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TM4C1294KCPDT: Oscillator schematic

Norbert Toth
Expert 1145 points
Part Number: TM4C1294KCPDT


Hi Folks,

in my previous education, a simple oscillator schematic that we can use for clocking microcontrollers, consist of a crystal and 2 ceramic capacitor going to the ground, but as I see the schematic in the guide, I noticed the serial connected resistor towards to OSC1 pin.

Can anybody explain me, why is it necessary?

Regards,

Norbert

  • 0
    TI__Guru*** 135355 points
    Hello Norbert,

    Certainly. From the device datasheet, the Rs inclusion is described as "Rs dissipates some of the power so the Max Dl crystal parameter is not exceeded."

    Furthermore in the device datasheet under the Main Oscillator Specifications section, we have a table of crystals and the recommend C1, C2, and Rs values which have been proven to work with our MCU's. Under this table you will that the NX3225GA-25.000M-STD-CRG-2 (crystal used on the LPad) is listed with recommended values and that those values align with our schematic.