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DRV 8432 in PWM and Dir mode

Derrek Curtis
Prodigy 20 points
Other Parts Discussed in Thread: LMD18201, DRV8412

Hello,

Im migraitng for a lmd18201 h bridge design to the DRV8432  I need a way to drive the H bridge in the same PWM and Dir format that I am currently using.  I will be using the DRV 8432 as a dual servo motor driverer.

 

Thanks

Derrek

  • 0
    TI__Guru** 114905 points

    Hi Derrek,

    The DRV8432 can be used to emulate PWM and DIR of the LMD18201 by using PWM_x and RESET_xx. For most settings, the pair of PWM_A/B or PWM_C/D are used to provide the desired drive. RESET_xx is used to set the output pairs into a high impedance state.

    Have you looked at the DRV8412 also. It is a lower current version of the DRV8432 that may fit your requirements.

  • 0 in reply to Rick Duncan
    Prodigy 20 points

    Rick,

    I looked at the drv8412 also as its specs are closer to the lmd18201 but the motors that I am driving are larger and I wanted some " headroom" just in case my calculations are off.

    So from your responce I would drive both PWM pairs A/B with the same PWM and use the reset pins for that pair as direction driving them out of phase ( one up one down is one direction the reverse is reversed).  Is there anything else I should know before going to layout.

     

    -Derrek

  • 0 in reply to Derrek Curtis
    TI__Guru** 114905 points

    Derrek,

    May I suggest that you order a DRV8432EVM from the TI estore? It is available for evaluation of the device and can save time in the long run.

    Also, the schematics and board files for the EVM are available at the DRV8432EVM product folder under Software. A zipped file contains this information.

    To completely match the truth table of the LMD18201, it appears as though M3/2/1 should be 000 (Dual Full bridge with cycle by cycle limit). This requires PWMA and PWMB to be driven separately, but allows all output conditions of the LMD18201 to be met.

    A few items to be aware of:
    1) The bootstrap architecture may be different. The DRV8432 cannot be operated at 100% duty cycle. Also please note the requested addition of a 5 Ohm resistor if using a cap larger than 220nF (page 11 under "Bootstrap Capacitor Under Voltage Protection".
    2) The cycle by cycle limit will disable both sides of the outputs when exceeded (OUT_A and OUT_B will enter high Z). To re-enable the outputs, both PWM_A and PWM_B must be pulsed. There is no FAULT indicator for this condition.

    There is more information on this subject at http://e2e.ti.com/support/applications/motor_drivers/f/38/p/296453/1033426.aspx#1033426