• State Resolved
  • Locked Locked
  • Replies 2 replies
  • Subscribers 82 subscribers
  • Views 828 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TMS320F28377D: VREFHI input current = (190uA, 130uA): Any conditions to change the level ?

Hideaki Nambu
Mastermind 9165 points

Other Parts Discussed in Thread: OPA320, OPA350

Hello,

On the DS SPRS880G page-{100, 102}, we see "VREFHI input current" is like 190uA or 130uA.

Then, does the current level changes significantly in any condions ? 

The level is not expect to be larger.

My point is, the value would get smaller when ADC or any blocks are disabled, or under any low-power mode.

I asked this to decide my Vref circuit for the VREFHIx input pins.

I know the pins need caps (DS p.16). It is out of the scope.

-n

  • 0
    TI__Guru 60865 points
    Hi Hideaki,

    The VREFHI average current will scale with the ADC sample rate; more or less samples means more or less current drawn in a fairly linear fashion. The numbers quoted in the DS are for maximum sampling rate. Having the buffered DAC powered up and referenced to VREFHI will also contribute some current draw (but the output current is sourced from the VDDA rail).

    Keep in mind that the instantaneous current drawn can be many times the average current. Because of this, we recommend in the DS that you place a fairly large capacitance on the VREFHI pin and drive that net with an op-amp with reasonable BW. We have found both OPA320 and OPA350 do a good job here.
  • 0 in reply to Devin Cottier
    Mastermind 9165 points
    Devin,
    Very clear. Thank you !