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TPS55288: High Side FET Broken When Changing Switch Frequency

Liam Sullivan
Prodigy 20 points
Part Number: TPS55288
Other Parts Discussed in Thread: CSD13202Q2, TPS55289

Tool/software:

Hello, 

I have been attempting to change the switching frequency for the TPS55288 by changing the resistor for the switching frequency on pin FSW. Ideally, I was looking to have a 600kHz+ switching frequency however when I switched out the resistor we currently have on board (50kOhm for 400kHz) for a 21.5kOhm for a ~900kHz switching frequency the high-side FET ended up blowing.  According my schematic capture and the datasheet everything seems to be configured correctly to be able to change this resistor anywhere from the range 9.09kOhm - 100kOhm. I was wondering if there was any specific reason as to why this FET broke, and was hoping to get an answer prior to putting on a new resistor for a 600kHz switching frequency configuration as these boards limited and don't want anymore broken FETs.

I have attached the schematic here. The FET in question that broke is Q6.

  • 0
    TI__Genius 14810 points

    Hi Liam,

    Thank you for reaching out.

    1.What is the input voltage range, output voltage, output current? CSD13202Q2 only has 12V VDS.

    2.Current compensation parameters are terrible. The loop must be unstable. Please help provide part number of output caps to calculate loop parameters/

    Regards,

    Mulin

  • 0 in reply to Mulin Yuan
    Prodigy 20 points

    Hi Mulin, 

    1. The input voltage range is 4.8V-8.4V with a output voltage of 6V with a max output of 5A. We should not have exceeded the 12V VDS from the input voltage. 

    2. The part numbers for the output caps are as follows:

    C45: CL10A105KA8NNNC
    C47: CL31A226KOHNNNE
    C58: CL31A226KOHNNNE
    C64: CL31A226KOHNNNE
    C65: 20SVPF56MX
    C39: UWT1V221MNL1GS



  • 0 in reply to Liam Sullivan
    TI__Genius 14810 points

    Hi Liam, due to bandwidth limitation, I will reply to you later this week. Thanks.

    Regards,

    Mulin

  • 0 in reply to Mulin Yuan
    TI__Genius 14810 points

    Hi Liam,

    Do you consider TPS55289 in this power level? It is full integrated. In some transient occasion Vin might increase, so 12V MOSFET is not recommended.

    For compensation parameters, recommend R79=10k, C66=10nF, C69=100pF.

    Current compensation parameters are extremely unreasonable. Device will work in huge vibration. So both TPS55288 and MOSFET have damage risk. Please use recommended parameters for evaluation.

    Regards,

    Mulin