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OUTLINE
’03.09.25
4-wire Serial Interface
Rx5C348A/B
The Rx5C348A/B are CMOS real-time clock ICs connected to the CPU by four signal lines, CE, SCLK, SI, SO,
and configured to perform serial transmission of time and calendar data to the CPU. The periodic interrupt
circuit is configured to generate interrupt signals with six selectable interrupts ranging from 0.5 seconds to 1
month. The 2 alarm interrupt circuits generate interrupt signals at preset times. As the oscillation circuit is
driven under constant voltage, fluctuation of the oscillator frequency due to supply voltage is small, and the time
keeping current is small (TYP. 0.35µA at 3V: Rx5C348A, TYP.0.55µA at 3V: Rx5C348B). The oscillation halt
sensing circuit can be used to judge the validity of internal data in such events as power-on; The supply voltage
monitoring circuit is configured to record a drop in supply voltage below two selectable supply voltage monitoring
threshold settings. The 32.768kHz clock output function (N-channel open drain output) is intended to output
sub-clock pulses for the external microcomputer. The 32-kHz clock circuit can be disabled by certain register
settings for the Rx5C348A but cannot be disabled by any register settings for the Rx5C348B. The oscillation
adjustment circuit is intended to adjust time counts with high precision by correcting deviations in the oscillation
frequency of the crystal oscillator. These models come in an ultra-compact SSOP10 (RS5C348A/B), SSOP10G
(RV5C348A/B), TSSOP10G (RT5C348B)
Package
SSOP10 (Pin Pitch 0.5mm, Height1.25mm,
6.4mm×3.5mm)
SSOP10G (Pin Pitch 0.5mm, Height1.2mm,
4.0mm×2.9mm)
TSSOP10G (Pin Pitch 0.5mm, Height0.85mm,
4.0mm×2.9mm)
32-kHz Clock Output
Controllable by command
Keeping output enabled
Controllable by command
Keeping output enabled
Keeping output enabled
RS5C348A
RS5C348B
RV5C348A
RV5C348B
RT5C348B
FEATURES
Timekeeping supply voltage ranging from 1.45 to 5.5V
Low power consumption
Rx5C348A: 0.35µA TYP (0.8µA MAX) at VDD=3V
Rx5C348B: 0.55µA TYP (1.0µA MAX) at VDD=3V
Only four signal lines (CE, SCLK, SI, and SO) required for connection to the CPU.
Maximum clock frequency of 2 MHz (with VDD = 5V)
Time counters (counting hours, minutes, and seconds) and calendar counters (counting years, months, days,
and weeks) (in BCD format)
Interrupt circuit configured to generate interrupt signals (with interrupts ranging from 0.5 seconds to 1 month)
to the CPU and provided with an interrupt flag and an interrupt halt
2 alarm interrupt circuits (Alarm_W for week, hour, and minute alarm settings and Alarm_D for hour and
minute alarm settings)
32-kHz clock output circuit (Nch. open drain output)
The Rx5C348A is designed to disable 32-kHz clock output in response to a command from the host computer
and the Rx5C348B is designed to keep 32-kHz output enabled.
Oscillation halt sensing circuit which can be used to judge the validity of internal data
Supply voltage monitoring circuit with two supply voltage monitoring threshold settings
Automatic identification of leap years up to the year 2099
Selectable 12-hour and 24-hour mode settings
Built-in oscillation stabilization capacitors (CG and CD)
High precision oscillation adjustment circuit
Ultra-compact SSOP10 (RS5C348A/B), SSOP10G (RV5C348A/B), TSSOP10G (RT5C348B)
CMOS process
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Rev.2.01
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RICOH [ RICOH ELECTRONICS DEVICES DIVISION ]
