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DRV2700: Possibility to use 2 DRVs to run 2 benders

Obinna Ezeilo
Intellectual 2385 points
Part Number: DRV2700

Hi team, 

My customer is considering the DRV2700 for their piezo benders and other piezo products.

One application with the PL128.10 is to move it at 200-300Hz full stroke. the PL128 is a bimorph piezo bender, and needs 3 connections. Please see -  https://static.piceramic.com/fileadmin/user_upload/physik_instrumente/files/datasheets/PL112-PL140-Datasheet.pdf

Questions:

- Can they use the DRV2700 for it and if yes, what will be the best values for the inductor, and other components around it?


ln a second application they need to run 2 of these benders, which exactly need to move in opposite direction. That means the references signal at pin2 needs to be opposite.

- Do they need 2 DRV's or can they do it in another way ? 

Thanks for the support, 

Obinna. 

  • 0
    TI__Guru* 84915 points

    Hi, Obinna,

    Yes, the DRV2700 will be a good option for this piezo load. Regarding the values, you would need to configure the DRV2700 in the conditions of figure 9 of the datasheet:

    https://www.ti.com/lit/ds/symlink/drv2700.pdf#page=7

    So, the feedback resistors for the boost voltage can be 806K and 36K in order to get around 30V Vbst (60Vpp). See some resistors calculation examples in the EVM Users Guide: https://www.ti.com/lit/ug/slou403c/slou403c.pdf#page=13

    The gain pins should be set at low level to configure 28.8dB.

    The inductor and Rext values can be similar to the EVM values: https://www.ti.com/lit/ug/slou403c/slou403c.pdf#page=25

    Regarding your question about the 2 piezo loads, these piezo loads will need to be connected opposite to each other. So, one piezo load will be receiving positive voltage level while the other one is receiving negative voltage.

    Please let me know if this is clear or if you have additional questions or comments.

    Best regards,
    Luis Fernando Rodríguez S.

  • 0 in reply to Luis Fernando Rodriguez S.
    TI__Intellectual 2385 points

    Hi Luis, 

    Your last point regarding connecting 2 piezo loads opposite to each other is not entirely clear. 

    The piezo bender can not be connected in opposite way. It has a + and – side. Please see below image. 

    or incase I misunderstood you, can you please send a drawing/sketch of of what you meant?

     Also, can two of these benders be used on one chip considering the frequency range described earlier - 200-300Hz?

    Lastly, if the RV2700 will be too small wrt power (more current) for example at higher frequencies (400-500Hz) what alternatives would you suggest?

     

    Thanks and looking forward to your feedback. 

    Obinna. 

  • 0 in reply to Obinna Ezeilo
    TI__Guru* 84915 points

    Hi, Obinna,

    Yes, I thought your bender had a differential input. The DRV2700 actually generates a differential output. With a differential input piezo, it could be used to move the actuator in opposite directions if the outputs are inverted (OUT+ to IN+ and OUT- to IN- with first device and OUT+ to IN- and OUT- to IN+ with the second device).

    The frequency range that you described is also supported. Actually, you may take a look at the typical characteristics from the datasheet for details about the supported frequency range based on the load capacitance:

    https://www.ti.com/lit/ds/symlink/drv2700.pdf#page=7

    Best regards,
    Luis Fernando Rodríguez S.

  • 0 in reply to Luis Fernando Rodriguez S.
    TI__Intellectual 2385 points

    Hi Luis, 

    Can the DRV2700 be setup with a second stage to increase the current? For instance, if the customer would like to drive a piezo (3uF) at 100Vpp and frequency of 500Hz - 1 KHz (triangle or sinusoidal) can the DRV2700 be used with an additional power stage to get the needed current ?

    Also, in terms of evaluation, which EVM would be most suitable for further testing for this application, DRV2700EVM or DRV2700EVM-HV500?

    Thanks for the support. 

    Obinna. 

  • 0 in reply to Obinna Ezeilo
    TI__Mastermind 18545 points

    Hello Obinna, 

    I am looking into the additional power question and will get back to you soon on that. 

    As for the EVMs, the DRV2700EVM-HV500 includes a flyback converter to increase the output voltage up to 500V. If you only need the 100Vpp, then you would be fine to use the DRV2700EVM for your testing. 

    Best Regards, 

    Justin Beigel

  • 0 in reply to Justin Beigel
    TI__Intellectual 2385 points

    Hi Justin, 

    Thanks for the feedback. I'll be looking forward to your response on the additional power question. 

    Kind regards, 

    Obinna. 

  • 0 in reply to Obinna Ezeilo
    TI__Mastermind 18545 points

    Hello Obinna, 

    While the DRV2700 cannot drive a 3uF load at your required voltage and frequency, you may be able to use a discreet solution to boost the output to achieve this. The second stage would need to make sure the load at the DRV2700 fits within the specs while being able to drive your 3uF load. There may be some amplifier you can use to do this, however, I do not have any recommendations or examples of this. 

    Best Regards, 
    Justin Beigel