56F8037 datasheet(41/180 Pages) FREESCALE

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Ceramic Resonator

56F8037 Data Sheet, Rev. 2

Freescale Semiconductor

Preliminary

Figure 3-1 External Crystal Oscillator Circuit

3.6 Ceramic Resonator

The internal crystal oscillator circuit is also designed to interface with a ceramic resonator in the frequency

range of 4-8MHz. Figure 3-2 shows the typical 2 and 3 terminal ceramic resonators and their circuits.

Follow the resonator supplier’s recommendations when selecting a resonator, since their parameters

determine the component values required to provide maximum stability and reliable start up. The load

capacitance values used in the resonator circuit design should include all stray layout capacitances. The

resonator and associated components should be mounted as near as possible to the EXTAL and XTAL pins

to minimize output distortion and start-up stabilization time.

Figure 3-2 External Ceramic Resonator Circuit

3.7 External Clock Input - Crystal Oscillator Option

The recommended method of connecting an external clock is illustrated in Figure 3-3. The external clock

source is connected to XTAL and the EXTAL pin is grounded. The external clock input must be generated

using a relatively low impedance driver.

Sample External Crystal Parameters:

Rz = 750 KΩ

Note: If the operating temperature range is limited to

below 85oC (105oC junction), then Rz = 10 Meg Ω

EXTAL XTAL

CL1

CL2

Crystal Frequency = 4 - 8MHz (optimized for 8MHz)

EXTAL XTAL

Sample External Ceramic Resonator Parameters:

Rz = 750 KΩ

EXTAL XTAL

CL1

CL2

Resonator Frequency = 4 - 8MHz (optimized for 8MHz)

3 Terminal

2 Terminal

56F8037 Datasheet(PDF) 41 Page - Freescale Semiconductor, Inc