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5V differential to 3.3V

Other Parts Discussed in Thread: SN65LVDS048A, TXB0106

The idea is to interface 5V differential signals from an encoder and hall sensors on a motor to the QEP and CAP peripherals of a F28035/28335 microcontroller. Is the only way to use TXB0106 to convert 5V to 3.3V  and then use SN65LVDS048A for the differential signals? Does anyone have any better ideas - would be nice to save board space.

  • please provide the output signal levels of the enocder output and the desired input signal levels of the controller.

    the solution you described sounds like 5V (single ended) to 3V single ended and then conversion to 3V differential.

    your requirement however sounds like 5V differential to 3V single-ended. is this correct?

    the 5V differential are varying between what common-mode potentials? 2.5V, 5V, 10V etc ???

    what are the absolute voltage levels of the two differential encoder output terminals with respect to ground?

    Thanks, TK 

  • Not quite. The A+ signal oscillates between 5V and 0V as does the A- signal. When one goes up, the other goes down. Same for the phase B, index and the three hall sensor outputs. I dont think I can say there is a common mode potential.

    The controller can accept 3.3V signals and so the idea is to convert A+ and A- to a single A signal and then step it down to 3.3V. 

    Thanks for getting back TK.

  • the circiut does it exactly what you said you need. If there is no common-mode potential then you need a difference -amp or instrumentation amp.

    if you need results, provide your sensor output schematic to the precision amplifier forum.

    good luck,

    TK