RICOH RS5C372A Datasheet

I2C bus SERIAL INTERFACE

REAL-TIME CLOCK ICs

RS5C372A/B

ELECTRONIC DEVICES DIVISION

NO.EA-044-9908

APPLICATION MANUAL

NOTICE

1. The products and the product specifications described in this application manual are subject to change or discontinuation of production without notice for reasons such as improvement. Therefore, before deciding to use the products, please refer to Ricoh sales representatives for the latest information thereon.

2. This application manual may not be copied or otherwise reproduced in whole or in part without prior written consent of Ricoh.

3. Please be sure to take any necessary formalities under relevant laws or regulations before exporting or otherwise taking out of your country the products or the technical information described herein.

4. The technical information described in this application manual shows typical characteristics of and example application circuits for the products. The release of such information is not to be construed as a warranty of or a grant of license under Ricoh's or any third party's intellectual property rights or any other rights.

5. The products listed in this document are intended and designed for use as general electronic components in standard applications (office equipment, computer equipment, measuring instruments, consumer electronic products, amusement equipment etc.). Those customers intending to use a product in an application requiring extreme quality and reliability, for example, in a highly specific application where the failure or misoperation of the product could result in human injury or death (aircraft, spacevehicle, nuclear reactor control system, traffic control system, automotive and transportation equipment, combustion equipment, safety devices, life support system etc.) should first contact us.

6. We are making our continuous effort to improve the quality and reliability of our products, but semiconductor products are likely to fail with certain probability. In order prevent any injury to persons or damages to property resulting from such failure, customers should be careful enough to incorporate safety measures in their design, such as redundancy feature, fire-containment feature and fail-safe feature. We do not assume any liability or responsibility for any loss or damage arising from misuse or inappropriate use of the products.

7. Anti-radiation design is not implemented in the products described in this application manual.

8. Please contact Ricoh sales representatives should you have any questions or comments concerning the products or the technical information.

June 1995

RS5C372A

OUTLINE

...................................................................................................

FEATURES

................................................................................................

BLOCK DIAGRAM

.....................................................................................

APPLICATIONS

.........................................................................................

PIN CONFIGURATION

................................................................................

PIN DESCRIPTIONS

..................................................................................

ABSOLUTE MAXIMUM RATINGS

...............................................................

RECOMMENDED OPERATING CONDITIONS

..............................................

DC CHARACTERISTICS

.............................................................................

AC CHARACTERISTICS

.............................................................................

RS5C372B

OUTLINE

...................................................................................................

FEATURES

................................................................................................

BLOCK DIAGRAM

.....................................................................................

APPLICATIONS

.........................................................................................

PIN CONFIGURATION

................................................................................

PIN DESCRIPTIONS

..................................................................................

ABSOLUTE MAXIMUM RATINGS

...............................................................

RECOMMENDED OPERATING CONDITIONS

............................................

DC CHARACTERISTICS

...........................................................................

AC CHARACTERISTICS

...........................................................................

RS5C372A/B

GENERAL DESCRIPTION

.........................................................................

FUNCTIONAL DESCRIPTIONS

.................................................................

1. Allocation of Internal Addresses

..................................................................

2. Registers

.............................................................................................

RS5C372A/B

APPLICATION MANUAL

CONTENTS

USAGES

..................................................................................................

1. Interfacing with the CPU

...........................................................................

2. Configuration of Oscillating Circuit and Time Trimming

........................................

3. Oscillator Halt Sensing

.............................................................................

4. INTRA Output and INTRB Output Pins (RS5C372A), INTR Output Pin (RS5C372B)

....

5. Typical Applications

.................................................................................

6. Typical Characteristic Measurements

............................................................

7. Typical Software-based Operations

...............................................................

PACKAGE DIMENSIONS

..............................................................................

TAPING SPECIFICATION

..............................................................................

