Document Number: 002-04721 Rev.*A
Page 32 of 74
MB966B0 Series
13. Handling Devices
Special care is required for the following when handling the device:
• Latch-up prevention
• Unused pins handling
• External clock usage
• Notes on PLL clock mode operation
• Power supply pins (V
cc
/V
ss
)
• Crystal oscillator and ceramic resonator circuit
• Turn on sequence of power supply to A/D converter and analog inputs
• Pin handling when not using the A/D converter
• Notes on Power-on
• Stabilization of power supply voltage
• Serial communication
• Mode Pin (MD)
13.1 Latch-up prevention
CMOS IC chips may suffer latch-up under the following conditions:
• A voltage higher than VCC or lower than VSS is applied to an input or output pin.
• A voltage higher than the rated voltage is applied between Vcc pins and Vss pins.
• The AVCC power supply is applied before the VCC voltage.
Latch-up may increase the power supply current dramatically, causing thermal damages to the device.
For the same reason, extra care is required to not let the analog power-supply voltage (AV
CC
, AVRH) exceed the digital
power-supply voltage.
13.2 Unused pins handling
Unused input pins can be left open when the input is disabled (corresponding bit of Port Input Enable register PIER = 0).
Leaving unused input pins open when the input is enabled may result in misbehavior and possible permanent damage of the device.
To prevent latch-up, they must therefore be pulled up or pulled down through resistors which should be more than 2k
.
Unused bidirectional pins can be set either to the output state and be then left open, or to the input state with either input disabled or
external pull-up/pull-down resistor as described above.
13.3 External clock usage
The permitted frequency range of an external clock depends on the oscillator type and configuration.
See AC Characteristics for detailed modes and frequency limits. Single and opposite phase external clocks must be connected as
follows:
13.3.1 Single phase external clock for Main oscillator
When using a single phase external clock for the Main oscillator, X0 pin must be driven and X1 pin left open.
And supply 1.8V power to the external clock.
X0
X1
