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Original question:

CSD75208W1015: Gate Clump Current

CSD75208W1015: Can the dual FET be used as a pair to make a current mirror?

Lanhua Zhang
Prodigy 210 points
Part Number: CSD75208W1015

What's the mismatch between these two FET inside?

Can the dual FET be used as a pair to make a current mirror? What's the expected accuracy or matching error?

Thanks.

  • 0
    TI__Mastermind 29525 points

    Hi Lanhua,

    Thanks for your interest in TI FETs. The CSD75208W1015 is a wafer level package - essentially a silicon die with BGA interconnect. Both FETs are on the same die and should be closely matched. However, TI has not characterized the FETs for matching. Both FETs are tested to the limits in the Static Characteristics specified in the datasheet with the exception of transconductance (typical value only). What parameters are critical for matching in your application? I can take a look at the characterization data collected during product development to see how closely these parameters match.

  • 0 in reply to John Wallace1
    Prodigy 210 points

    Thanks John.

    I am planning to use it as a current mirror to generate some current at the output. Hope the mismatch between two FET is less than 5% on transconductance when output current is in a 100mA range.

  • 0 in reply to Lanhua Zhang
    TI__Mastermind 29525 points

    Hi Lanhua,

    Thanks again for your interest in TI FETs. I pulled up the characterization data collected during product development. As I pointed out in my previous response, this doesn't include transconductance. Multiple samples from different lots were tested. The best indicator for matching the two devices from this data is threshold voltage. The mean threshold voltage was 0.7951mV and 0.7940mV, respectively for the two FETs across all samples tested. I also compared threshold voltage on a few individual devices and the matching was < 0.01mV or <1.25% on 0.8V typical threshold specified in the datasheet.  I have consulted with a colleague who was involved in the development of this device. He points out that the “Vth” as TI defines it, is the Vgs in saturation that gives 250uA of current (not the traditional analog Vth definition).  So the saturation Vgs at 250uA is in fact one point on the saturation region transfer characteristic, and it is a good indicator of gm_sat matching capability. Overall, we believe the two FETs will be very closely matched and should work satisfactorily in your application.

  • 0 in reply to John Wallace1
    Prodigy 210 points

    Thanks a lot for the explanation with details. That makes sense.

    Regards,