I've successfully used a P-channel MOSFET as a high side load switch for a LM3478 based tapped inductor booster. IIRC the off current was immeasurable, so sub 100nA. søndag den 6. juni 2021 kl. 19.33.50 UTC+2 skrev flata...@gmail.com:
> Thanks David, indeed you are absolutely right. The power supply with > LT1308B is very reliable and not as sensitive to layout design as other > ones that I have tried. > > LT1308B has in Iq of 0.01uA in stand-by, as you say. I've built your nixie > watch (picture attached) and in my design it seems to use 2.3uA. If I build > the HVPS on a breadboard, I can measure 0.1uA or less, which is great (I > guess the resolution of my multimeter Keysight U1241B cannot measure less > than 0.1uA accurately but that's great at 0.1uA or less). Of course I have > tried to troubleshoot my LT1308B HVPS with no success. In my quest for a > more efficient HVPS, I have designed a power supply using the MAX668 chip > (as per datasheet and similar to many commercial HVPS), this was tricky to > design with no noise, it works well now (after 6 different designs) however > the stand-by power is 2.4uA, as per datasheet. So I can have higher > efficiency than with LT1308B but also higher stand-by current (I believe > because MAX668 has an internal LDO). > > Which is why I was thinking whether I can use a high load switch to truly > bring shutdown current to zero using a power supply built around MAX668. Of > course, this is a bit of a (pointless) extreme challenge to reduce stand-by > current as much as possible to break even with solar panels, but that's > where the fun is for me. And of course I could keep on troubleshooting the > LT1308B design, it actually works perfectly other than it gives me higher > stand-by current than on the datasheet, not sure if that depends on the > design layout. But then again, I'm only a hobbyist and not an engineer, so > I may be missing something. > > So any suggestions on why my LT1308B draws more than 1uA with SHTN=0V > welcome (I have tried 4 different chips, same thing on the PCB, fine on the > breadboard). Or any other suggestions to use any other power supply with > perhaps a high load switch to bring standby current to less than 1uA, which > I worry is unnecessary additional components and introduces a potential > start-up delay. > > > Il giorno domenica 6 giugno 2021 alle 18:12:46 UTC+1 nixiebunny ha scritto: > >> Max, >> The LT1308B has a .01 uA typical, 1 uA maximum standby current when >> shut down, according to the data sheet, shown on page 2 as Iq (the >> third line with Vshdn = 0V). >> >> I don't think you have a problem here. >> >> >> On 6/6/21, Max DN <flata...@gmail.com> wrote: >> > Hello, >> > >> > I'm working on a solar powered nixie watch (similar to the Kopriso >> Nixie >> > watch). >> > >> > It's crucial that I dramatically reduce stand-by power as much as >> possible >> > and within 2.5uA, which is where the solar panels will balance off the >> > stand-by current. >> > >> > Regardless of which power supply I use, even using the shutdown pin, >> the >> > power supply still takes 2.5uA. This is perfectly in line with the >> > electrical specifications of the datasheets. >> > >> > So, my question is, can I 'brute force' a shutdown, effectively >> removing >> > the power from the VIN pin via a PNP high speed mosfet such as MMBTA42 >> or >> > it will introduce too much of a delay in starting the power supply? >> > >> > I'm going to try it on the fly but if anyone has any suggestions on how >> to >> > bring to 0 or to 0.01uA the stand-by current that would be great. >> > >> > As an example, I'm using the LT1308B DC/DC converter as on page 17 of >> the >> > datasheet >> > >> https://www.analog.com/media/en/technical-documentation/data-sheets/1308abfb.pdf >> >> > >> > Any suggestions will be much appreciated. >> > >> > Thank you, >> > Max >> > >> > -- >> > You received this message because you are subscribed to the Google >> Groups >> > "neonixie-l" group. >> > To unsubscribe from this group and stop receiving emails from it, send >> an >> > email to neonixie-l+...@googlegroups.com. >> > To view this discussion on the web, visit >> > >> https://groups.google.com/d/msgid/neonixie-l/d45edcd8-0176-4205-95f1-b04eb34a32f1n%40googlegroups.com. >> >> >> > >> > -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. To unsubscribe from this group and stop receiving emails from it, send an email to neonixie-l+unsubscr...@googlegroups.com. To view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/7caae337-e156-4ac6-9d76-548b451eddd5n%40googlegroups.com.
