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Original question:

DRV8432: DRV8432 in parallel full bridge mode to drive Peltier Module for heating and cooling - using EVAL8432 and own d...

DRV8432: PFB mode PWM

Sepeedah Zadeh
Expert 3140 points

Part Number: DRV8432

Hello team, 

My customer is trying to drive a consistent 14A load for an hour at a time with capabilities to switch current direction and maintain a constant current set point even if  resistance in the circuit is drifting. Would this be the appropriate device? I am still trying to understand what the load is and what motor voltage they need.

To achieve this we'd need to use Mode 3 of DRV8432. Datasheet is unclear about how to set input PWM in order to change direction. There is a mention that PWM_A and PWM_B are synchronized internally, what does that mean actually? Below is my understanding of how the input PWM signals should be used, please confirm. 

- For direction 1: PWM_A with desired duty cycle-MIN, PWM_B is low (a min of 1% is still needed to not stay in OC mode?)

- For direction 2: PWM_A is low (MIn 1% duty cycle needed), PWM_B with desired dutycycle -MIN

Thanks, 

Sepeedah

  • 0
    TI__Guru 56650 points

    Sepeedah,

    DRV8432 can support 14-A Continuous Current in Parallel Mode. But, please verify the thermal performance.

    If put bridge A and bridge B outputs together, we have to make sure both high side FETs synchronized on A bridge and B bridge.

    In parallel full bridge mode (mode 3), PWM_A controls both half bridges A and B, and PWM_B controls both half bridges C and D, while PWM_C and PWM_D pins are not used.

    Please check figure 15 for the parallel mode operation.

    One direction: PWM_A and PWM_B do PWM. PWM_C and PWM_D are low side FET on.

    Another direction:  PWM_C and PWM_D do PWM. PWM_A and PWM_B are low side FET on.

  • 0 in reply to Wang5577
    TI__Expert 3140 points

    Thank you Wang for the quick response. However I am still not clear what kind of PWM input I need to use for PWM_A and PWM_B and how to change direction in mode3. 

    You say:

    "Another direction:  PWM_C and PWM_D do PWM. PWM_A and PWM_B are low side FET on."

    However, PWM_C and PWM_D inputs are grounded in Mode 3, so how does that work? I may be misunderstanding here, so please clarify. Also the datasheet is lacking critical information regarding Mode 3 operation, do we have any other documentation that provides more detail on this mode?

    Best,

    Sepeedah

  • 0 in reply to Sepeedah Zadeh
    TI__Guru 56650 points

    Sepeedah,

    When the direction change requires the winding direction change.  Please check Figure 15.

    One direction: OUT_A and OUT_B do the PWM to regulate the winding current; OUT_C and OUT_D low side FETs are on with a small turn-on duty cycle.

    Another direction: OUT_C and OUT_D do the PWM to regulate the winding current; OUT_A and OUT_B low side FETs are on with a small turn-on duty cycle.