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DRV8830: What is the update rate of the DRV8830?

Guru 10685 points
Part Number: DRV8830

I've read the datasheet and cannot see anything about how often the driver will respond to updates. Is it 10Hz? 100Hz?

How often can it change the output power?

Hope my question is clear. Thanks.

  • Hello Ralph,


    I will be happy to help you out today. The response rate of the driver will be dependendant on its internal PWM Frequency. This information can be found in section 6.5 of the datasheet detailing electrical characteristics. For this particular driver it will be at a rate of 44.5 KHz. 

    Let me know if you have any other questions.

    Best,

    Pedro Arango Ramirez

  • The PWM frequency (it should say "duty cycle") has nothing to do with how quickly the output updates. I am asking, if I toggle the DRV8830 output motor power between, say 0x0 and 0x30, how often will the actual output voltage change?

    Does this make my question clearer?

  • Hello Ralph, 

    I believe I understand your question, you are asking how much time will elapse between giving an input and see that input reflected as an output. If so: 

    The PWM frequency will be the main bottle neck on how quick the output updates based on a given input. This device is voltage controlled such that the internal PWM will vary its duty cycle to create an average voltage drop that is seen through the output of the motor. When using I2C the read and write timings will be extremely fast, in the us to ns range as shown in table 6.6.

    However these changes are essentially affecting the duty cycle of the internal PWM that is driving the FETS. Therefore the signal will update in the next PWM cycle, which is the same as the PWM frequency. 

    Additionally, there will be several different timings for different events, for example:

    • On startup the device must wait at least 60us after power is applied to VCC to generate a START condition. 
    • On overcurrent: The motor current is sensed by monitoring the voltage across an external sense resistor. When the voltage exceeds a reference voltage of 200 mV for more than approximately 3 µs, the PWM duty cycle is reduced to limit the current through the motor to this value.
      • An overcurrent event must persist for approximately 275 ms before the fault is registered. After approximately 275 ms, a fault signaled to the host by driving the FAULTn signal low and setting the FAULT and ILIMIT bits in the serial interface register. Operation of the motor driver will continue

    However for your specific question between toggling outputs between two commands the device will update as soon as the next PWM cycle begins which at the latest should be at a rate of 44.5kHz.  

    Please do let me know if you have any other questions. 

    Best,

    Pedro Arango Ramirez