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DRV8231A: design question for the camera shutter application

Part Number: DRV8231A

Tool/software:

Hi Sir,

My customer would like to use DRV8231A to control the shutter motor on the digital camera.

But they found the sawtooth wave in the output current, which will cause abnormal shutter operation.

Since the competitor IC G2015 witch can provide a flat square wave in output current, Can DRV8231A provide the same output current with G2015? (refer to the below test report)

If DRV8231A cannot support it, please advise a correct solution. Thanks!

The below is design condition:

Shutter driver current: need constant current, 270mA(+/- 5%).
Resistance of Lens coil for shutter: 22 Ohm(+/- 10%).
Vm = 7.27V = 0.27*(Rdson+Rrnf+Rmotor)

DRV8231A and G2015 test report: DRV8231A and G2015 test report.xlsx

G2015 datasheet: 1212.G2015.pdf

The control current waveform on shutter motor module.

  • Hi Henry,

    The DRV8231A device employs a fixed off-time current regulation technique using current chopping to achieve efficient current control. This current chopping will cause the current waveform to rise and fall to maintain it's set current value. 

    What's the concern of using this fixed off time to control the current? Is there any difficulty driving the load?

    Best,

    David

  • Hi Sir,

    The customer would like the output current at 270mA(+/- 5%), how to modify the circuit to do that? could you please advise some comments? Thanks!

  • Hi Henry, 

    This looks to be the correct setup to set ITRIP = 270mA. 

    VREF = 3V

    RIPROPI = 7320

    AIPROPI = 1500uA/A

    ITRIP (A) x AIPROPI (μA/A) = VVREF (V) / RIPROPI (Ω)  

    What's the stall current and continuous current rating of the motor being used? Usually "shutter motors" are similar to a brushed-DC motor with these same ratings.

    Best,

    David

  • Hi Sir,

    Sorry, the shutter motor module did not have these parameters by you mentioned.

    Since the Ton time only has 15 msec, so the customer think they measured output current waveform is Inrush Current + Average Running Current + Stall Current, refer to the datasheet section 9.2.1.3.

    May I know there have any motor driver ICs same as the competitor device G2015 to operate circuit current for CC mode, and VM support up to 7.5V?

  • Hi Henry, 

    Unfortunately, we don't have any motor drivers that supports constant current control. The DRV8231A is primarily designed for voltage-based motor control, not constant current control. Most of our integrated motor drivers support current regulation, allows the device to limit the output current with a fixed off-time PWM chopping scheme. The VREF pin configures the current regulation level during motor operation to limit the load current.

    Best,

    David