• State TI Thinks Resolved
  • Locked Locked
  • Replies 1 reply
  • Answers 1 answer
  • Subscribers 82 subscribers
  • Views 349 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

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.

TMS320F2802: ADC pin connection Res and Cap

Terry Deng
Intellectual 2485 points
Part Number: TMS320F2802

Dears

Customer would like to know what is the detail function for ADCRESEXT resistor and ADCREFP/M cap? What their value affect the ADC performance?

The background is that customer product has MP many years and run well with using 10uf cap and 10K res. Recently they find their usage is actually difference with datasheet requirement 2.2uf and 22k res as below. Then they test ADCRESEXT res from 10K to 22K but found the ADC zero offset become worse. They would like to get our comment. 

d

  • 0
    TI__Guru* 75800 points

    Terry,

    The caps on ADCREFP/REFM act as a buffer to keep the output voltage on these pins stable during ADC operation.  Having 10uF vs 2uF will only increase the power up time at boot when ADC is first enabled(we spec 5ms with 2uF).  Once this is powered up then there will be no effect/difference for the ADC performance.

    The resistor in ADCRESEXT is used to set a bias current for both the reference generation and ADC components in the device.  A lower resistor would result in a higher current draw than expected and could cause the ADC to consume more power than is specified in the DS.  There may be some subtle differences in DNL/INL performance due to this as well.  I'm not sure if I would expect a change in ADC offset because of this.

    With that said, if customer has been in production for some time, and is satisfied with the ADC performance in their system with these values I think they can keep them at the existing value vs make a change.

    Best,

    Matthew