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BQ77915: Device Over Current Detection Problem that causes MOSFET Burnout

Pankaj Yadav1
Prodigy 120 points

Part Number: BQ77915

Hi,

We have checked all protections again and again, all individually protections(testing 1 protection at once) are working good, but when say device is in OTC(Over Temp. during Charge) protection that Closes charging MOSFET gate, charging stops. After charger removal,if we connect Load and start Discharging(when device is in OTC protection) at high Currents above OCD, then Device doesn't go under protection and fails to turn off MOSFETS, & that results in Mosfet Burnout.

We have also noticed same problem when OCC protection is present and Load is connected then device not going under OCD protection & results in burnout of MOSFETS. Please provide Solution of this as soon as possible.

Device:; BQ7791501 under 10S configuration

LD resistance: 470k

Rsns:2mOhm

We have faced this issue after starting Production & production also hauled due to this Problem.

Please provide Solution asap.

Regards 

  • 0
    TI__Guru* 81035 points

    Hi Pankaj,

    The device will attempt to enable the FETs to protect them from damage in the scenarios you describe (see Table 9-6 in the datasheet). Can you capture waveforms of the FET gates during these events to see if they are switching fast enough in relation to the events? The DSG and CHG FET gate resistors may need to be adjusted to adjust the rise / fall times for your system.

    Best regards,

    Matt