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UCC21710-Q1: FLT and RDY recovery condition

Part Number: UCC21710-Q1

Hi team,

My customer asks following questions, could you support?

(1) RDY condition in Table 3

In Table3, why does RDY stay HiZ while VCC is in PD?

(2) RDY recovery condition

Recovery from VCC/VDD under voltage : tRDYHLD time elapsed after VCC or VDD recover and exceed VCC_ON or VDD_ON threshold respectively, 

Recover from VDD/VEE open : similar to recovery from under voltage case?

(3) independency between RDY and FLT

FLT is related to OC, RDY is related to power supply condition, so FLT and RDY are independent each other also in recovery condition.

Is it correct?

best regards,

  • Hi,

    Due to US holiday, our expert will address your questions early next week when he is back in the office.

    Thanks,

    Krystian 

  • Hi Fujihara-san,

    Welcome to E2E!

    I can definitely help support! Find my comments to your questions below:

    1. This is likely a typo as it should not be the case. With VCC PD the status of RDY should be low as described in Section "8.3.3 VCC and VDD Undervoltage Lockout (UVLO)".

    2. tRDYHLD is the minimum time the RDY signal will remain low once its been triggered after a UVLO is detected. Once UVLO is detected the device will do one of three things:

    i. VDD/VCC recovers before tRDYHLD has elapsed

    • Device will wait for tRDYHLD to elapse
    • Once tRDYHLD has passed, the output will go back high along with RDY(1 in the image below)

    ii. VDD/VCC recover after tRDYHLD has elapsed

    • The output of the device will follow the same turn on timing characteristics (2 in the image below)

    iii. VDD/VCC never recovers

    • RDY will remain low and driver will remain off

    3. That is correct. FLT and RDY and independent from each other. A UVLO event will not trigger FLT.

    Best regards,

    Andy Robles