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ADS8167: On the Fly Mode latency

cuong thai
Prodigy 80 points
Part Number: ADS8167

Hello,

What is latency of On-The-Fly Mode? The second sentence of 7.4.1.2 of document SBAS817C state "the newly selected channel date are available TWO cycles after selecting the desired channel".

Then on Figure 44. ("On-The-Fly Mode, with No MUX Channel Selection Latency") shows there is only ONE Tcycle latency? Which one is correct?  ONE or TWO cycles latency?

Thanks

...

  • +1
    TI__Guru 62196 points

    Hello Cuong,

    Thank you for your post. I agree there is some confusing description in this section of the datasheet. 

    After reviewing Figures 42-44, my understanding is that On-the-Fly mode has only 1 cycle latency. This is reduced from the 2-cycle latency observed in Manual Mode. The difference appears to be that the MUX takes one complete cycle to change the output in Manual Mode. Figure 42 shows this as the command is sent in Cycle N, the MUX output (i.e. ADC input) is changed in Cycle N+1, and finally the conversion result is available in Cycle N+2.

    Figure 44 shows that in On-the-Fly Mode, the MUX output changes as soon as the 4-bit channel ID bit is captured. This new channel is converted and available to read in the next frame (i.e. one-cycle latency).

    Regards,

    Ryan

  • 0 in reply to Ryan Andrews
    Prodigy 80 points

    Thanks for you clarification. This eases my concern.