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DRV8412: DRV8412/8432/8332 variable current limit

Jan Zavrtalek
Prodigy 10 points
Part Number: DRV8412
Other Parts Discussed in Thread: DRV8962, , DRV8462

Hello, on DRV84x2 there is OC_ADJ pin to set current limit by resistor to AGND. Is it possible to use it as a variable current limit by appling external voltage or current by DAC?

I am thinking of the simplest option: to use MCU voltage DAC connected to OC_ADJ thru resistor. Is this possible?

Thank you, Jan

  • +1
    TI__Mastermind 37683 points

    Hi Jan,

    Jan Zavrtalek said:
    Is it possible to use it as a variable current limit by appling external voltage or current by DAC?

    Technically it may work but it is not recommended. A voltage is generated at the OC_ADJ pin by the driver sourcing a fix current to the external resistor. The voltage is then compared internally to set the appropriate OC limit. For this to work, the OC_ADJ voltage for each OC level needs to be know (shown below). If the sourcing current at the OC_ADJ pin is known, the voltage for each level can be easily calculated by multiplying the current with the resistance. However, in order for the device to remain operational during OC limiting, the OC protection type should be set to CBC (cycle-by-cycle) which does not support 100% duty cycle driving. OC latching  (other protection type) will latched the outputs during OC protection.

    Are you open to using another driver? We have the DRV8462/DRV8962 which is similar in spec to the DRV8412. The main exception being the lower operation PWM frequency of the DRV8462/8962. These two devices have built in current regulation that can be adjusted with a reference voltage pin. 

    Regards,

    Pablo Armet

  • 0 in reply to Pablo Armet
    Prodigy 10 points

    Hi Pablo, thank you for your answer.
    Currently we use DRV8432DKDR with parallel outputs to deliver current between 2 and 15 Amps at 30 Volts. Peak current limit is Cycle-By-Cycle in DRV8432, and software current limiting (torque control) is done in MCU.
    Because we want to simplify the design, I consider to (1) avoid current sense resistors and (2) use cheap 8bit MCU. So we need to offload software torque control.
    I am happy that you confirm me that the proposed method is possible.

    DRV8962DDVR seems to be ideal solution, I will use it as soon as it is available. So far I found it only in DDW package (only 5 Amps per output).
    Best regards, Jan