be gentle. ;-)I believe I too have a Fluke 8840 with a faulty 700013 - but before I venture to desolder everything, I wanted to know:How did you ascertained that this was indeed the faulty chip?Background:All DC readings are garbage, no autoranging. Display works. I removed the AC unit and placed it in another meter where it works just fine.All self tests except 11 fail. Voltages appear within specs, so the power supply seems ok.Following the manual, I can get correct voltages displayed when placing a voltage directly between TP103 and common low and I get a zero reading when shorting TP103 to common low. The front panel switches allow me to switch the ranges of the display, i.e. I can display 1.3V as 13V, 130V etc. So the ADC and the Voltage reference appear ok. With a short on the input, all ranges _do not_ display zeros. The manual says:If zero is not displayed for r3 and r5 with HI and LO shorted, then Z301 or U302-D is probably bad.Now, I also checked track and hold. The voltages on the chips are ok, but the waveforms are off - They don't extend below 0 far enough. The shape is similar, though.Hence, my question: Can you suggest another procedure to test whether U302 Chip, the Fluke 700013, is really at fault? I haven't given up the hope that the fault lies somewhere else ;-)Thanks in advance!Joerg

author: Kleinstein
author_rank: Super Contributor
timestamp: May 26, 2021, 06:49:03 pm
content: One should be able to test the input amplifier part up to the S&H stage separately. So set a range and check the result from a signal at the input at TP302 and directly at the S&H input (e.g. pin 17=18 of U301). There can be a little offset, but should not be much.When seeing which range does not work and how it fails one could than do a more specific test.

author: JoergR
author_rank: Contributor
timestamp: May 27, 2021, 12:04:51 pm
content: So the voltages appear ok at TP302 - in ratio 1:1 for ranges 0.2, 2, 20 and 1:100 for ranges 200 and 2000. The divider Z301 measures correctly as 18k, 2k.The switches for 4WOhm, IDC and AC path U301D, U302D und U302C are all open - as should be I suppose.Oddly, the switches U301A, U302A and U301B as well as U302B are also all open - so no signal appears at the input of Track and Hold Pin 14 of U301C. I would have expected that shorting any of these switches before the input to Track and hold would give sensible readings, but no such luck.

author: Kleinstein
author_rank: Super Contributor
timestamp: May 27, 2021, 03:28:42 pm
content: The switches at the input to the S&H stage should turn on 1 at a time. In the non AZ mode, this may be just the 1 selected input. In the AZ mode there should be some switching between the zero reading U301C and the selected input. For 4 wire ohms this should be with U301D (for ohms sense low) instead.For some inputs there is also a precharge phase with U301A. The sequence should be visible at the input to the S&H amplifier and also at the control signals to U301-U303.Besides the CMOS switches also the JFETs Q311 7 Q315 have to switch - a possible defect would be U305 (= LM339 and thus cheap).

author: JoergR
author_rank: Contributor
timestamp: May 28, 2021, 12:00:28 am
content: Hm, the LM339 is probably ok, the FET also send the signal through. I checked the logic inputs to the U301, U302, U303 and they are totally off. I hadn't done that before as with self tests and display working, I didn't suspect an error on the digital side. There is not a single high in AD0-AD7 that is supposed to come over the bus that appears on the inputs.... Other digital signals do appear to come in ok.I checked the uC, U202, with the procedure described in the manual and the signals come out as described (the 1kHz and the interrupts etc). Since the display is working and the self tests are performed and even the right voltages appear on the test point 302 during the self tests, I guess the uC is good.That leave U201 as the next suspect or the Adress Latch U219. I'll see what I can figure out there when checking the timing of signals between chips.

author: JoergR
author_rank: Contributor
timestamp: May 29, 2021, 02:56:41 am
content: So maybe there is progress. I checked the uC in my faulty device - a 8840A/AF and compared with my functional 8840A I found that the clock signal on pin#2 is very different. See the scope picture. Also, the clock pulses on the faulty device appear to have significant jitter on them.I tried exchanging the uCs between the devices. The uC from the faulty AF device would not work at all in the functional A. The uC from the functional A shows error 50 "guard crossing error" when placed in the faulty AF.I'm a bit at a loss here as I don't know whether I should expect compatebility anyhow. Chips are marked different. The AF has the chip seen in the picture. The functional A has a chip marked Zilog Z8.

author: Kleinstein
author_rank: Super Contributor
timestamp: May 29, 2021, 09:52:20 am
content: Probing the clock signal is tricky, as the cystal part can already react to the extra proble capacitance. AFAIR there are also differences in the clock pins - causeing much of the trouble with the replacement earlier in the thread. So changing the µCs may not work, even if both chips are OK.I the CPU is passing the self test, the AD0-7 lines should work OK, as reading the memory works. The switch specific part is mainly the CS2 signal for the latches.The control signal for the switches has 2 paths: one via AD0-7 directly from the CPU and one directly from the ADC circuit. The settings from the CPU side may not update regularly, more like only with a function change. The other meter to compare should show the expected signal, if not in the service manual.

author: coromonadalix
author_rank: Super Contributor
timestamp: May 29, 2021, 11:59:07 am
content: what probes do you have on your scope ?Do you have an x10 multiplier on them, it helps to get an higher impedance for measurements, you have x100 probes too ...

author: JoergR
author_rank: Contributor
timestamp: May 29, 2021, 01:43:45 pm
content: probes are Tektronix P6133, 1:10, 15pF - they come with the 100MHz scope, but of course it all depends on the capacitance in the oscillator, doesn't? Probe capacitance must be small with respect to that, or?

