MB90F474LPF datasheet(17/118 Pages) FUJITSU

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MB90470 Series

(6) Precautions for use of external oscillators (crystals)

The target value for the upper limit of oscillator (crystals) frequencies should be 20 MHz. Also, when operating

at internal frequencies of 16 MHz, the PLL multiplier should be used.

(7) Proper power-on/off sequence

The A/D converter power (AVCC, AVRH) and analog input (AN0 to AN7) must be turned on after the digital power

supply (VCC) is turned on. The A/D converter power (AVCC, AVRH) and analog input (AN0 to AN7) must be shut

off before the digital power supply (VCC) is shut off. Care should be taken that AVRH does not exceed AVCC. Even

when pins used as analog input pins are doubled as input ports, be sure that the input voltage does not exceed

AVCC.

Note : VCC

= VCC3 = VCC5

(8) Treatment of A/D converter power supply pins

Even if the A/D converter is not used, pins should be connected so that AVCC

= AVRH = VCC, and AVSS = VSS.

(9) Power-on procedures

In order to prevent abnormal operation of the internal built-in step-down circuits, voltage rise during power-on

should be attained within 50

µs (0.2 V to 2.7 V) .

(10) Stable power supply

Even within the operating range of the VCC supply voltage, rapid changes in supply voltage may cause abnormal

operation. As a basis for stable operation, it is recommended that voltage variation be restricted in order to limit

VCC ripple fluctuations (P-P values) to 10

% at commercial frequencies of 50 Hz to 60 Hz, and transient fluctuations

to 0.1 V/ms at instantaneous points such as power switching.

(11) Precautions for use of two power supplies

The MB90470 series usually uses the 3-V power supply as the main power source. With VCC3

= 3 V and

VCC5

= 5 V, however, it can interface with P20/A16 to P27/A23/PPG3, P30/A00/AIN0 to P37/A07/PWC1,

P40/A08/SIN2 to P47/A15/OUT5, P70/SIN0 to P77/SDA for the 5-V power supply separetely from the 3-V power

supply at all operation mode.

(Caution) The analog power supply for the A/D converter (AVCC, AVSS etc.) can only operate with the

3 V system.

(12) Crystal oscillator circuits during power-saving operation

When the power supply is lower than 2.0 V, the external crystal oscillator may not operate even when power is

on. For this reason, the use of an external clock signal is recommended.

(13) Caution : low-voltage flash models (2.4 V to 3.6 V/10 MHz) do not have security functions

(14) Treatment of unused input pins

N.C. (internally connected) pins should always be left open.

(15) When the dual-supply MB90470 series is used as a 1-supply device, use connections so that

X0A

==== VSS, and X1A ==== Open.

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