DSP56F803 datasheet(33/57 Pages) FREESCALE

33 / 57 page

56F803 Technical Data, Rev. 16

Freescale Semiconductor

3.5.2

Ceramic Resonator

It is also possible to drive the internal oscillator with a ceramic resonator, assuming the overall system

design can tolerate the reduced signal integrity. In Figure 3-8, a typical ceramic resonator circuit is

shown. Refer to supplier’s recommendations when selecting a ceramic resonator and associated

components. The resonator and components should be mounted as close as possible to the EXTAL and

XTAL pins. The internal 56F80x oscillator circuitry is designed to have no external load capacitors

present. As shown in Figure 3-7 no external load capacitors should be used.

Figure 3-8 Connecting a Ceramic Resonator

Note: Freescale recommends only two terminal ceramic resonators vs. three terminal resonators

(which contain an internal bypass capacitor to ground).

3.5.3

External Clock Source

The recommended method of connecting an external clock is given in Figure 3-9. The external clock

source is connected to XTAL and the EXTAL pin is grounded.

Figure 3-9 Connecting an External Clock Signal

Recommended Ceramic Resonator

Parameters:

Rz = 1 to 3 MΩ

fc = 8MHz (optimized for 8MHz)

EXTAL XTAL

56F803

XTAL

EXTAL

External

VSS

Clock

DSP56F803 Datasheet(PDF) 33 Page - Freescale Semiconductor, Inc