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MPC555
/
MPC556
CLOCKS AND POWER CONTROL
MOTOROLA
USER’S MANUAL
Rev. 15 October 2000
8-26
terization of production silicon. The goal is to keep the power consumption during
power up sequencing below the operating power consumption.
During the power down sequence the user needs to assert PORESET while VDDI and
VDDL are at a voltage equal or greater to 3 V. Below this voltage the power supply
chip can be turned off. If the turn off voltage of the power supply chip is greater than
0.74 V for the 3-V supply and greater than 0.8 V for the 5-V supply, then the circuitry
inside the MPC555 / MPC556 will act as a load to the respective supply and will dis-
charge the supply line down to these values. Since the 3-V logic represents a larger
load to the supply chip, the 3-V supply line will decay faster than the 5-V supply line.
Figure 8-13 No Standby, No KAPWR, All System Power On/Off
Power On
Power Off
Operating
See Note 1. See Note 2.
VDDH
VDD, NVVL,
QVDDL
KAPRR
VDDSRAM
VDDA, VRH
VDDSYN
VFLASH (5 V)
PORESET
HRESET
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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