author: Kleinstein
author_rank: Super Contributor
timestamp: May 29, 2021, 04:48:04 pm
content: The capacitance at the crystal is in the 20 pF range - so even a rather low capacitance probe can disturb the signal and cause asymmetry in the loading. The clock seems to be good enough, as the µC seems to be running.

author: JoergR
author_rank: Contributor
timestamp: May 30, 2021, 02:09:54 am
content: So back to the drawing board. I went back to measure the digital signals on the switching chips, this time not with the multimeter as I had done the first time, but with the scope ...they are ok and match what I measure in my functional device. I also figured out that in the 20V range, I can get a signal through to the track and hold. Then I get a decent signal on TP 103 - see the scope image and a reading that is stable albeit off by a factor of two. Note how the Track and Hold signal is not as symmetrical as in the functional device.I then checked the Lm339 again, too. In contrast to the manual, it shows -26.5V on pin 12. Its supposed to have -5.5V at zero input. However, here it seems the defective 8840A/AF and the functional 8840A differ in construction. The zener CR303 is connected to -15V in the functional 8840A and to -30V in the defective 8840A/AF. So this could be by design and I just don't have the right manual - or the zener is broken. The CR303 in the defective 8840A/AF has the same marking 74 6 610 as CR309/11 which are both 3.9V Zeners that clamp the output of the track and hold. So I guess its by design.That would be odd, though, as the LM339 is rated for symmetric supplies with +/- 18V max. Now +5/-26.5 doesn't exceed that differential, but still.The PCB of the defective AF states 8840A/AF-3001 Rev C, the functional A is Rev E - both are dated 1983, though.

author: Kleinstein
author_rank: Super Contributor
timestamp: May 30, 2021, 09:09:51 am
content: The -26 V at pin 12 of the LM399 should not be a big issue. The supply for the LM399 sould still be in the safe range. The difference would be mainly with the ability to also turn off a rather negative input signal, e.g. in the 4 Wire ohms mode or maybe (if supported) some ratio mode that uses the 4 Wire sense input as a 2nd input.On the othe side a more negative voltage needs the switching JFET to withstand a higher gate voltage with a large positive input votlage. Worst case there many be up to some +24 V before the clamps engage. So with a -26 V supply the JFET would have to withstand -50 V gate to source. With a negative signal from the active signal this case may still happen though.So I don't think the difference between the 2 vesions is that relevant, both should be OK, at least for the test / normal operation.If the 20 V range kind of works, but the 2 V range not, this indicates a problem allread before the S&H stage, like with U301BGetting at least some sensible signal out shows the U303 seems to be at least partially working. It may be interesting to see the input signal to the S&H stage constant in this test. It should change between 0 and the signal. A factor of 2 error would also be visible on the scope - so is the factor 2 error allready at the input to the S&H stage or only at the output or maybe even a problem with the ADC ?AFAIK the signal may be slightly asymmetric from an amplifiers offset, but not that much.

author: JoergR
author_rank: Contributor
timestamp: May 30, 2021, 03:07:45 pm
content: Hm, the ADC itself is most certainly not broken. When putting a short across TP103 (the output of Track and Hold) and Reference Low, I get close to zero counts, 16 to be exact in the 2V range (everthing below 35 would be fine). When putting a voltage below 2V between TP103 and Reference Low in the 2V range, the display shows the correct value with opposite sign, just as should be according to the manual. Changing ranges just changes the decimal point in the display, but not the digits.I do think U301B is a problem due to the 2V range not working and I guess that's what brought me here in the first place. But let's leave that aside for the moment and focus on the Track and Hold if we can.The input to the Track and Hold does appear to be working as intended in the 20V range. See the attached images. It oscillates between 1/10 of the input signal and GND as should be and no factor of 2 to be seen. This is true for both positive and negative input voltages.One can also see the output of the track and hold in comparison - the high part of the signal is not amplified, but the low part of the signal is for positive voltages and the opposite is true for negative voltages.The Z303 measures correctly. The digital inputs on U303 I measured and they correspond to my functional device. I wonder if some of the capacitances in T&H could be at fault or the current limiter (?) CL301 - it's high side is at zero volts. I'll make more comparisons with my functional device.

author: Kleinstein
author_rank: Super Contributor
timestamp: May 30, 2021, 06:10:45 pm
content: The ouput of CL301 at around 0 V is about OK. It should about follow the input to the S&H stage with a little offset in the 0 - 1 V range.If needed one could check the current from CL301 by looking at the drain voltage / input to the OP to see how much current is flowing.As the track and settle phase seem to work I would expect the problem in the hold phase.It somehow looks like the signal in the hold phase is about doubled for some reason - which is odd, as there are no 2 equal resistors to make it double.I see absolutely no reason how a broken capacitor could double the voltage - leakage would more like reduce the voltage. It would be more like having the switch U303 B not turning off. The divider would than be with 2 of the switches.The low side of C308 may tell the difference.

author: JoergR
author_rank: Contributor
timestamp: May 30, 2021, 09:52:51 pm
content: Indeed, the signal on the low side of C308 - measured at U303-13/14/16 is different from the functional device. See the scope shots. It also shows a larger amount of ripple. But at this point, I'm pretty convinced that the switch ICs need replacements. I'll desolder them and see if I can pin down the defective switches and thus make sense out of the behavior observed. Thanks a lot to kleinstein for being so helpful!

