BQ2057W: BQ2057WSNTR

Hello

What can you tell me about the input voltage?

When the BQ2057W fails does pass transistor Q1 also fail?

Hi

The transistor Q1 does not fail when BQ2057W fails. But the input voltage is fluctuating, while it does not fluctuate when the board works okay 

The input voltage is 9v and charging current at 0.5A. The battery used is Li-Ion 

The input voltage is switching after 2-3 cycles of charging 

Regards

The input voltage is 9v and charging current at 0.5A. The battery used is Li-Ion 

The input voltage is switching after 2-3 cycles of charging 

Regards

Reviewed schematic and do not see issues.

Input voltage of 9V should be OK.

If you replace the BQ2057 does the PCB work? 

One theory on the fail and damage to BQ2057 is a short on Q1 Source to Gate.  Common fail mode for MOSFET is a S to G short.  In this condition the current into BQW2057 CC pin would be high (no limiting element) and would lead to damage you are seeing.

In the failed boards have you seen other damage, does replacing the BQ2057 fix the boards?

The MOSFET doesnt fail. Once we replace the BQ2057, the issue gets fixed and the board works.

Attached screenshots of the waveforms at the different pins -on working and not working boards

On the damaged IC do you see a short on any of the pins?

High current on one of the pins can cause a fail but most of the pins are connected to input voltage, 1, 2, 3, 8.  They do not have current limiting resistors.

High voltage on the pins, but Vin is only 9V and max voltage is Vin +0.3V.

In the below image TS is both high and low, is the label correct?

yes,, actually the label has to be pin 5

The oscillation on Pin 7, CC look like a problem, this should be a DC level.  But not clear what is causing this.

What are you using for an load, is this a battery or battery simulator?

It is a Li-Ion battery that is being used. 

Hi

Can you measure a failed unit, check for short between pins and ground?

This may help to ID the area that is causing the problem.

There is no short between pins and ground. But IC is getting heated up

On the failed ICs pins do you see any difference when you measure with an ohm meter?

Just to confirm your design is a BQ2057W, Dual Cell not BQ2057C single cell?

The BQ2057C is mentioned in the post title?

Can you send layout plots for review?

The design is with BQ2057W. Couldnt select BQ2057W as it was not listing in the drop down menu

Attaching layout files

regards

I have updated the P/N to BQ2057W in title.

Have you been able to compare the pin to ground resistance of a good and bad unit?

On layout the copper under Q1 looks small vs the heat that it can generate.  Are you seeing any thermal issues on Q1?

Yes, the Q1 gets heated.

W.r.t. the ground resistance, 

Working board: Pin 1, 3, 7, 8: 20K, Pin 2: 1M, Pin 4: 10K, Pin 5:1K, 

Failed Board: Pin 1:17K, Pin2: 264 ohms, Pin 3: 514 Ohms, Pin 4: 700 ohms, Pin 5: 615 Ohms, Pin 7: 674 Ohms, Pin 8: 1.68K

I have some thoughts on the transistor and will contact you.