3-WIRE REAL-TIME CLOCK
S-35190A
Rev.2.4_00
2. Measurement of oscillation frequency
When the S-35190A is turned on, the internal power-on detector operates and a signal of 1 Hz is output from the INT pin
to select the crystal oscillator and optimize the Cg value. Turn the power on and measure the signal with a frequency
counter following the circuit configuration shown in Figure 46.
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
×
×
×
×
=
VDD
XIN
10 kΩ
10 kΩ
SIO
C
g
10 kΩ
SCK
S-35190A
XOUT
INT
Frequency
counter
Open
CS
VSS
Figure 46 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.
37
SII [ SEIKO INSTRUMENTS INC ]
