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DRV8305: DRV8305 Current Sense Amplifier

Adam
Expert 1215 points
Part Number: DRV8305

I have DRV8305N with TMS320F2838*S.

Want to design ADC input circuit according to SPRACT6A.

CSA OpAmp has 2MHz of GBP.

According to Analog Engineer Calculator with the seetings from picture I should have min 17MHz GBP driving amplifier.

So should I add additional OpAmp buffer between CSA output and ADC input?

Or maybe I should make higher Acquisition Time? I want to use 16bit single ADC with 3.3VREFHI

What kind of error will I have having 2MHZ buffer instead of 17MHz?

What are your suggestions what should I do?

Im desiging PMSM motor controller.

Regards, 

Adam

  • 0
    TI__Genius 14050 points

    Hi Adam,

    Thank you for posting to the Motor Driver's forum!

    I will aim to provide a response by the end of next week.

    Best,

    ~Alicia

  • 0
    TI__Genius 14050 points

    Hi Adam,

    I am looping in the C2000 to help answer your question.

    Best,

    ~Alicia

  • 0
    TI__Guru** 115470 points
    Adam said:
    So should I add additional OpAmp buffer between CSA output and ADC input?

    Not necessary since there are three embedded PGA on DRV8305 which can be connected to the ADC pin of C200. You may just just need to add a RC filter between the output of DRV8305 PGA and the ADC input of C2000.

    Adam said:
    Or maybe I should make higher Acquisition Time? I want to use 16bit single ADC with 3.3VREFHI

    That depends on the current sensor, not the ADC. The embedded PGA could be fine for the 16bit single ADC.

    Adam said:

    What kind of error will I have having 2MHZ buffer instead of 17MHz?

    What are your suggestions what should I do?

    A higher GBP and slew rate of the amplifier or PGA can help to sample the current signals if the current sampling window is not enough. The 2MHz could be enough for inline current sensor or three-shunt current sensor.