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UC2875: Frequency setting problem

shuang Cao
Intellectual 385 points
Part Number: UC2875

How to choose  resistance and capacitance of the FREQSET pin? There is no formula for frequency calculation in the manual. For example, I need 35kHz.
In addition, the chip in the 50 degree environment, the frequency will be reduced by 4kHz, automatic reply at normal temperature, this phenomenon is normal? Thanks!

  • 0
    TI__Mastermind 26735 points
    Hi Shuang,

    You can select your Rt and Ct values based on the frequency vs resistance graph on page 7 of the datasheet. It is possible to see some variation in the switching frequency over temperature based on the temperature coefficients of the resistor and capacitor connected to the FREQSET pin and variance in the internal oscillator over temperature.

    Best Regards,
    Ben Lough