s-35392a Seiko Instruments Inc., s-35392a Datasheet - Page 19

• Manufacturer Part Number: s-35392a
• Description: 2-wire Real-time Clock
• Manufacturer: Seiko Instruments Inc.

Rev.1.3
Low Power Supply Voltage Detection Circuit
Circuits Power-on and Low Power Supply Voltage Detection
The S-35392A 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, be sure to initialize the circuit. Without initializing,
Read in the next BLD flag is done after sampling, the BLD flag gets reset to “0”. In this case, be sure to initialize although
the BLD flag is in “0” because the internal circuit may be in the indefinite status.
Figure 21 shows the changes of the POC flag and BLD flag due to V
Status register 1
reading
Sampling pulse
Detection voltage
_00
POC flag
BLD flag
BLD flag
BLD flag
reading
V
V
DD
DD
15.6 ms
Figure 20 Timing of Low Power Supply Voltage Detection Circuit
1 s
Hysteresis width
0.15 V approximately
1 s
Figure 21 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
2-WIRE REAL-TIME CLOCK
Release voltage
Stop
Low power supply
voltage detection
voltage
Stop
S-35392A
V
SS
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