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ADS7038: Oversampling Function (OSR), Averaging, and Mode of Operation

Part Number: ADS7038

Tool/software:

Hello E2E Experts,

Good day.

First, in the datasheet, it says that "in autonomous mode of operation, samples from analog input channels that are enabled in the AUTO_SEQ_CH_SEL register are averaged sequentially," does this means that the averaging is spanning over all the selected input channels?
 
Also, my input bandwidth is 8kHz per channel, so if I want to oversample by 4x, it would be 32kSps per channel.  If I want to average by 2, then the data rate per channel is 16kSps, correct?  What is the best setup for this scenario (OSR setting, mode, etc.)?   In addition, If the max sampling rate can handle it, I would like to use up to 4 chips (32 input channels).  Can I share the same SPI port, with a separate CS to each ADC chip?
Regards,
TI-CSC
  • Hello,

    When averaging is enabled, channel 1's samples are first averaged, then channel 2, and so on. In autonomous mode, this applies for whichever channels are enabled in the AUTO_SEQ_CH_SEL register. So you cannot choose to oversample and average one channel while not also oversampling and averaging the others.

    Your averaging factor will be equal to your oversampling rate. If you are oversampling by 4x (setting OSR_CFG register to 10b), you will average by 4x. If you wish to sample your signal at 8 ksps, and set an OSR of 4x, you are effectively sampling at 32 ksps, but your data rate will remain at 8 ksps. You won't "see" that you are oversampling when you are reading your data, but the data will be the average of multiple samples. I hope this is enough to help you make a determination.

    You can share the same SPI port with multiple ADS7038 devices as SDO is in high-impedance mode when CS is high.

    Best,
    Joel