hybridfree/eevblog-posts huggingface dataset:
Why Does a Battery Have Continuous Discharge Graphs that Go Beyond Its Ratings? - Page 1
Forum section: electronics / beginners

author: MeerkatAirforce
author_rank: Newbie
timestamp: September 29, 2018, 05:11:20 pm
content: I noticed that a battery I was looking at (https://d2ei442zrkqy2u.cloudfront.net/wp-content/uploads/2018/09/28082537/2018-September-DL123_0918-002.pdf) has a maximum continuous discharge current rating of 60mA, but the continuous discharge graph on its data sheet shows data from 10mA all the way up to 1000mA.What does the maximum current rating mean if it can be characterized at higher currents than that?Is a battery safe to use beyond its "maximum continuous discharge current"?Context: I was looking for a battery that could supply ~120mA for a little DSO138 oscilloscope that wouldn't die in half an hour.

author: ArthurDent
author_rank: Super Contributor
timestamp: September 29, 2018, 06:20:24 pm
content: Where I’ve seen the DL123 used is in camera where the drain would generally be fairly low but when using the flash there would be a high current pulse and that’s probably why they have the pulse rating of .9A, 3sec on, 27 sec off. It could also be used in LED flashlights of moderate drains. Using it in high power flashlights or other applications where it would have a 1000Ma drain would cause the initial voltage under load to be about 2.5 instead of 3.3 and it would only last 1 hour. Single use batteries like this aren’t that practical for high energy applications because of the higher cost for a short life. The maximum continuous rating is for a typical use where you would use it on for some longer period of time and the maximum drain is the maximum safe allowable drain under any conditions. Try to draw more current than that and bad things may happen including overheating or violent battery failure.If the DL123 is used in low drain applications it will last a fairly long time and in smoke detectors I’d expect it to last a couple of years and still be o.k. when you replace it as recommended for safety reasonsIt looks like if 3.3VDC would work for your small scope the DL123 would last about 10 hours. If you don’t need it to be portable I’d suggest a line operated power supply so you don’t have to worry about the charge left in the battery.Note: I just checked the specs and it looks like the DSO138 will operate from 9-14 volts so one DL123 battery won't work unless you use 3 cells or one cell and a DC-DC converter, which, because of less than 100% efficiency, would further shorten battery life. Google DSO138 and battery and you can get some ideas what others have tried.
Why does an LED act like this? - Page 1
Forum section: electronics / beginners

author: Falcon69
author_rank: Super Contributor
timestamp: November 24, 2014, 08:04:41 pm
content: Okay, I've experienced this numerous times, and I don't know what's happening.I have an 0603 LED soldered to a circuit board I am working on. When I place my multi-meter on the diode setting and test the LED when it is NOT soldered on the board, it lights up.However, when I solder it to the board, it does not. So I unsolder it from the board and connect to the multi-meter. It works again.Why does it not light on the circuit board when the multi-meter's leads are connected directly to the cathode and anode of the LED?Thanks in advance for your input in clearing up this mystery.

author: Mr.B
author_rank: Unknown
timestamp: November 24, 2014, 08:07:01 pm
content: You would need to show us more of the circuit.What other components are having an influence on the test conditions...

author: SeanB
author_rank: Super Contributor
timestamp: November 24, 2014, 08:08:40 pm
content: Possible you have a pad extending under the LED and shorting it out. Check resistance across the device in circuit to see.

author: Falcon69
author_rank: Super Contributor
timestamp: November 24, 2014, 08:34:12 pm
content: well, it is connected to a rather large set of traces (1mm then branches off to rest of circuit at .6 and .4 and .4 and .4). then is connected to a voltage regulators output. Could it be reading resistance off all that?It lights up perfectly fine if I connected 5 volts and ground across it. But doesn't light when a multi-meter is connected (using it's diode output)

author: jlmoon
author_rank: Unknown
timestamp: November 24, 2014, 08:40:55 pm
content: Have a schematic?Alternate component loading on diode test function of your meter?

author: Zero999
author_rank: Super Contributor
timestamp: November 24, 2014, 08:52:57 pm
content: Quote from: jlmoon on November 24, 2014, 08:40:55 pmI'd suspect that's the most likely reason why this is happening.

author: Falcon69
author_rank: Super Contributor
timestamp: November 24, 2014, 09:17:11 pm
content: okay, that makes sense.Maybe the added resistance of the traces and the other components in-line are effecting the current through the Multi-Meter and it isn't supplying enough current to light the thing.I have 16 other led's in the circuit, and they light up with the multi-meter, however, they are not connected to as many components are such large traces.

author: SL4P
author_rank: Super Contributor
timestamp: November 25, 2014, 04:34:40 am
content: Multimeter red-black is often the opposite voltage polarity in diode test mode(electron flows vs current flow).But providing a circuit would be a good starting place for us to comment.Remember your metermayalso source more current than the LED wants to see - so it may work (for a little while) but not in the future.
Why does eagle not fill in the ground plane around pads? - Page 1
Forum section: electronics / beginners

author: SethGI
author_rank: Regular Contributor
timestamp: May 28, 2017, 12:41:09 am
content: Hi,This is a random question I've been wondering about for a while. When you have a ground plane in Eagle (or any polygon for that matter) and you add a pad that's connected to ground, why does it draw those four traces to the pad instead of just filling in everything?I attached a picture as an example.Thanks!-Seth

author: Richard Crowley
author_rank: Super Contributor
timestamp: May 28, 2017, 12:49:22 am
content: It is for thermal isolation. If you tried to solder a component lead in a hole in a large ground plane, the large copper area would sink away the heat rapidly and make soldering difficult and/or damaging to the board and component.