author: JoergR
author_rank: Contributor
timestamp: May 31, 2021, 10:30:32 pm
content: So here is the first one - U303. Only switch A seems to work as needed. Switch B never opens when a static high is on the latch and B, C and D drop about 0.6V when closed - indicating an on resistance of 1.7kOhm which seems a little excessive, but it could explain the false readings.

author: Kleinstein
author_rank: Super Contributor
timestamp: June 01, 2021, 06:34:15 am
content: 1.7 KOhms sounds rather high for the on resistance. With the large area used for the swtiches I would habe expected lower resistance, though the use in the ohms past suggests that the switches are pretty low leakage. AFAIK the switches have a NMOS and CMOS part in parallel. The 1.7 K could be just one of those 2 halves and would than depend on the common mode voltage. There is a slight chance the other half of the switch was damaged by overload from driving it too hard. Another possibly explaination would be some supply missing (e.g. broken bond wire or trace) so that maybe one polatiry never truns on and the other never truns off.At least the 1.7 K would be high enough to explain why it still kind of worked for a gain of 2. The other involved switch would likey be similar resistance.For the replacement it may be interesting to know of the latches are transparent latches reacting on the level like the 74xx75 (though other polarity) or D-type flipflops (like 74HC74) reacting on the transitions only. The chips are connected relatively direct to the CPU bus and thus get valid data only for a relatively short time.The 74xx75 would definitely need an inverter for the latch signal, but still not so sure it would be right or if something like 74AC175 may be better.

author: richipedia
author_rank: Contributor
timestamp: June 03, 2021, 01:54:48 pm
content: Quote from: Kleinstein on June 01, 2021, 06:34:15 amThank you for pointing that one out. In my opening post, I already mentioned that the original 700013 are transparent while the latch input pin is low. However, for my replacement, I chose 74AC175, which are flip flops, not latches.On my first veraboard prototype, I used 74AC573 latches, which do the job.However, I do not know if the difference in behavior between latch and flip-flop is relevant.

author: richipedia
author_rank: Contributor
timestamp: June 03, 2021, 02:39:42 pm
content: Quote from: Kleinstein on December 27, 2020, 06:27:02 pmI just tried to get an estimate for leakage current using a power supply at 5 V and a DMM in mV mode. The DMM has an input resistance of R_M=10 MOhm, so the voltage reading V_M should give me an indication of the leakage current I_L = V_M / R_M.The DG411 switch I measured has ca. 0,05 nA ... 0,11 nA of leakage, which matches the typical figure in the datasheet.On the other hand, the 700013 I measured has ca. 6 pA ... 15 pA of leakage. One order of magnitude less, just like the DG211. That's a good excuse to order some DG211.Thank you again, Kleinstein!Does anybody have a clue how relevant switch charge injection is for this application?

author: Kleinstein
author_rank: Super Contributor
timestamp: June 03, 2021, 03:39:58 pm
content: I don't think the charge injection should matter very much. It may make a small difference at the S&H stage, but I would not expect very much difference as the capacitor is quite large (470 nF) - less charge injection should still be better. Chances are there is a correction parameter to compensate from the calibration.The 74AC573 should be essentially the 6 channel equivalent to the 74HC77/75. It should be active high and thus the wrong polarity. A tranparent latch has a kind of hold and an a transparent mode. The D-flip flop takes over the input only at the transition, and thus no tranparent phase, but a defiend time to copy the input data.The HC175 should read the data at the positive edge and thus at the end of the /CS2 or /CS3 pulse. As far as I understand the bus protocoll this should be OK. However I don't know the bus with the /DS /DM signals.The /CS2 / CS3 signals come from an 74LS... , at least in the plan. So the latch / flipflop should be a HCT or ACT version. The AC / HC version may no reliably detect the high level (an extra pull up may help as a quick fix).

author: richipedia
author_rank: Contributor
timestamp: June 03, 2021, 03:58:14 pm
content: Quote from: Kleinstein on June 03, 2021, 03:39:58 pmI corrected for the wrong polarity using an inverterQuoteAnother big trap for young players. The Z8 microcontroller also uses TTL voltage levels.I think it's time for me to make a new replacement, using HCT, ACT or even LS logic and the venerable DG211I might also make the board a little smaller. If i had the AC option PCB, it would collide with the replacement boards.

author: JoergR
author_rank: Contributor
timestamp: June 03, 2021, 07:21:46 pm
content: Glad you join the discussion again richipedia. I'm learning a lot here about logic families - much like Montagues and Capulets it seems...One question I still have:Quote from: softfoot on May 29, 2020, 08:57:06 pmSo why choose the normally closed version of the chip for the replacement?For what its worth, when I checked the input signals to the 700013 chips in my devices, they would always switch several microseconds before the clock signal goes low and would stay at their level several microsecods until after the clock goes high again. From that, it seems that D-Flip-Flops would be just fine. But then, I only thoroughly checked in 20V mode and it may be different in other ranges.

author: richipedia
author_rank: Contributor
timestamp: June 03, 2021, 07:43:08 pm
content: Quote from: JoergR on June 03, 2021, 07:21:46 pmI guess that's what people do with a 3 year old thread about an unfinished projectQuotePlease take a moment to look at my schematic:https://www.eevblog.com/forum/testgear/replacement-for-fluke-700013-ic-(quad-spst-analog-switch)/?action=dlattach;attach=1139450The control signal for the analog switches comes from a NAND gate, so the switch should be conducting when the control signal is low and vice versa.I should check what exactly happens at power on, to make sure that no opposing switches are turned on at the same time.QuoteMaybe the latched inputs on the devices you checked do not change in between cycles. The fact that the switch output changes before the clock edge might be a hint that only the unlatched inputs have changed.

