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541
CHAPTER 25 STAND-BY FUNCTION
(2) Is the input level to each input pin appropriate
Set the voltage level input to each pin within the range from the V
SS
voltage to the V
DD
voltage. If a voltage outside
of this range is applied, not only does the consumption current increase, but the reliability of the
m
PD784216 is
negatively affected.
In addition, do not increase the middle voltage.
(3) Are internal pullup resistors needed
Unnecessary pull-up resistors increase the consumption current and are another cause of device latch-up. Set
the pull-up resistors to the mode in which they are used only in the required parts.
When the parts needing pull-up resistors and the parts not needing them are mixed together, externally connect
the pull-up resistors where they are needed and set the mode in which the internal pull-up resistors are not used.
(4) Are the address bus, the address/data bus, etc. handled appropriately
The address bus, address/data bus, and RD and WR pins have high impedances in the STOP and IDLE modes.
Normally, these pins are pulled up by pull-up resistors. If the pull-up resistors are connected to the power supply
that is backed up, the current flows through the pull-up resistors when the low input impedance of the circuit
connected to the power supply that is not backed up, and the consumption current increases. Therefore, connect
the pull-up resistors on the power supply side that is not backed up as shown in Figure 25-10.
The ASTB pin has a high impedance in both the STOP and IDLE modes. Handle in the manner described in
(1) above.
Figure 25-10. Example of Handling Address/Data Bus
V
DD
IN/OUT
CMOS IC, etc.
V
SS
Power supply that is
not backed up
V
DD
ADn
(n = 0-7)
μ
V
SS
Power supply that is
backed up
PD784216
Set the input voltage level applied to the WAIT pin in the range from the V
SS
voltage to the V
DD
voltage. If a
voltage outside of this range is applied, not only does the consumption current increase, but the reliability of the
m
PD784216 is negatively affected.