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Is the pull-up or pull-down resistor needed for unused input pins?

Latest Updated:03/25/2009

Question:

Is the pull-up resistor or pull-down resistor necessary for unused input pins? (Is it OK to connect it directly with VCC or GND?)

Answer:

The pull-up resistor or pull-down resistor is necessary for unused input pins.

The influence of the spike noise in the power supply line is received directly when connecting it directly with VCC or GND without resistors, and the possibility of causing the malfunction grows.

Moreover, if the input protection circuit of CPU is destroyed due to unforeseen circumstances, excessive current flows to CPU and the possibility to fatal destruction grows.

Therefore, it is recommended that the pull-up or pull-down resistor should be turned on for unused input pins (or input/output pins that does the input setting).

Suitable Products
SH7144, SH7145
SH7065
SH7058
SH7055
SH7050, SH7051
SH7052, SH7053, SH7054
SH7047, SH7049, SH7105, SH7107, SH7109
SH7046, SH7148, SH7101, SH7048, SH7104, SH7106, SH7108
SH7040, SH7041, SH7042, SH7043, SH7044, SH7045
SH7032, SH7034, SH7034B
SH7032
SH7020, SH7021
SH7018
SH7014, SH7016, SH7017
SH7011