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Figure 2. Reference oscillator circuit
Table 2. Components of the oscillator circuit
Symbol
Description
RS
Bias Resistor
RF
Feedback Resistor
• When Low-gain is selected, internal RF will be selected,
and external RF is not required.
• When High-gain is selected, external RF(1M Ohm) need
to be connected for proper operation of crystal. For
external resistor, up to 5% tolerance is allowed.
X1
Quartz Crystal / Ceramic Resonator
C
XTAL
Stabilizing Capacitor
C
EXTAL
Stabilizing Capacitor
The load capacitors are dependent on the specifications of the crystal and on the board capacitance. It is recommended to have
the crystal manufacturer evaluate the crystal on the PCB.
4.2 Suggestions for the PCB layout of oscillator circuit
The crystal oscillator is an analog circuit and must be designed carefully and according to the analog-board layout rules:
• External feedback resistor [Rf] is not needed because it’s already integrated.
NXP Semiconductors
Clock circuitry
Hardware Design Guidelines for S32K1xx Microcontrollers , Rev. 3, December 2018
Application Note
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