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BUF634A: Small DC motor drive

David Pfaltzgraff
Expert 2475 points
Part Number: BUF634A
Other Parts Discussed in Thread: BUF634, THS6012

I have a requirement to drive a small brushed DC motor with a linear voltage. The typical operating point is around 3V at 40mA, but may be as high as 5V a 65mA.

Because of noise generated, PWM operation is not acceptable.

Provided that there is sufficient heat dissipation, is this an optimum part? Or, is there a better choice?

Thanks, Dave

  • 0
    TI__Mastermind 23226 points

    Hi Dave,

    The BUF634A will have no problem driving 65mA at 5V. The efficiency will be just be lower than for a PWM, (Class D) drive. I

    Don't forget to account for inrush current, which will will be several times higher than for steady state load current.

    The current for a brushed motors will not be constant either. Since the motor is an inductor, its drive current will linearly increase with a DC voltage until the brush commutates to the next stage, and its drive current will look like a sawtooth. To make sure the BUF634 output does not droop as current output increases, you can use it inside of an amplifier loop as shown in page 1 of the datasheet. However, you also can just use the BUF634A as a stand alone to buffer for an analog voltage if maximizing motor power input is not critical.

    Best regards,

    Sean 

  • 0 in reply to Sean Cashin
    Guru 48395 points

    Really good detail Sean, 

    I will say in other applications looking for a high output +/-15V supply stage, a sort of hidden audio amp has proven useful. This part, the TPA6120, is a smaller lower cost version of the THS6012 dual CFA ADSL driver. Very capable device buried inside the audio line, no TINA model so use the THS6012 model if a dual device might be useful for you (also, the TPA6120 datasheet is pretty sparse, but it is the same die as the THS6012 - that datasheet has more detail).