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DRV5057: How to use two DRV5057 to output complementary PWM

Part Number: DRV5057
Other Parts Discussed in Thread: , DRV5055-Q1

Hi team,

The customer uses DRV5057 as the sensor chip of the brake foot valve. Foot valve is required to output 2 complementary PWM signals. Customer would like to know If he uses two DRV5057, how could he output complementary PWM?

Thanks.

Annie

  • Annie,

    It is a little difficult to provide a recommendation without more insight to the format of the complementary PWM.  If we are looking for a truly complementary output where one device is on while the other is off, I do no think this can be practically achieved using two DRV5057 as we do not have control over the synchronicity of the clocks.  However, it might be more reasonable to use an inverter to generate the second signal using only one DRV5057. If the timing delay is of concern, a buffer with similar propagation delay could be used on the original signal for better alignment of the two signal paths.

    I have also seen PWM formats referred to a complementary where there is a slight overlap (or dead time) expected between the outputs, and we would be looking to examine the difference between the two signals.  This is harder to produce, and would likely require a device such as a complimentary output generator specifically designed to generate this kind of signal.

    Thanks,

    Scott

  • Hi Scott,

    Thanks for your answer.

    Customer only wants to use two DRV5057s to output PWM with complementary duty cycles, without considering the difference in phase. Can this be achieved? Is it possible to place the two pieces in reverse?

    Thanks,

    Annie

  • Annie,

    I do not think this will work quite as you described.  Opposing outputs can be created with the sensors placed facing opposite poles or with the package flipped, but we cannot guarantee any sort of timing alignment. 

    The quiescent duty cycle is 50%, and will shift downward for a North pole and upward for a South pole. I believe that the on cycle is always first, so the two outputs will not appear to be perfectly inverted.

    If the edge timing is not of concern, then rotating the second device would be easiest using the TO-92 package. There will be some offset required between the two devices, so care should be taken to ensure they experience symmetrical field components. I would place them both offset from the magnet center by the same amount along a plane of symmetry for the magnet.  If using SOT-23, then the flipped device will need to be placed on the opposite side of the PCB, and matching will be more difficult to achieve.

    Thanks,

    Scott

  • Hi Scott,

    Could you recommend a suitable TO-92 packaged chip? 

    • TO-92
    • Meet AEQ-100
    • PWM output or analog output
    • Both single-channel and dual-channel are acceptable, preferably dual-channel

    Best regards,

    Annie

  • Annie,

    The only AEQ-100 rated Hall Effect sensor we offer with PWM output is DRV5057-Q1.  Unfortunately this is only offered in the SOT-23 packaging.  So, for this application it would be necessary to orient the magnet in such a way that each sensor is exposed to symmetrically opposed field vector components.  This requires more layout space and care should be taken to keep the magnet centered between the two sensors. The sensitivity option (A1-A4) would depend on the strength of the magnet and the amount of travel they are sensing.  

    Here is a possible magnet orientation:

    If the TO-92 option is still more attractive, then an analog output device might be an option.  DRV5055-Q1 could work for this same application.  It is offered in the TO-92 package, and has several sensitivity options as well. The basic functionality is the same as DRV5057-Q1.  The output will be at mid supply (instead of 50% duty cycle) when no field is present.  A North field (directed from top of the package to bottom) will force the output to a lower voltage where a South pole (directed bottom to top) will produce a higher voltage.

    Thanks,

    Scott