Dec. 15 ’97
I
2
C-bus Serial Interface
Real Time Clock (8pin SSOP)
RS5C372B
s
OUTLINE
The RS5C372B is a CMOS type real-time clock which is connected to the CPU via 2-wire and capable of serial
transmission of clock and calendar data to the CPU. The RS5C372B can generate various periodic interrupt
clock pulses lasting for long period (one month), and alarm interrupt can be made by days of the week, hours,
and minutes by two incorporated systems. Since an oscillation circuit is driven at a constant voltage, it
undergoes fluctuations of few voltage and consequently offers low current consumption (0.5µA at 3V). It also
provides an oscillator halt sensing function applicable for data validation at power-on and other occasions and
32kHz clock output (CMOS output) for an external micro computer. The product also incorporates a time
trimming circuit that adjusts the clock with higher precision by adjusting any errors in crystal oscillator
frequencies based on signals from the CPU. The crystal oscillator may be selected between 32.768kHz or
32.000kHz types. Integrated into an ultra compact and ultra thin 8 pin SSOP package, the RS5C372B is the
optimum choice for equipment requiring small sized and low power consuming products.
s
Features
q
Time keeping voltage 1.45V to 6.0V
q
Lowest supply current 0.5µA TYP (0.9µA MAX) at 3V(25°C)
(0.9µA MAX) at 3V(-40 to +85°C)
2
q
Connected to the CPU via only 2-wire (I C-bus interface, max.400KHz, address 7bits)
q
A clock counter (hours, minutes, and seconds) and a calendar counter (leap years, years, months, days,
and days of the week) in BCD codes
q
Interrupt to the CPU (period of one month to half second, with interrupt flag, interrupt halt function)
(/INTR)
q
Two systems of alarm functions (days of the week, hours, and minutes) (/INTR)
q
Oscillation halt sensing to judge internal data validity
q
Clock output of 32.768kHz(32.000kHz) ( output controllable via a register)
(32KOUT:CMOS push-pull output)
q
Second digit adjustment by ±30 seconds
q
Automatic leap year recognition up to the year 2099
q
12-hour or 24-hour time display selectable
q
Oscillation stabilizing capacity (CG, CD) incorporated
q
High precision clock error adjustment circuit
q
Oscillator of 32.768kHz or 32.000kHz may be used
q
CMOS logic
q
Package:8pin SSOP
2
*) I C-bus is a trademark of PHILIPS ELECTRONICS N.V.
s
Block Diagram
COMPARATOR_A
32KOUT
32kHz OUTPUT
CONTROL
COMPARATOR_B
OSCIN
OSC
OSCOUT
ALARM_A REGISTER
(WEEK,MIN,HOUR)
ALARM_B REGISTER
(WEEK,MIN,HOUR)
VDD
DIVIDER
CORREC
-TION
DIV
TIME COUNTER
(SEC,MIN,HOUR,WEEK,DAY,MONTH,YEAR)
VSS
OSC
DETECT
ADDRESS
DECODER
ADDRESS
REGISTER
SCL
I/O
CONTROL
/INTR
INTERRUPT CONTROL
SHIFT REGISTER
SDA
-1-
RICOH [ RICOH ELECTRONICS DEVICES DIVISION ]