author: ataradov
author_rank: Super Contributor
timestamp: May 28, 2017, 01:51:18 am
content: And you can disable this in the polygon properties. Look for checkbox called "Thermals".

author: KL27x
author_rank: Super Contributor
timestamp: May 28, 2017, 06:47:06 am
content: And to control individual pads, you will want to do that in the library part. There, you can select/deselect thermals as well as paste/cream layer and stopmask for each pad.Generally, I want to avoid solid connection between pads and ground plane, except where it will actually make an improvement to the board. E.g., on parts that are gonna run hot and be the limiting factor. Or I suppose with high speed/fidelity signals it may make a difference.Even thermals can slow down hand-soldering. Where I am going to hand solder I will sometimes use a single trace to connect pads - and then connect that trace to the pour/polygon a ways away. The downside is this will prompt inquiry from my board manufacturer, slowing the turnaround, a tad.
Why does hp e3610a has two pass transistors? - Page 1
Forum section: electronics / beginners

author: Farrow
author_rank: Contributor
timestamp: January 10, 2021, 09:41:34 am
content: I'm learning all the ins and outs of a linear power supply. Trying to design my own, reading Hp's old power supply app note (Very helpful). Im trying to replicate the e3610a psu and by looking at the schematic I see they have ditched the mosfet approach and switched to a more conventional darlington setup. but I'm getting confused here, are they using both darlingtons in parallel to distribute the power dissipation or using one as CV and the other one as a CC pass element?

author: SeanB
author_rank: Super Contributor
timestamp: January 10, 2021, 11:27:36 am
content: All 4 are in parallel, in 2 strings of 2 parallel transistors, likely done so they can easily have current limiting for each pair of 2, and 4 overall because it reduces the heat dissipated in any transistor, plus also allows them to offer a lower current units with the same basic circuit board, only changing the transformer and removing one of the pairs. That way the designers only have to match a pair of transistors at a time, and thus makes assembling easier. You can see the entire drive circuit is duplicated from Q2 to get the 2 drive circuits.
Why does MC34063 switch behave so? - Page 1
Forum section: electronics / beginners

author: beowulfenator
author_rank: Contributor
timestamp: January 13, 2021, 08:53:49 pm
content: Hi!I'm trying to understand how the switch inside the MC34063 works. I've put together a test circuit.I thought I'd see a rectangular waveform on pin 1, the switch being open for 6t and pulling pin 1 low to ground, then the switch being closed for 1t and letting pin 1 go high to supply voltage trough the resistor. Here's what I measure, though.The probes are 10x, so vertically one cell = 1V. The upper trace is from the timing capacitor (pin 3). The lower trace (on pin 1) I don't quite understand.When the switch is open, pin 1 is slightly above ground (PN junction voltage?). But then when the switch closes, the trace abruptly falls below 0, and then it slowly climbs up but not anywhere near the supply voltage. I can also see that it's "accelerating", the increase begins slow and then goes faster and faster.Can anyone tell me what is going on here?

author: mikerj
author_rank: Super Contributor
timestamp: January 13, 2021, 10:31:54 pm
content: That 27k pull-up is way to much resistance, don't forget that transistor would be switching up at 1.5 Amp in it's intended use, so you may be seeing leakage effects.Also use a separate resistor to supply the driver transistor on pin 8 from Vcc, as it's wired you've configured like a Darlington which will not be able to pull down very close to 0v.

author: beowulfenator
author_rank: Contributor
timestamp: January 14, 2021, 12:16:55 pm
content: Thank you!I've increased the load by changing the resistor to 1K, and the numbers are now exactly as in the datasheet (down to roughly 1V and up to almost Vcc).
Why does MOSFET pin naming seem backwards? - Page 1
Forum section: electronics / beginners

author: ksoviero
author_rank: Contributor
timestamp: July 03, 2021, 02:10:40 pm
content: So with BJTs the pins are collector for the high side and emitter for the low side, which makes sense because the current flows into the collector and out of the emitter. However, with MOSFETs thedrainis connected to the high side and thesourceis connected to the low side. Which seems backwards.Are MOSFETs using electron current vs BJTs conventional current or is there some meaning behind the names that I'm not grasping?Thanks!

author: magic
author_rank: Super Contributor
timestamp: July 03, 2021, 02:19:44 pm
content: In NPN and N-MOSFET the charge carriers are (negative) electrons flowing from the emitter/source to the collector/drain in reverse direction to conventional current flow.In PNP and P-MOSFET the charge carriers are (positive) holes flowing from the emitter/source to the collector/drain in the same direction as conventional current flow.Seems to make sense

author: ejeffrey
author_rank: Super Contributor
timestamp: July 04, 2021, 12:10:38 am
content: Your understanding of BJT names is backwards. These names are relative to the "interior" of the device. Think of it like a vacuum tube. The emitter "emits" electrons in an NPN transistor or holes in PNP. Those carriers (that don't get trapped in the base) are collected by the "collector"The FET source and drain are the same way.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: July 04, 2021, 02:04:21 pm
content: https://xkcd.com/567/
why does my esp32c3 xiao not uploading code? - Page 1
Forum section: electronics / beginners

