GMS81C2012 datasheet(76/92 Pages) HYNIX

76 / 92 page

GMS81C2020/GMS81C2120

Hyundai Micro Electro nics

preliminary

Nov. 1999 Ver 0.0

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 practical.

Note: In the STOP operation, the power dissipation asso-

ciated with the oscillator and the internal hardware

is lowered; however, the power dissipation associat-

ed 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 voltage level (VDD/VSS);

however, when the input level becomes higher 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 that current flow through port

doesn't exist.

First conseider the 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 unfirmed voltage level

(not VSSor VDD) is applied to input pin, there can be little

current (max. 1mA at around 2V) flow.

If it is not appropriate to set as an input mode, then set to

output mode considering there is no current flow. Setting

to High or Low is decided considering its relationship with

external circuit. For example, if there is external pull-up re-

sistor then it is set to output mode, i.e. to High, and if there

is external pull-down register, it is set to low.

Figure 21-2 Application Example of Unused Input Port

INPUT PIN

VDD

GND

VDD

Weak pull-up current flows

VDD

internal

pull-up

INPUT PIN

VDD

Very weak current flows

VDD

OPEN

i=0

GND

When port is configured as an input, input level should

be closed to 0V or 5V to avoid power consumption.

* Pull-up is Metal Option

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