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LM74701-Q1: ENTDLY and T(DRV_EN)

Masatoshi Oguri
Expert 4780 points
Part Number: LM74701-Q1

Hello,

There are 2 similar parameters in the datasheet: ENTDLY and T(DRV_EN). I would like you to confirm if the 75us in the below equation in p.12 of the datasheet is actually ENTDRY.

T(DRV_EN) = 75 µs + C(VCAP) × V(VCAP_UVLOR) / 300uA

I guess the above equation is the only correct information about ENTDLY and T(DRV_EN), otherwise full of wrong information. In the figure 8-1 in the same page, there is no 75us (or it might be too short to be obvious in the figure). In p.6 ENTDLY is defined as “Enable (low to high) to Gate Turn On delay” with 75us (typ). But I believe 75us is too short for CVCAP to charge up to V(VCAP_UVLOR). I guess it should be the same 75us above. Moreover in the top figure in p.10, ENTDLY is the time to CVCAP to charge up to 90%. But 75us is again too short for it. So I would like you to confirm that ENTDLY is actually the time from EN to the charge pump to start charging, then for the gate driver to enable there will be the time to charge CVCAP as defined by the above equation.

Thank you.

Regards,

Oguri (TIJ automotive FAE)

  • 0
    TI__Guru 57737 points

    Hi Oguri,

    When the enable is pulled low, the charge pump is disabled. The charge pump will slowly discharge.

    TDRV_EN is applicable when the EN is pulled high during initial startup or when the charge pump capacitor is completely discharged.

    ENTDLY is applicable when EN is pulled high with charge pump capacitor voltage already > UVLO threshold which means the charge pump cap has not yet completely discharged. This can happen when the EN pin toggled OFF  and ON before the charge pump is discharged.  

    For most of the application use cases, TDRV_EN may be relevant and applicable.