author: rizlesz2000
author_rank: Contributor
timestamp: October 29, 2023, 05:38:00 pm
content: i brought myself an esp32 but when i tried to uplad the code it saysA fatal error occurred: Could not open COM6, the port doesn't existFailed uploading: uploading error: exit status 2it was success when i first uploaded the code and the code worked fine. But now it always gave me this error. I set my baud rate to 115200 and installed esp32 frimware and i did everything mentioned in the website. So what is the problem? i dont want to dump the board

author: tooki
author_rank: Super Contributor
timestamp: October 30, 2023, 04:35:23 pm
content: Will it accept an upload if you manually enter programming mode?1. Press the B (boot) button and keep it held2. Press the R (reset) button3. Release the reset button4. Release the boot button.See also the section “Strapping pins” onhttps://wiki.seeedstudio.com/XIAO_ESP32C3_Getting_Started/
Why does my mobile phone battery still work - Page 1
Forum section: electronics / beginners

author: makebit
author_rank: Unknown
timestamp: October 10, 2025, 04:59:46 pm
content: Hi,I have a Samsung SM-J330FN mobile smartphone which i bought new in 22nd May 2018.I hardly ever used it.From 2019 to March 2025 i did not use it at all.However, it works fine now.Surely the battery should have self-discharged to a ruinously low voltage over those disused years. And the battery should be dead?

author: RoGeorge
author_rank: Super Contributor
timestamp: October 10, 2025, 10:24:44 pm
content: Self discharge for Li-ion is rather low. It is not unheard for a charged battery to still keep some charge after many years. Maybe not all of them, but some will do.To give an example, I have in test a weight scale, in which the normal CR2032 coin cell battery was replaced with a Li-ion from a former GSM modem (produced around 2010 or so). I've charged that battery almost 3 years ago, and the weight scale is still working. Measured its voltage yearly, out of curiosity:https://www.eevblog.com/forum/beginners/li-ion-cell-instead-of-a-cr2032-for-a-domestic-wight-scale/msg5751629/#msg5751629

author: BillyO
author_rank: Super Contributor
timestamp: October 11, 2025, 01:40:18 am
content: Samsung are one of the best manufacturers of small Lithium batteries. It would not surprise me if they but their best specimens in their own products.I have some Samsung 18650 cells I took out of the battery pack from a circa 1996 IBM think pad. They work fine. Capacity is down 18% from spec. but hell. these things are old enough to have grade school kids!

author: amyk
author_rank: Super Contributor
timestamp: October 11, 2025, 01:44:06 am
content: Self-discharge is also an exponentially decreasing curve, so it will gradually take longer to discharge as it discharges.

author: inse
author_rank: Super Contributor
timestamp: October 11, 2025, 07:26:45 am
content: I wonder why no one noticed the most obvious explanation: the little battery smurfs secretly recharged it regularly

author: Bud
author_rank: Super Contributor
timestamp: October 11, 2025, 04:42:37 pm
content: The phone has an antenna, so it is harvesting free energy and through the circuit feeds it back to the battery to charge it which compensate for self discharge.

author: makebit
author_rank: Unknown
timestamp: October 12, 2025, 02:07:42 pm
content: The phone has an antenna, so it is harvesting free energy and through the circuit feeds it back to the battery to charge it which compensate for self dischargeWouldnt actually surprise me if there is truth in this.....the phone co's would secretly support it, as they want peoples phones running for as long as poss, so they can cream in more money from calls etc.I used to work with someone who did antenna harvesting.

author: tggzzz
author_rank: Super Contributor
timestamp: October 13, 2025, 10:35:10 am
content: Caution.It is believed that makebit==Treez/Faringdon/ocset/zenerbjt etc etc
Why does my switching regulator circuit deliver 4.4V instead of 1.2V? - Page 1
Forum section: electronics / beginners

author: soFPG
author_rank: Frequent Contributor
timestamp: May 29, 2021, 07:52:02 pm
content: Hello,it seems like I am not even capable of building a correct switching regulator circuit. My idea was that this circuit should produce 1.2V from 5V input (see attachment).However, what I am getting is 4.4V.Any idea why this could be (datasheet of JW5033S:https://datasheet.lcsc.com/szlcsc/1906281506_JoulWatt-Tech-JW5033S_C324577.pdf)?

author: AndyC_772
author_rank: Super Contributor
timestamp: May 29, 2021, 08:01:25 pm
content: What are the pin numbers, and which package are you using? The two options are different.

author: soFPG
author_rank: Frequent Contributor
timestamp: May 29, 2021, 08:07:27 pm
content: Ye, you have the finger right on the spot.My footprint is wrong

author: Monkeh
author_rank: Super Contributor
timestamp: May 29, 2021, 08:12:32 pm
content: Quick fix: Put the chip on upside down.

author: soFPG
author_rank: Frequent Contributor
timestamp: May 29, 2021, 08:13:35 pm
content: I don't think this will do it. I switched BST and FB

author: Monkeh
author_rank: Super Contributor
timestamp: May 29, 2021, 08:15:45 pm
content: Ah, well, if you didn't flat out use the wrong pinout in its entirety, no, that won't work.

author: AndyC_772
author_rank: Super Contributor
timestamp: May 30, 2021, 12:19:24 pm
content: Quote from: soFPG on May 29, 2021, 08:07:27 pmPro tip:Alwaysinclude pin numbers on every schematic symbol, unless it's just for a 2 pin passive.Also, not that it applies in this particular case, butalwaysmakeeverypin on a device visible, especially any exposed pads on QFN and similar packages.
why does OCXO have lowest noise? - Page 1
Forum section: electronics / beginners

author: fonograph
author_rank: Frequent Contributor
timestamp: May 06, 2017, 11:14:40 am
content: Sure there are low phase noise TCXO and other types of quartz clocks but the lowest noise clock a manufacturer makes is always OCXO,all these super low noise clocks with -140db/10hz at 10mhz carrier are all OCXO,I dont know why.I understand the advantage of oven for long term stability but the jitter/phase noise is short time window thing,freqency drift and phase noise are different thing.I actualy think that the high temperature should increase the noise becose higher temperature = more thermal noise yet these hot crystals that are baking at 70 degrees celsius are order of magnitude superior in terms of noise compared to non ovenizer clocks.

