Problem with TC1262 regulator

Hi all,
I’ve setup a circuit like the one depict here.

In brief, FG1 is Lipo Fuel Gauge; and U3 is 3.3V voltage regulator; other are ESP8266-12 and a ds18B20 temp sensor.

I first tried on breadboard => OK.
So i moved to protoype board and it does not work as expected… Actually I have only 1.4V on TC1262 output and so EXP8266 input which is definitely not enough…My input source is a Lipo wihich is measured @4.2V (fully charged)
I tried with another power source ( direct connection to Gnd and Vcc rail) and everything is OK thus I assume no short nor connection pb…
On TC1262 it’s written “TC12623.3VAB” : according to datasheet it’s 3.3V model (the one I’d expect to have …)
Please refer to images for details…
Any ideas of such issue ?? Or investigation path?
Thx

I first tried on breadboard => OK.
So i moved to protoype board and it does not work as expected

So the only thing to say is that you have not moved the circuit successfully, you made some sort of mistake. Now all we have to do is to find it.

The reduction of output voltage suggests something is drawing too much current.

  1. Measure the current that the system is drawing. Is it more than you expect?

  2. Remove devices until the voltage recovers.

  3. If the voltage never recovers look for shorts and miss connections around the power regulator.

  4. Rebuild on bread board and check again.

Thanks for the advice actually, I set two additionnal pins on the board for direct power (ie wihtout regulator). When I connect these pin to 3.3v adapter for breadboard (like this one

) it 's OK...

Can you please specify at which point to measure current. I'm Ok for voltage, but a little more in trouble with current :confused:
In addition now everything is soldered will be a little more difficult to dissasemble. Anyway I'll give a try !

thx

Can you please specify at which point to measure current.

Total current from the supply.

actually, I set two additionnal pins on the board for direct power

Very very stupid idea.

Can't measure any current.... For sure,either I'm doing something wrong or no current (??)I'll bet for 1st option.
WHy a so bad idea? For sure I do not use both source simultaneously.
Nonethelles, I plugged external source to the regulator and same result...Definitelty charging regulator / the way it's wired.

Using an output pin to provide power is a very bad idea because the output impedance is high and the supply will not be well regulated. It is also very easy to over current the pin and damage the output pin.

Thanks for your advice about other input...
I applied your advice, unsoldering,back to breadboard (OK) and moving to proto board :everything's all right, seem I missed ground connection for TC1262... ::slight_smile:
Prb solved.