FOR AUTOMOTIVE 105°C OPERATION 2-WIRE REAL-TIME CLOCK

S-35390A H Series

Seiko Instruments Inc.

39



Adjustment of Oscillation Frequency

1. Configuration of crystal oscillation circuit

Since the crystal oscillation circuit is sensitive to external noise (the clock accuracy is affected), the following measures

are essential for optimizing the configuration.

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

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

• Locating the GND layer immediately below the crystal oscillation circuit is recommended.

• Locate the bypass capacitor adjacent to the power supply pin of the S-35390A H Series.

S-35390A H Series

XOUT

XIN

 (typ.)

 (typ.)

Crystal oscillator: 32.768 kHz

*1.

*2.

direction that it advances.

*3.

Design the board so that the parasitic capacitance is within 5 pF.

Figure 49 Connection Diagram 1

XIN

XOUT

VSS

8

7

6

5

1

2

3

4

S-35390A H

Series

Locate the GND layer in the

layer immediately below

Crystal

oscillator

Figure 50 Connection Diagram 2

2. Oscillation characteristics is subject to the variation of each component such as substrate parasitic

circuit, pay sufficient attention for them.