MB91F467DA datasheet(22/137 Pages) CYPRESS

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Document Number: 002-04613 Rev. *A

Page 22 of 137

MB91460D Series

5. Handling Devices

5.1 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.

5.2 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 (2KΩ 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.

5.3 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

F 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

F (use a X7R ceramic capacitator) to VCC18C

pin for the regulator.

5.4 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.

5.5 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.

Example of using opposite phase supply

X0 (X0A)

X1 (X1A)

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