I2C bus SERIAL INTERFACE

REAL-TIME CLOCK IC

RS5C372A

OUTLINE

The RS5C372A is a CMOS type real-time clock which is connected to the CPU via 2-wires and capable of serial

transmission of clock and calendar data to the CPU.

The RS5C372A 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 (TYP. 0.5µA at 3V). It also provides an oscillator halt sensing function applicable for data validation at power-on and other occasions and 32-kHz clock output for an external micro computer. (Nch. open drain output) 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 from 32.768kHz or 32.000kHz types. Integrated into an ultra compact and ultra thin 8 pin SSOP package, the RS5C372A is the optimum choice for equipment requiring small sized and low power consuming products.

FEATURES

• Time keeping voltage: 1.45V to 6.0V

• Lowest supply current: 0.5µA TYP. (0.9µA MAX.) : 3V (25˚C)

(1.0µA MAX.) : 3V (–40 to +85˚C)

• Connected to the CPU via only 2-wires (I

C bus Interface, MAX.400kHz, address 7bit)

• A clock counter (counting hours, minutes, and seconds) and a calendar counter (counting leap years, years,

months, days, and days of the week) in BCD codes

• Interrupt to the CPU (period of one month to one second, interrupt flag, interrupt halt function) (INTRA, INTRB)

• Two systems of alarm functions (days of the week, hours, and minutes) (INTRA, INTRB)

• Oscillation halt sensing to judge internal data validity

• Clock output of 32.768kHz (32.000kHz) (output controllable via a register)

...

(Nch. open drain output)

• Second digit adjustment by ±30 seconds

• Automatic leap year recognition up to the year 2099

• 12-hour or 24-hour time display selectable

• Oscillation stabilizing capacity (C

G, CD) incorporated

• High precision time trimming circuit

• Oscillator of 32.768kHz or 32.000kHz may be used

• CMOS logic

• Package: 8pin SSOP

Note

· I2C bus is a trademark of PHILIPS ELECTRONICS N.V.

· Purchase of I

C components of Ricoh Company, Ltd. conveys a license under the Philips I2C Patent Rights to

use these components in an I

C system, provided that the system comforms to the I2C Standard Specifica-

tion as defined by Philips.

RS5C372A

BLOCK DIAGRAM

COMPARATOR_A

ALARM_A REGISTER

(WEEK,MIN,HOUR)

ALARM_B REGISTER

(WEEK,MIN,HOUR)

COMPARATOR_B

TIME COUNTER

(SEC,MIN,HOUR,WEEK,DAY,MONTH,YEAR)

ADDRESS

DECODER

SHIFT REGISTERINTERRUPT CONTROL

32kHz OUTPUT

CONTROL

DIVIDER

CORREC

-TION

DIVOSC

OSCIN

OSCOUT

OSC

DETECT

I/O

CONTROL

VSS

SCL

SDA

VDD

INTRA

INTRB

PIN CONFIGURATION

• 8pin SSOP

INTRB

SCL

SDA

VSS

VDD

OSCIN OSCOUT

INTRA

7 6 5

APPLICATIONS

• Communication devices (multi function phone, portable phone, PHS or pager)

• OA devices (fax, portable fax)

• Computer (desk-top and mobile PC, portable word-processor, PDA, electric note or video game)

• AV components (portable audio unit, video camera,camera, digital camera or remote controller)

• Home appliances (rice cooker, electric oven)

• Other (car navigation system, multi-function watch)

RS5C372A

PIN DESCRIPTIONS

Pin No.

Symbol Name Description

2 SCL Serial Clock Line

This pin is used to input shift clock pulses to synchronize data input/output to and from the SDA pin with this clock. Up to 6V beyond VDD may be input.

3 SDA Serial Data Line

This pin inputs and outputs written or read data in synchronization with shift clock pulses from the SCL pin. Up to 6V beyond V

DD may be input. This pin functions

as an Nch open drain output.

5 INTRA Interrupt Output A

This pin outputs periodic interrupt pulses and alarm interrupt (Alarm_A, Alarm_B) to the CPU. This pin is off when power is activated from 0V. This pin functions as an Nch open drain output.

