MC80F0804D View Datasheet(PDF) - Unspecified
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MC80F0804D Datasheet PDF : 120 Pages
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MC80F0704/0708/0804/0808
18.4 Minimizing Current Consumption
The Stop mode is designed to reduce power consumption. To
minimize current drawn during Stop mode, the user should turn-
off output drivers that are sourcing or sinking current, if it is prac-
tical.
INPUT PIN
VDD
VDD
internal
pull-up
i
GND
VDD
X
Weak pull-up current flows
VDD
O
OPEN
O
INPUT PIN
OPEN
i
VDD
i=0
O
Very weak current flows
X
i=0
GND
O
When port is configured as an input, input level should
be closed to 0V or 5V to avoid power consumption.
Figure 18-9 Application Example of Unused Input Port
OUTPUT PIN
ON
OFF i
GND
X
ON
OPEN
OFF
O
VDD
ON
O OFF
In the left case, much current flows from port to GND.
OUTPUT PIN
ON
VDD
L
OFF
VDD
L
OFF i
GND
ON i=0
GND
X
O
In the left case, Tr. base current flows from port to GND.
To avoid power consumption, there should be low output
to the port .
Figure 18-10 Application Example of Unused Output Port
Note: In the STOP operation, the power dissipation associated
with the oscillator and the internal hardware is lowered; however,
the power dissipation associated with the pin interface (depending
on the external circuitry and program) is not directly determined by
the hardware operation of the STOP feature. This point should be
little current flows when the input level is stable at the power volt-
age level (VDD/VSS); however, when the input level becomes high-
er than the power voltage level (by approximately 0.3V), a current
begins to flow. Therefore, if cutting off the output transistor at an I/
O port puts the pin signal into the high-impedance state, a current
flow across the ports input transistor, requiring it to fix the level by
pull-up or other means.
It should be set properly in order that current flow through port
doesn't exist.
First consider the port setting to input mode. Be sure that there is
no current flow after considering its relationship with external
circuit. In input mode, the pin impedance viewing from external
MCU is very high that the current doesn’t flow.
But input voltage level should be VSS or VDD. Be careful that if
unspecified voltage, i.e. if uncertain voltage level (not VSS or
October 31, 2011 Ver 1.03
93
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