Ultra low power, clean 30V power supply + ultra low power high speed comparator? - Page 1
Forum section: electronics / projects

author: Spirit532
author_rank: Frequent Contributor
timestamp: June 28, 2019, 08:40:18 pm
content: I'm working on a radiation detector based on a scintillation crystal and a silicon photomultiplier, and I'm stuck with a few decisions regarding low power operation.SiPMs are basically a massively parallel array of single-photon avalanche photodiodes operating in reverse bias in the Geiger region, at roughly 30V. When a photon hits the SiPM,someSAPDs fire, so you get a current proportional to the number of photons.While I do have a working prototype of this detector already, it's consuming an abysmal ~1000-1100uA at 3V, which is completely unacceptable for a device meant to operate continuously in standby mode for weeks or months on small batteries.So here's two interesting problems:1: What's the easiest way to build a very low power(<30uA average) power supply capable of delivering ~30V at no load(the average SiPM current with a scintillator is in the nA range) with less than10mVp-pof noise? The noise is critical, as the signal from a SiPM is very very tiny.2: How do you detect a 20-80mV, 50-200nspulse and turn it into a longer digital output for counting(interrupts)? Most nanopower/micropower comparators have a minuscule bandwidth and a very low slew rate. I'm guessing I'd have to build something discrete.It's also possible to operate the SiPM in current mode with a transimpedance amp, but high slew rate, high bandwidth, ultra low power opamps simply don't exist as far as I'm aware.

author: David Hess
author_rank: Super Contributor
timestamp: June 28, 2019, 09:03:57 pm
content: Quote from: Spirit532 on June 28, 2019, 08:40:18 pmDoes the 10mVpp only apply to high frequency noise or does that include regulation?If regulation is not a problem, then I think any burst mode or hysteretic boost controller can meet your requirements with passive filtering. These have the advantage of the lowest quiescent power and are commonly used for micropower regulators.QuoteI might have it set the state of a CMOS flip-flop which is then reset by the counter but that still leaves how to amplify the signal enough without drawing too much power.QuoteWhat about integrating the current output and periodically reading the output voltage and resetting it as needed? Each pulse should create a step in the integrated output.Or integrate the output with a low integration capacitance making a charge amplifier. What is the minimum amount of charge which must be detected?

author: 2N3055
author_rank: Super Contributor
timestamp: June 28, 2019, 09:05:58 pm
content: Take a look at this for some ideashttps://indico.cern.ch/event/615174/contributions/2481471/attachments/1557307/2449642/Photomultiplier.pdfhttps://www.mdpi.com/2072-666X/9/10/507/htmhttps://wikihost.uib.no/ift/images/0/05/MagneLauritzenMasters.pdfTons of stuff on Google...

author: Spirit532
author_rank: Frequent Contributor
timestamp: June 28, 2019, 09:38:38 pm
content: Quote from: David Hess on June 28, 2019, 09:03:57 pmRegulation can be within +-20mV or so, going beyond that will make a rather nonlinear response. The gain rises very very rapidly, with some of my SiPMs shooting through an order of magnitude with just 100mV.It's 10mV p-p foranynoise above ~1kHz, I'm afraid, or it'd need amplification(again, not low power for this high of a speed).Quote from: David Hess on June 28, 2019, 09:03:57 pmA discrete flip flop? I don't think 100ish mV is enough to flip something digital, and that's a very high energy photon(cosmic ray-ish).Quote from: David Hess on June 28, 2019, 09:03:57 pmThe idea is for the host device to sleep until there's an interrupt on one of the inputs, rather than continuously sampling and determining whether there was another particle or not.The charges are pretty tiny, though I don't have any figures.Quote from: 2N3055 on June 28, 2019, 09:05:58 pmHigh power, large stuff is easy. Slap in a few 100V/us slew opamps with a massive GBWP, a filtered high voltage supply, and you'll get a clean signal.Miniaturizing this stuff and making it ultra low power is the hard part.Here's an earlier test with an opamp and a bit of pulse stretching:

author: cur8xgo
author_rank: Regular Contributor
timestamp: June 28, 2019, 09:58:05 pm
content: Well if I wanted to have a fun afternoon I would get the sim going and see if I could detect these pulses by:arranging a circuit which nulls itself with a time constant much slower than the pulse width but much faster than the typical time between pulsesand design it so it consumes basically no power once its nulledthen this pulse upsets the balance and causes some kind of cascade or avalanche which either greatly increases the pulse voltage or the pulse length or boththere are physical analogies to this so I think it might be workable..and has probable been done a million timesalso might want to consider using the fast rise time of the pulse to ring a resonant circuit of some kind of in that way extend the pulse "length"

author: cur8xgo
author_rank: Regular Contributor
timestamp: June 28, 2019, 10:02:31 pm
content: also I hate to be that guy but what about just using bigger batteries

author: Spirit532
author_rank: Frequent Contributor
timestamp: June 28, 2019, 10:11:06 pm
content: I understand the "that guy" argument here, but a 3-4Ah battery, when used conservatively, would probably only last around 3 months. It's not bad, but I'd prefer that this device could be integrated into something that can be forgotten for a year or more, but still raise an alarm if you're in a high field. It's also basically the size of the entire planned device, which is not particularly nice or compact. An optimal scintillator size is ~8x8x30mm, the SiPM is another 6x6x1mm including the housing and PCB. The circuit could probably fit in a 10x10mm board, especially if it's a double-sided load.

author: cur8xgo
author_rank: Regular Contributor
timestamp: June 28, 2019, 10:18:02 pm
content: Quote from: Spirit532 on June 28, 2019, 10:11:06 pmWell I think this is a great project and the technical challenge here is a real juicy one...probably has been done before so there should be something out there..as far as long-term short pulse monitors..I think a physical analogy would help drive the circuit design.....the pulse is a short low energy kick..its distinguishing features are its quickness.If you flick a tuning fork it vibrates for a longggg time

author: Spirit532
author_rank: Frequent Contributor
timestamp: June 28, 2019, 10:24:35 pm
content: Quote from: cur8xgo on June 28, 2019, 10:18:02 pmThere is - just not SiPM-based.Regular dosimeters based on Geiger-Muller tubes have rather strong signals and generally don't care about massive voltage ripple. Most GM tubes have plateaus of 50V or more, so a 300V power supply with 20V of ripple is absolutely acceptable. They also don't have anything charge-proportional. A particle hitting always means it's a loud and clear discharge, rather than having to discriminate ultra low energy particles(in terms of NORM anyway) that are barely above the self-counting noise floor of the bare SiPM.That's why most, even cheap, GM-based dosimeters can operate for months or even years on a couple of AA batteries. The Gamma Scout lasts so long it doesn't even have a battery compartment - once it dies, you just send it in for re-calibration and battery swap.

author: David Hess
author_rank: Super Contributor
timestamp: June 29, 2019, 07:51:39 am
content: Quote from: Spirit532 on June 28, 2019, 09:38:38 pmWhat I suggested is still doable but with that regulation requirement, I would use a micropower linear post regulator. Micropower circuits do not have good frequency response so filtering between the output of the switcher and linear regulator will need to be carefully designed.20 millivolts out of 30 volts is 667ppm so accuracy over temperature is going to be a problem.QuoteI meant using an integrated flip-flop as a pulse stretcher but it will require a fast amplifier which is problematical for a low power circuit. See below.A discrete flip-flop with low threshold voltage which is fast enough to respond to a 100 millivolt trigger is possible but I am not sure it can be done within your power budget.QuoteA charge amplifier removes the requirement for high bandwidth as long as fast response is not required so supply current can be very low. The tricky part then becomes drift. The output of the charge amplifier can directly feed an interrupt line through a low current schmitt trigger; I would use a micropower comparator here.Limiting the DC gain of the charge amplifier may be enough to remove calibration requirements. For an integrator, this means placing a large value feedback resistor across the integration capacitor to absorb any changes in input leakage current. Sometimes a T-network is used with two resistors and a capacitor to ground to remove the requirement for a high value resistor; the shunt capacitor lowers gain at DC to 1 to prevent amplifying the input offset voltage.The processor then needs a way to reset the charge amplifier after being triggered.

