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CHAPTER 1 OVERVIEW
1.10
Handling Device
Special care is required for the following when handling the device:
• Preventing latch-up
• Treatment of unused pins
• Stabilization of power supply voltage
• Using external clock
• Power supply input pins (V
• Pull-up/pull-down resistors
• Crystal Oscillator Circuit
• Turning-on Sequence of Power Supply to A/D Converter and Analog Inputs
• Connection of Unused Pins of A/D Converter if A/D Converter is unused
• Precautions at power on
• Note on operation during PLL clock mode
■ Handling the Device
●
Preventing latch-up
CMOS IC chips may suffer latch-up under the following conditions:
• A voltage higher than V
• A voltage higher than the rated voltage is applied between V
• The AV
Latch-up may increase the power supply current drastically, causing thermal damage to the device.
Therefore, the maximum voltage ratings must not be exceeded. By the same token, make sure that the
analog supply voltage (AVCC and AVRH) should not exceed the digital supply voltage.
●
Treatment of unused pins
Leaving unused input pins open may result in misbehavior or latch up and possible permanent damage of
the device. Therefore they must be pulled up or pulled down through resistors. In this case those resistors
should be more than 2 kΩ. Unused bidirectional pins should be set to the output state and can be left open,
or the input state with the above described connection.
●
Stabilization of power supply voltage
If the power supply voltage varies acutely even within the operation assurance range of the V
supply voltage, a malfunction may occur. The V
As stabilization guidelines, stabilize the power supply voltage so that V
value) in the commercial frequencies (50 Hz to 60 Hz) fall within 10% of the standard V
voltage and the transient fluctuation rate becomes 0.1V/ms or less in instantaneous fluctuation for power
supply switching.
22
/V
)
CC
SS
or lower than V
CC
power supply is applied before the V
CC
is applied to an input or output pin.
SS
and V
CC
voltage.
CC
power supply voltage must therefore be stabilized.
CC
CC
.
SS
CC
ripple fluctuations (peak to peak
power supply
CC
power
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