Notes On Handling Devices - Fujitsu MB90460 Series Hardware Manual

CHAPTER 2 NOTES ON HANDLING DEVICES
2.1

Notes on Handling Devices

When handling devices, pay special attention to the following eight items or
procedures:
• Strict observation of maximum rated voltage (latch-up prevention)
• Stabilization of supply voltage
• Power-on
• Treatment of unused input pins
• Treatment of A/D converter power pin
• Notes on external clock
• Caution on operation during PLL clock mode
• Power supply pin
• Analog power-on sequence of A/D converter
■ Notes on Handling Devices
●
Strict observation of maximum rated voltage
A latch-up may occur on a CMOS IC if a voltage higher than Vcc or lower than Vss is applied to an input
or output pin other than medium-to-high voltage pins. A latch-up may also occur if a voltage higher than
the rating is applied between Vcc and Vss. A latch-up causes a rapid increase in the power supply current,
which can result in thermal damage to an element. Take utmost care that the maximum rated voltage is not
exceeded.
When turning the power on or off to analog circuits, be sure that the analog supply voltages (AVcc and
AVR) and analog input voltage do not exceed the digital supply voltage (Vcc).
●
Stabilize of supply voltages
Even within the operation guarantee range of the Vcc supply voltage, a malfunction can be caused if the
supply voltage undergoes a rapid change. For voltage stabilization guidelines, the Vcc ripple fluctuations
(P-P value) at commercial frequencies (50 to 60 Hz) should be suppressed to "10%" or less of the reference
Vcc value. During a momentary change such as when switching a supply voltage, voltage fluctuations
should also be suppressed so that the "transient fluctuation rate" is 0.1 V/ms or less.
●
Power-on
To prevent a malfunction in the built-in voltage drop circuit, secure "50 µs (between 0.2 V and 2.7 V)" or
more for the voltage rise time during power-on.
●
Treatment of unused input pins
An unused input pin may cause a malfunction if it is left open. Every unused input pin should be pulled up
or down.
●
Treatment of A/D converter power pin
When the A/D converter is not used, connect the pins as follows: AVcc = Vcc, AVss = AVR = Vss.
24