author: Kleinstein
author_rank: Super Contributor
timestamp: June 29, 2019, 08:22:42 am
content: I don't think the ripple would be such a big problem - it just needs a relatively large capacitor for filtering. At 30 V it could be tricky to find a suitable low power and low noise linear regulator though - though there could be a few. I would be more worried about low frequency noise than higher frequency ripple.The idea with a charge amplifier sounds very good, as it reduces the need for high speed parts. The charge amplifier could end up being more like a pulse stretcher. However the amplitude after the charge amplifier will be likely rather small, so that it would need amplification first.It is essentially impossible to build a fast discrete low power comparator, as parasitic capacitance is critical and very small transistors would be needed. The comparators build in low power µCs are relatively good, as they use a relatively fine structure CMOS process, normally not found with analog parts.The nice point about the charge amplifier solution would be that it could still read the pulse hight

author: Marco
author_rank: Super Contributor
timestamp: June 29, 2019, 04:24:13 pm
content: Quote from: Spirit532 on June 28, 2019, 08:40:18 pmUltra-low-power boost converter like MAX17220 witha cascode MOSFETfollowed by ultra low power linear regulator like STLQ020PUR with some more external transistors so it can form a higher voltage linear regulator? (Can't immediately find any description of such a circuit, but should be possible.)QuoteTheunbuffered inverter tricktrick seems interesting, one of the inverters is biased linearly with a 10k-100k feedback resistor to become a transimpedance amplifier. Then more unbuffered inverters as amplifiers (if they are on the same die they should be biased linearly by the DC coupled output of the transimpedance one). Maybe some of the very low voltage logic families will be fast enough at low enough supply voltage to work and low enough power.The On Semiconductor SiPMs with fast outputs look interesting too, no need for signal processing to detect multiple events close together.

author: David Hess
author_rank: Super Contributor
timestamp: June 29, 2019, 05:53:15 pm
content: Quote from: Marco on June 29, 2019, 04:24:13 pmOperating a CMOS inverter in its linear region gives good sensitivity and frequency response but at the cost of high power.Quote from: Kleinstein on June 29, 2019, 08:22:42 amI have built these kinds of circuit before and the problem was always high frequency noise from the switching converter coupling through the detector (or supply connections) into the discriminator. It is not insurmountable but care must be taken filtering the output from the switching regulator.There are lower noise options but the micropower requirements in this case dictate a hard switched micropower switching controller.

author: Marco
author_rank: Super Contributor
timestamp: June 29, 2019, 06:14:09 pm
content: Quote from: Kleinstein on June 29, 2019, 08:22:42 amDoes pulse height actually mean anything useful though? The number of optical photons per high energy photon depend on the energy, which is an unknown. AFAICS pulse height is either irrelevant or constant (if the SiPM is saturated).

author: Marco
author_rank: Super Contributor
timestamp: June 29, 2019, 06:19:51 pm
content: Quote from: David Hess on June 29, 2019, 05:53:15 pmAnything which has amplification at >100 MHz is relatively high power ... but does it give good bang for buck when you don't really care much about linearity?What would a RF BJT need to be biased at to allow a decent trans-impedance amplifier to be made at those speeds? 100 uA?

author: David Hess
author_rank: Super Contributor
timestamp: June 29, 2019, 06:57:04 pm
content: Quote from: Marco on June 29, 2019, 06:19:51 pmIt does not matter how linear it is if it draws too much power.QuoteIt would be lower than the bias required for an FET. At the same current, bipolar transistors have greater transconductance than FETs meaning higher gain-bandwidth product.

