Motorola MPC533 Reference Manual page 1110

Power-Up/Down Sequencing
K.8.2 Power-Up/Down Option B
A less stringent power-up sequence may be implemented if 2.6-V compliant pins and dual
2.6-V/5-V compliant pins are NOT connected to the 5-V supply with a pull-up resistor or
driven by 5-V logic during power-up/down.
The option B power-up sequence (excluding V
1. V > V
DDH DDL
Thus the V supply group can be fully powered-up prior to power-up of the V
DDH
supply group, with no adverse affects to the device.
The requirement that V
the pad logic for dual 2.6-V/5-V compliant pins and 2.6-V pins. The diodes are forward
biased when V is greater than V
DDL
Figure K-5 illustrates the power-up sequence if no keep-alive supply is required.
Figure K-6 illustrates the power-up sequence if a keep-alive supply is required. The
keep-alive supply should be powered-up at the same time or before both the high voltage
and low voltage supplies are powered-up.
Figure K-5. Option B Power-Up Sequence Without Keep-Alive Supply
K-16
PRELIMINARY—SUBJECT TO CHANGE WITHOUT NOTICE
- 0.5 V (V cannot lag V
DDH
cannot lag V
DDH DDL
and will start to conduct current.
DDH
V cannot lag V by more than 0.5 V
DDH DDL
MPC533 Reference Manual
) is:
DDKA
by more than 0.5 V)
DDL
by more than 0.5 V is due to ESD diodes in
0.5-V lag
DDL
V
DDH
V
DDL
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