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DRV8881: Toff Period

Sagar Sadasivan
Prodigy 205 points
Part Number: DRV8881
Other Parts Discussed in Thread: DRV8886AT

Customer question:

"The DRV8881 describes a Toff time. From the datasheet it seems like Toff only comes into affect once the current threshold is hit. Does the Toff period also occur any time the PWM cycle goes low?

For example blue is the PWM signal with a 1us period. When it goes low, does Toff apply for 10, 20, or 30us until the output is driven high again with the next positive PWM pulse?"

  • 0
    TI__Guru** 114905 points
    Hi Sagar,

    You are correct. Once the current threshold is reached, the device switches to off time. The off time can be slow decay, mixed decay, or fast decay.

    Please note the output PWM frequency is determined by many factors, such as VM, VREF, sense resistor, and motor parameters. The frequency may change at each step in the indexer table.

    Have you considered using the DRV8886AT instead? If it meets your voltage and current requirements, the device is easier to use and requires fewer external components?