author: Spirit532
author_rank: Frequent Contributor
timestamp: June 29, 2019, 08:42:15 pm
content: Quote from: David Hess on June 29, 2019, 07:51:39 amThat'd be 1200ppm, since +-20 is fine. Could probably push it a bit further, maybe +-40-50mV, but with higher drift the gain might become an issue.Quote from: David Hess on June 29, 2019, 07:51:39 amI'm estimating that the maximum count rate will be around 2-5kHz for really high radiation fields on such a small crystal(several mSv/hr), so it may be an option worth exploring.Quote from: Marco on June 29, 2019, 04:24:13 pmA cascode setup would require quite a serious supply voltage and current to swing an external mosfet, which is outlined in that article, so I'd probably need another boost just to supply this boost...You can see the OnSemi(formerly SensL) SiPM in that video, though using the regular output. The fast output is only really useful for single-photon counting applications, here we're counting thousands to millions of photons(depending on particle energy) as an analog signal(see below).Quote from: Marco on June 29, 2019, 06:14:09 pmYes, it does. The SiPM is never saturated, as the only purpose of a SiPM is tonotget saturated, by multiplying the number of mini-SAPDs(Whichdoget saturated, but there's thousands of them and some do, some don't. It's sort of like an R2R DAC in that regard.).The output is directly(and mostly linearly) proportional to the energy of the incoming particle. Thus, you can do spectroscopy in a tiny package.However, for this low-power version I explicitlydon'tneed spectroscopy(or could have a second circuit that can be put to sleep when not in alarm mode), and I'd like to use the SiPM in a saturation-like mode, with just a simple digital output after a certain energy threshold.SiPMs are not clean - they can have several MHz of self-count rate, but the pulse heights are generally a very small number of SAPDs firing, so it's usually much lower than actual photon amplification signals, so a basic height discriminator cuts off garbage below the ~10keV(equivalent-ish with a CsI:Tl crystal) level, which is not very useful regardless.You can see that self-counting noise in the video linked above. It's just below the useful scintillation signal.

author: Kleinstein
author_rank: Super Contributor
timestamp: June 29, 2019, 09:07:57 pm
content: The comparator inside the AVRs (e.g. Mega88PA and similar) uses some 50 µA at 3 V. I don't know for sure how fast the comparator can react, but it is not that slow and to my surprise also reasonable low noise / jitter (e.g. < 5 mV with a 1 V/µs slope). So the comparator may be just good enough to catch the pulses.

author: cur8xgo
author_rank: Regular Contributor
timestamp: June 29, 2019, 09:24:12 pm
content: just to be clear...operational duty cycle must be 100%? cant do 10ms on 990ms off, or some kind of randomized duty cycle which statistically results in the same end result? Could increase battery life an order of magnitude and make the circuit much easier to designI mean if you are in a high field do you really need to know that (can it be known?) only by being on constantly?

author: Spirit532
author_rank: Frequent Contributor
timestamp: June 29, 2019, 10:01:31 pm
content: It takes a while to stabilize the power supply and get a good background average, so yes, 100%.

author: 2N3055
author_rank: Super Contributor
timestamp: June 30, 2019, 12:10:44 am
content: These guys made front end that would use something about 60uA..Is that good enough.. ?Also a portable battery powered unit..https://aisberg.unibg.it/retrieve/handle/10446/77221/126298/TDUnibg1002866.pdf

author: Spirit532
author_rank: Frequent Contributor
timestamp: June 30, 2019, 12:37:42 am
content: Their choice of opamp is not particularly ideal - my prototype uses theMicrel(now Microchip) MIC860, which has a bandwidth of 4MHz and a slew rate of 4V/us while only consuming 40uA. Faster, lower noise, lower power.Their frontend(transistor-based, as suggested earlier here) consumes over 1.5mA in total, which somewhat crushes the point of having an ultra low power opamp.I was thinking of using another MIC860 as a comparator with an adjustable threshold voltage(just above noise), with a bit of pulse stretching through feedback. Rise and fall times don't really matter in this case, since it's only going to be triggering a rising edge interrupt.The real issue here is the power supply - say we have a budget of ~80uA for the amplification and "digification" of the signal, and another 50-80uA for the power supply. How do we get a clean, 28.5-33V(depends on the chosen SiPM, but that covers basically all of them) supply that, at no(or very little, nA) load would give us less than 10mVp-p of higher frequency noise(above 1kHz), and less than less than ~20-30mV of ripple?The current consumption issue mainly sits in the realm of the power supply.

