S-35390A Datasheet, PDF (39/54 Pages) Seiko Instruments Inc – 2-WIRE REAL-TIME CLOCK

Rev.2.4_00
2-WIRE REAL-TIME CLOCK
S-35390A
2. Measurement of oscillation frequency
When the S-35390A is turned on, the internal power-on detector operates and a signal of 1 Hz is output from the INT1
pin to select the crystal oscillator and optimize the C_g value. Turn the power on and measure the signal with a frequency
counter following the circuit configuration shown in Figure 51.
If 1 Hz signal is not output, the power-on detector does not operate normally. Turn off the power and then turn it on
again. For how to apply power, refer to “„ Power-on Detector and Register Status”.
Remark If the error range is ±1 ppm in relation to 1 Hz, the time is shifted by approximately 2.6 seconds per month
(calculated using the following expression).
10^–6 (1 ppm) × 60 seconds × 60 minutes × 24 hours × 30 days = 2.592 seconds
1 kΩ
1 kΩ
SDA
SCL
Open
or pull-up
INT2
VDD
XIN
S-35390A
XOUT
INT1
VSS
Cg 10 kΩ
Frequency
counter
Figure 51 Configuration of Oscillation Frequency Measurement Circuit
Caution
1. Use a high-accuracy frequency counter of 7 digits or more.
2. Measure the oscillation frequency under the usage conditions.
3. Since the 1 Hz signal continues to be output, initialization must be executed during normal
operation.
Seiko Instruments Inc.
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