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CSD23280F3: PMOS FET used for polarity-reversal input protection for TI bq25505 energy harvester chip

Ellis Cave
Prodigy 120 points
Part Number: CSD23280F3
Other Parts Discussed in Thread: BQ25505, , CSD23202W10

The TI bq25505 support group has recommended a PMOS FET to protect from polarity reversals on the bq25505 input that I am using in a new design. TI support (Ricardo) provided a document: http://www.ti.com/lit/an/slva139/slva139.pdf explaining the PMOS input protection method. However, the bq25505 has a cold start voltage on Vin(cs) of 600mv, so I need a PMOS FET that  has a gate-source threshold voltage Vgs less than -0.6V with the lowest possible Rds(on). Otherwise the FET could prevent the bq25505 from cold starting. The CSD23280F3 has a VGSTH of -0.65V. Does TI have a FET that can meet these requirements.? The actual max source-drain current will be less than 100ma from a small wind turbine, so high power is not required, just low VGSTH.

  • 0
    TI__Mastermind 31935 points

    Hi Ellis,

    Thanks for your interest in TI FETs. I did a search and the CSD23202W10 has the lowest typical VGS(th) = -0.6V. TI tests and specifies threshold voltage at ID = -250uA & T = 25C. Keep in mind, the datasheet limits are -0.4V to -0.9V and that's all  we can guarantee. I pulled up the characterization data when this FET was developed and the maximum measured value was just few mV over -0.6V. Please note, these are samples from 3 lots and may not reflect the actual lot-to-lot variation over a larger production sample size. The magnitude of the threshold voltage has a negative temperature coefficient of -7mV/C, nominally. As you heat the part, the threshold is lower and at lower temperatures the threshold increases.

  • 0 in reply to John Wallace1
    TI__Mastermind 31935 points

    Hello Ellis,

    Following up to see if you have any additional questions. I will assume that this adequately answered your questions if I don't hear back in the next day.

  • 0 in reply to John Wallace1
    TI__Mastermind 31935 points

    Hi Ellis,

    Thanks again for your interest in TI FETs. I am going to close this thread. Please feel free to contact me if you still have questions.