ADC3641: Recommended R value for single ended input

Art Tkachenko

Prodigy 10 points

Part Number: ADC3641

What is the recommended value for R in Figure 8-6 https://www.ti.com/lit/ds/symlink/adc3641.pdf

Thank you, Art

over 3 years ago

0 Chase W over 3 years ago

TI__Mastermind 24180 points

Hi Art,

I am checking on this for you. Kindly await a further response.

Regards, Chase

+1 Chase W over 3 years ago in reply to Chase W

TI__Mastermind 24180 points

Hi Art,

We suggest to use a light 1kΩ termination resistor to bias the input to VCM.

Regards, Chase

0 Art Tkachenko over 3 years ago in reply to Chase W

Prodigy 10 points

Thank you, Chase.

0 Art Tkachenko over 3 years ago in reply to Chase W

Prodigy 10 points

Hi Chase,

After further review of our design, we would like to know if we can go higher than 1kQ. We are very power limited and we have a large number of these ADC in the design. With 1V swing, we get 1mW lost over the resister. What is the upper limit for this resister value?

Thank you,
Art

0 Chase W over 3 years ago in reply to Art Tkachenko

TI__Mastermind 24180 points

Hi Art,

Below is a figure from the datasheet showing input resistance and capacitance vs input frequency. This is a differential input resistance, so divide this value in half and you will find the max resistor to bias this single ended input is 4k if operating at very low frequencies, and as frequencies increase the resistance will decrease exponentially. I would suggest to stay with 1kΩ and try to increase this resistance on one of your design to see if the performance change is acceptable. You may even test without this termination just to see how well the internal termination is on its own.

Regards, Chase

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ADC3641: Recommended R value for single ended input