author: Kleinstein
author_rank: Super Contributor
timestamp: June 03, 2021, 08:24:07 pm
content: Chances are high that both latiches and D-Fliflops would work. The switches are accessed similar to memory. So there is a CS pulse to activate the chip if a suitable address (actually a large block) and the control signals are there. The data should than be valid for a relatively short time (likely 0.2-1 µs range) and in this time the latching signal should get a short pulse. The difference between a latch and Flipflop would be when the switched would change: with the latch the change would be just after the start of the pulse and the signal at the end of the pulse (which should be the same as at the start) would be preserved.With a Flipflop the data just befor the end would be transfered to the switch - so a slightly later change, but essentially the same result. The exact timing (10s of ns range) may be a bit different. It could make a difference with timing just at the edge -- however than it is not clear how fast the fluke chip is.Both DG211 or DG212 could work - just need to have the suiteable logic chip in front (74xx00 = NAND or 74xx08 = AND).The start up condition may indeed be a bit tricky. It may take quite some time until the CPU initiallizes the switches. So the initial state may be there for quite some time and multiple switches on could cause trouble.

author: JoergR
author_rank: Contributor
timestamp: June 03, 2021, 08:26:58 pm
content: I had seen that you drive the switches with a NAND and so your design is fully equivalent in function - it couldn't function otherwise. I just wondered why you choose the combination NAND + Normally Closed switch over AND + Normally Open switch - just availability of chips or was there a deeper reason behind that? In fact, one could solder AND + Normally Open switch into your PCBs and it would work just the same, wouldn't it?The difference may come only when someone applies a voltage on the input of the DMM without the meter being powered - then it might make a difference? That could occur if someone turns the multimeter off while the inputs are still connected or has forgotten to turn it on when the test circuit is already connected etc.

author: richipedia
author_rank: Contributor
timestamp: June 03, 2021, 08:45:15 pm
content: Quote from: JoergR on June 03, 2021, 08:26:58 pmAn AND gate is made up of a NAND gate followed by an inverter, so the NAND gate has shorter propagation delay.One could argue that a DG211 might be a DG212 with extra inverters before the inputs or vice versa, I honestly don't know.Using the NANDs and the DGx11 seemed more natural to me, 3 years ago, but anyhow, we're already splitting hairs.QuoteAbsolutely.QuoteI believe that the difference between the DG211 and the DG212 is basically that one of them has an extra inverter at the digital control input whereas the other doesn't. The actual switches are probably made of ordinary enhancement type FETs - no use of fancy depletion type FETs for the "normally closed" type, at least in my opinion. The terms "normally open" and "normally closed" probably are misleading.Also, I just measured one of my DG411 ICs: switch resistance is ca 20 MOhm when unpowered

author: edavid
author_rank: Super Contributor
timestamp: June 07, 2021, 09:42:15 pm
content: Quote from: richipedia on June 03, 2021, 08:45:15 pmUsually the switch cell is driven by complementary signals from the input buffer. To change the control signal polarity, those drive signals are routed to the opposite inputs of the switch cell. No extra inverter is needed, just a wiring change.

author: JoergR
author_rank: Contributor
timestamp: June 11, 2021, 07:51:12 am
content: Just got recommended this on eBay - seems like someone is already going to production with this ;-)It uses a DG212 and an unidentified second chip - likely a uC?

author: Kleinstein
author_rank: Super Contributor
timestamp: June 11, 2021, 07:57:25 am
content: The task for the logic is not really suited for a µC (needs to react quite fast, e.g. some 300-1000 ns for the latch pulse). Possible, but I would more expect some PLD / CPLD - though here the 5 V compatibility could be tricky.

author: JoergR
author_rank: Contributor
timestamp: June 11, 2021, 08:38:59 am
content: Something like an ATF16V8, maybe? Those are 5V.

author: Kleinstein
author_rank: Super Contributor
timestamp: June 11, 2021, 09:07:25 am
content: The PLD looks plausible and should work.

author: Dakkahun
author_rank: Contributor
timestamp: June 12, 2021, 07:46:12 am
content: Hello.I found some information about the development process of that clone:https://groups.io/g/Fluke-DMM/topic/8840a_project_130007_clone/80985930?p=,,,20,0,0,0::recentpostdate%2Fsticky,,,20,2,0,80985930andhttps://groups.io/g/Fluke-DMM/topic/fluke_8840a_8842a_8840af/83314606?p=,,,20,0,0,0::recentpostdate%2Fsticky,,,20,2,0,83314606The final solution uses a "Custom preprogrammed CMOS logic."

author: JoergR
author_rank: Contributor
timestamp: June 29, 2021, 09:42:48 pm
content: So the boards on my vertical layout that I had posted previously came and lo and behold - the worked perfectly - except that I mixuped up the order of the output switches.... So I've removed that post from the thread and fortunately only one person had downloaded it... Sorry for that. Back to the drawing board and inspired by the horizontal setup posted above, I made another layout with correct switches this time. The boards came a couple of days ago. I've put sockets on the main PCB this way the daughterboards are raised high enough to be clear of all other parts. With U301-303 replaced all self tests passed!DC voltage and current appear to work fine. Only in the low AC current range around 1mA there is a larger error - but I guess that can be fixed with calibration as I had previously erased all calibration values. I've used the DG411 and the 74AC logic chips. Only the Ohms circuit still gives me trouble. It only measures correctly on the 20k range and outputs the correct current of 1mA. So I suppose I also have to replace the remaining two 700013 ... I need to order the DG211 first, though.If someone is still in need of replacements - I have a few PCBs to spare.Thanks a lot again for the help I got here!

