BQ25121A: No output power

Michael Hagmann

Part Number: BQ25121A

Hello

In a design with a BQ25121A, I have the problem that on some PCB's no output power gets generated. All pins are soldered correctly as far as I can measure from the outside. If I power the device with 5V at IN (pin A2) with no battery connected, current consumption is about 6mA. Voltage on PMID then is only 40mV. At SW, no voltage gets generated. On other PCB's the voltage gets set to the expected 2.5V (behind the inductor at VSYS of course). Resistor at IPRETERM is 4.99k, at ISET 1k and at ILIM 665R.
If I power the device via BAT input, the output gets set to 2.5V. But only powering via VIN, it doesn't work. I can measure a diode voltage of 0.6V from GND to IN, so the IN-pin is soldered. Seems to me like Q1/Q2 (block diagram in the datasheet page 17) does not switch on. What could be the problem here?
Do you have any hint if this is a solder problem, a design problem or a chip-fault?

Thank you for your support

over 3 years ago

0 Nick Brylski over 3 years ago

TI__Mastermind 19195 points

Hi Michael,

It is possible there has been EOS damage or solder issue, are you able to charge the battery when it is connected?

Thanks,

Nick

0 Michael Hagmann over 3 years ago

Prodigy 20 points

Hi Nick

Thank you for your answer.

Exact behavior is as follows:
If I connect the battery first, no output voltage gets generated. If I then connect 5V at VIN, 2.5V output voltage gets generated. Current at VIN is about 6mA, current of the battery is 1.4mA (out of the battery). So the battery does not get charged.
Now I can disconnect 5V at VIN and the 2.5V on the output stays active.
If I disconnect the battery instead and keep the 5V at VIN, the output power gets disabled.

So I can not charge the battery via VIN and no output power gets generated if no battery is connected.

Best regards,
Michael

0 Nick Brylski over 3 years ago in reply to Michael Hagmann

TI__Mastermind 19195 points

Hi Michael,

Can you attach the schematic for review? How many units are you seeing this issue on.

Thanks,

Nick

0 Michael Hagmann over 3 years ago in reply to Nick Brylski

Prodigy 20 points

Hi Nick

As this is confident data, is it possible to send it to you via mail? Or a portal that is not public?

Thank you, best regards

Michael

0 Nick Brylski over 3 years ago in reply to Michael Hagmann

TI__Mastermind 19195 points

Hi Michael,

I sent you a friend request with my contact details.

Thanks,

Nick

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BQ25121A: No output power