4556 datasheet(61/145 Pages) RENESAS

61 / 145 page

Rev.3.02

Dec 22, 2006

page 61 of 142

REJ03B0025-0302

4556 Group

Fig. 57 Bypass capacitor across the VSS line and the VDD line

2. Connection of bypass capacitor across VSS line and VDD line

Connect an approximately 0.1

µF bypass capacitor across the VSS

line and the VDD line as follows:

• Connect a bypass capacitor across the VSS pin and the VDD pin

at equal length.

• Connect a bypass capacitor across the VSS pin and the VDD pin

with the shortest possible wiring.

• Use lines with a larger diameter than other signal lines for VSS

line and VDD line.

• Connect the power source wiring via a bypass capacitor to the

VSS pin and the VDD pin.

VSS

VDD

VSS

VDD

N.G.

O.K.

(3) Wiring to CNVSS pin

Connect CNVSS pin to a GND pattern at the shortest distance.

The GND pattern is required to be as close as possible to the GND

supplied to VSS.

In order to improve the noise reduction, to connect a 5 k

Ω resistor

serially to the CNVSS pin - GND line may be valid.

As well as the above-mentioned, in this case, connect to a GND

pattern at the shortest distance. The GND pattern is required to be

as close as possible to the GND supplied to VSS.

The CNVSS pin of the One Time PROM is the power source input

pin for the built-in One Time PROM. When programming in the

built-in One Time PROM, the impedance of the CNVSS pin is low to

allow the electric current for writing flow into the One Time PROM.

Because of this, noise can enter easily. If noise enters the CNVSS

pin, abnormal instruction codes or data are read from the built-in

One Time PROM, which may cause a program runaway.

Fig. 56 Wiring for the CNVSS pin of the One Time PROM

About 5k

Ω

VSS

The shortest

CNVSS

(Note)

Note: This indicates pin.

4556 Datasheet(PDF) 61 Page - Renesas Technology Corp

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