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TMS320F28379D: How much current does reference input pin draw

Sheldon He
Expert 8585 points

Part Number: TMS320F28379D

Hi expert,

My customer wondering how much current will be drawn from VREFHIA/VREFHIB/VREFHIC/VREFHID when ADC is wokring. How could we estimate this?

BTW, will it be feasible to mount 10 ohm to 51 ohm resistor in series in reference volatge source and change capacitor value to 1uF?

Thanks

Sheldon

  • 0
    TI__Guru 60865 points

    Hi Sheldon,

    No, you shouldn't mount a resistor in series with the VREF inputs.  You really want your reference driver to be as low impedance / high bandwidth as possible.

    We do specify a typical average VREFHI current in the datasheet as 130uA in 12-bit mode.  With a 10 ohm resistor, this would result in an IR drop of 0 to 1.3mV or up to 1.6 LSBs, so you would lose up to log2(1.6) = 0.7 bits of performance.  For 50 ohms you would lose about 8.1 LSBs or 3 bits of performance.