ADS8686S: Input Configuration

Cameron Perl

Part Number: ADS8686S
Other Parts Discussed in Thread: ADS8555, ADS8556

Hey team,

I had a quick question come up while trying to find a part that meets a customer's needs. I think that the ADS8686S seems like the best fit based on the below requirements, but the issue is their input from a pressure transducer appears to have outputs not referenced to the power supply. Can the input for the ADS be configured as a pseudo differential input?

Requirements are as follows:

Architecture	Number of Bits	Sampling Rate/Sec	Number of Inputs	Input Type	Data Interface	Reference Type	Supply Voltage	Throughput	Features
SAR	16	1M	6	Fully Diff	SPI	Int / Ext	Single supply (5V)	1MSPS	Simultaneous Sampling

Thanks for the advice,

Cameron

over 4 years ago

0 Dale Li over 4 years ago

TI__Mastermind 45155 points

Hi Cameron,

ADS8686S only supports a single-ended input signal. However, there is an alterable solution to capture a differential signal by utilizing dual simultaneous sampling channels on the ADS8686S. This solution needs a little bit software work to get the differential information on the controller. Please see the block diagram below.

Let me know know if you need more details on this solution.

Thanks& regards,

Dale

0 Cameron Perl over 4 years ago in reply to Dale Li

TI__Expert 5295 points

Hey Dale,

Thanks for the input - the customer is thinking the device would be overkill for the solution based on the number of channels (seeing as they only need 6). The issue I see is that this might be the best part option for them.

I asked if there were some requirements that could change and got the fact that the sampling rate could be slower and the data interface could also be Serial; input type can be similar to the ADS.

Is there a better solution in the 0.5 or 0.63 MSPS?

Thanks!
Cameron

0 Dale Li over 4 years ago in reply to Cameron Perl

TI__Mastermind 45155 points

Hi Cameron,

Except this solution, another solution using a HV instrumentation amplifier or op-amp can be considered to convert a differential signal to a single-ended signal. See some app notes below. A 6-ch simultaneous-sampling ADC (ADS8586S or ADS8555/ADS8556) can be used.

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

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

Circuit for driving an ADC with an instrumentation amplifier in high gain

Circuit for driving high-voltage SAR ADCs for high voltage, true differential signal acquisition

Best regards,

Dale