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ADS1271 External Sync

Marco Omedè
Prodigy 20 points
Other Parts Discussed in Thread: ADS1271

Dear all,

I'm trying to use the A/D converter ADS1271 configured in SPI Format.


What I want is to use the Sync to syncronize the acquisition each 50ms.

I generate a signal at 2kHz with duty cycle 50%, but I tried also at different duty cycle.

The master clock is 27MHz and the SPI clock is 15MHz.

The result is that the AD seems to be "dead", the data ready is always flat.

I can see the DRDY only if I get high the Sync signal using the AD in free running.

Do you have a suggestion to understand where I'm in wrong?

Many thanks in advance.

Best regards.

Marco

  • 0
    TI__Guru 66286 points
    Hi Marco,

    The 2kHz signal you are generating is used to toggle the /SYNC pin? Assuming a 50% duty cycle, this means that the /SYNC pin will be high for only 250us. If you wish to toggle the /SYNC pin every 50ms, you need a 20Hz 50% duty cycle signal.

    I'm not sure which mode you are using (High-Speed, High-Resolution, or Low-Power), but at the fastest data rate with a 27MHz input clock, the settling time required after a /SYNC pulse (tNDR) is 1.2ms (256/27MHz * 128). /DRDY will remain high until tNDR has elapsed, which explains what you were observing.

    Best Regards,