PWM to voltage level

Discussion in 'The Projects Forum' started by drkidd22, Oct 30, 2011.

  1. drkidd22

    Thread Starter New Member

    Apr 6, 2011
    2
    0
    Hello All,

    I'm working on a project for motor control using an A3979 Microstepping DMOS Driver from AllegroMicro. In order to minimize board size I will be using the output of a microchip microelectronic to set the voltages for current ref and stepping mode. So I'm thinking of anput of 5Khz 3.3V PWM signal, not sure about that yet, but I basically want to voltages from 200mV up to around 2.2V.

    I'm trying to figure out how can I accomplish this? Low pass filter? Op-Amp?
     
  2. crutschow

    Expert

    Mar 14, 2008
    13,006
    3,232
    To get dc from a PWM output you run it through a low-pass filter. To minimize ripple it should be a least second-order or higher, which can be readily achieved with an op amp active-filter circuit. The cut-off frequency should be as low as possible which still give you the response time you need for the DC voltage changes.

    A simple way to design active filters is the free filter design software from TI.
     
  3. wayneh

    Expert

    Sep 9, 2010
    12,118
    3,042
    A frequency-to-voltage circuit with a 555 is an option if you have control over the PWM frequency, not just its duty cycle.
     
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