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CCS/BOOST-DRV8711: DRV8711

Ali El-Zaghal
Intellectual 280 points
Part Number: BOOST-DRV8711
Other Parts Discussed in Thread: DRV8711

Tool/software: Code Composer Studio

Hi,

I am using DRV8711 with brushed DC motor and there are two PWM modes configured using [PWMMODE] bit in TOFF register as follow:

0: Use internal indexer.
1: Bypass indexer, use xINx inputs to control outputs.

Then here i have two questions:

1. Can the internal indexer used to control the speed of brushed dc motor to avoid using external signals from the MCU's PWM modules and just configure it using SPI interface or it is only control the micro stepping of a stepper motor type !!

2. If it could be used only for stepper one then in section 7.3.4 "current regulation" in the data sheet, what is the meaning of the following sentence: 

* The current through the motor windings is regulated by an adjustable fixed-off-time PWM current regulation
   circuit.

, and could TOFF value changes on PWM duty in case of using brushed DC or it only regulates the current through stepper motor types !!

  • 0
    TI__Guru 56650 points

    Hello,

    1. If use the indexer mode, the output current can be changed as the table 4 lists AOUT and BOUT current. 

    I have question about "control the speed of brushed dc motor". Do you want to do close loop speed control or open loop speed control?

    BTW, if you know what output current you want, you just use Torque register to set that current up in "bypass indexer mode". I am not sure why do you want to use 'indexer mode" to set the output current?

    2. The current through the motor windings current is adjustable for both "Indexer mode" (for a stepper motor) or "Bypass indexer mode" (for a brushed motor).

    The winding current can be adjusted by changing Torque register value. Even the torque register value different to control the different winding current, the TOFF time can be fixed that will give a fixed PWM frequency with a certain operating condition to reduce the audible noise.

    Why do you want TOFF value change in a brushed motor application?