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DRV8846: DRV8846 VREF input current and Rsense selection

Andrew V
Intellectual 280 points
Part Number: DRV8846

I have a couple of questions.

1) What's the input impedance of the VREF analog input? I'd like to make sure VREF can be set from an external DAC with somewhat limited current capability. The specsheet says that VREF input current is less than 1 μA for VREF range 1-3.3V, should I assume the input is at least 1M? What about VREF less than 1V?

2) What is a recommended range and main considerations for choosing the Rsense? 

  • 0
    TI__Guru 56650 points

    Andrew,

    1. I would think VREF below 1V is not a realistic situation for DRV8846. With 1Vref, the IFS*Rsense= 167mV. The current regulation accuracy should be worse than 3.3V VREF setting. Specially, for small micro-step setting. If we don't need such low current application, I would increase Rsense a little bit.

    From 1V~3.3V input, the VREF maximum input leakage current is 1uA. Yes. You are right, the input resistance at least 1M.

    2. That is based on the minimum IFS setting to you want:

    a. Keep IFS*Rsense > 167mV

    b. Keep Rsense power dissipation lower than its package allowing power dissipation.