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CSD87503Q3E: Second mosfet dies after soldering onto the pcb

Aslan Turabekov
Prodigy 170 points
Part Number: CSD87503Q3E
Other Parts Discussed in Thread: BQ24170

I am using the csd87503q3e in a BQ24170 charger design. While tracing the PCB, I forgot to connect the second gate to the ACDRV output of the charger IC. Since I already ordered the prototype PCB I decided to use a jumper wire to connect the second gate to the first one. After checking the mosfet for any shorts, I notice that there is a resistance across the second gate and second drain, while the first mosfet is fine. I checked the mosfets before soldering them and they were working as expected. I ordered the csd87503q3e from digikey, so I am certain that they are not fake. Every other component was already soldered onto the PCB and I was using an antistatic wristband. 

  • 0
    TI__Mastermind 30835 points

    Hi Aslan,

    Thanks for your interest in TI FETs. Sorry that you're having problems. Can you share your schematic? Have you probed the FETs to confirm VGS is as expected? The charger IC has a charge pump and needs to provide VGS >= 4.5V to guarantee the on resistance of the FETs. How much resistance do you measure between the gate and drain? Normally, that should be a very high resistance. I am assuming the first FET is connected to the input or adapter voltage. There are connections between the second FET and the charger IC that could affect the resistance measurements in circuit. You can also check the body diode of the FETs by measuring from source to drain. Let me know what else I can do help you debug your circuit.

  • 0 in reply to John Wallace1
    TI__Mastermind 30835 points

    Hi Aslan,

    Thanks again for your interest in TI FETs. I am following up to see if you have resolved your issue. Can I be of any additional assistance? I'll give it another 24 hours and if I don't hear back from you, then I will assume your issue is resolved and close this thread.

  • 0 in reply to John Wallace1
    TI__Mastermind 30835 points

    Hi Aslan,

    Thanks for reaching out to TI for support. Since I have not heard back from you, I assume you're assume your issue has been resolved and I will close out this thread. Feel free to contact us again if you run into any problems.