Precautions When Handling Devices - Fujitsu MB90895 Series Hardware Manual

CHAPTER 2 HANDLING DEVICES
2.1

Precautions when Handling Devices

This section describes the precautions against the power supply voltage of the device
and processing of pin.
I Precautions when Handling Devices
G
Voltage not exceeding maximum ratings (preventing latch-up)
• For a CMOS IC, latch-up may occur when a voltage higher than V
input to the I/O pin other than medium-/high-voltage withstand I/O pins, or when a voltage that exceeds
the rated voltage is impressed between V
• Latch-up may cause a sudden increase in supply current, resulting in thermal damage to the device.
Therefore, the maximum voltage ratings must not be exceeded.
• When turning the analog power supply on and off, the analog supply voltage (AV
analog input voltage should not exceed the digital supply voltage (V
G
Handling un-used pins
If unused input pins remain open, a malfunction or latch-up may cause permanent damage, so take
countermeasures such as pull-up or pull-down using a 2 kΩ or larger resistor. Leave unused input pins open
in the output state or, if left in the input state, treat them in the same manner as for input pins in use.
G
Precautions when using external clock
When an external clock is used, drive only the X0 pin and open the X1 pin. Figure 2.1-1 "Example of
Using External Clock" shows an use example of external clock.
G
Precautions when not using sub clock
If an oscillator is not connected to the X0A and X1A pins, connect the X0A pin to Pull-down resistor and
leave the X1A pin open.
G
Precautions during operation of PLL clock mode
If the PLL clock mode is selected, the microcontroller attempt to be working with the self-oscillating circuit
even when there is no external oscillator or external clock input is stopped. Performance of this operation,
however, cannot be guaranteed.
16
Figure 2.1-1 Example of Using External Clock
Open
and V
CC SS
X0
X1
MB90895 Series
or a voltage lower than V
CC
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CC
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