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AM2634: Inquiry Oscillator Impact and Compensation Measures

Lawrence Wang
Intellectual 1400 points

Part Number: AM2634

Hi experts,

The AM2634 can use an internal oscillator, but the internal oscillator has a certain degree of error, as indicated in the manual:

Additionally, the oscillator directly affects SCI anomalies and PWM accuracy, as shown in the manual:

Questions

  1. What is the quantitative relationship between oscillator error and SCI/PWM error? For example, if the oscillator has a 3% error, how much error will this cause in PWM?
  2. Can the oscillator error be detected, and how can this error be compensated?
  • 0
    TI__Prodigy 220 points

    1. The absolute error of the frequency of input oscillator is multiplied in the PLL output, So, the % error of the output remains the same as % error of the input.

    2. The snippet shared by you, that captures the range of operation of the Oscillator, is from TMS320F280015x Real-Time Microcontrollers datasheet
    Please find the snippet from AM263x Datasheet for the 10 MHz RCOSC (internal oscillator) present in our device:

    Based on our Characterization data, the trimmed frequency drifts based on temperature and VDDA voltage variations but are well within the min-max specs defined.
    The oscillator error can be detected at any point of time by observing the 10 MHz RCOSC on CLKOUT0 or CLKOUT1 pin. Please find snippet below from the register addendum to enable the same.

    There are no trim registers available for the 10 MHz RCOSC in our device to compensate for the error at any given temperature or voltage condition.

    For accuracy, XTAL is recommended over RCOSC as clock source for EPWM, SCI.