author: Kleinstein
author_rank: Super Contributor
timestamp: May 06, 2017, 11:29:18 am
content: The tuning / trimming elements in TCXOs or VCXOs usually adds a small a mount of noise to. They have a kind of voltage controlled capacitor and these are not that perfect (they add a small amount of damping) and the controlling voltage can also have some noise.The crystal oven are more like 50-55 C, not 70 C. At this temperature a different orientation of the crystal is used. This also has an influence on the crystal internal damping and noise.Due to the usually higher price class for the oven crystals also other parameters like purity and vacuum tend to be better, as there is not much market for low quality OCXOs.

author: jpb
author_rank: Super Contributor
timestamp: May 06, 2017, 01:23:31 pm
content: Also OCXOs can select the temperature to maintain so can be set to operate at a turning point where there is little change going on.OCXOs are often (not always) SC cut crystals while cheaper TCXOs are typically AT cut.I would guess that things like hermetic sealing also help (though again this is only true for some) and also keeping constant temperature probably also helps to maintain very tight voltage regulation within the package.But looking at different options amongst OCXOs, stability and low phase noise don't always go together. Some very expensive OCXOs with low phase noise can have worse temperature specs than some cheaper OCXOs.
Why does one schematic view of the PCB show C177 while another omits it - Page 1
Forum section: electronics / beginners

author: Pyral
author_rank: Contributor
timestamp: October 07, 2025, 02:50:44 am
content: I am in the middle of recapping my RD5370 tape deck as you know. I was double checking the orientation of a capacitor, and I noticed a discrepancy. The bottom view of the PCB eliminates C177, which disagrees with what is on the board IRL and the top view schematic.Am I reading the schematic wrong or did they eliminate the part for some reason? The top view is C139->C177->R146, and the bottom view is C139->R146.They also have some capacitor voltages wrong, one capacitor is listed as being 16v, yet the original capacitor put in is a 50v. There aren't multiple versions of the PCB. My service manual version is from 5-79, the model came out in '78.

author: ataradov
author_rank: Super Contributor
timestamp: October 07, 2025, 04:51:08 am
content: Maybe a mistake, or may be they decided to bypass that capacitor. It is a frequency dependent compensation, so it is possible that they decided it was not needed.I would follow the board and replace with a similar capacitor.Higher nominal voltage is fine, they likely substituted with what they could get at a time.

author: PGPG
author_rank: Frequent Contributor
timestamp: October 07, 2025, 09:26:04 am
content: It looks that at PCB:- the R146+C177 order was reversed (for serial connection it is not important),- C177 was shorted.Updating the documentation those times was harder than nowadays so only PCB picture was corrected.

author: Pyral
author_rank: Contributor
timestamp: October 07, 2025, 03:49:21 pm
content: Can I still rely on the polarity shown in the schematic being correct? Dont want a fire cracker going off on my pcb.I sort of noted the orientation but I’m not 100%, and they didn’t print the polarity on the pcb for this one capacitor.

author: ataradov
author_rank: Super Contributor
timestamp: October 07, 2025, 03:53:27 pm
content: Yes, it is correct.

author: Pyral
author_rank: Contributor
timestamp: October 08, 2025, 06:44:39 am
content: It is correct. I found a photo I took where it was in the background. And I plugged it in since then and it didn't explode.I'll post a photo tomorrow for anyone experiencing this trap.
Why does scope manual say "AC position measurements cannot be made wrt ground"? - Page 1
Forum section: electronics / beginners

author: The Jonald
author_rank: Newbie
timestamp: March 30, 2018, 02:08:32 am
content: Hello all. I have a Philips PM3214 oscilloscope. A link to the service manual including schematic is at the end of this post. The scope's internal power supply is encased in a plastic enclosure and isolated; ie, the scope is floating. The manual says (p21) that AC-coupled measurements, ie those made with the AC coupling switch on, cannot be made with respect to ground. It's my understanding that the AC coupling switch only introduces a capacitor to block the DC component of the input signal. So why can the scope measure w.r.t. ground with DC coupling, but not AC coupling?Manual:https://drive.google.com/open?id=16UFPu6yb8_UQ1O0_klhKMPjxyJU1AFDC

author: Nerull
author_rank: Frequent Contributor
timestamp: March 30, 2018, 12:56:48 pm
content: By virtue of filtering out the DC, you have now referenced the signal to the average signal level and not ground.AC coupling will turn the red signal into the green signal. Its values cannot be ground referenced because if they were, the waveform would not move.You can not look at any point on the AC-coupled waveform and know what its value w.r.t ground is, because you are not seeing the full signal. You have to include the DC offset to know that.

author: David Hess
author_rank: Super Contributor
timestamp: March 30, 2018, 07:56:59 pm
content: It is just saying that when AC coupling is used, the reference to ground is lost so DC measurements are not possible.