author: richipedia
author_rank: Contributor
timestamp: June 30, 2021, 02:38:58 pm
content: That mechanical design looks very nice. Good combination of THT and SMD parts to use space efficiently!

author: JoergR
author_rank: Contributor
timestamp: July 01, 2021, 08:15:14 pm
content: In hindsight, and looking at the pictures now, I feel that the switch chip should be moved over a bit to the edge of the board. The header pins don't need to be below the center of the chip. That would give the capacitors a bit more space. Oh well, ... I'm attaching the KiCad Files if someone still needs those.I got the DG212 chips today and combined them with 74AC08 AND gates and now the meter is all up and running again.That's the nice thing about richipedia's design, one can choose different chip combinations DGX12 + 08 AND or DGX11 + 00 NAND on the same board.

author: Kjo
author_rank: Regular Contributor
timestamp: July 03, 2021, 10:49:52 pm
content: I spent a good deal of time during COVID working on the same concept and reported progress at the Fluke list over at groups.io.I started by trying to use a PIC16F15323 to control a DG212B. It has 4 CLBs that can implement registered logic independent of theinstruction counter. Fluke timing for the 700013 is not that critical, but it wouldnt work in all 700013 positions.I also tried 2 versions using 4000 series and 74HC series. Still had some issues.Finally I landed on a 2-chip solution with a PLD & DG212B.That version worked flawlessly and is only 40% bigger than the 700013 IC itself.Assembly is all SMD in SOIC packages & 4 0603 capacitors.I put together a kit for the MK5 version for $18.95.https://www.hollywoodcontrols.com/phpFluke/HC700013P.phpI also have a Z8611 clone I am looking at kiting. Similar to others out there. Based on U8840M.You can also find pretty much all the ROMs that are in the wild there too.kjo - KO3Y

author: Noopy
author_rank: Super Contributor
timestamp: July 07, 2021, 03:53:41 am
content: TiN had sent me an ADG444B. I have thought about posting it in my "normal" Die-Thread but since you are talking a lot about analog switches (DG211) I will post the ADG444 here.The die is 1,9mm x 1,7mm. You can easily spot the four switches.The datasheet describes a ADG444Awhich is fabricated with an buried oxide layer to isolate the integrated transistors. The isolation prevents latch-up but probably also reduces leakage and crosstalk.The die doesn´t look like to have this isolation layer.In the OPA627 (https://www.richis-lab.de/Opamp22.htm) we have seen that it is possible to see an isolation layer at the side of a die.But this is the B-version of the ADG444. No isolation to be expected.A 1993 design.Internal naming?We see six mask revisions.Nice big transistors.Etch marker or mask alignment help.Now that is a nice pin 1 marker!Here we see one switch built with two big transistors (PMOS and NMOS).That is interesting:The bulk of the upper transistor T1 is connected to Vdd. That is probably the PMOS. It´s switched with Ga.The lower transistor T2 has to be the NMOS. It´s switched with Gb. It´s bulk is connected to Vss by a third transistor switched with Ga (NMOS). So the Vss for better isolation is only connected to T2 in the off state.At the lower end of T2 you see the metal layer connecting the channel with the bulk. In on state the channel is conducting connecting source and bulk. The higher bulk potential gives you a lower on resistance.ADG441 and ADG442 have an internal voltage regulator for the logic supply. That is probably the circuit in the middle of the die. In the ADG444 it´s just connected to Vdd and GND. With a small metal layer change you can connect Vl.https://www.richis-lab.de/aswitch02.htm

author: magic
author_rank: Super Contributor
timestamp: July 07, 2021, 06:37:13 am
content: Quote from: Noopy on July 07, 2021, 03:53:41 amNo, not really. There are many techniques for dielectric isolation and the old Harris/Burr-Brown method of fusing wafers in just one. Not really convenient and not really cheap and, according to one TI guy I have read, not scalable to modern large wafers. Supposedly the 21st century way to SOI is deep ion implantation of oxygen atoms and annealing to react them with the silicon.

author: Noopy
author_rank: Super Contributor
timestamp: July 07, 2021, 07:13:08 am
content: Quote from: magic on July 07, 2021, 06:37:13 amThat is a translation artefact. I wanted to say "we have seen thatsometimesit is possible to see an isolation layer at the side of a die."Sorry folks!

