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DRV8847: current regulation and Vext

Masaharu Takahashi
Expert 4170 points
Part Number: DRV8847

hi, All.

i've been asked by customer for below question.

please support it.

Q1

correct for below?

in case of 100% TRQ(connect to GND), should Torque be "1"

in case of 50% TRQ(connect to Vext, should Torque be "0.5"

the following sentence is confused.

"Torque is the torque scalar, the value of which depends on the input on TRQ pin. "

it sounds like that there are + polarity figure on TRQ.

there are only 2 thing on Torque such as 1 or 0.5. right ?

in case of 0.5,  we can see "0.5" but not for "1" but Torque.

Q2.

what is the Vext ?

there are nothing description about Vext.

should customer use voltage same as VM or any specification ?

Q3.

is it ok if we could make TRQ pin floating if customer doesnt use?.

  • 0
    TI__Guru 56650 points
    Masaharu-san,

    Sorry for the delay.
    1. Yes. in case of 100% TRQ(connect to GND), should Torque be "1"; in case of 50% TRQ(connect to Vext, should Torque be "0.5".
    Yes. TQR only has two options: 0.5 or 1.
    2. Vext should be external supply for logic circuit. Page 17 note (1) has the definition. Also, you can find Vext on Figure 15, 16. It could be a pull-up source for logic circuit, nFault pin, TRQ pin.... So, the voltage range should follow the TRQ pin spec or any pin spec which uses Vext as a pull-up source.
    3. Firgure 15 shows the TRQ pin has an internal pull-down resistor. If you leave TRQ pin float, it will be low.
  • 0 in reply to Wang5577
    TI__Expert 4170 points
    hi, Wang-san.

    thanks your answer.
    does it mean that customer can make it floating . right?
  • 0 in reply to Masaharu Takahashi
    TI__Guru 56650 points
    Masaharu-san,

    Firgure 15 shows the TRQ pin has an internal pull-down resistor. If you leave TRQ pin float, it will be low. Torque be "1".