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DRV8662EVM: fail to output with the External Analog Input Mode and External PWM Input Mode

Boyuan Huang
Prodigy 135 points
Part Number: DRV8662EVM
Other Parts Discussed in Thread: DRV8662

Hello team,

I use the DRV8662EVM to output a ±100V signal. When I choose the External Analog Input Mode, the external input signal I use is a 250Hz 1.8Vpp sine wave and when I choose External PWM Input Mode the input signal is a 10KHz 1.8Vp PWM wave. But both of them cannot achieve ±100V, so

1. Where is the problem?

2. What are your suggest signal when I choose External Analog Input Mode and External PWM Input Mode?

Best wishes,

Boyuan Huang

  • 0
    TI__Genius 17660 points

    Hello Boyuan, 

    I am looking into this but I have a few questions for you in the meantime.

    Does your board give you the expected output voltage when using the included waveforms?

    What voltage are you getting on the output when using your external signals?

    Lastly, can you confirm that you are using a second order filter for your 10kHz PWM signal?

    Thank you, 

    Justin Beigel

  • 0 in reply to Justin Beigel
    Prodigy 135 points

    Hi Justin,

    1. This board does not give the waveforms I expected.

    2. The voltage I get is 0V when I choose Mode 8 in  in Table 2. Default EVM Modes

    3. I do not connect the external filter, I just use the DRV8662 EVM, it contains the second order filter I think.

    Best wishes,

    Boyuan Huang

  • 0 in reply to Boyuan Huang
    TI__Guru* 95175 points

    Hi Boyuan,

    We'll take a look at your inputs and provide further comments as soon as possible,

    Best regards,
    -Ivan Salazar
    Applications Engineer - Low Power Audio & Actuators

  • 0 in reply to Ivan Salazar
    Prodigy 135 points

    Hi Ivan,

    Do you find the solution to my problems? I am looking forward to your respond as soon as possible, because this is a urgent and important part in our program. Thanks a lot.

    Best wishes,

    Boyuan Huang

  • 0 in reply to Boyuan Huang
    TI__Genius 17660 points

    Hello Boyuan, 

    I have not been able to recreate the problem yet. In the meantime, lets try to figure out why you do not have the correct output when using the example waveforms.

    1. What voltage are you using for Vbat? 
    2. What is the capacitance of your load? 
    3. What is the rated voltage of your load? 

    Best Regards, 

    Justin Beigel

  • 0 in reply to Justin Beigel
    Prodigy 135 points

    Hi Justin,

    1. I use 3.7V voltage for the power supply, therefore Vbat is 3.7V in the schematic in the file I send you.

    2. I use oscilloscope to test the output voltage, so there is actually no load, or you can say the load is an oscilloscope.

    3. the same as the question 2.

    So, Why do I get 0V when I choose Mode 8? Do you have the same problem when you do the same operation? Could you please write me the step you did when you operate a DRV8662 EVM without copying from the file? Maybe I could find more details from your descriptions, which could be helpful for me.

    Best wishes,

    Boyuan Huang

  • 0 in reply to Boyuan Huang
    TI__Genius 17660 points

    Hello Boyuan, 

    I am not seeing the same problem with my EVM. Here are the steps I am taking to test: 

    1. Connect the oscilloscope and load to the EVM 
      1. I did test with and without the load 
    2. Remove the jumpers JP2 and JP3
    3. Connect the EVM to power
      1. I used 3.3V for this
    4. Turn on the power 
    5. Put the EVM in mode 8 (all LEDs lit up)
    6. Start the external input
      1. Differential sine wave at 1.8Vpp and 250Hz

    Without the load, the output waveform is smaller than with the load but I still have an output with a higher voltage than my input. With the EVM, I left the low pass input filter on when using an analog input because the frequency of the sine wave is low enough that it is not an issue. 

    Are these the same steps that you have been using? 

    Best Regards, 
    Justin Beigel

  • 0 in reply to Justin Beigel
    Prodigy 135 points

    Hi Justin,

    I do did the same steps as you did, you said "Without the load, the output waveform is smaller than with the load but I still have an output with a higher voltage than my input. " Could you please show me the figure of the output? Maybe I could see it more clearly.

    What do you mean " With the EVM, I left the low pass input filter on when using an analog input" ? How to leave the low pass filter on? Just connecting the input sine wave at 1.8Vpp and 250Hz to the input port without JP2 and JP3 means the low pass filter on?

    Best wishes,

    Boyuan Huang

  • 0 in reply to Boyuan Huang
    TI__Genius 17660 points

    Hello Boyuan, 

    For the unloaded test, I got a 21.27Vpp output with a 1.8Vpp input. Here is a capture of the output: 

    When I say I left the filter, I just mean that I did not remove it. Sometimes the filter will be removed (desoldered) if not using a PWM input but it is not necessary to remove since we are testing with both analog input and a PWM. The only modification I made to the EVM was to remove those two jumpers. 

    Best Regards, 
    Justin Beigel

  • 0 in reply to Justin Beigel
    TI__Genius 17660 points

    Hello Boyuan,

    Since I haven't heard from you in a while, I am closing this thread. If you have any other questions, feel free to respond here or open a new thread.

    Best Regards
    Justin Beigel