1 INTRB Interrupt Output B

This pin outputs 32.768kHz clock pulses (when 32.768kHz crystal is used), periodic interrupt pulses to the CPU or alarm interrupt (Alarm_B). It outputs 32.768kHz when power source is activated from 0V. This pin functions as an Nch open drain output.

7 OSCIN Oscillator Circuit 6

OSCOUT

Input/Output

8 VDD

Positive Power Supply Input

4 VSS

Negative Power Supply Input

These pins configure an oscillator circuit by connecting a 32.768kHz or 32.000kHz crystal oscillator between the OSCIN–OSCOUT pins. (Any other oscillator circuit components are built into the RS5C372A.)

The VDD pin is connected to the positive power supply and VSS to the ground.

ABSOLUTE MAXIMUM RATINGS

(Vss=0V)

Symbol Item Conditions Ratings Unit

VDD Supply Voltage –0.3 to +7.0 V

VI Input Voltage SCL, SDA –0.3 to +7.0 V

VO1 Output Voltage 1 SDA –0.3 to +7.0

VO2 Output Voltage 2

INTRA, INTRB

–0.3 to +12

PD Power Dissipation Topt=25˚C 300 mW

Topt Operating Temperature –40 to +85 ˚C

Tstg Storage Temperature –55 to +125 ˚C

ABSOLUTE MAXIMUM RATINGS

Absolute Maximum ratings are threshold limit values that must not be exceeded even for an instant under

any conditions. Moreover, such values for any two items must not be reached simultaneously. Operation

above these absolute maximum ratings may cause degradation or permanent damage to the device. These

are stress ratings only and do not necessarily imply functional operation below these limits.

RS5C372A

RECOMMENDED OPERATING CONDITIONS

(Vss=0V, Topt=–40 to +85˚C)

Symbol Item Conditions MIN. TYP. MAX. Unit

VDD Supply Voltage 2.0 6.0 V

VCLK Timekeeping Voltage 1.45 6.0 V

32.768

XT Oscillation Frequency or kHz

32.000

VPUP1 Pull-up Voltage 1 SCL, SDA 6.0 V

PUP2 Pull-up Voltage 2

INTRA, INTRB

10.0 V

DC CHARACTERISTICS

Unless otherwise specified: Vss=0V, VDD

=3V, Topt=–40 to +85˚C, Oscillation frequency=32.768kHz, or 32.000kHz(R1=30kΩ)

Symbol Item Pin name Conditions MIN. TYP. MAX. Unit

VIH

“H” Input Voltage SCL, SDA 0.8VDD 6.0 V

VIL “L” Input Voltage SCL, SDA –0.3 0.2VDD V

IOL1

INTRA, INTRB

OL1=0.4V 1 mA

IOL2 SDA VOL2=0.6V 6 mA

ILK Input Leakage Current SCL

I=6V or Vss

–1 1 µA

VDD=6V

Output Off State SDA, INTRA, VO=6V or Vss

–1 1 µA

Leakage Current INTRB VDD=6V

DD=3V, Topt=25˚C

DD1 VDD SCL, SDA=3V 0.5 0.9 µA

Output=OPEN

VDD=3V,

DD2 VDD

Topt=–40 to +85˚C

1.0 µA

SCL, SDA=3V Output=OPEN

VDD=6V

DD3 VDD SCL, SDA=6V 0.8 2.0 µA

Output=OPEN

Internal Oscillation Capacitance 1

OSCIN 10 pF

Internal Oscillation Capacitance 2

OSCOUT 10 pF

Output Current

Standby Current

1) The mode outputs no clock pulses when output is open (output off state). For consumption current (output: no load) when 32kHz pulses are output from INTRB, see “USAGES, 6. Typical Characteristic Measurements”

RS5C372A

AC CHARACTERISTICS

Unless otherwise specified : VSS=0V, Topt=–40 to +85˚C, Crystal=32.768kHz or 32.000kHz

