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DRV8432EVM issues with Dual Full Bridge with Single pwm in

Shane Corbin
Prodigy 70 points

I am using the DRV8432EVM to power 2 DC motors in dual full bridge mode with a single PWM input(PWM_A).  I have the motor hooked up accross OUT_A and OUT_B as suggested by the datasheet Page 15 Figure 8.   The problem is that instead of a 12V pwm signal(0Vlo to 12Vhi) in either the positive or negative region I get a 24V pwm signal(-12Vlo to +12Vhi) giving me an average voltage of 0 and hence no power.  The datasheet does does say that in this mode PWM_B complements PWM_A... I don't see the usefullness of this mode if this is the recommended circuit.  I am thinking I need to switch to dual full bridge with 2PWM and leave one of the two outputs at 0% duty cycle and just drive one at a time.   Could someone please help shed some light on this situation please.  I am confusing myself trying to figure this out.

Thanks in advance,

Shane

  • 0
    TI__Expert 3405 points

    Hi Shane,

    Make sure you have GND_A and GND_B connected to ground and the PVDD_A and PVDD_B connected to +12V.  To make things easier, you may want to make sure you have the device in mode 4 as described on page 14.  In order to put the device in Mode 4, follow the table on page 3 in the datasheet setting M3 to "0", M2 to "1", and M2 to "1".  Now when you change the voltage at PWM_A you should see the state change from +12VDC as meansured from OUT_A to OUT_B to +12VDC as measured from OUT_B to OUT_A.