ADS8686S: Differential Input to ADC

Hi Pedaiah,

Thanks for choosing ADS8686S in your design.

1. ADS8688S only supports single-ended input, so there is no problem to convert your +2.5V signal directly, however for your differential +/-3.3V, the simplest way is using an instrumentation amplifier or precision amplifier to convert from differential signal to single-ended signal.

2. No, the voltage on AIN_xAGND pin should be limited to -0.3V and +0.3V to achieve the performance specified in the data sheet.

3. Please refer to some cookbooks below: 

Circuit for driving a high-voltage SAR with an instrumentation amplifier

Circuit for driving high-voltage SAR ADC with a buffered instrumentation

Thanks & regards,

Dale

Dear Dale,

Thank you for the quick response and valuable feedback.

As per your suggestion, We are going ahead with ADS8686S for Single ended analog signal to digital conversion and INA828 or similar for Differential analog signal to single ended analog conversion.

Once we finish the circuit using ADS8686S and INA828, we would like to review from you.

1. Can you please share your mail id to share the circuit later personally?

2. We do also have a requirement of single to differential ended converter. Can you please suggest us a Device?

Thanks and Regards,

Pedaiah G

Hi Pedaiah,

1. I have requested friendship on this forum. Please let me know your signal's characteristic (differential signal range, CM voltage, frequency etc.) so that I can help you check if INA828 is a proper device for you.

2. There are a couple of solutions to do that, below is a good cookbook for SE to differential signal with op-amp:

    Single-ended to differential using a two op-amp circuit

Also, you can use a fully-differential amplifier (FDA), please see another cookbook:

    Single-ended-to-differential circuit using an op amp and fully-differential amplifier (FDA) for bipolar signals

Best regards,

Dale