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DRV8873: 100% duty without PWM

Taku Murayama
Intellectual 1220 points
Part Number: DRV8873
Other Parts Discussed in Thread: DRV8876

I have questions about the operation of two types of motor drivers, DRV8873 and DRV8876.

I am considering the above driver in the device currently under design.

As for control, we are considering operation at logic level by GPIO.
The “nSLEEP” and “disable” pins should be logically fixed because I/O of the CPU is insufficient.
If the “nSLEEP” and “disable” pins are fixed and the ph/EN control mode is set, the brake is the only way to stop the motor.
If possible, we would like to use the output as a Hi-Z state instead of a brake like a stop.
Therefore, in PWM control mode, “nSLEEP” and “disable” pins can be set to Hi-Z state by only logic change of the control line (IN1, IN2) with fixed pins. (Even if the speed change is required during the evaluation of the actual machine, the PWM mode can be supported, so it is also an insurance.)
Is this possible? (DRV8873 states that 100% duty is acceptable.)

  • 0
    TI__Mastermind 22200 points

    Hey Murayama-san,

    What is the current requirement of the design?  DRV8873 10A is much more than DRV8876 3.5A. 

    Would DRV8251A work for you? It has automatic sleep mode (OUT1 and OUT2 both Hi-Z) entered after both IN1 and IN2 == 0 for >1ms.  

    Then you only need 2 pins from MCU - IN1 and IN2.  

    Best,

    Jacob

  • 0 in reply to Jacob Thompson
    TI__Intellectual 2200 points

    Hi Jacob-san,

    Thank you for your answer.

    Customer is considering to use DRV8873 with 100% duty PWM.

    And they have question about current sensing of DRV8873. Could you support these please?

    1. Is it Ok to use equation: R(sense) = k * 5V / Io  in case of connecting of Fig.14 in datasheet?
    2. Does Rsense make V(PROPI) with I(PROPI)? 

    Many thanks,
    Goto

  • 0 in reply to Shuhei Goto
    TI__Mastermind 22200 points

    Hey Gotosan, 

    Shuhei Goto said:
    Is it Ok to use equation: R(sense) = k * 5V / Io  in case of connecting of Fig.14 in datasheet?

    Yes, equation is still corect even when connecting the sense resistors together.  Note that In this configuration, the current-sense output is proportional to the sum of the currents flowing through the both high-side FETs.

    Shuhei Goto said:
    Does Rsense make V(PROPI) with I(PROPI)? 

    Yes, exactly.  This allows a MCU ADC to read the device current instead of needing external current sensing.  

    Best,

    Jacob