author: tautech
author_rank: Super Contributor
timestamp: March 30, 2018, 08:20:42 pm
content: Quote from: The Jonald on March 30, 2018, 02:08:32 amOnly the signal amplitude and frequency can be measured in AC coupled mode.To see the DC offset part of the signal you must use DC coupling and maybe at a higher V/div setting if the signal has a large DC offset.

author: The Jonald
author_rank: Newbie
timestamp: March 31, 2018, 01:34:59 am
content: That's what I thought. I was afraid it was telling me something I didn't understand about how to hook the scope into a circuit. Thanks for removing my confusion.

author: David Hess
author_rank: Super Contributor
timestamp: March 31, 2018, 03:43:49 am
content: Quote from: tautech on March 30, 2018, 08:20:42 pmSome oscilloscopes include an "offset" function which allows a DC offset to be removed from the signal before amplification. For instance in an extreme case, up to 10 volts might be removed at 1mV/div allowing DC measurements to be made between 9.996 and 10.004 volts without using AC coupling. This is like having a position control with a range of +/- 10,000 divisions.
Why does the passive highpass filter give such results in spice analysis? - Page 1
Forum section: electronics / beginners

author: electronx
author_rank: Regular Contributor
timestamp: December 01, 2023, 09:41:01 am
content: I am designing a passive high pass filter, here are the values: 2M ohms and 1uf cut-off frequency is 0.07Hz +-20V and when I apply a 1 khz sinus signal, I get such a result. What is the reason for this? The voltage level looks like this ım using pspice

author: iMo
author_rank: Super Contributor
timestamp: December 01, 2023, 09:52:05 am
content: Because your resistor is 2 Milliohm?Try with 2Meg or 2000k..

author: Chalcogenide
author_rank: Regular Contributor
timestamp: December 01, 2023, 09:53:28 am
content: There is a chance that you placed a 2 mOhm resistor instead of a 2MOhm; check the current across the resistor.SPICE is typically not case sensitive, so the 1e6 multiplier is usually written as "MEG" (or just use scientific notation to be always sure).

author: electronx
author_rank: Regular Contributor
timestamp: December 01, 2023, 10:03:20 am
content: Thank you all .I feel super noob now

author: MarkT
author_rank: Frequent Contributor
timestamp: December 02, 2023, 08:27:35 pm
content: I'd say Spice is just dumb here, its a real gotcha... I suppose the justification is Spice originally was written in Fortran using punched cards... I doubt it understands p v. P either (pico / peta) - not that petaohm resistors are a thing!

author: TimFox
author_rank: Super Contributor
timestamp: December 02, 2023, 08:35:15 pm
content: SPICE is backwards-compatible for its notation.The original SPICE, in compiled Fortran on Hollerith cards, was not case-sensitive, so "m" or "M" always means "milli" and for 106one needs to write "Meg" or "MEG".Similarly, "p" always means "pico" and "u" always means "micro".

author: MrAl
author_rank: Super Contributor
timestamp: December 03, 2023, 11:44:40 am
content: Hi,Just to verify that it is a 0.002 Ohm resistor and not a 2M resistor (2M as we usually write 2 megohms) the theoretical calculation comes out to:Vout=251.327 nVwhich matches your plot result closely.If you had an actual 2 megohm resistor here, it would have came out very very close to 1v.For reference, the theoretical calculation comes out to:Vout=(2*pi*f*C*R)/sqrt(4*pi^2*f^2*C^2*R^2+1)with f, C, and R positive, and pi=3.14159265...
Why does the SB2 have a sharp corner in the package, does he have any effect? - Page 1
Forum section: electronics / beginners

author: caipeiqq
author_rank: Newbie
timestamp: January 15, 2019, 12:57:55 am
content: When I saw this strange package while watching ST's demo board, why would he draw a sharp corner shape?

author: tsman
author_rank: Frequent Contributor
timestamp: January 15, 2019, 01:01:56 am
content: SB = Solder Bridge. You connect between the two pads with a blob of solder.
Why does this boost converter not use a rectifying schottky diode? - Page 1
Forum section: electronics / beginners

author: DanInvents
author_rank: Contributor
timestamp: January 09, 2023, 08:14:02 am
content: Hi!I'm in the process of designing a PCB that incorporates the TPS61230A. The idea is to step up the voltage from a 1S LiPo battery to 5.2 V and a maximum current output of 2.3A.I have read the datasheet and I understand how boost converters work but, where is the diode to rectify the AC waveform?As an attachment there is the schematics of the converter and the necessary external components.Thank you for the help!

author: wasedadoc
author_rank: Super Contributor
timestamp: January 09, 2023, 08:17:39 am
content: The FET between pins 5 and 7 is a synchronous rectifier.

author: fourfathom
author_rank: Super Contributor
timestamp: January 09, 2023, 08:18:26 am
content: I assume that the internal MOSFET is used as a synchronous active rectifier. These are switched on and off at the appropriate times and can have less loss than even a Schottky diode.

author: DanInvents
author_rank: Contributor
timestamp: January 09, 2023, 08:25:01 am
content: Thank you for your quick answers! This is very interesting, this way I can save space in the design.

author: MrAl
author_rank: Super Contributor
timestamp: January 09, 2023, 10:10:01 am
content: Quote from: DanInvents on January 09, 2023, 08:25:01 amHi,I have to agree with everyone else that mosfet connected to pin 7 looks like it is being used for synchronous rectification.That simply means that it is turned on by the control circuit at the time when a normal diode would conduct. The voltage drop across it from drain to source will be lower than with a Schottky (in theory) so the efficiency should be higher.The Cbst is a boost strap capacitor that is used to raise the internal voltage of the ic chip so it can better drive the mosfets.
Why does this ON datasheet totally look like an AD datasheet? - Page 1
Forum section: electronics / beginners

author: JoeN
author_rank: Frequent Contributor
timestamp: September 20, 2015, 10:21:06 am
content: Even an ADish part name. Did they collaborate on this?http://www.onsemi.com/pub_link/Collateral/ADP3418-D.PDFConfused...

