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MB91725 Series
DS07-16914-1E
29
■ HANDLING DEVICE
For latch-up prevention
If a voltage higher than VCC (VCC5, VCCE) or a voltage lower than VSS is applied to an I/O pin, or if a voltage
exceeding the ratings is applied between VCC and VSS pins, a latch-up may occur in CMOS IC. If the latch-up
occurs, the power supply current increases excessively and device elements may be damaged by heat. Take
care to prevent any voltage from exceeding the maximum ratings in device application.
Also, the power supply (AVCC, AVRH) to the analog system, analog input, and power supply to high-current output
buffer pins must not exceed the digital power supply (VCC) when the power supply to the analog system and
high-current output buffer pins is turned on or off.
In the correct power-on sequence, turn on the digital power supply (VCC) and analog power supplies (AVCC,
AVRH) simultaneously. Or, turn on the digital power supply (VCC) first, and then turn on analog power supplies
(AVCC, AVRH).
Treatment of unused pins
If unused input pins are left open, they may cause a permanent damage to the device due to device malfunction
or latch-up. Connect a 2k
Ω or higher resistor to each of unused input pins for pull-up or pull-down processing.
Also, if I/O pins are not used, they must be set to the output state for releasing or they must be set to the input
state and treated in the same way as for the input pins.
Power supply pins
The device is designed to ensure that if the device contains multiple Vcc or Vss pins, the pins that should be at
the same potential are interconnected to prevent latch-up or other malfunctions. Further, connect these pins to
an external power supply or ground to reduce unwanted radiation, prevent strobe signals from malfunctioning
due to a raised ground level, and fulfill the total output current standard, etc. As shown below , all VSS power
supply pins must be treated in the similar way. If multiple VCC or VSS systems are connected, the device cannot
operate correctly even within the guaranteed operating range.
The power supply pins should be connected to VCC and VSS of this device at the low impedance from the power
supply source.
In the area close to this device, a ceramic capacitor having the capacitance larger than the capacitor of C pin is
recommended to connect as a bypass capacitor between VCC and VSS pins.
V
CC
V
SS
V
CC
V
CC
V
SS
V
SS
V
CC
V
CC
V
SS
V
SS