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DRV8256: How to chose TOFF pin setting

Toshiaki Yamada
Prodigy 40 points
Part Number: DRV8256

Hi

I will use DRV8256 with Smart tune Ripple Control mode (slow DECAY mode). 

I would like to know how to set TOFF pin.

Should I set "1" (High) the same as DECAY mode ("1") or is there any method to select this setting?

B.R, Yamada

  • +1
    Prodigy 40 points

    To be honest I can not understand the description in Chapter 7.3.2 in the specification document.

  • 0 in reply to Toshiaki Yamada
    TI__Guru 55335 points

    Yamada-san,

    Toff is not applicable to Smart Tune Ripple control.  It has no effect when in this decay setting, so you can choose anything for this pin.

    Instead of using TOFF like the other decay modes, STRC uses a Peak and Valley current to determine off time.  Off time is then variable depending on current in the winding.

    Section from datasheet below:

    Smart tune Ripple Control operates by setting an IVALLEY level alongside the ITRIP level. When the current level reaches ITRIP, instead of entering slow decay until the tOFF time expires, the driver enters slow decay until IVALLEY is reached. Slow decay operates similar to mode 1 in which both low-side MOSFETs are turned on allowing the current to recirculate. In this mode, tOFF varies depending on the current level and operating conditions.

    Regards,

    Ryan