mc68hc908ap8a Freescale Semiconductor, Inc, mc68hc908ap8a Datasheet - Page 87

• Manufacturer Part Number: mc68hc908ap8a
• Description: M68hc08 Microcontrollers
• Manufacturer: Freescale Semiconductor, Inc

Care should be taken with PCB routing in order to minimize signal cross talk and noise. (See
Acquisition/Lock Time Specifications
performance.)
6.4 I/O Signals
The following paragraphs describe the CGM I/O signals.
6.4.1 External Filter Capacitor Pin (CGMXFC)
The CGMXFC pin is required by the loop filter to filter out phase corrections. An external filter network is
connected to this pin. (See
6.4.2 PLL Analog Power Pin (V
V
potential as the V
6.4.3 PLL Analog Ground Pin (V
V
potential as the V
Freescale Semiconductor
DDA
SSA
is a ground pin used by the analog portions of the PLL. Connect the V
is a power pin used by the analog portions of the PLL. Connect the V
To prevent noise problems, the filter network should be placed as close to
the CGMXFC pin as possible, with minimum routing distances and no
routing of other signals across the network.
Route V
capacitors as close as possible to the package.
DD
SS
Note: Filter network in box can be replaced with a 0.47µF capacitor, but will degrade stability.
pin.
pin.
DDA
Figure
carefully for maximum noise immunity and place bypass
MCU
Figure 6-3. CGM External Connections
MC68HC908AP A-Family Data Sheet, Rev. 3
0.22 µF
6-3.)
1 kΩ
DDA
for routing information, filter network and its effects on PLL
SSA
)
)
CGMXFC
NOTE
NOTE
10 nF
V
SSA
V
DDA
C
0.1 µF
BYP
DDA
SSA
V
DD
pin to the same voltage
pin to the same voltage
6.8
I/O Signals
87