author: softfoot
author_rank: Contributor
timestamp: August 29, 2021, 11:58:26 pm
content: Quote from: JoergR on July 01, 2021, 08:15:14 pmAre there a set of gerber files for this variant ?? I know I could generate them from within Kicad using the project in the zip file, but I am unfamiliar with Kicad and I'd hate to send off to JLCPcb and end up with rubbish.Regards,Dave

author: Kjo
author_rank: Regular Contributor
timestamp: September 05, 2021, 01:43:19 am
content: The F700013 clone kit is rather east to assemble if you follow the instructions in sequence. It is about as small as possible without a custom IC. It takes me about 30min to assemble one, so the assembled version is a bit more expensive. But it is also tested. I have not seen enough demand to have a shop do the assembly.Kjo - KO3Y

author: Noopy
author_rank: Super Contributor
timestamp: November 24, 2021, 09:17:01 am
content: We have seen this 700013 here:Quote from: Noopy on April 17, 2021, 07:28:10 pmNow I have two older revisions of the 700013 that are in a really bad condition.I called the first one, the newer one, revision B while this one I will call revision A.This one was a U301.Remember the internal construction.Attention: This is the old die!I was told switches A and B are dead. Switches C and D can only be controlled by the direkt control through Pin 8.Now that doesn´t look very good.But first things first. That is an older revision than the first 700013 I have taken pictures of. The die has the same size and the structures are quite the same too. I assume it was just an update to fit into a different (new?) manufacturing process.1982, same as in the first revision. They didn´t change the design year.684597A, probably an internal naming.The sunny mountains on the left side have been removed to the later revision.The symbols under the mask revisions allow us to check the alignment of some of masks.Test structures and "the melody" are the same as in the Revision B.The damage in the control part is significant. The silicon has discolored over a large area and the metal layer has disappeared in several places. I´m not sure what triggered the destruction. The large discolorated areas indicate a longer thermal overload. The GND feed line, which contacts the wide horizontal GND distribution in the center of the control circuit has melted. Destroyed structures can be found where within the circuit the direct control lines of switches A and B arrive. The input circuit for the buffered control line of switch A has been severely damaged. The output line for switch B has disappeared.The destroyed circuits have no direct connection. I assume that due to an initial fault, the temperature of the die and consequently the leakage currents increased significantly. The uncontrolled current flows then ultimately caused the circuit parts to degenerate.The destruction fits to the fault pattern of the device. Switches A and B can no longer be controlled because the control circuit is destroyed. Switches C and D can only be controlled by the direct inputs. The buffered inputs are controlled by a circuit in the upper left corner of the die. Due to the massive damage in this area the signal path is blocked.In the switcher part of the die there is discoloration all over the bondpad area and some of the big switches are damaged. Here we can see one with a molten gate line. Keep in mind, the big transistors are not used in the 700013.

author: Noopy
author_rank: Super Contributor
timestamp: November 24, 2021, 09:18:12 am
content: The second dead 700013 was a U302.Big areas of the die are destroyed but here most of the destruction is located in the control part of the 700013.Besides some other destruction in the control circuit of the switches A and B the two 5V supply lines are interrupted.In the control circuit of the switches C and D there is global damage too.There are interesting dendrites!https://www.richis-lab.de/aswitch03.htm

author: Kleinstein
author_rank: Super Contributor
timestamp: November 24, 2021, 10:17:30 am
content: The prime suspects for the damage is a latch up. So substrate currents current triggering a parasitic SCR to short the supply. AFAIK the CMOS switches are in principle susceptible to this kind of failure. Newer chips improved on this, making it harder to trigger.The "dendrites" look indeed strange. This too could be a process leading to failure. It could be still something (like a fungus) growing an top of the chip, with little effect on the function.

author: Noopy
author_rank: Super Contributor
timestamp: November 24, 2021, 10:21:38 am
content: My first assumption was latch-up too but as a result of a latch-up I would have expected a major damage at one point and the rest looking "good" not this all over the die mess.

author: Noopy
author_rank: Super Contributor
timestamp: December 20, 2021, 04:47:01 am
content: I wasn´t sure about posting the ADG441 here too. But since the topic is about analog switch replacement I think it makes sense.After looking into the ADG444 (https://www.richis-lab.de/aswitch02.htm) I was interested in the ADG441 with it´s integrated logic supply.The ADG444 appeared to having the logic supply integrated too but doesn´t use it. "Unfortunately" I wasn´t able to confirm that the ADG444 and the ADG441 are the same because here we have a new design!The ADG441 die is a little smaller than the ADG444 die, 2,1mm x 1,3mm.ADG444 was a 1993 design. ADG441 is a 2004 design.And now I think I can tell you more about these numbers.BV is probably Beaverton. Analog does some development there.A94 seems to be this analog switch project. In the ADG444 the name was followed by a 2, perhaps a variant.The last letter is a C. In the ADG444 it was a B. That is probably the revision.The analog switches are in the four corners (red). Above and under these switches there are the control circuits (blue). In the middle of the die there seems to be the voltage regulator for the logic supply (white). At the lower edge there are two big structures probably for overvoltage protection (yellow).Between the potentials to be connected there is a p-MOS transistor pair (blue) and an n-MOS transistor pair (red). The larger transistor is probably the p-MOSFET since these usually have slightly worse characteristics. The bond pads are connected to electrodes that are alternately passed over the transistors where they contact the drain and source of both transistor pairs.At the bondpads of the analog switches there are obviously protection structures (white). The area in the lower left corner (green) seems to be necessary for controlling the transistors. At the bottom there is a relatively large transistor. Probably this one connects the bulk potential of the n-MOS transistor with the negative supply like in the ADG444. This reduces the leakage current when the device is switched off.https://www.richis-lab.de/aswitch04.htm

