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CHAPTER 2 HANDLING DEVICES
2.1
Notes on Handling Devices
This section lists points to note regarding the power supply voltage, pins, and other
device handling aspects.
I Notes on handling devices
G Take great care not to exceed the maximum rated voltage (prevent latchup).
Latchup may occur on CMOS ICs if voltage higher than VCC or lower than VSS is applied to input and
output pins other than medium- to high-voltage pins, or if voltage higher than the ratings is applied between
VCC and VSS.
When latchup occurs, power supply current increases rapidly and might thermally damage elements. When
using, take great care not to exceed the absolute maximum ratings.
Also, take care to prevent the analog power supply (AVCC) and analog input from exceeding the digital
power supply (VCC) when the analog system power supply is turned on and off.
G Stabilizing supply voltage is important.
A rapid fluctuation of VCC power supply voltage could cause malfunctions, even if it occurs within the
operation assurance range of the voltage. As stabilization guidelines, it is recommended to control power so
that VCC ripple fluctuations (P-P value) will be less than 10% of the standard VCC value at the commercial
frequency (50 to 60 Hz) and the transient fluctuation rate will be less than 0.1 V/ms at the time of a
momentary fluctuation such as when power is switched.
G Treatment of unused input pins
Leaving unused input pins open could cause malfunctions. They should be connected to a pull-up or pull-
down resistor.
G Treatment of N.C. pins
Be sure to leave (internally connected) N.C. pins open.
G Note to Noise in the External Reset Pin (RST)
If the reset pulse applied to the external reset pin (RST) does not meet the specifications, it may cause
malfunctions. Use caution so that the reset pulse less than the specifications will not be fed to the external
reset pin (RST).
G Treatment of power supply pins on microcontroller with A/D converter
Connect to be AVCC = VCC and AVSS = VSS even if the A/D is not in use.
G Precautions when using an xternal clock
Even when an external clock is used, oscillation stabilization delay time is required for power-on reset and
wake-up from stop mode.