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TCAN1473-Q1: Question about Normal mode to Sleep mode

Chase Jeong
Mastermind 7730 points
Part Number: TCAN1473-Q1


Tool/software:

Dear TI experts,

I got a question from my customer about Normal mode to Sleep mode.

In the page 26 of datasheet, I can see Device Functional Modes.

1. To go to "Go-to-sleep-mode" from "Normal mode", I should apply EN=Hign and nSTB=Low.

2. To go to "Sleep mode" from "Go-to-sleep-mode", I just do nothing, just t_GOTOSLEEP(min 20us~max 50us) passes, device will automatically go to "Sleep mode" from "Go-to-sleep-mode". -> Am I right?

3. Anyway my customer has to make minimum current consumption, so my customer has to make EN pin to low as fast as they can.

So here are my questions;

1) Can TCAN1473-Q1 maintain "Sleep mode" even EN pin is floating after the device is successfully go to "Sleep mode"?

2) What is the stable maximum time which is from "Normal mode" to "Sleep mode"?

I am asking it because "Go-to-sleep-mode" is just the passing state, and maybe you have the information about the maximum time from "Normal mode" to "Sleep mode" including t_GOTOSLEEP.

For example, It takes 100us including t_GOTOSLEEP from "Normal mode" to "Sleep mode" successfully, my customer can make EN pin floating exactly after 100us for minimum current consumption.

3) Similar as question 1. In the table 7-4, it says that Sleep mode is EN=High and nSTB=Low. But I want to know the device can maintain "sleep mode" even EN pin changes to floating once the device is go to "sleep mode" successfully.

Please check these issues. Thanks.

Best regards,

Chase

  • 0
    TI__Genius 14532 points

    Hi Chase,

    Thanks for reaching out!

    Chase Jeong said:
    2. To go to "Sleep mode" from "Go-to-sleep-mode", I just do nothing, just t_GOTOSLEEP(min 20us~max 50us) passes, device will automatically go to "Sleep mode" from "Go-to-sleep-mode". -> Am I right?

    Yes, but to be clear EN must high and a time greater than tGOTOSLEEP must pass first. Both of these conditions are necessary.

    Chase Jeong said:
    1) Can TCAN1473-Q1 maintain "Sleep mode" even EN pin is floating after the device is successfully go to "Sleep mode"?

    Yes, EN can be floating while TCAN473 is in Sleep mode. 

    Chase Jeong said:
    2) What is the stable maximum time which is from "Normal mode" to "Sleep mode"?

    This is still the tGOTOSLEEP time which has a maximum of 50us. This value can be used as the longest time it will take before the device enters Sleep mode where INH will be high impedance. Note that a pull down resistor should be added to the INH pin for a quicker transition to GND since this pin is high impedance and not driven low. 

    Chase Jeong said:
    3) Similar as question 1. In the table 7-4, it says that Sleep mode is EN=High and nSTB=Low. But I want to know the device can maintain "sleep mode" even EN pin changes to floating once the device is go to "sleep mode" successfully.

    Once TCAN1473 is in Sleep mode, EN is irrelevant. It can be either high, low or floating to save power. 

    Leaving Sleep mode largely depends on the VIO and VCC supplies and the nSTB pin, while EN level merely determines which mode it will enter into. This is detailed in the state machine which you shared above.

    Let me know if that helps or if you have any further questions!

    -Ethan

  • 0 in reply to Ethan Sempsrott
    Mastermind 7730 points

    Dear Ethan,

    Thank you for your support.

    Let me ask you more about Q2.

    It seems that it takes very very little time (maybe ignorable) from "Normal mode" to "Go-to-sleep mode" because you said  that 50us is longest time from "Niormal mode" to "Sleep mode". And this maximum 50us is same as the time from "Go-to-sleep mode" to "Sleep mode".

    Could confirm once again that my thinking is right?

    Best regards,

    Chase

  • 0 in reply to Chase Jeong
    TI__Genius 14532 points

    Hi Chase,

    I double checked with our design engineer just to be sure, and the total time is indeed tGOTOSLEEP (50us) from Normal mode to Sleep mode. 

    Let us know if you have any other questions!

    -Ethan