I/O conditions: V

IH=0.8×VDD, VIL=0.2×VDD, VOL=0.2×VDD, CL=50pF

Symbol Item Conditions MIN. TYP. MAX. Unit

fSCL SCL Clock Frequency 0 100 kHz tLOW SCL Clock “L” Time 4.7 µs tHIGH SCL Clock “H” Time 4.0 µs

tHD ; STA Start Condition Hold Time 4.0 µs

tSU ; STO Stop Condition Setup Time 4.0 µs tSU ; STA Start Condition Setup Time 4.7 µs

tSU ; DAT Data Setup Time 250 ns tHDH ; DAT “H” Data Hold Time 0 ns tHDL ; DAT “L” Data Hold Time 35 ns

tPL ; DAT

SDA “L” Stable Time After Falling of SCL

2.0 µs

tPZ ; DAT

SDA off Stable Time After Falling of SCL

2.0 µs

Rising Time of SCL and SDA (Input)

1000 ns

Falling Time of SCL and SDA (Input)

300 ns

tSP

Spike Width that can be Removed

50 ns

with Input Filter

) For detailed information refer to “USAGES, 1.2 Transmission System of I2C bus.”

• VDD≥2.0V (supports standard mode I2C bus)

SCL

SDA(IN)

SDA(OUT)

S Sr P

LOW

tHD;STA tHDH;DAT

Start condition

tSU;DAT

tPL;DAT

Stop condition

tHIGH

tHDL;DAT

tPZ;DAT

tHD;STA tSP

tSU;STA

tSU;STO

Repeated start condition

RS5C372A

Unless otherwise specified : VSS=0V, Topt=–40 to +85˚C, Crystal=32.768kHz or 32.000kHz

I/O conditions: V

IH=0.8×VDD, VIL=0.2×VDD, VOL=0.2×VDD, CL=50pF

Symbol Item Conditions MIN. TYP. MAX. Unit

fSCL SCL Clock Frequency 0 400 kHz

tLOW SCL Clock “L” Time 1.3 µs

tHIGH SCL Clock “H” Time 0.6 µs

tHD ; STA Start Condition Hold Time 0.6 µs

tSU ; STO Stop Condition Setup Time 0.6 µs tSU ; STA Start Condition Setup Time 0.6 µs

tSU ; DAT Data Setup Time 100 ns tHDH ; DAT “H” Data Hold Time 0 ns tHDL ; DAT “L” Data Hold Time 35 ns

tPL

; DAT

SDA “L” Stable Time After Falling of SCL

0.9 µs

tPZ ; DAT

SDA Off Stable Time After Falling of SCL

0.9 µs

Rising Time of SCL and SDA (Input)

300 ns

Falling Time of SCL and SDA (Input)

300 ns

tSP

Spike Width that can be Removed

50 ns

with Input Filter

) For detailed information refer to “USAGES, 1.2 Transmission System of I2C bus.”

• VDD≥2.5V (supports fast mode I2C bus)

SCL

SDA(IN)

SDA(OUT)

S Sr P

LOW

tHD;STA tHDH;DAT

Start condition

tSU;DAT

tPL;DAT

Stop condition

tHIGH

tHDL;DAT

tPZ;DAT

tHD;STA tSP

tSU;STA

tSU;STO

Repeated start condition

I2C bus SERIAL INTERFACE

REAL-TIME CLOCK IC

RS5C372B

OUTLINE

The RS5C372B is a CMOS type real-time clock which is connected to the CPU via 2-wires 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 (TYP. 0.5µA at 3V). It also provides an oscillator halt sensing function applicable for data validation at power-on and other occasions and 32-kHz clock output for an external micro computer. (CMOS output) 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 from

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.

