WAKE-UP TIMER IC

PIN-SELECTABLE WAKE-UP TIMER IC

S-35720 Series

14

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Configuration of Crystal Oscillation Circuit

become a factor to worsen the clock accuracy. Therefore, the following steps are recommended for optimizing the

configuration of crystal oscillation circuit.

• Locate the bypass capacitor adjacent to the power supply pin of the S-35720 Series.

• Place the S-35720 Series and the quartz crystal as close to each other as possible, and shorten the wiring.

• Increase the insulation resistance between pins and the board wiring patterns of XIN and XOUT.

• Do not place any signal or power lines close to the crystal oscillation circuit.

• Locate the GND layer immediately below the crystal oscillation circuit.

(In the case of a multi-layer board, only the layer farthest from the crystal oscillation circuit should be located as the GND

layer. Do not locate a circuit pattern on the intermediate layers.)

XIN

XOUT

S-35720

Quartz crystal: 32.768 kHz

Ω

Ω

Parasitic

Figure 14 Configuration of Crystal Oscillation Circuit

VSS

S-35720

Top view

XIN

XOUT

Shield the perimeter with GND

Quartz crystal

Locate the GND layer in the

layer immediately below

(In the case of a multi-layer board, only

the layer farthest from the oscillation circuit

should be located as the GND layer.

Do not locate a circuit pattern on the

intermediate layers.)

Figure 15 Example of Recommended Connection Pattern Diagram

Caution Oscillation characteristics are subject to the variation of each component such as board parasitic

capacitance, parasitic resistance, quartz crystal, and external capacitor. When configuring crystal

oscillation circuit, pay sufficient attention for them.