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DRV8910-Q1: How to understand ACTIVE OLD

Oliver Tang
Genius 12290 points

Part Number: DRV8910-Q1

Hi Team,

I'm trying to understand why a false flag can occur during current re-circulation if synchronous rectification is ON?

Also why IOUT2_LS below IOLD will trigger a fault? Does it mean that detecting circuit is still active at falling edge of IOUT2_LS?

BR,

Oliver Tang

  • 0
    TI__Guru 55695 points

    Oliver,

    I have assigned this.  Please allow 24 hours for a response.

    Regards,

    Ryan

  • 0 in reply to Ryan Kehr
    TI__Mastermind 47965 points

    Hi Oliver,

    Thank you for your question. First of all, negative current flow is related to HS FET, not LS FET. 

    Please refer 8.3.3.5.1.1 Negative-current OLD in datasheet. 

    Figure 61 shows the negative current re-circulation through the high-side FET when synchronous rectification isON (i.e. HB2_FW = 1). In this scenario, HS FET is ON.  Although HS FET is ON, current is lower than the positive OLD threshold. Therefore the device can show a false open-load fault. 

    "Negative-current OLD mode" can avoid this false open-load fault. 

    regards

    Shinya Morita