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DRV8312EVM current scaling circuits

James Baker76
Prodigy 210 points

Other Parts Discussed in Thread: BOOSTXL-DRV8301

Hi.

The DRV8312EVM Rev. D current scaling circuits seem to be different from what is recommended in the SPRUHJ1F user guide chapter 5.

The feedback resistors and biasing resistors don't come out to the same resistance. (i.e. 19.1K is not equal to 28.7K || 49.9K) on the A,B,C phase circuits.

And on the total current circuit, 38.3K is not equal to 57.6K || 49.9K.

Am I missing something here or are these values in error for this type of difference circuit with split resistor biasing?

I measured the output of the op-amps with a large current running through the phase and the output voltage (converted to the current seen by the op-amp) is not consistent with what I saw when I measured the phase current directly with a meter.

Can you please advise?

Thanks.

Jim

  • 0
    TI__Guru** 119680 points
    Jim,
    you are correct in that the circuit is not as we recommend. This EVM design was done a very long time ago...I want to say 2010 at the latest. Since then we changed the circuit for measuring current to make sure we supplied with 1.65V. This circuit uses 2.5V supply which we turn into a Vref of 1.58715 = 2.5V * (49.9 / (49.9+28.7))

    and 28.7 || 49.99 = 18.22 K

    If designing your own board highly recommend you follow the UG and kit examples like BOOSTXL-DRV8301