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ADS1235EVM: question(console and filter)

Part Number: ADS1235EVM
Other Parts Discussed in Thread: ADS1235

Hello Experts,

My customer has question as follows.
[Question 1]
I decided to check the settings from the console.
Offset calibration was done with SYOCAL command, but with GANCAL command, SYGCAL command was selected with gain 1V/V register setting, but it changed from 5mV to 200mV.There was a formula in, but I do not understand this relationship well, could you tell me about the relationship and the operation?
The image of what you want to do is as follows.
Code: -53 => Code: 0 (sensor input voltage 0 mV) SYOCAL command?
Code:8250 => Code:5000 (sensor input voltage 5mV)
Code:16552 => Code:10000 (sensor input voltage 10mV)

[Question 2]
I would like to measure the filter using data rates 2.5, 5, 10, 100 sps.
Looking at the noise table in Table 1 of the ADS1235 data sheet, the Sinc4 filter suppresses the noise the most.
The FIR filter is set by default, but is there a disadvantage with the Sinc4 filter?

Best Regards,

  • Hi Yasushi Fujiwara,

    For question #1: section discusses how to perform calibration without using the calibration commands e.g. SYSOCAL, etc. If you want to use the calibration commands, refer to section Note that to use the GANCAL command you must input a near full-scale signal (95% of FS) to your system. This input signal should be very low noise and accurate because this signal is what the ADC uses to perform the calibration.

    For question #2: the sinc4 filter takes longer to settle compared to the FIR - see Table 6. The settling time for an FIR filter is similar to a sinc1, whereas the sinc4 filter has about 4x longer settling time. The sinc4 filter also has better 50/60Hz rejection - see Table 5