MB90455 Series
13
Caution on Operations during PLL Clock Mode
If the PLL clock mode is selected, the microcontroller attempt to be working with the self-oscillating circuit even
when there is no external oscillator or external clock input is stopped. Performance of this operation, however,
cannot be guaranteed.
Sequence of turning on power of A/D converter and applying analog input
Be sure to turn on digital power (Vcc) before applying signals to the A/D converter and applying analog input
signals (AN0 to AN7 pins).
Be sure to turn off the power of A/D converter and analog input before turning off the digital power source.
Be sure not to apply AVR exceeding AVcc when turning on and off. (No problems occur if analog and digital
power is turned on and off simultaneously.)
Handling pins when A/D converter is not used
If the A/D converter is not used, connect the pins under the following conditions: “AVcc=AVR=Vcc,” and
“Avss=Vss”
Note on turning on power
For preventing malfunctions on built-in step-down circuit, maintain a minimum of 50
μ
s of voltage rising time
(between 0.2 V and 2.7 V) when turning on the power.
Stabilization of supply voltage
A sudden change in the supply voltage may cause the device to malfunction even within the specified Vcc
supply voltage operating range. Therefore, the Vcc supply voltage should be stabilized.
For reference, the supply voltage should be controlled so that Vcc ripple variations (peak-to-peak values) at
commercial frequencies (50 Hz to 60 Hz) fall below 10
%
of the standard V
CC
supply voltage and the coefficient
of fluctuation does not exceed 0.1 V/ms at instantaneous power switching.