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ADS8686SEVM-PDK: About A/D conversion

Part Number: ADS8686SEVM-PDK
Other Parts Discussed in Thread: ADS8686S

ADS8686S-EVM is used to obtain the A/D value of each CH. As a test, I am using a DC generator to apply voltage directly to each channel, but when I convert the obtained value to voltage with 16 bits, it differs from the input voltage.
If you calculate with 14bit, the value will be close to the input voltage. So, when I checked the data sheet, I found a place where it was written that the LSB changes depending on the analog input settings.
(7.3.4 Programmable Gain Amplifier (PGA) --- P.32)
There is a register to set the analog input range, but how should I set it if I want to calculate with 16 bits?
Also, 0b and 11b seem to be the same in the AIN_* settings of this register, but what is the difference?

  • Hi ,

    First, 00b and 11b input range setting for AIN_xA/B in the RANGE_XX registers are same, ADS8686S ADC will set the input range to +/-10V for either 00b or 11b setting. By default, the input range for all ADC channels are +/-10V.

    Can you please let me know if your SPI configuration on your microcontroller is CPOL = 0 and CPHA = 1? If possible, please upload your SPI timing (/CS, SCLK, SDO and SDI) here which will be helpful to address the issue. It will be great if  your timing is captured with an oscilloscope.