author: Vgkid
author_rank: Super Contributor
timestamp: June 30, 2019, 03:59:23 am
content: While not geiger mueller, have you thought about modifying an older epd. The ones we have at work last some time on a single aa batery.

author: Spirit532
author_rank: Frequent Contributor
timestamp: June 30, 2019, 04:00:33 am
content: That's like suggesting I buy a bicycle and turn it into a chair instead of building a table...And FWIW, their sensitivity is 2-5 orders of magnitude less than the crappiest GM tubes. Scintillators have 2-4 orders of magnitude higher sensitivity than the best GM tubes.

author: Marco
author_rank: Super Contributor
timestamp: June 30, 2019, 06:48:26 am
content: Quote from: Spirit532 on June 29, 2019, 08:42:15 pmDon't see why, a simple BSS123 should suffice at 3V. You won't be switching a whole lotta current. Use a low noise avalanche diode for the upper leg of the feedback divider.QuoteIt also seems useful for very high counts, if high energy photons strike the scintillator every say 10 ns you can still detect that. On the slow output those pulses pile up, the fast output will gives distinct pulses. You essentially get a well designed CR pulse shaper for free. That said, to detect pulses that fast you need even more bandwidth, so for low power and low counts I guess it doesn't make much sense.TLV7011 seems the most appropriate comparator to me, increase the anode resistor to say 220 Ohm and the pulse should last long enough for it.

author: Someone
author_rank: Super Contributor
timestamp: June 30, 2019, 06:50:40 am
content: Quote from: Kleinstein on June 29, 2019, 08:22:42 amThere are many linear regulators hitting these specifications, but things like capacitor leakage and board contamination start to become an issue down at these low currents. Its not difficult to reach the OPs requirements for power. The glaring problem is thermal sensitivity as noted already:Quote from: David Hess on June 29, 2019, 07:51:39 amAnd that is before considering the thermal characteristics of the SiPM its self, though the discrimination technique planned by the OP makes it less sensitive than it could have been. For reference Hamamatsu include temperature compensation on their MPPC (SiPM) supplies.

author: Marco
author_rank: Super Contributor
timestamp: June 30, 2019, 06:59:07 am
content: 20 mV shift of the cathode voltage is going to do very little to the gain of the SiPM, hardly a problem.20 mV ripple is more annoying.

author: IconicPCB
author_rank: Super Contributor
timestamp: June 30, 2019, 08:07:16 am
content: lm723?

author: Wolfgang
author_rank: Super Contributor
timestamp: June 30, 2019, 09:21:34 am
content: Quote from: IconicPCB on June 30, 2019, 08:07:16 amYes, absolutely. But with a PNP pass transistor, and a Wenzel cleanup shunt. If you need to be absolutely sure, make a preregulator, too.

author: Marco
author_rank: Super Contributor
timestamp: June 30, 2019, 09:26:31 am
content: Not exactly ultra low power.

author: Spirit532
author_rank: Frequent Contributor
timestamp: June 30, 2019, 04:31:10 pm
content: Quote from: Marco on June 30, 2019, 06:48:26 amIf high energy photons strike the scintillator every 10 nanoseconds, the issue you should be worried about is your body evaporating. What are you doing inside a live fissioning reactor anyway?Quote from: Someone on June 30, 2019, 06:50:40 amWith a clean power supply, temperature compensation isn't really required for counting. It'll be clean and linear enough to provide a rough(+-10% is standard) dose rate estimate, and certainly more than enough to alert you if things go sour.