author: RobertHolcombe
author_rank: Frequent Contributor
timestamp: September 20, 2015, 11:37:16 am
content: From the ON Semiconductor wiki"In January 2008, ON Semiconductor completed the acquisition of the CPU Voltage and PC Thermal Monitoring Business from Analog Devices, Inc., for $184 million."The ADP3418 was included in the acquisition

author: JoeN
author_rank: Frequent Contributor
timestamp: September 21, 2015, 02:53:36 am
content: After paying $184 million they had no money left to change the datasheet format...Thanks. I wonder why AD sold that line off.

author: Richard Crowley
author_rank: Super Contributor
timestamp: September 21, 2015, 03:10:42 am
content: Quote from: JoeN on September 21, 2015, 02:53:36 amBut then it is a moot point, since it appears to be obsolete regardless.And anyway, why change it? TI data sheets still have that same clunky design from the 1960s.

author: ShawnD
author_rank: Contributor
timestamp: September 26, 2015, 02:12:30 pm
content: Quote from: Richard Crowley on September 21, 2015, 03:10:42 amAnd the National Semiconductor parts just have a TI cover page stuck on the front.
Why does TI invented ovn logic symbol like his one? Where is reference for that? - Page 1
Forum section: electronics / beginners

author: mustafakerb
author_rank: Contributor
timestamp: May 26, 2022, 04:23:01 pm
content: from Ti datasheet SN74LVC07A, where to find table reference with this expanded logic symbols? Thx.

author: xrunner
author_rank: Super Contributor
timestamp: May 26, 2022, 04:34:53 pm
content: Open collector (or Drain) symbol. It's used, just search for "open collector" and look at Google images ...

author: ejeffrey
author_rank: Super Contributor
timestamp: May 26, 2022, 04:42:09 pm
content: I've definitely seen it used for open collector / open drain outputs, but I don't know of a comprehensive or authoritative reference that would cover this.

author: gamalot
author_rank: Super Contributor
timestamp: May 26, 2022, 05:03:22 pm
content: It's IEEE standard:https://www.ti.com/lit/ml/sdyz001a/sdyz001a.pdf

author: AlfBaz
author_rank: Super Contributor
timestamp: May 26, 2022, 05:08:27 pm
content: Also defined in IEC 617-12:1991

author: Terry Bites
author_rank: Super Contributor
timestamp: May 26, 2022, 05:19:32 pm
content: Yes "the new logic symbols" introduced a mere 38 years ago. The symbols we all politely ignore. I have correctly identified this symbol as a pantograph gate. Used in Y-Fronts I believe.

author: mustafakerb
author_rank: Contributor
timestamp: May 28, 2022, 01:12:08 am
content: Many thanks for all of you for clear explanation and especially for the links!
Why doesn't this UC3842 circuit work? - Page 1
Forum section: electronics / beginners

author: Pentium100
author_rank: Frequent Contributor
timestamp: June 09, 2013, 07:04:59 am
content: Hi, I am trying to replace a blown primary side of a power supply (48V -> 3.3V), because some of the original components cannot be identified (and I do not have a second device to use as a reference). It was made from a 40106 chip and a bunch of discrete transistors. Since I could not figure out how to do that, I decided to use a UC3842 chip with the original transformer (I know the frequency is about 200kHz).This is my test ircuit (yes, powered on 26V for now, I need to see whether it works at all):I turned it on and nothing happened. I though the chip was bad so I placed a new one. Same thing. The oscillator is working, but there is no output (and there should be output because VFB is at about 1V, I tried connecting it to ground too). I though I should figure out if the output is actually in sinking mode or just off, to do that I briefly connected a 120Ohm resistor between the power supply and pin 6 of the chip and to my surprise it started working and kept working after I removed the resistor. It keeps working until I raise VFB to above 2.5V (or disconnect he power), then the output stops and does not start, even if I reduce the VFB to 0V. I have not checked whether it adjusts the duty cycle based on the feedback yet.The same happens whether the output FET or the transformer is connected or not.Why does this happen and how to make the chip start properly?

author: SeanB
author_rank: Super Contributor
timestamp: June 09, 2013, 10:03:55 am
content: R4 should be 100k, and you might want to rearrange the feedback loop so that pin 1 is above 1V on startup so that the chip does not go into shut down. A 100n cap across the opto transistor should make it start more reliably.

author: Pentium100
author_rank: Frequent Contributor
timestamp: June 09, 2013, 03:27:26 pm
content: Quote from: SeanB on June 09, 2013, 10:03:55 amThe pin1 is at 4V at startup. I will try to use 100k resistor.Quote from: AcHmed99 on June 09, 2013, 10:22:52 amThe transformer does not have an aux winding. I kept the secondary side original, the optocoupler is connected trough a zener diode or a similar circuit - the voltage to its LED depends sharply on the secondary voltage.Forgot about the Vgs limit. I though of using a linear regulator to supply power to the chip, so higher chip voltage = less hot regulator. he FET is still working though, but I will limit the voltage to 19V or so (the chip needs 17.5V to start).