author: Noopy
author_rank: Super Contributor
timestamp: January 03, 2022, 05:26:15 am
content: Nobody complained about me posting analog switches here so I will go on with it.RCA CD74HCT4067, a 16 channel analog switch for 0-5V. It´s bidirectional therefore a multiplexer/demultiplexer.The die is 2,7mm x 2,3mm.I found no RCA datasheet but you can see the internals in a Texas Instruments Datasheet.Interesting point: The inverter/AND combination slows down the switch on while the switch off is faster. That´s important so you have never two active switches in parallel.You can find every part of the schematic on the die. On the right side there are the input circuits for the channel selection and enable (red/yellow). In the middle of the die a circuit generates 16 signals for the channel selection (blue). Around this circuit you can see 16 driver circuits for the analog switches (purple). At the edges of the die there are the 16 analog switches (green).The Vcc supply is connected to the outer frame and quite massive to the analog switches. The analog bus is quite wide too.I3706B or 13706B, probably an internal naming.Input protection: A current limit resistor (green) and two clamping diodes (red/blue).Enable input circuit, you can see the push-pull output stage in the lower area.The input circuits for the channel selection are placed in parallel each putting out a differential signal.Making 16 signals out of the 4Bit channel selection.The analog switch driver is a little confusing...The analog switch is interesting. We have a NMOS and a PMOS (blue/red). The PMOS is quite large.Each transistor has two frame structures. The outer frame is permanently connected to Vcc and isolates the switch (cyan). Around the PMOS the inner frame is permanently connected to Vcc too. That´s probably the bulk potential. Around the NMOS the bulk potential is switchable (green).As will be shown in a moment in the off state the driver circuit connects the bulk of the NMOS to GND. That guarantees a high isolation resistance. The two analog switch transistors each have a small section that connects the bulk potential of the NMOS to the input potential when switched on (green). The higher potential provides a lower resistance. This explains the much smaller area of the NMOS transistor. In the case of an analog switch matching PMOS and NMOS is particularly important so the resistance doesn´t vary too much over the input voltage range.Back to the driver circuit we can find the driver for the PMOS (red) and the much smaller driver of the NMOS (blue).There are two transistors in series connecting the NMOS bulk with GND (green). One transistor is controlled by the input signal, one is controlled by the PMOS gate signal. That´s probably for switching time optimization.https://www.richis-lab.de/aswitch05.htm

author: Kleinstein
author_rank: Super Contributor
timestamp: January 03, 2022, 08:18:38 am
content: Looks like the switch part of the logic sereis CD74HCT4067 uses the same topology as the dedicated analog switches like the DG4xx.PS. the labeling has a minor glitch: there is 2 x I14 and no I15.

author: Noopy
author_rank: Super Contributor
timestamp: January 03, 2022, 08:32:08 am
content: Thanks for the hint! I have just changed the I14 to I15.There is a little difference to the DG4xx:In the ADG444 it looks like the NMOS bulk is switched from GND to the input just with the NMOS.In the CD74HCT4067 the NMOS bulk is switched from GND to the input with the NMOS and the PMOS.I´m sure that changes the behavior just a little bit but perhaps it makes the resistance a little more linear over the input voltage range.

author: Kleinstein
author_rank: Super Contributor
timestamp: January 03, 2022, 08:50:39 am
content: How the bulk is switched should not make much difference for the resistance, as it should finally get there. It could effect the dynamics / charge injection though. I am a bit surprized to see the slightly more complicated circuit with the cheap logic series, though no real cost difference for the extra p channel.

author: Noopy
author_rank: Super Contributor
timestamp: January 03, 2022, 08:59:08 am
content: Hm, you are right, it's more a dynamic thing...Quote from: Kleinstein on January 03, 2022, 08:50:39 amPerhaps the process generated worse transistors so you had to compensate for that with a more complex circuit? Just guessing...

author: Noopy
author_rank: Super Contributor
timestamp: February 20, 2022, 05:53:38 am
content: One more analog switch?Siliconix DG411 contains four switches SPST-NO. You can buy DG412 with four NC or DG413 with two NO and two NC.The DG411 can switch up to 40V while supplied with 44V. The resistance of the switch is 35. Switching time is typically 100ns. Power consumption is less than 35µW.In the datasheet you can find a quite complete schematic. I have colored it.The input stage can be driven with a different voltage level than the analog switch itself. There is an inverter in the first place (cyan). The input is protected with clamping diodes and a series resistor. There is an additional diode clamping VL against V+. That is important because the substrate is connected to V+. If there is a higher voltage than V+ there is current flow through the substrate.The inverter generates a differential signal for the first differential amplifier (red). This amplifier converts the high level to V+. The second differential amplifier (blue) converts the low level to V-.There are two inverters (yellow/pink). The first one probably can be bypassed to switch between a NO and a NC switch. We will talk about the analog switch itself later (green).Datasheet contains a pictures of the metal layer. Datasheet states the size with 2760µm x 1780µm x 485µm. There is even a specification of the metal layer. It´s SiAl with a thickness of 1,2µm +/-0,1µm. Adding silicon is important so the aluminium doesn´t migrate into the silicon structures shorting them. Passivation is 0,8µm +/-0,1µm of silicon nitride.SiliconixDesign is from 1987. CHSN could be initials of the developers.I assume switching between DG411, DG412 and DG413 was done by changing the metal layer. These characters could be markings for the different variants.Except for the power supply there are four perfect symmetrical areas containing the four analog switches.Most of the area is occupied by the two big transistors, the NMOS and the PMOS.The analog switch itself looks quite complex but it isn´t. You have the NMOS (blue) and the PMOS (red). Bulk of the PMOS is connected to V+. Bulk of the NMOS is switched between the S pin and V- (green) like we have seen in the other analog switches.We have clamping diodes to protect the structure.I´m not sure why they have integrated the capacitors.I assume they stabilize the gate potential against the input signal.You can find nearly everything we talked about on the die. There are the protection diodes and the series resistor of the control input (pink).There is the input stage supplied with VL and GND (white) and the rest of the driver stage (yellow) supplied V+ and V-.You can find the two bulk switches (green) and the capacitos (cyan). One of the capacitors is bigger. That´s probably because on the other side there is one of the bulk MOSFETs increasing the capacitance of this path.But there is no (clearly visible) protection diode at the input of the analog switch. That´s strange.Of course it´s possible that these diodes are parasitic elements but I don´t see a straight path to the supply. That´s even more puzzling compared to the accurate input protection of the control input.https://www.richis-lab.de/aswitch06.htm

