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TPS78227 - vibration motor direct drive

Argail
Expert 2080 points
Other Parts Discussed in Thread: TPS782

Hi everyone,

Sorry if the question has already been asked, but I can't find it.

I'm looking to drive a micro vibrating motor like this : http://www.smt-sanyo.co.jp/english/products/pdf/vibration.pdf

The 3089 precisely, 2.7V nominal voltage, 90mA peak current. It is possible to drive it directly with the TPS78227 LDO?

I juste have to add the two uF capacitors required, no diode or other protective circuit?

 

Best regards

  • 0
    TI__Expert 8890 points

     

    Hello Argail,

    I am not familiar with the operating environment for this motor.  Several of TI's parts might serve well in this application depending on the severity of the environment: the TPS71727 might serve as alternative.  The higher the PSRR, for instance the better the LDO can respond to load changes and noise.  In most industrial applications where there is large amount of noise and transients I would always err on the conservative side by recommending additional input and output capacitance.  Adding 2-10uF of capacitance never hurts, unless the cost is prohibitive. 

    Regards

    Bill

     

  • 0 in reply to Bill Stokes
    Expert 2080 points

    Thanks for the input, I'm not used with analogical problem, I was afraid for backward current, voltage peak or such funny things.

    For this reason I was wondering to use a diode (or other things) on Vout. Normally when using a component which has a coil, a protective diode is required to protect high voltage produced when the load is switched off (if drived with a transistor). But I don't know if it is required with a TPS782.

     

    I've planned to put the two capacitance in input and output. Are X5R - 0603 ok or tantalium is better?(we have high space constraints)

    Edit: The answer is on datasheet's page 10

    "The TPS782 series are designed to be stable with standard ceramic capacitors with values of 1.0mF or larger at the output. X5R- and X7R-type capacitors are best because they have minimal variation in value and ESR over temperature. Maximum ESR should be less than 1.0Ω."

  • 0 in reply to Argail
    TI__Expert 8890 points

    Hello Argail,

    Since we do not know the level of the inductive spikes I would agree that perhaps a diode in series with the LDO output should be used for added protection as well as any recommended fylyback/zener diode protection that might go across the inductor windings.  The capacitance that you have suggested is appropriate.  It is unnecessary to use a tantalum capacitor.

    Good Luck

    Bill 

  • 0
    TI__Guru 50090 points

    Hi Argail,

     

    I agree with everything the Bill mentions as well. Another thing to consider when selecting a ultra low Iq LDO is that its transient response will be a lot slower than an LDO with a higher Iq. This is related to why the PSRR on the TPS717xx is better than the TPS782xx.

     

    I would recommend trying samples of each as Bill and I are both not familiar with the motor you are planning to use.

     

    Regards,

     

    John