MB90F347CE datasheet(25/85 Pages) FUJITSU

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MB90340E Series

Sequence for Turning On the Power Supply to the A/D Converter and Analog Inputs

Make sure to turn on the A/D converter power supply (AVCC, AVRH, AVRL) and analog inputs (AN0 to AN23)

after turning-on the digital power supply (VCC).

Turn-off the digital power after turning off the A/D converter supply and analog inputs. In this case, make sure

that the voltage does not exceed AVRH or AVCC (turning on/off the analog and digital power supplies simulta-

neously is acceptable).

Connection of Unused A/D Converter Pins when the A/D Converter is Used

Connect unused pins of A/D converter to AVCC

= VCC, AVSS = AVRH = AVRL = VSS.

Crystal Oscillator Circuit

The X0, X1 pins and X0A, X1A pins may be possible causes of abnormal operation. Make sure to provide bypass

capacitors via the shortest distance from X0, X1 pins and X0A, X1A pins, crystal oscillator (or ceramic oscillator)

and ground lines, and make sure, to the utmost effort, that the oscillation circuit lines do not cross the lines of

other circuits. It is highly recommended to provide a printed circuit board art work surrounding X0, X1 pins and

X0A, X1A pins with a ground area for stabilizing the operation.

For each of the mass-production products, request an oscillator evaluation from the manufacturer of the oscillator

you are using.

Pull-up/down resistors

The MB90340E Series does not support internal pull-up/down resistors (except for the pull-up resistors built into

ports 0 to 3). Use external components where needed.

Using external clock

To use an external clock, drive the X0 pin and leave the X1 pin open.

10. Precautions when not using a sub clock signal

If you do not connect pins X0A and X1A to an oscillator, use pull-down handling on the X0A pin, and leave the

X1A pin open.

11. Notes on operation in PLL clock mode

If PLL clock mode is selected, the microcontroller attempt to be working with the self-oscillating circuit even when

there is no external oscillator or the external clock input is stopped. Performance of this operation, however,

cannot be guaranteed.

12. Notes on Power-On

To prevent the internal regulator circuit from malfunctioning, set the voltage rise time during power-on to 50

µs

or more (0.2 V to 2.7 V)

13. Stabilization of power 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.

Stabilize the power supply voltage as follows as a standard level of stabilization.

MB90340E Series

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