S-35390A Seiko Instruments, S-35390A Datasheet - Page 17

• Manufacturer Part Number: S-35390A
• Description: 2-Wire Real Time Clock
• Manufacturer: Seiko Instruments

Rev.1.2
Status register_1
reading
Sampling pulse
Power Supply Voltage Detector
Caution In case the power supply voltage falls and returns after the latch circuit latches “H”, the
Latch circuit
output
S-35390A has an internal power supply voltage detector, which monitors drops in the power supply voltage
by reading the BLD flag. This circuit samples the voltage for only 15.6 ms per second. If the power supply
voltage drops below the detection voltage (V
of internal status register_1 is set to “1”, and sampling stops. Detection voltage and release voltage have
approximate 0.15 V (Typ.) of hysteresis width respectively (Refer to “ Characteristics ”). Once “1” is
detected in the BLD flag, no detection operation is performed unless initialization is performed or the BLD
flag is read by the status register_1 access command, and “1” is held in the BLD flag. Sampling resumes
only when the subsequent communication action is initialization or BLD flag read.
In addition, if this BLD flag is “1” after the power supply voltage is recovered, it must be initialized.
BLD flag
_00
BLD flag can be read as “1” by a status register_1 accsess command first. After that the
sampling is resumed and the read-out of the next BLD flag is performed, the BLD flag is
reset and read as “0”. Refer to the timing chart below.
Detection
voltage
V
DD
15.6 ms
(0)
Figure 16 Timing of Power Supply Voltage Detector
1 s
Hysteresis width
0.15 V approximately
1 s
Seiko Instruments Inc.
Stop
DET
), the BLD latch circuit latches the “H” level, bit 6 (BLD flag)
2-WIRE REAL-TIME CLOCK
Release
voltage
Stop
(1)
Stop
S-35390A
(0)
17