MB91F467DA datasheet(21/140 Pages) FUJITSU

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MB91460D Series

DS07-16612-2E

■ HANDLING DEVICES

Preventing Latch-up

Latch-up may occur in a CMOS IC if a voltage higher than (VDD5, VDD35 or HVDD5) or less than (VSS5 or HVSS5)

is applied to an input or output pin or if a voltage exceeding the rating is applied between the power supply pins

and ground pins. If latch-up occurs, the power supply current increases rapidly, sometimes resulting in thermal

breakdown of the device. Therefore, be very careful not to apply voltages in excess of the absolute maximum

ratings.

Handling of unused input pins

If unused input pins are left open, abnormal operation may result. Any unused input pins should be connected

to pull-up or pull-down resistor (2K

Ω to 10KΩ) or enable internal pullup or pulldown resisters (PPER/PPCR)

before the input enable (PORTEN) is activated by software. The mode pins MD_x can be connected to VSS5 or

VDD5 directly. Unused ALARM input pins can be connected to AVSS5 directly.

Power supply pins

In MB91460D series, devices including multiple power supply pins and ground pins are designed as follows;

pins necessary to be at the same potential are interconnected internally to prevent malfunctions such as latch-

up. All of the power supply pins and ground pins must be externally connected to the power supply and ground

respectively in order to reduce unnecessary radiation, to prevent strobe signal malfunctions due to the ground

level rising and to follow the total output current ratings. Furthermore, the power supply pins and ground pins of

the MB91460D series must be connected to the current supply source via a low impedance.

It is also recommended to connect a ceramic capacitor of approximately 0.1

μF as a bypass capacitor between

power supply pin and ground pin near this device.

This series has a built-in step-down regulator. Connect a bypass capacitor of 4.7

μF (use a X7R ceramic

capacitator) to VCC18C pin for the regulator.

Crystal oscillator circuit

Noise in proximity to the X0 (X0A) and X1 (X1A) pins can cause the device to operate abnormally. Printed circuit

boards should be designed so that the X0 (X0A) and X1 (X1A) pins, and crystal oscillator, as well as bypass

capacitors connected to ground, are located near the device and ground.

It is recommended that the printed circuit board layout be designed such that the X0 and X1 pins or X0A and

X1A pins are surrounded by ground plane for the stable operation.

Please request the oscillator manufacturer to evaluate the oscillational characteristics of the crystal and this

device.

Notes on using external clock

When using the external clock, it is necessary to simultaneously supply the X0 (X0A) and the X1 (X1A) pins. In

the described combination, X1 (X1A) should be supplied with a clock signal which has the opposite phase to

the X0 (X0A) pins. At X0 and X1, a frequency up to 16 MHz is possible.

(Continued)

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