BQ24610: LODRV MOSFET blowing on battery plugin

Michael McAdam

Part Number: BQ24610

Tool/software:

I am trying to design a battery charger that fits within a larger system. It uses two 11.1V Li Ion battery packs connected in series to create a nominal 22.2V battery.

See schematic here: battery-charger-24v.pdf

When I connect the batteries, the board gets damaged in some way that means that power BATT and GND become shorted together. Using a thermal imaging camera shows the LODRIV mosfet getting very hot, although I can't be sure that this part is the one that gets damaged or if it is the IC itself. Doing some basic probing it does seem like the MOSFET gets damaged. I had this issue and then replaced the MOSFET with one rated much higher (100V) and it is still giving issues.

Other notes about the design:

We are not worried about limiting the AC adapter current
We are aiming for battery longevity so the charge current is set to 0.5A and the charge voltage to 23.5V
The batteries have their own battery protection IC so there is no thermistor.
The BATT output is connected to a diode on another board (but the board gets damaged before being attached to the other board, so I think unlikely to be the source of the problem)

9 months ago

0 Christian Moyer 9 months ago

TI__Mastermind 31396 points

Hello Michael,

I see no obvious issue with your schematic, I recommend confirming that you followed the BQ24610 layout guideline:Layout Guidelines and Example (6).pdf

Best Regards,

Christian.

0 Michael McAdam 9 months ago in reply to Christian Moyer

Prodigy 40 points

Hey Christian,

I've read through the layout guidelines and nothing leaps out at me as being particularly out of place. Probably the only thing is the mention of AGND which the BQ24610 doesn't mention at all in the datasheet so I don't have a single point of connection.

Here are the PCB design files if you can glean any information that I have missed: PCB Layout.zip

I've actually found a number of similar topics that talk about damage when hot plugging a battery without an AC adapter connection:

https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/1180492/bq24610-bq24610-battery-plug-in-and-out-bq24610-hidrv-mos-lodrv-mos-damage

https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/605333/bq24610-bq24610-and-lower-drive-mosfet-blow-apart-when-battery-voltage-is-applied-without-an-adapter-source

https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/1126294/bq24610-bq24610-without-adapter-when-the-battery-insert-bq24610-damage

But doesn't seem like any of these came to any clear conclusions.

I unfortunately can't scope this issue as I only have one board left and I don't want to potentially miss the event and have no more boards left to test.

My best bet seems to be that the voltage spike as a result of the inrush current is damaging both the chip and the LODRIV mosfet, but there is not mention of this in the BQ24610 datasheet.

0 Christian Moyer 8 months ago in reply to Michael McAdam

TI__Mastermind 31396 points

Hello Michael,

I've found customers with similar issue place a Schottky diode between SRN and the resistor feedback network to block reverse current. Since you don't have a system load this could be a quick and simple fix to avoid the inrush of current from hot plugging the battery. If you use this method, I recommend also adding an extra 10uF capacitor after the diode on the battery side.

Best Regards,

Christian.

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BQ24610: LODRV MOSFET blowing on battery plugin