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Drv8837 drive questions

Guowen Sun
Prodigy 60 points
Other Parts Discussed in Thread: DRV8837, DRV8839, DRV8832

According to the datasheet, IN1 inputs PWM（high is 3.3V），IN2 inputs HIGH，then OUT1 outputs LOW and OUT2 outputs PWM(high is 5V)

IN2 inputs PWM（high is 3.3V），IN1 inputs HIGH，then OUT2 outputs LOW and OUT1 outputs PWM(high is 5V)

We can drive the coils with max 5V(it can be adjusted by PWM Duty Cycle) and can change its direction by input.

1. Is this circuit right?

2. I have tried three devices, Two of them are OK(They can achieve the function mentioned before). But the last one only can output one direction, It can not change its output direction even if I change its input. Is it because this device has been destroyed. It has a strange burned smell. But, I don't know how to result in this situation. Why this situation can happen?

3. Is it allow to input two HIGH at the same time? What should I take care when I use DRV8837?

4. Because of the load I connect is a coil(many circles of copper wires), it is a Inductive Element. It is Anti-EMF destroy the drv8837?How to Eliminate the Anti-EMF especially when we change the output direction. Is it OK for drv8837 in this condition if we do not add protective circuit? 

5. What is the PWM frequency range I can input?

6. Is it need to add Filter circuit after the dvr8837 output?  

7. If you have any advice, Please tell me.

Thank you!

  • 0
    TI__Expert 8885 points

    Guowen,

    1.  Is this circuit right?  Your understanding of device PWM logic is correct. Circuit seems to be right but i will confirm after knowing the value of R1/R2. Can you please tell me these values?

    2. Device failure: Is GND pad beneath the device soldered to GND. I do not see it in schematic. There is probability of device getting damaged due to over-temperature without floating GND Pad.

    3.  Is it allow to input two HIGH at the same time? Yes that's perfectly fine. Device has dead-time protection in build between top and bottom device, so you need not to worry about this.

    4. Because of the load I connect is a coil(many circles of copper wires), it is a Inductive Element. It is Anti-EMF destroy the drv8837?How to Eliminate the Anti-EMF especially when we change the output direction. Is it OK for drv8837 in this condition if we do not add protective circuit? 

    DRV8837 has inductive energy freewheeling doides, so it all right to connect inductive load across it. No external protection is required.

    5. What is the PWM frequency range I can input?

    Max frequency is limited by OUTput rise time+falltime+2* delay times with respect to IN signal. Refer to 6.6 of data-sheet, this comes to 700nsec , means max PWM can go upto 1.4MHz. Of-course device may get thermally limited before reaching such high frequencies.

    6. Is it need to add Filter circuit after the dvr8837 output? 

    This depends upon end-application requirments, typically motor drive application does not need external fitlter. You are better judge here to decide about this,

     7. If you have any advice, Please tell me

    check device GND PAD is connected and soldered properly to PCB GND.

    Best Regards

    Milan-Motor Application Team

  • 0 in reply to Milan Rajne
    Prodigy 60 points

    Hi  Milan，

    Thank you for your answer. R1=1ohm,R2=10 ohm and C3 are Filter circuit, But it does not make much difference from the experimental results. So I may remove it, drv8837 output connect to coils directly.

    I think the package of drv8837 is too small, it is hard to solder on the PCB, maybe we did not solder it well. So could you give me some advice, we want to repalce drv8837 by other device. Do you know other device that have the same function as drv8837. We have space for large package device. We just want the device could enhance the input PWM Vcc=3.3V to 5V PWM, and could be changed its output directon.

    Look forward to your answer.Thank you!

  • 0 in reply to Milan Rajne
    Prodigy 60 points

    Milan Rajne said:

    Guowen,

    1.  Is this circuit right?  Your understanding of device PWM logic is correct. Circuit seems to be right but i will confirm after knowing the value of R1/R2. Can you please tell me these values?

    2. Device failure: Is GND pad beneath the device soldered to GND. I do not see it in schematic. There is probability of device getting damaged due to over-temperature without floating GND Pad.

    3.  Is it allow to input two HIGH at the same time? Yes that's perfectly fine. Device has dead-time protection in build between top and bottom device, so you need not to worry about this.

    4. Because of the load I connect is a coil(many circles of copper wires), it is a Inductive Element. It is Anti-EMF destroy the drv8837?How to Eliminate the Anti-EMF especially when we change the output direction. Is it OK for drv8837 in this condition if we do not add protective circuit? 

    DRV8837 has inductive energy freewheeling doides, so it all right to connect inductive load across it. No external protection is required.

    5. What is the PWM frequency range I can input?

    Max frequency is limited by OUTput rise time+falltime+2* delay times with respect to IN signal. Refer to 6.6 of data-sheet, this comes to 700nsec , means max PWM can go upto 1.4MHz. Of-course device may get thermally limited before reaching such high frequencies.

    6. Is it need to add Filter circuit after the dvr8837 output? 

    This depends upon end-application requirments, typically motor drive application does not need external fitlter. You are better judge here to decide about this,

     7. If you have any advice, Please tell me

    check device GND PAD is connected and soldered properly to PCB GND.

    Best Regards

    Milan-Motor Application Team

    Hi  Milan，

    Thank you for your answer. R1=1ohm,R2=10 ohm and C3 are Filter circuit, But it does not make much difference from the experimental results. So I may remove it, drv8837 output connect to coils directly.

    I think the package of drv8837 is too small, it is hard to solder on the PCB, maybe we did not solder it well. So could you give me some advice, we want to repalce drv8837 by other device. Do you know other device that have the same function as drv8837. We have space for large package device. We just want the device could enhance the input PWM Vcc=3.3V to 5V PWM, and could be changed its output directon.

    Look forward to your answer.Thank you!

  • 0 in reply to Guowen Sun
    TI__Expert 8885 points

    Guowen,

    You may look into DRV8839 and DRV8832, they have bigger package than DRV8837.

    Best Regards

    Milan-Motor Application Team