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No output with MCP1700-3302E (lemmy.dbzer0.com)

submitted 1 year ago* (last edited 1 year ago) by Froghut@lemmy.dbzer0.com to c/askelectronics@discuss.tchncs.de

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I'm trying to build a esp8266 weather station and got some MCP1700-3302E to power the esp8266 from a lipo. But when I connect the lipo to the MCP1700 (looking at it flat spot at the front, ground left, Vin in the middle and Vout on the right) I get no output at Vout. I googled and could not find anything. I tested 5 different ones and it's the same for all of them. Could I just have a batch of broken ones? Edit: attached a picture of my very simple test setup Edit 2: I just connected three lipo directly to Vin, that seems to work without any problems (at least for a few days now)

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[–] BigDanishGuy@sh.itjust.works 2 points 1 year ago* (last edited 1 year ago) (1 children)

The "typical application circuits" on page 2 in the datasheet https://ww1.microchip.com/downloads/en/DeviceDoc/MCP1700-Data-Sheet-20001826F.pdf shows both input and output being decoupled with a 1µF cap, have you tried that? I haven't worked with the MCP1700, but I have had other LDOs fry themselves because the decoupling malfunctioned.

[–] Froghut@lemmy.dbzer0.com 1 points 1 year ago (1 children)

I initially tried with those capacitors but decided to also try without them - perhaps you're right and I broke my LDOs by doing that :/

[–] BigDanishGuy@sh.itjust.works 1 points 1 year ago

I'm not saying that your LDOs are fried. What I am saying is that some LDOs don't take too kindly on not having the company of some nice caps.

What just caught my eye is that the datasheet specifies ceramic non-polar caps. That seems a bit weird. Just drawing a non-polar would have made sense, but specifying that it is a ceramic is strange. Using a ceramic makes sense, I mean there are 5 times the ceramic 1uF caps on digikey than there are electrolytics, but it should be technologically agnostic... I'd probably try to get some 1uF ceramics for testing.

[–] joulethief@compuverse.uk 1 points 1 year ago (1 children)

Unlikely. Have you measured the voltage present at Vin?

[–] Froghut@lemmy.dbzer0.com 1 points 1 year ago (1 children)

Yes, I measured across ground and Vin and it shows ~4V. Across ground and Vout 0V.

[–] joulethief@compuverse.uk 1 points 1 year ago (1 children)

Just to be sure: positive probe on Vin, negative probe on GND, measurement shows no minus sign?

[–] Froghut@lemmy.dbzer0.com 1 points 1 year ago (1 children)

Yes, that's what I did and what it shows. I also attached a picture of my test setup just in case I did something wrong there

[–] joulethief@compuverse.uk 1 points 1 year ago (1 children)

Huh, that's weird. Double checking the part markings would've been my next suggestion, but the picture shows they're correct. Maybe try a 1kOhm load resistor across Vout and GND, though in theory you should be able to see the output voltage without it.

[–] Froghut@lemmy.dbzer0.com 1 points 1 year ago

I tried with the resistor, same thing, 0V. I made two images showing the measurements