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Original question:

ADS1258: ADS1258 External ADC Inputs Reading Error

ADS1258: About some sampling frquency questions

Gabriel Wang1
Genius 4715 points
Part Number: ADS1258
Other Parts Discussed in Thread: ADS131M08

Dear Expert

As for ADS1258, our company used this chip to do a project of 8 channels of 2KHz sampling frequency (that is, the sampling frequency of each channel is 16KHz). Now the project has a new requirement -- to use ADS1258 chip to achieve 8 channels of above 16KHz sampling frequency.

1.According to the chip manual and actual test verification, the maximum sampling frequency of a single channel of ADS1258 in the automatic scanning mode is 23.7KHz, which is consistent with my requirement -- a total of 16KHz sampling frequency of 8 channels (means the sampling rate to save a single channel is:8* 16KHz = 128KHz) is far away. Is there any way to solve it?

2.In addition: Although it has been measured and stated in the manual, I still want to confirm whether the maximum sampling rate of 23.7kSPs in the automatic scanning mode is the highest sampling rate for a single channel. Is there any method to make the total sampling rate of 23.7kSPs for multiple channels?Also want to know, at 16MHz external crystal oscillator, SPI clock signal SCLK frequency can support to how much Hz?

  • 0
    TI__Guru 52296 points

    Hi Gabriel,

    The ADS1258 cannot sample as fast as you need for this specific application. The digital filter inside of the ADC needs time to settle, which is why the overall data rate is reduced for multiplexed applications. So, as you noted, the maximum sample rate for 1-ch in auto-scan mode is 23.7kSPS; for 8 channels, that is 23.7 / 8 = ~3kSPS.

    I would recommend in this case to consider an ADC like the ADS131M08, which is an 8-ch simultaneous sampling ADC that can sample at speeds up to 32kSPS. Since this ADC is simultaneous sampling, that means that you can sample up to 32ksps/channel without any throughput loss.

    Please review this ADC and see if it will meet your needs. If not, please let me know why and we can try to identify a different ADC.

    -Bryan