Renesas Hitachi H8S/2191, Hardware Manual, Page: 1060 / 1065

Rev. 2.0, 11/00, page 1033 of 1037
Appendix E Usage Notes
E.1 Power Supply Rise and Fall Order
Figure E.1 shows the order in which the power supply pins rise when the chip is powered on, and
the order in which they fall when the chip is powered down. If the power supply voltages cannot
rise and fall simultaneously, power supply operations should be carried out in this order.
At power-on, wait until the microcomputer section power supply (V
CC
) has risen to the
prescribed voltage, then raise the other analog power supplies.
At power-down, drop the analog power supplies first, followed by the microcomputer section
power supply (V
CC
).
When powering up and down, ensure that the voltage applied to the pins does not exceed the
respective power supply voltage.
V
CC
, AV
CC
V
CC
AV
CC
SV
CC
Vin
: Microcomputer section power supply voltage
: A/D converter power supply voltage
: Servo section power supply voltage
: Pin applied voltage
SV
CC
V
CC
, AV
CC
SV
CC
Vin Vin
Figure E.1 Power Supply Rise and Fall Order
In power-down modes (except sleep mode), the analog power supplies can be turned off to
reduce current dissipation. When the microcomputer section power supply (V
CC
) is dropped to
the backup voltage in a power-down mode, the order shown in figure E.2 should be followed.
Make sure that the voltage applied to the pins does not exceed the respective power supply
voltage.
The A/D converter power supply (AV
CC
) should be set to the same potential as the
microcomputer section power supply (V
CC
). In all power-down modes except sleep mode, AV
CC
is turned off inside the device. At this time, the AV
CC
current dissipation is defined as AISTOP.