MC68HC708AS48 FREESCALE [Freescale Semiconductor, Inc], MC68HC708AS48 Datasheet - Page 122

• Manufacturer Part Number: MC68HC708AS48
• Description: Advance Information
• Manufacturer: FREESCALE [Freescale Semiconductor, Inc]

Clock Generator Module (CGM)
8.10.3 Choosing a Filter Capacitor
Advance Information
122
Temperature and processing also can affect acquisition time because
the electrical characteristics of the PLL change. The part operates as
specified as long as these influences stay within the specified limits.
External factors, however, can cause drastic changes in the operation of
the PLL. These factors include noise injected into the PLL through the
filter capacitor, filter capacitor leakage, stray impedances on the circuit
board, and even humidity or circuit board contamination.
As described in
external filter capacitor, C
the PLL. The PLL is also dependent on reference frequency, f
supply voltage, V
chosen with supply potential and reference frequency in mind. For
proper operation, the external filter capacitor must be chosen according
to the following equation. Refer to
(PLL)
the value of C
For the value of V
operating. If the power supply is variable, choose a value near the
middle of the range of possible supply values.
This equation does not always yield a commonly available capacitor
size, so round to the nearest available size. If the value is between two
different sizes, choose the higher value for better stability. Choosing the
lower size may seem attractive for acquisition time improvement, but the
PLL can become unstable. Also, always choose a capacitor with a tight
tolerance ( 20% or better) and low dissipation.
for the value of f
Clock Generator Module (CGM)
FACT
8.10.2 Parametric Influences on Reaction
DD
DDA
.
. The value of the capacitor, therefore, must be
, choose the voltage potential at which the MCU is
RDV
C
F
F
=
and
, is critical to the stability and reaction time of
C
FACT
21.10 CGM Component Information
8.4.2 Phase-Locked Loop Circuit
V
------------ -
f
RDV
DDA
MC68HC708AS48
MOTOROLA
Time, the
RDV
—
Rev. 4.0
, and
for