That's great to hear as a confirmation. As soon as I get a chance to spend some time on the bench, I'll give it a try. It should be quick enough. I'm going to use a standard MMBTA42, please let me know what you have used, if you can share that piece of information.
Thanks Christian. Il giorno domenica 6 giugno 2021 alle 21:17:00 UTC+1 Christian Riise Wagner ha scritto: > 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 [email protected]: > >> 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 <[email protected]> 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 [email protected]. >>> > 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 [email protected]. To view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/17d59dd9-1645-42f1-a87a-c528c1944fe3n%40googlegroups.com.
