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XTR300EVM: Current and voltage output possible using a PWM from a Raspberry PI?

Kevin Granados
Prodigy 10 points
Part Number: XTR300EVM
Other Parts Discussed in Thread: XTR300,

I've been able to get a voltage output using a PWM using the Evaluation Module however, have not been able to get a current output. The voltage Also has not been perfectly accurate from the documentations provided by Texas Instruments here: http://www.ti.com/lit/ug/sbou034a/sbou034a.pdf

Is there any solution or helpful feed back to get a zero output from PWM set to a 0% duty cycle? as well as getting a current output from this chip/Evaluation Module using a PWM from a Raspberry PI?

  • 0
    TI__Guru 51706 points

    Hello Kevin,

    The XTR300 requires a low noise, stable input analog voltage signal to convert the input voltage to output current.  The PWM signal needs to be converted to a low noise, low offset analog voltage output, prior being applied to the XTR300.

    Therefore, a low-pass filter is required between the PWM output and the XTR300 input, and the order of the low-pass filter and the corner frequency of the filter needs to be carefully designed depending on the ripple noise tolerance requirements in the application, and the PWM frequency.  For your information, below is a application discussing the design trade offs between the low pass filter and the output error ripple when converting the micro-controller PWM to analog output voltage. 

    https://www.ti.com/lit/ug/tidu027/tidu027.pdf

    What is the amplitude and frequency of the PWM signal?   What is the Nth order of the low-pass filter used between the PWM output and XTR300 input to generate the analog voltage? What is the corner frequency of the filter? 

    Can you show a compete schematic showing all the connections of the XTR300EVM to the controller, including the low pass filter between the XTR and the controller, Ros and Rset resistor values, all XTR300EVM jumper settings, etc?

    Thank you and Regards,

    Luis