S-35199A01 Datasheet, PDF (44/54 Pages) Seiko Instruments Inc – 3-WIRE REAL-TIME CLOCK

3-WIRE REAL-TIME CLOCK
S-35199A01
Rev.1.0_00
„ Adjustment of Oscillation Frequency
1. Configuration of oscillation
Since crystal oscillation is sensitive to external noise (the clock accuracy is affected), the following measures are
essential for optimizing the oscillation configuration.
(1) Place the S-35199A01, crystal oscillator, and external capacitor (C_g) as close to each other as possible.
(2) Increase the insulation resistance between pins and the substrate wiring patterns of XIN and XOUT.
(3) Do not place any signal or power lines close to the oscillator.
(4) Locating the GND layer immediately below the oscillator is recommended.
(5) Locate the bypass capacitor adjacent to the power supply pin of the S-35199A01.
Parasitic capacitance Cpi
XIN
Rf
Cg
Crystal oscillator: 32.768 kHz
CL = 6 pF^*1
XOUT
Rd
Cg = 0 to 9.1 pF
Cpi, Cpo < 5 pF _{Parasitic capacitance Cpo}
Cd
Oscillation internal constant
standard values:
Rf = 100 MΩ
Rd = 100 kΩ
Cd = 8 pF
S-35199A01
*1. When using the crystal oscillator with a C_L value of 7 pF, externally connect C_d if necessary.
Figure 54 Connection Diagram 1
Locate the GND layer in the layer
immediately below
Cg
Make all the wiring reverse
from the crystal oscillator
Crystal oscillator
VSS A2 A3
XIN B2 B3
XOUT C2 VDD
D1 D2 D3
S-35199A01
Top View
Surface wiring
Rear surface
wiring
Figure 55 Connection Diagram 2
Caution
44
1. When using the crystal oscillator with a C_L exceeding the rated value (7 pF) (e.g : C_L = 12.5 pF),
oscillation operation may become unstable. Use a crystal oscillator with a C_L value of 6 pF or 7 pF.
2. Oscillation characteristics is subject to the variation of each component such as substrate parasitic
capacitance, parasitic resistance, crystal oscillator, and C_g. When configurating oscillator, pay
sufficient attention for them.
Seiko Instruments Inc.