author: Kleinstein
author_rank: Super Contributor
timestamp: February 20, 2022, 07:46:16 am
content: Quote from: Noopy on February 20, 2022, 05:53:38 amChances are the capacitors are there to reduce the charge in jection / switching spike. The P-MOS transistor is quite a bit larger than the NMOS and thus more gate charge there.

author: Noopy
author_rank: Super Contributor
timestamp: February 20, 2022, 08:32:37 am
content: Quote from: Kleinstein on February 20, 2022, 07:46:16 amThat perfectly makes sense!

author: Noopy
author_rank: Super Contributor
timestamp: October 29, 2022, 08:13:17 pm
content: TiN had sent me a Siliconix DG408. It is an 8-channel analog multiplexer. Like the DG411, the DG408 can be supplied with up to 44V and then allows switching of potentials up to 40V. The typical Rdson is minimally higher at 40Ω. The switching times are just above 100ns and thus correspond to the switching times of the DG411.The datasheet of the DG408 contains a circuit diagram that shows how the device works. Three inputs allow the selection of one switch. In addition there is an enable interface. All inputs have protection diodes and are supplied by an internal voltage regulator. A level shifter adjusts the level of the control signals before they pass through a decoder circuit that controls the eight switches. An interesting fact is the simpler construction of the actual analog switch compared to the DG411. In the DG411, the bulk potential of the NMOS transistor is varied during switching, whereas in the DG408 it is just tied to V-. Protection diodes are integrated in the analog switch area too.At first glance, the specifications of the DG408 and the DG411 look very similar. However, the diagrams in the datasheets show that the Rdson varies more with the DG408 than with the DG411. These characteristic curves look similar at first glance too, but you have to consider the different step sizes of the vertical axes.The dimensions of the die are 2,4mm x 1,7mm. The distribution of the function blocks is easy to see. In the right area, there are two big transistors arranged around each of eight bondpads. The bondpad that contacts all analog switches is on the right edge. In the left area and between the analog switches the control circuit is integrated. The capacitor in the upper left corner probably belongs to the internal voltage regulator.The DG408 was designed 1994 by Siliconix. While the DG411 had the characters CSHN, the letters CSICI are found here. Perhaps these are the initials of the developers. Perhaps there is a manufacturing process behind the abbreviation. The C in the second line seems to have its own meaning. It could be that the revision is depicted here.Exposing the die has damaged the metal layer somewhat. Some smaller areas have dissolved.On the analog switches, it is noticeable that the PMOS and NMOS transistors have a very different contacting. One transistor is connected with diagonal leads. These are usually square drain and source regions that alternate within a line and are offset from line to line. The other transistor has horizontal and vertical contact strips, respectively. Here, the drain and source seem to be designed as larger strips. Probably the shapes optimize the electrical properties so that the resistance is as constant as possible.https://www.richis-lab.de/aswitch07.htm

author: Noopy
author_rank: Super Contributor
timestamp: December 26, 2022, 04:49:29 am
content: Quote from: Noopy on February 20, 2022, 05:53:38 amWe had the DG411 now let´s compare it with the DG444. The Siliconix DG444 is a 4-channel analog switch like the DG411. The two devices have many things in common. However, when an analog switch is closed, the DG411 offers a lower resistance of 35Ω maximum. In the case of the DG444, one must expect up to 85Ω. In return, the parasitic capacitances of the DG444 are lower. The typical charge displacement of 1pC is just one fifth as large as with the DG411. In addition to the DG444 with NO switches, the DG445 offers the same switches as NC types.The circuit diagram shown in the datasheet contains the same parts as in the datasheet for the DG411.The datasheet includes an image of the metal layer and specifies the size of the die as 2,16mm x 1,76mm. It is thus noticeably smaller than the die of the DG411.The metal layer on the die largely corresponds to the representation in the datasheet. Apparently, just the additional markings and labels have changed somewhat.Different inscriptions are shown in each corner of the die, including the Siliconix logo and the year 1988.The string CSHM is probably the internal designation for this type of analog switch. On the DG408 the characters CSICI are shown, on the DG411 it is the characters CSHN.As on the DG411, there is also a character string that presumably identifies the variant of the metal layer and thus the analog switch. It seems very likely that on the same die, besides the DG444, the DG445 can also be realized.Some areas, such as the structures at the inputs, are built in the same way as the DG411. The large switching transistors have the same structures, but are much smaller. This was to be expected due to the specifications. Interesting is the capacitor on the right of the left bondpad. This capacitor makes it possible to keep the charge injection low during switching. The capacitor offers several surfaces that can be connected as required to optimize this effect.In the center there are some unused elements. Maybe the inversion of the control logic is realized here (DG444/DG445).The printing on this DG444 looks significantly different from the DG444 above. The second line seems to be a date code. This would make the analog switch shown here 3 years younger.It turns out that it is the same die.https://www.richis-lab.de/aswitch08.htm