author: David Hess
author_rank: Super Contributor
timestamp: July 01, 2019, 10:09:36 am
content: Quote from: Spirit532 on June 29, 2019, 08:42:15 pmI looked at something like this for a proportion counter a couple years ago. The charge amplifier catches everything through continuous integration but the ability to distinguish adjacent pulses depends on bandwidth just like a transimpedance amplifier. The difference is every pulse is captured even at low bandwidth; pulses which are too close together are combined.The problems are how to handle drift since a charge amplifier will happily integrate any leakage current at its input and how to reset it. The leakage current can be cancelled with a temperature compensated bias current cancellation circuit or through an automatic calibration routine. Limiting DC gain with a resistive feedback network like I described (AC shunted t-network) also helps and may be sufficient.Resetting the output between counts can be done with the various integrator reset methods but I suspect a better way would be to subtract a fixed amount of charge similar to how a charge balancing ADC works. This allows the charge amplifier to continuously integrate the input without missing anything.

author: Spirit532
author_rank: Frequent Contributor
timestamp: July 01, 2019, 07:07:03 pm
content: The issue here is the power supply. Signal processing doesn't incur that much cost.

author: Marco
author_rank: Super Contributor
timestamp: July 01, 2019, 07:30:25 pm
content: Quote from: Spirit532 on June 30, 2019, 04:31:10 pmOn second thought I don't think any ready made boost converters will do you much good, they are tuned for far too high a frequency and far too low a turn on time AFAICS. How about simply having a MSP430 in low power mode 3, pulsing a BSS123 for 1 tick of a 32768 Hz crystal clock at ~1 kHz to boost the voltage using a 100 mH inductor? Then just a question of how to tune the pulse frequency, I'd guess error amplifier and using the ADC in the microcontroller (or maybe use a microcontroller which can do ultra low power PWM but has a better ADC like the MSP432). Due to the low currents and the relatively large smoothing capacitor it doesn't need to be very fast. No linear regulator or ripple killer is really necessary, with a 100k/100nF smoothing filter ripple would be dominated by the SiPM current pulses (might have to increase the output capacitor a little more to give the microcontroller time to respond to varying pulse counts).The TLV7011 seems the best ultra low power comparator around, with ~5nF SiPM and ~200 Ohm anode resistor it should be fast enough ... connect the output to a MSP430 external clock input for a timer to count.

author: David Hess
author_rank: Super Contributor
timestamp: July 01, 2019, 11:04:04 pm
content: Quote from: Spirit532 on July 01, 2019, 07:07:03 pmThe digital side does not but the analog side will if it requires high bandwidth.I do not consider the power supply to be the most difficult part.

author: Spirit532
author_rank: Frequent Contributor
timestamp: July 02, 2019, 03:43:42 am
content: Quote from: David Hess on July 01, 2019, 11:04:04 pmRead what I said about the analog part with MIC860 on page 1 and what Marco said about the comparators.The power supplyisthe most painful part right now.

author: GEOelectronics
author_rank: Regular Contributor
timestamp: July 26, 2019, 09:24:23 pm
content: Quote from: Spirit532 on June 28, 2019, 08:40:18 pmThis preamp might be a start: pic attachedGeorge Dowell

author: Spirit532
author_rank: Frequent Contributor
timestamp: July 26, 2019, 09:25:29 pm
content: I love the scrubbed out chip names.

author: GEOelectronics
author_rank: Regular Contributor
timestamp: July 26, 2019, 09:40:22 pm
content: all are CA3096George Dowell

author: Neomys Sapiens
author_rank: Super Contributor
timestamp: July 27, 2019, 01:32:34 am
content: If I recall it correctly, one of the famous LT circuit collections did contain something on detector supplies.Maybe AN45, but could habe been another DC/DC-related one too.

author: Marco
author_rank: Super Contributor
timestamp: July 28, 2019, 05:12:52 am
content: These detectors are really into a class of their own as far as power consumption goes though.How about using an ultra low power oscillator with output enable such as OV-7604-C7 and using a low power comparator to switch their output on/off as a pulse skipping boost converter? Similar to the Theremino power supply, but even lower power because you're not running any logic ICs in linear mode.

