• State Resolved
  • Locked Locked
  • Replies 2 replies
  • Subscribers 51 subscribers
  • Views 945 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.

CC2540/CC2541 ADC input capacitance

John123
Prodigy 50 points


The CC254X seems to have a discrete time sigma delta ADC with switched capacitance input. What is the value of the input capacitance of this ADC?

Similar questions have been asked before, unfortunately without answer:

http://e2e.ti.com/support/low_power_rf/f/538/t/322407.aspx
http://e2e.ti.com/support/low_power_rf/f/538/t/299631.aspx


It would be really helpful if somebody could give me an approximate value!

  • 0
    TI__Guru 56590 points

    Hello John,

    Approximate is the key here as each design will have slightly different input capacitance.

    When sampling, the equivalent resistance of the input is simulated to be around 176kOhms worst case. The switched capacitance resistance is 1/(C*f), where f=4MHz sampling frequency, so the internal capacitance is about 1.4pF. In addition the pads contribute to about 1pF capacitance and your PCB traces will have some capacitance.

  • 0 in reply to Eirik V
    TI__Guru 56590 points

    PS: As I said above it is simulated, I do not have measured results.