mpc823rg Freescale Semiconductor, Inc, mpc823rg Datasheet - Page 125

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

Clocks and Power Control
5.4.2.1 POWER SWITCHING EXAMPLE. An example of a switching scheme for an
optimized low-power system is illustrated in Figure 5-16.
Switch 1 and 2 (SW1 and SW2) can be combined into a single switch if VDDSYN and VDDH
are supplied by the same source. If VDDL is fed with 3.3V, SW2 and SW3 can be combined
into one switch. The TEXP pin, if enabled, is asserted by the MPC823 when the real-time
clock or timebase time value matches the value programmed in its associated alarm register
or when the periodic interrupt timer or decrementer decrements their value to zero. The
TEXP pin is negated when you write a 1 to the TEXPS bit in the PLPRCR.
If the voltage to the KAPWR rises too slow, the OSCM (supplied by KAPWR) will take longer
to stabilize the OSCCLK. The maximum KAPWR rise time must be less than 1.7V/ms for a
32kHz input frequency.
MPC823
Figure 5-16. External Power Supply Scheme
Freescale Semiconductor, Inc.
For More Information On This Product,
VDDSYN
VDDH
VDDL
KAPWR
TEXP
MPC823 REFERENCE MANUAL
SWITCH
Go to: www.freescale.com
LOGIC
SW1
SW2
SW3
BACKUP
SUPPLY
2.5-3.3V
POWER
MAIN POWER
3.3V
SUPPLY
2.2V
MOTOROLA