MB91F585ASH datasheet(35/176 Pages) CYPRESS

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Document Number: 002-04665 Rev *A

Page 34 of 175

MB91580M/S Series

Handling Devices

The latch-up prevention and pin processing are explained below.

 For latch-up prevention

If a voltage higher than VCC 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 analog power supplies (AVCC0, AVCC1, AVRH0, AVRH1) and analog input must not exceed the digital

power supply (VCC5) when the power supply to the analog system is turned on or off.

In the correct power-on sequence, turn on the digital power supply voltage (VCC5) and analog power supply voltages

(AVCC0, AVCC1, AVRH0, AVRH1) simultaneously. Alternatively, turn on the digital power supply voltage (VCC5) first,

and then turn on the analog power supplies (AVCC0, AVCC1, AVRH0, AVRH1).

 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 in following figure, 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.

 Power Supply Input Pins

VCC

VSS

VCC

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