FEATURES

• Time keeping voltage: 1.45V to 6.0V

• Lowest supply current: 0.5µA TYP. (0.9µA MAX.) : 3V (25˚C)

(1.0µA MAX.) : 3V (–40 to +85˚C)

• Connected to the CPU via only 2-wires (I

C bus Interface, MAX.400kHz, address 7bit)

• A clock counter (counting hours, minutes, and seconds) and a calendar counter (counting leap years, years,

months, days, and days of the week) in BCD codes

• Interrupt to the CPU (period of one month to one second, interrupt flag, interrupt halt function) (INTR)

• Two systems of alarm functions (days of the week, hours, and minutes) (INTR)

• Oscillation halt sensing to judge internal data validity

• Clock output of 32.768kHz (32.000kHz) (output controllable via a register)

...

(CMOS output)

• Second digit adjustment by ±30 seconds

• Automatic leap year recognition up to the year 2099

• 12-hour or 24-hour time display selectable

• Oscillation stabilizing capacity (C

G, CD) incorporated

• High precision time trimming circuit

• Oscillator of 32.768kHz or 32.000kHz may be used

• CMOS logic

• Package: 8pin SSOP

Note

· I2C bus is a trademark of PHILIPS ELECTRONICS N.V.

· Purchase of I

C components of Ricoh Company, Ltd. conveys a license under the Philips I2C Patent Rights to

use these components in an I

C system, provided that the system comforms to the I2C Standard Specifica-

tion as defined by Philips.

RS5C372B

BLOCK DIAGRAM

COMPARATOR_A

ALARM_A REGISTER

(WEEK,MIN,HOUR)

ALARM_B REGISTER

(WEEK,MIN,HOUR)

COMPARATOR_B

TIME COUNTER

(SEC,MIN,HOUR,WEEK,DAY,MONTH,YEAR)

ADDRESS

DECODER

SHIFT REGISTERINTERRUPT CONTROL

32kHz OUTPUT

CONTROL

DIVIDER

CORREC

-TION

DIVOSC

OSCIN

OSCOUT

32KOUT

OSC

DETECT

I/O

CONTROL

VSS

SCL

SDA

VDD

INTR

PIN CONFIGURATION

• 8pin SSOP

32KOUT

SCL

SDA

VSS

VDD

OSCIN OSCOUT

INTR

7 6 5

APPLICATIONS

• Communication devices (multi function phone, portable phone, PHS or pager)

• OA devices (fax, portable fax)

• Computer (desk-top and mobile PC, portable word-processor, PDA, electric note or video game)

• AV components (portable audio unit, video camera,camera, digital camera or remote controller)

• Home appliances (rice cooker, electric oven)

• Other (car navigation system, multi-function watch)

RS5C372B

PIN DESCRIPTIONS

Pin No.

Symbol Name Description

2 SCL Serial Clock Line

This pin is used to input shift clock pulses to synchronize data input/output to and from the SDA pin with this clock. Up to 6V beyond VDD may be input.

3 SDA Serial Data Line

This pin inputs and outputs written or read data in synchronization with shift clock pulses from the SCL pin. Up to 6V beyond V

DD may be input. This pin functions

as an Nch open drain output.

5 INTR Interrupt Output

This pin outputs periodic interrupt pulses and alarm interrupt (Alarm_A, Alarm_B) to the CPU. This pin is off when power is activated from 0V. This pin functions as an Nch open drain output.

1 32KOUT

32-kHz Clock Output

The 32KOUT pin is used to output 32.768kHz clock pulses (when 32.768kHz crystal is used). Enabled at power-on from 0volts. CMOS output. The RS5C372B can disable 32-kHz clock output in response to a command from the host computer.

7 OSCIN Oscillator Circuit 6

OSCOUT

Input/Output

8 VDD

Positive Power Supply Input

4 VSS

Negative Power Supply Input

The VDD pin is connected to the positive power supply and VSS to the ground.

