7643 datasheet(118/424 Pages) RENESAS

118 / 424 page

Rev.2.00

Aug 28, 2006

page 101 of 103

REJ09B0133-0200

OVERVIEW

7643 Group

USAGE NOTES

Oscillator Connection Notice

The built-in feedback register (1 M

Ω) and the dumping resistor

(400

Ω) is internally connected between pins XIN and XOUT.

Power Source Voltage

When the power source voltage value of a microcomputer is less

than the value which is indicated as the recommended operating

conditions, the microcomputer does not operate normally and may

perform unstable operation.

In a system where the power source voltage drops slowly when

the power source voltage drops or the power supply is turned off,

reset a microcomputer when the power source voltage is less than

the recommended operating conditions and design a system not

to cause errors to the system by this unstable operation.

Power Supply Pins Treatment Notice

Please connect 0.1

µF and 4.7 µF capacitors in parallel between

pins Vcc and Vss, and pins AVss and AVcc.

These capacitors must be connected as close as possible be-

tween the DC supply and GND pins, and also the analog supply

pin and corresponding GND pin.

Wiring patterns for these supply and GND pins must be wider than

other signal patterns.

These filter capacitors should not be placed near the LPF pins as

they will cause noise problems

Reset Pin Treatment Notice (Noise

Elimination)

If the reset input signal rises very slowly, we recommend attaching

a capacitor, such as a 1000 pF ceramic capacitor with excellent

high frequency characteristics, between the RESET pin and the

Vss pin.

Please note the following two issues for this capacitor connection.

(1) Capacitor wiring pattern must be as short as possible (within

20 mm).

(2) The user must perform an application level operation test.

LPF Pin Treatment Notice

All passive components must be located as close as possible to

the LPF pin.

0.1

µF

680 pF

LPF pin

AVSS pin

1 k

Ω

Fig. 94 Passive components near LPF pin

•In Vcc = 3.3 V operation, connect the Ext. Cap. pin directly to the

Vcc pin in order to supply power to the USB transceiver. In addi-

tion, you will need to disable the DC-DC converter in this

operation (set bit 4 of the USB control register to “0”.) If you are

using the bus powered supply in Vcc = 3.3 V operation, the DC-

DC converter must be placed outside the MCU.

•In Vcc = 5 V operation, do not connect the external DC-DC con-

verter to the Ext. Cap. pin. Use the built-in DC-DC converter by

enabling the USB line driver.

•Make sure the USB D+/D- lines do not cross any other wires.

Keep a large GND area to protect the USB lines. Also, make sure

you use a USB specification compliant connecter for the connec-

tion.

XIN

enable

lock

FSE

USBC5

enable

USB Clock

(48 MHz)

USB FCU

enable

USBC7

USB

transceiver

enable

USBC7

DC-DC converter

enable

USBC4

current

mode

USBC3

Ext. Cap.

D+

D-

Frequency Synthesizer

Note 1

Notes 1: In Vcc = 3.3 V, connect to Vcc. In Vcc =5 V, do not connect the external DC-DC

converter to the Ext. Cap pin.

2: The resistors values depend on the layout of the printed circuit board.

Note 2

Fig.95 Peripheral circuit

AVss and AVcc Pin Treatment Notice (Noise

Elimination)

An insulation connector (Ferrite Beads) must be connected be-

tween AVss and Vss pins and between AVcc and Vcc pins.

USB

Transceiver

Treatment

(Noise

Elimination)

•The Full-Speed USB2.0 specification requires a driver -imped-

ance 28 to 44

Ω. (Refer to Clause 7.1.1.1 Full-speed (12 Mb/s)

Driver Characteristics in the USB specification.) In order to meet

the USB specification impedance requirements, connect a resis-

tor (27

Ω to 33 Ω recommended) in series to the USB D+ pin and

the USB D- pin.

In addition, in order to reduce the ringing and control the falling/

rising timing of USB D+/D- and a crossover point, connect a ca-

pacitor between the USB D+/D- pins and the Vss pin if necessary.

The values and structure of those peripheral elements depend on

the impedance characteristics and the layout of the printed circuit

board. Accordingly, evaluate your system and observe waveforms

before actual use and decide use of elements and the values of

resistors and capacitors.

•Connect a capacitor between the Ext. Cap. pin and the Vss pin.

The capacitor should have a 2.2

µF capacitor (Tantalum capaci-

tor) and a 0.1

µF capacitor (ceramic capacitor) connected in

parallel. Figure 95 for the proper positions of the peripheral com-

ponents.

USAGE NOTES

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