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ADS127L01: Frame Sync Master + Daisy-Chain

Evan Cornell
Expert 1380 points
Part Number: ADS127L01

I realize the ADS127L01 datasheet specifies that Frame Sync Master does not support daisy-chain mode. 

However, I would like use 8 ADS127L01 on a design, one as Frame Sync Master (let's call this one ADS#0) to generate SCLK & FSYNC for the other 7 (in frame sync slave mode). Can the DOUT of the ADS#0 be fed into the DAISY-IN of a slave ADS#1, as well as the clocks? 

The remaining 6 ADS devices (ADS#2-7) would all be given ADS#0's SCLK and FSYNC, and each configured in DAISY-CHAIN (2 ADS per data line). So ultimately, I would have ADS#0 SCLK/FSYNC and 4 data lines going to host processor. 

If this scheme is workable, would it be recommended to run ADS#0's SCLK & FSYNC thru a clock buffer of some sort, since it would be fanned out to 7 other devices?

Thanks,
Evan

  • 0
    TI__Guru 57296 points
    Hi Even,

    Thank you for your post.

    The issue I see with this proposal is that the FSYNC period from the master device (ADC0) is only long enough to fit 32 SCLKs, where the SCLK frequency that is output from ADC0 will be equal to exactly 32 x fDATA. When you daisy-chain 2 devices in Frame-Sync Mode, the FSYNC period from ADC0 will still match the data rate, but your SCLK will need to be twice as fast = 64 x fDATA in order to fit the data from both devices in the frame.

    Best Regards,