mpc823rg Freescale Semiconductor, Inc, mpc823rg Datasheet - Page 122

• Manufacturer Part Number: mpc823rg
• Description: Mpc823 Powerquicc Integrated Communications Processor For Portable Systems
• Manufacturer: Freescale Semiconductor, Inc

5.3.5.2 THE SYSTEM PHASE-LOCKED LOOP PINS. The internal frequency of the
MPC823 and the output of the CLKOUT pin depends on the quality of the crystal circuit and
the MF bit in the PLPRCR. The SPLL contains the following dedicated pins that are isolated
from common power and ground.
• VDDSYN—The power supply pin for the analog SPLL circuitry. You must provide a
• VSSSYN—A ground reference pin for the analog SPLL circuitry. You must provide a
• VSSSYN1—A ground reference pin for the analog SPLL circuitry. You must provide a
• XFC—The external filter capacitor pin that connects to the off-chip capacitor for the
TBS BIT IN SCCR
well-regulated voltage to this pin via an extremely low impedance path to the VDD
power rail. The SPLL power plane must be isolated from the VDD power plane with an
LC filter, which gives you the best performance. A 0.1 F bypass capacitor must
connect VDDSYN and VSSSYN and be as close to the chip as possible. To reduce the
noise from the open EXTAL pin, pull it to ground when you are not using it.
low impedance path from VSSSYN to the ground plane.
low impedance path from VSSSYN1 to the ground plane.
SPLL filter. One terminal of the capacitor is connected to XFC while the other terminal
is connected to the VDDSYN pin. For proper SPLL operation, you must supply a
minimum parallel parasitic resistance value of 30M . The value of the XFC capacitor is
based on the value of the MF field in the PLPRCR.
1
0
0
0
MULTIPLY
FACTOR
RANGE
Table 5-4. XFC Capacitor Values Based on the MF Field
MF > 4
MF
4
MODCK1 AT
Freescale Semiconductor, Inc.
CAPACITANCE
RESET
(580 *MF) - 100
For More Information On This Product,
—
MINIMUM
0
1
1
830 * MF
Table 5-3. TMBCLK Dividers
MPC823 REFERENCE MANUAL
Go to: www.freescale.com
XFC CAPACITOR VALUES
RECOMMENDED
CAPACITANCE
(680 * MF) - 120
1100 * MF
MF + 1
1, 2
> 2
—
—
CAPACITANCE
(780 * MF) - 140
CLOCK SOURCE
MAXIMUM
1470 * MF
GCLK2
EXTAL
EXTAL
OSCM
Clocks and Power Control
UNIT
TMBCLK DIVISION
pF
pF
16
16
4
4
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