RV5C387A_03 datasheet(36/49 Pages) RICOH

Part #	RV5C387A

Description	I2C bus SERIAL INTERFACE REAL-TIME CLOCK IC WITH VOLTAGE MONITORING FUNCTION

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Manufacturer	RICOH [RICOH electronics devices division]

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RV5C387A

36

3. Oscillation Halt Sensing and Supply Voltage Monitoring

The oscillation halt sensing circuit is configured to record a halt in the oscillation of 32.768-kHz clock pulses. The

supply voltage monitoring circuit is configured to record a drop in supply voltage below a threshold voltage of 2.1 or

1.6 volts. For these functions, the real-time clock has two flag bits (ie. the XSTP bit for the former and the VDET bit

for the latter) in which 1 is set once and this setting is maintained until 0 is written.

When the XSTP bit is set to 1 for the oscillation halt sensing circuit, the VDET bit is reset to 0 for the supply voltage

monitoring circuit. The relationship between the XSTP and VDET bits is shown in the table below.

XSTP

VDET

Conditions of supply voltage and oscillation

00

No drop in supply voltage below threshold voltage and no halt in oscillation

01

Drop in supply voltage below threshold voltage and no halt in oscillation

1

*

Halt on oscillation

Supply voltage

Threshold voltage (2.1 or 1.6 volts)

Setting XSTP and

VDET bits to 0

Setting XSTP and

VDET bits to 0

Internal initialization

period

(1 to 2 seconds)

Setting VDET bit to 0

Oscillation by 32.768-kHz clock pulses

Normal voltage detector

Supply voltage monitoring (VDET)

Oscillation halt sensing (XSTP)

When the XSTP bit is set to 1 in the control register 2, the F6 to F0, WALE, DALE, CLEN2, 12/24, TEST, CT2, CT1,

CT0, VDSL, VDET, SCRATCH, CLEN1, CTFG, WAFG, and DAFG bits are reset to 0 in the oscillation adjustment

register, the control register 1, and the control register 2. The XSTP bit is also set to 1 at power-on from 0 volts. Note

that the XSTP bit may be locked to 0 and the internal register broken upon instantaneous power-down.

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RV5C387A Datasheet(PDF) 36 Page - RICOH electronics devices division

RV5C387A Datasheet(HTML) 36 Page - RICOH electronics devices division

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