author: Ghydda
author_rank: Regular Contributor
timestamp: June 11, 2013, 06:48:08 am
content: Have you probed U1 pin 6 with a scope? What does it show?My first thought, when reading that the oscillator works but no output is measured, was that you need to apply some leading edge blanking to the Isense input (pin 3). The schematic posted by AcHmed99 shows how this is done.
why have separate current and voltage source? - Page 1
Forum section: electronics / beginners

author: funkimunky
author_rank: Contributor
timestamp: July 19, 2012, 10:36:15 am
content: I am learning about circuit analysis from a book and circuits with a separate current source and separate voltage source keep cropping up. Do these types of circuits exist in the real world and if so what kinds of applications do they serve?Just to quantify my knowledge about ee I am a total beginner.

author: IanB
author_rank: Super Contributor
timestamp: July 19, 2012, 10:42:29 am
content: They are idealized extremes that can be used to support an understanding of how real circuits work. All real sources are somewhere in between one or the other.Most real power sources like a battery for example approximate a voltage source, but current sources can crop up as useful elements in some kinds of circuit design.You could model a real source equally well as a voltage source with a series resistance or a current source with a parallel resistance. Viewed from outside both would behave exactly the same.

author: funkimunky
author_rank: Contributor
timestamp: July 19, 2012, 11:13:37 am
content: Thanks for the reply it makes sense now. They just separate the voltage and the current so they can be ideal current and voltage sources to make it easier to understand.I take it for learning circuit design you only need one power supply, I was worried that I might need to get another one.

author: Unknown
author_rank: Unknown
timestamp: July 19, 2012, 12:56:18 pm
content: Most lab supplies can do both constant voltage (voltage source) and constant current (current source), depending on how you set the limits.
Why Household Radiator Flips RCB/CBP? - Page 1
Forum section: electronics / beginners

author: Boris_yo
author_rank: Frequent Contributor
timestamp: January 09, 2012, 09:46:46 pm
content: For 5 years radiator was not switched and when finally switched, it flips RCB (or CBP). This is all information i have for the moment.What can cause this?

author: gxti
author_rank: Frequent Contributor
timestamp: January 10, 2012, 03:30:00 am
content: Does it have a earth pin? If it's very dusty inside there could be leakage current from hot to earth, which would trip a RCD (but not a current trip breaker).

author: ikrel
author_rank: Contributor
timestamp: January 14, 2012, 12:57:43 pm
content: If it is sharing a neutral with another circuit, it can cause a trip.
Why I frequently see MOSFETs with a reversed diode in parallel with drain source - Page 1
Forum section: electronics / beginners

author: king.oslo
author_rank: Frequent Contributor
timestamp: January 20, 2012, 12:39:18 am
content: Hello there,Will somebody insimple termsexplain to me why I frequently see designs where MOSFETs have a reversed diode in parallel with drain and source?I have googled the subject. I understand the very lowest basics of P- and N-FETS (and diodes, including Schottky), but that's about it.Thanks,Marius

author: amspire
author_rank: Super Contributor
timestamp: January 20, 2012, 12:58:00 am
content: Are you talking about the internal reversed biased diode in a mosfet?In a N channel MOSFET, you have a P doped silicon substrate, and the source and drain are N doped regions within the substrate. So in normal operation, both the source and the drain are in fact diode junctions to the substrate. The source is also connected to the substrate as for the gate to work properly as the substrate has to be at the same potential as the source. There are actually some small signal MOSFETs that have the substrate connected instead to a separate fourth pin, but these are now increasingly rare, and I have never seen it done in a power MOSFET.So in normal operation, the drain region is a reverse biased diode junction to the substrate which is connected to the source. If the drain voltage is taken below the source voltage, this diode junction is now forward biased.Richard

author: king.oslo
author_rank: Frequent Contributor
timestamp: January 20, 2012, 01:21:19 am
content: Thanks.1. In the datasheet for the MAX8792 page 11, the low side fet has a diode, whilst the other doesn't. What does this do?http://datasheets.maxim-ic.com/en/ds/MAX8792.pdf2. So this is true: Are you saying that NFETs always work as a reversed diode between drain and source? When voltage is lower at source drain relative to source, voltage flows from d-s?3. What about PFETs? Are they forward biased diodes?Thank you for your time.M

author: amspire
author_rank: Super Contributor
timestamp: January 20, 2012, 01:37:16 am
content: N and P mosfets have a reversed biased diode gate to source. P channel MOSFETS have a N substrate with P source and gate. So it is the same story, just that everything is opposite.Now the diode on Page 11 is a different story. On most IC's, including the MAX8792, you cannot take any pin to more then 0.3V below the negative supply pin or the IC can latch up. The inbuilt reverse biased diode in a MOSFET will only limit the reverse voltage to 0.7 to 1V below the negative supply when the inductor causes pin 4 to go negative, so you need to add an extra Schottky diode across the low side MOSFET with a turn on voltage of under 0.3 volts.That IC will be turning ON the low side MOSFET when pin 4 is being dragged down, so it wouldn't surprise me if that circuit would work fine without the Schottky, but if just once the MOSFET does not turn on in time, the MAX IC will latch up. Adding the Schottky diode is an extra level of protection.It is all about protecting the control IC.Dave did a great blog about this:
Why is input resistance missing on a lot of OP Amp data sheets? - Page 1
Forum section: electronics / beginners

author: bap8guy
author_rank: Newbie
timestamp: April 28, 2022, 08:22:39 pm
content: Usually I can find input resistance for Op Amps given in the data sheet, but not always.I have been looking to identify the input resistance of an LTC1150, but could not find it. I assume there must be a way of determining what it is from the data they give, but I don't know how.

