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DRV2667: DRV2667 Frequency Settings

Matsuda Kohei
Prodigy 20 points
Part Number: DRV2667
Other Parts Discussed in Thread: DRV2700, DRV2901, LM5155

Tool/software:

We are planning to use the DRV2667 in our upcoming project.

Could you please provide information on the setting ranges for both the resonant frequency of the piezoelectric element (as the base frequency) and the AM modulation frequency? The reason for my inquiry is that while the specification sheet mentions a maximum of 500Hz, it does not clearly specify which frequency this limit applies to. I would like to use a base frequency range of 100kHz to 600kHz, with an AM frequency range of approximately 1Hz to 500Hz.

Thank you for your assistance.
DRV2667_AM

  • 0
    TI__Genius 10542 points

    Hi,

    Modulating at these high frequencies should not be an issue. This was designed for haptic devices operation in the <500Hz range. Any high frequency content up in the 100kHz range will be rejected. 

    The datasheet has two specifications to help understand this:

    1. The C_L (load capacitance) table, section 6.3. This specification can be interpreted as the bandwidth of the device per the setting
      1. For example, at VBST = 105 V, Frequency = 500 Hz, VOUT = 200 VPP, you can drive a 50nF load
    2. The open-load bandwidth, no load, is further down in the datasheet, section 6.5.
      1. At 100Vbst, 200Vpp, the un-loaded bandwidth is 5kHz.
  • 0 in reply to Kelly Griffin
    Prodigy 20 points

    Hi, Kelly
    Thank you for the helpful answer.

    I'm in serious trouble here. I need to drive a piezo element at 1kHz to 600kHz. Do you happen to know any driver ICs that can handle that? I'd really appreciate any help you can give me.

  • 0 in reply to Matsuda Kohei
    TI__Genius 10542 points

    This is highly dependent on your load. How much power do you need to drive your load at 600kHz?

    What is the capacitance you are driving? How high of voltage do you need? 

  • 0 in reply to Kelly Griffin
    Prodigy 20 points

    Hi, Kelly
    I apologize for the delay. The operating conditions are as follows:

    Voltage: 0-30V
    Current: Unknown
    Capacitance: 12.8nF

  • 0 in reply to Matsuda Kohei
    TI__Mastermind 20431 points

    Hi, Kohei

    as our team is on holiday leave on Monday.

    team will reply you asap after get back to office.

    thanks

    jesse

  • 0 in reply to Matsuda Kohei
    TI__Genius 10542 points

    Thanks (and thanks Jesse) - this capacitance is quite low, so it won't be too hard to find a solution here depending on how optimized you need it to be. DRV2700 datasheet section 8.2.1.2.8 has some power calculations for driving a piezo. If you use those numbers, the peak capacitor current is ~1.45A. 

    Unfortunately, in our product line, everything is more in the audio or haptics frequency range. Parts that are capable of that frequency and voltage may be very large because they are made to support higher power. For example, DRV2901 could meet your requirements (far exceeds the current needed). You need an external boost converter to be paired with it, like LM5155. Also, you need to control the PWM inputs with a controller. 

  • +1 in reply to Kelly Griffin
    Prodigy 20 points

    Hi Kelly, Thank you very much for your invaluable assistance. Our team will now proceed with internal discussions regarding the implementation of the DRV2901 in our project.
    I am deeply grateful to you.