Datasheet

Oscillator
MC68HC912Dx128C Colpitts Oscillator Specification
MC68HC912DT128A — Rev 4.0 Technical Data
MOTOROLA Oscillator 209
13.4.4 MC68HC912Dx128C DC Blocking Capacitor Guidelines
Due to the placement of the resonator from EXTAL to VSS and the
nature of the microcontroller’s inputs, there will be a DC bias voltage of
approximately (VDD–2V) across the pins of the resonator. For some
resonators, this can have long-term reliability issues. To remedy this
situation, a DC-blocking capacitor can be placed in series with the
crystal, as shown in Figure 13-3.
The value of the DC-blocking capacitor should be between 0.1 and
10nF, with a preferred value of 1nF. This capacitor must be connected
as shown in Figure 13-3. If connected thus, all other oscillator
specifications and guidelines continue to apply.
Frees
cale Semiconductor,
I
Freescale Semiconductor, Inc.
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