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DRV2700: How to Select DRV2700 EVM Options to Support 30uF Load?

Wayne Chen (ex FAE)
Guru 15950 points
Part Number: DRV2700

Hi Sirs,

We are surveying the DRV2700 to support 5uF piezo actuator with 4 ~ 6 pcs in parallel with 200Vpp output, thus the total load capacitance should be around 20uF~30uF. Can we drive those units with single DRV2700 device? There are DRV2700EVM and DRV2700EVM-HV500 options. Which option is ok for 30uF load capacitance?  

Thank you and Bets regards,

Wayne Chen
02/20/2017

  • 0
    TI__Guru* 95175 points
    Hi Wayne,

    I moved your post to the Haptics forum. My colleague might be able to provide you better support on this device.

    Best regards,
    -Ivan Salazar
    Texas Instruments
  • 0 in reply to Ivan Salazar
    Guru 15950 points
    Thank you Ivan,

    We have another idea to use four 3.7uF piezo actuators in series. With 480V outut configuration, we can apply 120V to each actuator with 0.93uF capacitance totally. Is this idea doable to drive four piezo actuators with single DRV2700?

    By the way, does the DRV2700 support 10Hz to 200Hz otuput range?

    Thank you and Best regards,

    Wayne Chen
    02/21/2017
  • 0 in reply to Wayne Chen (ex FAE)
    TI__Expert 8701 points

    Hi Wayne,

    The DRV2700EVM can drive up to 100Vp, 200Vpp - differentially, across the outputs. The DRV2700EVM-HV500 can drive up to 500Vp on a single ended output. For each EVM, the output capacitance will directly effect the output bandwidth. The bandwidth is also dependent on the boost voltage. This is shown in figures 9-12 of the datasheet. Reference figure 12: boost = 105V; max frequency for a 1uF load is ~30Hz.

    For a 30uF load, the boost voltage of the DRV2700 will most likely sag or decrease when the output is activated. This is because the part cannot source enough current to charge the large capacitive load. After some time (>1s), the load will be charged to 100V. When you switch to charge the OUT- terminal, the boost will again decrease as the part fights to charge the load. So can the piezo be driven, yes; but only at a frequency less than 1Hz.
    You would see similar effects on the DRV2700EVM-500HV with the 4*3.7uF load.

    These parts were not designed to drive such high capacitive loads.

  • 0 in reply to Kelly Griffin
    Guru 15950 points
    Hello Kelly,

    Thank you for your advise. Can we use 4 pcs piezo in series to make 0.93uF equivlent capacitance 0.93uF? How long to charge to 480V for the DRV2700-HV mode? If the answer is negative, would you please provide suggestion of the DRV2700 EVM option?

    Thank you and Best regards,

    Wayne Chen
    02/24/2017
  • 0 in reply to Wayne Chen (ex FAE)
    TI__Expert 8701 points
    Hi Wayne,

    Driving this capacitance to 480V would take ~0.5s. The flyback design is meant to drive <200nF capacitance. My suggestion would be to use multiple DRV2700 drivers for each piezo element.