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TICPAL22V10Z-25C: Operations during power down

Louie
Expert 3180 points
Part Number: TICPAL22V10Z-25C

Hello,

My customer had the following question:

This part has two different modes: Turbo Mode and Zero power. With Zero power, the data sheet says the device  powers down if there isn't any input activity for 40ns. In our system, we see a change of 70mA-80mA difference in current between devices in the two different modes. I know there's a speed penalty for using the Zero Power mode, but I don't understand how the internal logic or outputs handle the power down.

1. Is there someone at TI who can explain if our outputs are still driven when a power down occurs

2. How is the data that is internal to the PAL (saved states) kept valid, even in power down mode?

Thank you,

Louie

  • 0
    TI__Guru 62930 points
    Louie,
    unfortunately, these are some pretty old devices. I will see what information I can dig up to help answer this.
    Regards,
    Wade
  • 0 in reply to Wade Vonbergen
    TI__Guru 62930 points
    Louie,
    I did not find an description of exactly how the turbo bit works. However, it is clear that it only impact speed of the device. The outputs will still be driven.
    I am speculating that some internal biasing is disabled to save power when this is set. When a transition is detected, it must re-enable the biasing circuit to propagate the signal. This causes a delay.

    With all my research, the only impact I have noted is this is trade-off on performance and power.
    I am sure there is more accurate description of how this works somewhere. However, I am confident in answer above.
    If this answers your question, please click "This Resolved My Question"
    Regards,
    Wade
  • 0 in reply to Wade Vonbergen
    TI__Expert 3180 points
    Hello Wade,

    Just for clarification:
    1) You are stating that the outputs will still be driven when a power down occurs?
    Could you pull scope traces or show some kind of data to confirm this?
    2) You said that you speculate that an internal biasing is disabled to save power (power down mode), since there is a delay that happens when the biasing is re-enabled, could you also pull a scope trace of this as well?

    Thank you so much for the hard work,
    Louie
  • 0 in reply to Louie
    TI__Guru 62930 points
    Louie,
    Unfortunately I do not have units or a programming station readily available.
    However, it is conclusive that the device is still operational when turbo bit is off, and the device goes to "zero" power state. The zero power or power down terminology is misleading. It should really be called standby mode.
    Only dynamic parameters are affected by turbo mode. This can be seen from all the dynamic specifications.
    None of the DC specifications are impacted by turbo mode. Thus, they are still driven.
    Additionally, the zero power mode would be completely useless if it did not drive when going into standby.

    To specifically answer your questions.
    1) Yes
    2) The datasheet shows a normalized plot of propagation delay CLK to Q with turbo bit set and not. It also has plot of supply current vs frequency of both. As frequency increases the power savings of entering standby mode is diminished. Operation of the counter is not impacted when turbo mode is off. Additionally, all the AC parameters that are affected by turbo mode have separate specifications indicating the differences in limits.

    Regards,
    Wade