Need a datasheet for a IC (8 pins) of Power Suply Inverter (Motorolla charger)

UMirz.1 · ‎2020-07-23

I got a Motorolla Charger (PSM4604A):

This is the circuit:

This adapter gives 4.2 V but i need a 5.2 V to charge my smartphone, so i have to rise this constant voltage. But here is a problem. On cold part of circuit there are 3 IC that doing something including voltage control. One of them with 6 pins. But other two, with 8 pins, are relative to each other. This one:

And this one:

This two Chip made by STMicro - B941 & B942 are sort of comparators maybe, or amplifiers. The one that lays on own vertical miniboard does the job of current protection(B941). The other lays on main motherboard(B942) doing Voltage Control. But I couldn't find datasheet of it. I think this mark B942 is not full, gotta have some other codes that helps to search datasheet. So if anybody can help please respond. Thanks in advance.

Peter BENSCH · ‎2020-07-31

The numbers B941/B942 are the date codes, not the device numbers. Both devices appear to be LM358DT, which is a dual opamp.

You may have to search for the reference voltage device, which usually is something like a 431 derivative. There will be some voltage divider resistors at its input, sensing the output voltage of the supply and comparing it with 1.25V/2.5V, depending on the variant of 431. Check the resistors at that voltage divider and after calculating its new value modify the high side one connected to the output voltage to get the required 5.2V.

Good luck!

/Peter

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UMirz.1 · ‎2020-08-09

Hi, Peter! Problem's already solved! But thanks for responding. About date codes didn't know, that's new for me. Yes, first time I tried to find a near located couple of resistors(voltage devider), but what I found and changed(Ohms), didn't change main constant Voltage. Therefore I became to a dicision to change in order the nominal of all resistors that passes my eyes, by PARALLELING them with another 100K resistant. So I got the one. Here it is:

To get the rising up to 5.2 V, it has to be stayed there a 320K resistor in paralel. Thats all.