author: edavid
author_rank: Super Contributor
timestamp: April 28, 2022, 08:42:01 pm
content: It's not a meaningful or useful parameter, because op amp inputs are not resistive.The LTC1150 datasheet has input bias current and input offset current values, which are what you need for design.

author: magic
author_rank: Super Contributor
timestamp: April 28, 2022, 09:00:05 pm
content: Input bias current does vary with input voltage, both common mode and differential, particularly in simple bipolar inputs.The ratio of input voltage change to the resulting bias current change is sometimes quoted as "input resistance".It should be fairly high for CMOS, i.e. the current doesn't depend much on voltage.Similar thread here:https://www.eevblog.com/forum/projects/why-doesnt-the-vendor-specify-the-input-impedance-or-bias-currents/

author: Terry Bites
author_rank: Super Contributor
timestamp: April 29, 2022, 11:28:26 am
content: In general this is not a useful or meaningful design parameter. It seems to be quoted more often for pico amp and femto amp bias amps. That is the selling point after all. You aslo see it on high speed opamp datasheets. This is how it is measured.Understanding opamp parameters :www.ti.com/lit/pdf/sloa011A great guide to applications as well:www.ti.com/lit/pdf/sboa092

author: David Hess
author_rank: Super Contributor
timestamp: April 30, 2022, 01:45:12 am
content: Input resistance is rarely important.If you must know, then measure it. Setup an input bias current test and make two measurements with two different common mode voltages.

author: Kleinstein
author_rank: Super Contributor
timestamp: April 30, 2022, 03:36:44 am
content: The LTC1150 has even more detailed information than just an input resistance: there is a typical curve for the input current as a function of common mode voltage. This curve shows, that a simple resistance is not a good description.
Why is it recommended to use diodes and resistors for UART communication - Page 1
Forum section: electronics / beginners

author: sarose
author_rank: Newbie
timestamp: December 04, 2020, 05:51:21 am
content: Why is it recommended to use diodes and resistors for serial communication as shown in the circuit given? It is given in datasheet of SIM800C. Why we cannot directly connect TX and RX?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: December 04, 2020, 06:19:08 am
content: Guessing DTE is 5V TTL or something.Tim

author: Ian.M
author_rank: Super Contributor
timestamp: December 04, 2020, 08:20:02 am
content: Well that's one of the less dodgy interface circuits in a somewhatcrappy datasheet(see page 25). .The SIM800C runs at a nominal 4.0V, so with 0.6V-0.7V diode Vf drop you'll get pretty close to 3.3V levels if the 3.3V DTE's got CMOS outputs. On the module side it shifts the UART1_RXD level up by one diode drop. Note that although the datasheet specifies Voh-min and Vol-max it doesn't specify at what current, so its insufficient for designing a passive level shifter properly!However, no matter what voltage (between 1.8V & 5.5V) the DTE uses for logic levels, one could simply use a bunch of 74LVC1T45 or 74LVC2T45 dual supply level shifters (depending on how many digital signals in each direction you need), and get much lower quiescent power consumption, and better signal quality with far more drive strength on the digital interface lines.
Why is my circuit breaker tripping - Page 1
Forum section: electronics / beginners

author: justinjja
author_rank: Regular Contributor
timestamp: January 11, 2017, 03:19:29 am
content: I'm trying to move 2 of my 6 Mining computers from my laundry room to my garage.All 6 computers run fine when powered by a dryer socket (240v 30a)According to my Killawatt, the 2 computers pull 1500W (0.99 PF) in my garage.The whole garage, and only the garage is on a single 20A breaker (120V)When I try to connect the computers via powerline adapter I trip my breaker within 1hr.But if I unplug everything except the computers, and switch them to Wifi, the breaker never trips.The breaker is just a standard 20A breaker.The wall socket is a GFI (The gfi isn't tripping, the breaker is)So it looks like, either a power line adapter, an AC line filter, or a power strip is tripping my breaker.Which of those would make the most sense?So far I have not had the breaker trip while opening/closing the 1/3hp garage door (W/ all the computers running too)

author: rstofer
author_rank: Super Contributor
timestamp: January 11, 2017, 05:18:17 pm
content: It could very well be a defective breaker. The fact that it takes an hour means it is tripping on Long Time current, not Instantaneous. The breaker should be able to hold its rated current indefinitely but we use an 80% factor for maximum load. At 120V, a 20A breaker should be able to handle 2400W and we derate that to 1920W. So, your load need to be less than 1920W and it seems this is the case as long as I am reading the "2 computers pull 1500W" as the combined load.Generally, molded case circuit breakers can carry an overcurrent for quite some time so even if you were running close to 1920W, the garage door motor running wouldn't last long enough to trip the loaded breaker.So, change out the breaker and see what happens. Also, look for a loose connection at the breaker because this extra heating is all it takes to make the breaker trip.

author: turbotemp
author_rank: Newbie
timestamp: January 11, 2017, 05:38:29 pm
content: So, check the draw on the breaker with a clamp meter.

author: justinjja
author_rank: Regular Contributor
timestamp: January 12, 2017, 06:29:58 am
content: Narrowed it down to a power strip. Not sure how that works.My best guess is the circuit breaker is fast, and the power strip is slow.The power strip (15A rated) was close enough to briefly disconnect then reconnect the load, and that caused a power surge that tripped the 20a circuit breaker?Sounds a little out there, but that's all I can think of.