s-35399a02 Seiko Instruments Inc., s-35399a02 Datasheet - Page 24

• Manufacturer Part Number: s-35399a02
• Description: 2-wire Real-time Clock
• Manufacturer: Seiko Instruments Inc.

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BLD flag reading
Sampling pulse
BLD flag
Status register 1
reading
2-WIRE REAL-TIME CLOCK
S-35399A02
Low Power Supply Voltage Detection Circuit
Circuits Power-on and Low Power Supply Voltage Detection
The S-35399A02 has a low power supply voltage detection circuit, so that users can monitor drops in the power supply
voltage by reading the BLD flag (B1 in the status register 1). There is a hysteresis width of approx. 0.15 V (Typ.) between
detection voltage and release voltage (refer to “
detection circuit does the sampling operation only once in one sec for 15.6 ms.
If the power supply voltage decreases to the level of detection voltage (V
sampling operation stops. Once “1” is detected in the BLD flag, no sampling operation is performed even if the power
supply voltage increases to the level of release voltage or more, and “1” is held in the BLD flag. After initialization, or once
the BLD flag is read, the BLD flag is automatically set to “0” to restart the sampling operation.
If the BLD flag is “1” even after the power supply voltage is recovered, the internal circuit may be in the indefinite status. In
this case, be sure to initialize the circuit.
Figure 29 shows the changes of the POC flag and BLD flag due to V
POC flag
BLD flag
V
DD
Detection
voltage
V
DD
15.6 ms
Figure 28 Timing of Low Power Supply Voltage Detection Circuit
1 s
Hysteresis width
0.15 V approximately
1 s
Figure 29 POC Flag and BLD Flag
Seiko Instruments Inc.
Stop
Characteristics (Typical Data)” ). The low power supply voltage
Low power supply
voltage detection
voltage
DD
fluctuation.
DET
) or less, “1” is set to the BLD flag so that
Release
voltage
Stop
Low power supply
voltage detection
voltage
Rev.1.0
Stop
_00
V
SS