MB90F523B Datasheet, PDF (17/99 Pages) Fujitsu Component Limited. – 16-bit Proprietary Microcontroller

MB90520A/520B Series
s HANDLING DEVICES
Take note of the following points when handling devices :
• Do not exceed maximum rated voltage (to prevent latch-up)
• Supply voltage stability
• Power-on precautions
• Power supply pins
• Crystal oscillator circuit
• Notes on using an external clock
• Precautions when not using sub-clock mode
• Treatment of unused pins
• Treatment of N.C. pins
• Treatment of pins when A/D converter is not used
• Sequence for connecting and disconnecting the A/D converter power supply and analog input pins
• Shared use of general-purpose I/O ports and LCD controller/driver SEG/COM pins
• Conditions when output from ports 0 and 1 is undefined
• Initialization
• Notes on using the DIV A, Ri and DIVW A, RWi instructions
• Notes on using REALOS
Device Handling Precautions
• Do not exceed maximum rated voltage (to prevent latch-up)
Latch-up occurs in CMOS ICs if a voltage greater than VCC or less than VSS is applied to an input or output pin
(other than a high or medium withstand voltage pin) or if the voltage applied between VCC and VSS exceeds
the rating. If latch-up occurs, the power supply current increases rapidly resulting in thermal damage to circuit
elements. Therefore, ensure that maximum ratings are not exceeded in circuit operation.
Similarly, when turning the analog power supply on or off, ensure the analog power supply voltages (AVCC,
AVRH, DVCC) and analog input voltages do not exceed the digital voltage (VCC) .
Also ensure that the voltages applied to the LCD power supply pins (V3 to V0) do not exceed the power supply
voltage (VCC) .
• Supply voltage stability
Rapid changes in supply voltage may cause the device to misoperate, even if the voltage remains within the
allowed operating range. Accordingly, ensure that the VCC supply is stable.
The standard for power supply voltage stability is a peak-to-peak VCC ripple voltage at the mains supply
frequency (50 to 60 Hz) of 10% or less of VCC and a transient voltage change rate of 0.1 V/ms or less when
turning the power supply on or off.
• Power-on precautions
To prevent misoperation of the internal regulator circuit at power-on, ensure that the power supply rising time
(0.2 V to 2.7 V) is at least 50 µs.
• Power supply pins
When multiple VCC and VSS pins are provided, connect all VCC and VSS pins to power supply or ground externally.
Although pins at the same potential are connected together in the internal device design so as to prevent
misoperation such as latch-up, connecting all VCC and VSS pins appropriately minimizes unwanted radiation,
prevents misoperation of strobe signals due to increases in the ground level, and keeps the overall output
current rating.
Also, ensure that the impedance of the VCC and VSS connections to the power supply are as low as possible.
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