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ADS114S08: ADS114S08IPBSR Max Frequency aquisition

Marcos Chiele
Prodigy 10 points

Part Number: ADS114S08
Other Parts Discussed in Thread: ADS1158, ADS1258

Hello all.

We are developing an accelerometer reader with 12 channels.

For the data convertion, we are using ADS114S08IPBSR ADC converter.

The aquisition frequency that we need, on each channel, is 600 hz.

After some analisys, I checked that the max sample rate of ADS114S08IPBSR is 4000 SPS.

So, if I need to multiplex the channels (reading one channel per time), the max frequency that I can have is 4000/(nbr of channels)?

Is it possible to read all the channels at the same time without multiplexing them?

Thanks in advance.

  • +1
    TI__Guru** 113765 points

    Hi Marcos,

    Welcome to the E2E forum! The ADS114S08 has a single ADC with a mux so therefore can only convert one input channel at a time.  As to the throughput rate, it will be worse than 4000sps/12.  There are two different digital filters that can be used for this device.  One is a sinc3 filter where three conversions will be required before there is valid output following a mux channel change or the low-latency filter where the first conversion following a mux change requires 406us plus the mux switching delay time (see table 13 in the ADS114S08 datasheet).  The fastest total throughput including communication transfer time will be around 464us per channel times 12 channels gives about 5.6ms for overall throughput (about 180 complete cycles be second).

    So you will need something faster when using a mux, or a device that has the ability for simultaneous sampling.  One possible mux device would be the ADS1158 that has auto-scan and the ability to meet your timing requirements.

    Best regards,

    Bob B

  • 0 in reply to Bob Benjamin
    Prodigy 10 points

    Thank you very much Mr. Benjamin.

    I will change the PN to ADS1158  or similar.

    Is there some sample code to the suggested PN?

    Thanks again.

  • 0 in reply to Marcos Chiele
    TI__Guru** 113765 points

    Hi Marcos,

    The example code is posted for the 24-bit version (ADS1258) and can be adapted easily to the ADS1158 where instead of reading 24-bits of conversion data you only read 16.

    https://www.ti.com/tool/download/SBAC222

    Best regards,

    Bob B