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DRV110APWR PICK bypassed

matt kinberger
Prodigy 50 points

Other Parts Discussed in Thread: DRV110

Greetings.

I am currently using a DRV110APWR driver to actuate a solenoid valve.  My configuration is such that pick time is 100mS (keep uF), Rsense is 1 ohm, OSC 100K, pick/hold current 1.2A/150mA (both 66.5K).  The circuit works appropriately 98% of the time, and occasionally glitches and goes directly to hold (pwm) after only 100uS.  The keep capacitor does not charge and the solenoid does not actuate.

There is a noise spike seen at Rsense when EN goes high, however filtering this has not resolved the issue.

The scope image below is a sample of a failed pick. 

ch 1:  Solenoid (pulled through an nds355an)

ch 2: EN line at pin 13

ch 3: Rsense

ch 4: Ckeep

Any help will be greatly appreciated.

  • 0
    TI__Genius 9975 points

    Hello Matt Kinberger,

    Welcome to our forums and thank you for your question.

    I will ask the person responsible for support of this product to reply to your inquiry.

    Best regards,

    Jose

  • 0 in reply to Jose Duenas
    TI__Intellectual 1915 points

    Matt, would you please give me more details about the solenoid i.e. inductance and serial resistor values Do you have a freewheeling diode across it? If so, which type and how many? Then at which voltage is operating?

    Best regards, Alain.

  • 0 in reply to AlainC
    Prodigy 50 points

    Of course, Alain thank you.

    The Solenoid is a 5V, 1.8W MAC valve (BV210A-CA1-00-BKSA-CBA) L=15 mH (as measured)

    I am concerned that the issue is occurring prior to the solenoid even being actuated, when the EN pin goes high (straight from MSP 430 @ 3.3V), the comparator is switching the VREF mux prematurely to VHold as described in my previous post.  VKeep sees a noise spike well before the gate drive turns the solenoid on.

    The DRV110 setup is here:

  • 0 in reply to matt kinberger
    TI__Intellectual 1915 points

    Thank you Matt! I realized this after asking the question as whatever inductance value it should not affect this keep function. Anyway, in a mean time I have asked design team to unarchive device database to see if we could reproduce this issue in simulation. I'll check and let you know the outcome (it might take at least a few days).

    Best regards, Alain. 

  • 0 in reply to AlainC
    TI__Intellectual 1915 points

    Answer is pretty strainght forward: the peak voltage seen on KEEP pin triggers the "KEEP" threshold of internal comparator therefore the device is automatically switching to the HOLD current regulation. So we need to understand the source of this spike, but we don't see how it could come from the device itself. Would it be possible that some cross coupling at PCB level may interfere with KEEP signal? I can review PCB layout if you'd like to see whether this could ocur or not.

    Best regards, Alain.