Datasheet

56F803 Technical Data, Rev. 16
28 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:
R
z
= 1 to 3 MΩ
f
c
= 8MHz (optimized for 8MHz)
EXTAL XTAL
R
z
f
c
56F803
XTAL
EXTAL
External
V
SS
Clock