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DRV8837: CE Emission Failure

Part Number: DRV8837

I am failing a CE emissions test with peaks that starting around 150mhz to 190mhz. One I remove the DRV8837 from the circuit the peaks disappear. I know the IC has built in charge pump running 30mhz..35mhz and this is exactly the spacing I see marker to market of the peaks. I am thinking that the peaks are a harmonic of the charge pump frequency. Is this a good assumption and what has been done in the past to fix the issue. I have 2 .1uf caps on 3.3vdc power pic and same on the VM power pins as close to the IC as possible.  

  • Hi Richard,

    Thanks for your question. Let me check with my team on this issue.

    James Lockridge

    Motor Drives

  • In reply to James Lockridge19:

    Hi Richard,

    In the past, we have seen customers reduce emissions when they try the following things:

    - Place a 10 nF capacitor between OUT1 and OUT2. Do this as close to the IC pins as possible.
    - Add a 1 uF capacitor on the VCC pin and the VM pin in addition to the 0.1 uF capacitor. Make sure the 0.1 uf capacitor is closer to the IC.
    - Use at least 10 uF capacitor on VM for bulk capacitor.
    - Emissions also decrease if you use a lower supply voltage (if possible).

    James Lockridge

    Motor Drives

  • In reply to James Lockridge19:

    Mr Lockridge,

    Thank you for the prompt reply. I will be prototyping soon and retesting. I have one other question: if we do not have success in passing CE testing is there another IC H-Bridge motor driver in the family that operates similar and is known for having less emissions? 2A output or so. Static IN1 and IN2 inputs with no PWM.....For my future design are there plans for any new drivers with maybe 3A to 5A capability?

    Thank You.

    Rick Brannan  

  • In reply to Richard Brannan:

    Rick,

    What supply rail voltage do you need? Also, do you only want to drive one motor from the IC, or would you also be interested in devices that can drive two motors?

    James Lockridge

    Motor Drives

  • In reply to James Lockridge19:

    I am running VCC at 3.3VDC and VM at 6VDC. Battery operated dispenser. I only need to drive one motor. I am using a microchip PIC if that matters and consuming about 150ua when the motor is not running. The motor will have startup current to the 1.8A max limited and then run on about 120ma for 600 mili seconds. It is only while motor is running that we fail the test. IE when DRV8837 is in sleep mode there are acceptable emissions. Also unhooking motor completely does not get rid of the noise.

    Thank You.
  • In reply to Richard Brannan:

    Richard,

    I haven't heard of any issues on the DRV8830/2/4/6 devices, so those may be ones to consider.

    We have some new devices that may also work for you. We are currently sampling them. The DRV8847 and DRV8876 I tested for radiated emissions myself on the EVM, and the results are good. They can do about 2 A and 1.7 A RMS current, respectively. The DRV8873-Q1 should be able to do a bit more than 3.5 A RMS. If you need much higher currents, the DRV8412 and DRV8413 are other devices to consider.

    James Lockridge

    Motor Drives