MB91F522DKBPMC datasheet(44/280 Pages) CYPRESS

44 / 280 page

Document Number: 002-04662 Rev. *F

Page 44 of 280

MB91520 Series

Handling Devices

This section explains the latch-up prevention and pin processing.

 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 supply (AVCC, AVRH) and analog input must not be exceed the digital power supply (VCC) when the

power supply to the analog system is turned on or off.

In the correct power-on sequence of the microcontroller, turn on the digital power supply (VCC) and analog power supplies

(AVCC, AVRH) simultaneously. Or, turn on the digital power supply (VCC), 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 malfunction or latch-up. Connect at

least a 2

kΩ resistor to each of the unused 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 figure 1, 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.

Figure 1 Power Supply Input Pins

The power supply pins should be connected to VCC and VSS pins 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 use as a bypass capacitor between VCC and VSS pins.

Vss

Vcc

Vss

Vcc

Vss

Vcc

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