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DRV8962EVM: 0.5 Volt Amplitude - 2.5 to 5 MHz noise in Current Reading Signals and PWM Signals

Amin Kamalzadeh
Prodigy 30 points
Part Number: DRV8962EVM

Hi,

I am using DRV8962EVM in an application for Brushless DC linear motor control.

A see a huge noise with 0.5 volt amplitude at 2.5-5 Mhz, only when turning on the power supply to the DRV8962EVM board.

The noise appears to be in the (shunts) current reading outputs of the board (J17, J18, J20), and also at the PWM signals injected into the board from a STM32f405 discovery board. The PWM signals are clean (no noise) when the DRV8962EVM board power is disconnected.

I appreciate your help on resolving this noise issue.

We do need a cleaner current reading feedback from the board to implement some current-signal-based algorithm.

Thank you,

Amin Kamalzadeh

  • 0
    TI__Expert 6750 points

    Hi Amin,

    If possible could you provide answers to the following questions to better diagnose this issue:

    Is there a common ground between the STM32f405 discovery board and the DRV8962EVM?

    How long is the PWM signal wire?

    Were the appropriate jumpers removed from J4, J8 headers for you PWM signal?

    Is the noise present without the injected PWM with only EVM running?

    Also, could you please provide the following:

    - Motor voltage, VM

    - frequency

    - Current and voltage readings from o-scope

    Best,

    David

  • 0 in reply to David Medis
    Prodigy 30 points

    Hi David,

    Thanks a lot for your follow up.

    Yes, there is a common ground between STM32f405 and DRV8962EVM.

    The PWM wires are about 20 cm in length.

    Yes jumpers on the PWM signal and enable pins have been removed from J4 & J8.

    The noise disappears from the PWM signals on STM32f405 if I disconnect the PWM wires from DRV8962EVM. As soon as the PWM signals is engaged with the DRV, the noise appears on the PWM signals. Also if I disconnect the VIN power, and  DRV8962EVM is powered only through USB, the noise is not there. However the signals of VIN power supply connector on DRV8962EVM is also clean of that noise, so the noise is not from the power supply.

    Motor voltage is connected to 0-24 volt power supply. So max voltage is 24 volt. But at no load condition, the mean voltage is about 12 volts.

    PWM frequency is 164 KHz

    Voltage reading from the scope on 3 motor lines look like a PWM at 164 kHz with mean value of ~12 volt on 3 motor ends.

    Current reading from the J17, J18, and J20 are also close to zero at no load condition.

    Thank you,

    Amin

  • 0 in reply to Amin Kamalzadeh
    TI__Mastermind 19010 points

    Hey Amin,

    Thanks for all the info! 

    Do you see this noise on the VM line or only the PWM input lines?  

    And does this voltage noise occur when you aren't driving the motor, like when nSLEEP is LOW?  I'm wondering if this is from your power supply and only manifests above a certain current level, such as when the motor is spinning even at no-load.  Do you have a different power supply you could try, or maybe just a 12V battery? 

    Have you tried a different USB cable/port or another computer/dock?  Trying to rule out if this is USB-related noise since it's such a high frequency.  

    I've asked some more experienced coworkers for help and will let you know what they tell me as well.  

    Regards,

    Jacob