author: GEOelectronics
author_rank: Regular Contributor
timestamp: July 28, 2019, 01:46:47 pm
content: "While I do have a working prototype of this detector already, it's consuming an abysmal ~1000-1100uA at 3V, which is completely unacceptable for a device meant to operate continuously in standby mode for weeks or months on small batteries.".Can you post results of the detector portion? I haven't seen many successful attempts at building these regardless of the total current. You mention 1mA current as abysmal. To me that's good, if it is for the whole system, that would put it in line with a PM1703M system which can run for a month on a single AA battery, logging etc right on along.George Dowell

author: Marco
author_rank: Super Contributor
timestamp: July 28, 2019, 04:59:59 pm
content: AFAICS simply using a large enough anode resistor (which increases the pulse duration) with a TLV7011 will allow detection with very low power consumption (5 uA for the comparator).Use an OV-7604-C7 oscillator driving a BSS123 and some large inductor (1-100 mH) for a boost converter to get 30V. With an ultra low power comparator like the TLV7031 to turn the output of the oscillator on or off and to pull the gate down through a diode when it's turned off. This would have an irrelevant quiescent current of around 1 uA.

author: Spirit532
author_rank: Frequent Contributor
timestamp: July 29, 2019, 03:09:14 am
content: Quote from: GEOelectronics on July 28, 2019, 01:46:47 pmThere's a short video on page 1 showing how it works, but other than that - I can get around 0.9-3cps/uSv/h(compared a few other meters) with a 10x10x30mm CsI:Tl crystal and the MicroFC-60035 SiPM from ON Semi(SensL), depending on how touchy I get with tweaking SiPM bias and amp gain. Not particularly reliably, but a prototype is a prototype.Quote from: GEOelectronics on July 28, 2019, 01:46:47 pmPSU and amp only at the moment. Given the recent suggestions, I should be able to get it much lower, which will get it closer to the Radiation Pager lifetimes, but much smarter.Quote from: Marco on July 28, 2019, 04:59:59 pmCan you elaborate? The SiPM will go through a MIC860 to get amplified first. I don't think the TLV7011 can operate at an extremely low voltage(3-25mV pulses).Quote from: Marco on July 28, 2019, 04:59:59 pmThat is a great idea! I'll throw something together when I get the time, working on a different project right now(DIY SEM, no microamps required here...).This could also be very useful for a high voltage SMPS for generic geiger-muller tubes, since the plateaus are much bigger there(10V ripple @ 410V is acceptable). A GM tube power supply that pulls <10uA on average would be a hit as well, though there's a bigger issue of high voltage measurement and hooking a boost up to a multiplier there.

author: GEOelectronics
author_rank: Regular Contributor
timestamp: July 29, 2019, 03:25:36 am
content: Can you elaborate? The SiPM will go through a MIC860 to get amplified first. I don't think the TLV7011 can operate at an extremely low voltage(3-25mV pulses)."Have you considered going with a CZT direct?By the way the PM1703 uses something very similar you your prototype.Geo

author: Spirit532
author_rank: Frequent Contributor
timestamp: July 29, 2019, 03:26:54 am
content: CZT is an order of magnitude less sensitive and an order of magnitude more noisy, not to mention the rather painful prices, with not much benefit.SiPMs with scints are the way to go at this point. Maybe in the future something will change.

author: Marco
author_rank: Super Contributor
timestamp: July 29, 2019, 08:15:49 am
content: The openlabs project I linked earlier which used an inverter for amplification said they got a 200 mv out of their scintillator sipm combo. That would be enough for the comparator.

author: Marco
author_rank: Super Contributor
timestamp: July 29, 2019, 04:30:22 pm
content: The diode is not necessary with the ov-7604-c7, I thought it went high impedance when OE is low, but it actually pulls the clock output low according to the application manual.

author: Marco
author_rank: Super Contributor
timestamp: July 31, 2019, 05:12:14 pm
content: Quote from: Spirit532 on July 29, 2019, 03:09:14 amBTW, I have no idea how accurate it is, but Spice says a BFP720ESD common emitter amplifier has a gain bandwidth product of 340 MHz at 30 uA bias current ...I suspect it will be quite a bit higher than MIC860 even IRL. You don't really need the DC coupling or class AB push pull output of the MIC860 so a high ft low current RF transistor amplifier will almost certainly do better. A BFU710F might do a little better still, but the BFP720ESD is less fragile.