ABSOLUTE MAXIMUM RATINGS

(Vss=0V)

Symbol Item Conditions Ratings Unit

VDD Supply Voltage –0.3 to +7.0 V

VI Input Voltage SCL, SDA –0.3 to +7.0 V

Output Voltage 1 SDA –0.3 to +7.0

VO Output Voltage 2

INTR

–0.3 to +12 V

Output Voltage 3

32KOUT

–0.3 to VDD+0.3

PD Power Dissipation Topt=25˚C 300 mW

Topt Operating Temperature –40 to +85 ˚C

Tstg Storage Temperature –55 to +125 ˚C

ABSOLUTE MAXIMUM RATINGS

Absolute Maximum ratings are threshold limit values that must not be exceeded even for an instant under

any conditions. Moreover, such values for any two items must not be reached simultaneously. Operation

above these absolute maximum ratings may cause degradation or permanent damage to the device. These

are stress ratings only and do not necessarily imply functional operation below these limits.

RS5C372B

RECOMMENDED OPERATING CONDITIONS

(Vss=0V, Topt=–40 to +85˚C)

Symbol Item Conditions MIN. TYP. MAX. Unit

VDD Supply Voltage 2.0 6.0 V

VCLK Timekeeping Voltage 1.45 6.0 V

32.768

XT Oscillation Frequency or kHz

32.000

VPUP1 Pull-up Voltage 1 SCL, SDA 6.0 V

PUP2 Pull-up Voltage 2

INTR

10.0 V

DC CHARACTERISTICS

Unless otherwise specified: Vss=0V, VDD

=3V, Topt=–40 to +85˚C, Oscillation frequency=32.768kHz, or 32.000kHz(R1=30kΩ)

Symbol Item Pin name Conditions MIN. TYP. MAX. Unit

VIH

“H” Input Voltage SCL, SDA 0.8VDD 6.0 V

VIL “L” Input Voltage SCL, SDA –0.3 0.2VDD V

IOH “H” Output Current 32KOUT VOH=VDD–0.5V –0.5 mA

IOL1

INTR, 32KOUT

OL1=0.4V 1 mA

IOL2 SDA VOL2=0.6V 6 mA

ILK Input Leakage Current SCL

I=6V or Vss

–1 1 µA

VDD=6V

Output Off State SDA, INTR VO=6V or Vss

–1 1 µA

Leakage Current 32KOUT VDD=6V

DD=3V, Topt=25˚C

DD1 VDD SCL, SDA=3V 0.5 0.9 µA

Output=OPEN

VDD=3V,

DD2 VDD

Topt=–40 to +85˚C

1.0 µA

SCL, SDA=3V Output=OPEN

VDD=6V

DD3 VDD SCL, SDA=6V 0.8 2.0 µA

Output=Open

Internal Oscillation Capacitance 1

OSCIN 10 pF

Internal Oscillation Capacitance 2

OSCOUT 10 pF

“L” Output Current

Standby Current

1) The mode outputs no clock pulses when output is open (output off state). For consumption current (output: no load) when 32kHz pulses are output from 32KOUT, see “USAGES, 6. Typical Characteristic Measurements”

RS5C372B

AC CHARACTERISTICS

Unless otherwise specified : VSS=0V, Topt=–40 to +85˚C, Crystal=32.768kHz or 32.000kHz

I/O conditions: V

IH=0.8×VDD, VIL=0.2×VDD, VOL=0.2×VDD, CL=50pF

Symbol Item Conditions MIN. TYP. MAX. Unit

fSCL SCL Clock Frequency 0 100 kHz tLOW SCL Clock “L” Time 4.7 µs tHIGH SCL Clock “H” Time 4.0 µs

tHD ; STA Start Condition Hold Time 4.0 µs

tSU ; STO Stop Condition Hetup Time 4.0 µs tSU ; STA Start Condition Setup Time 4.7 µs

tSU ; DAT Data Setup Time 250 ns tHDH ; DAT “H” Data Hold Time 0 ns tHDL ; DAT “L” Data Hold Time 35 ns

tPL ; DAT

SDA “L” Stable Time After Falling of SCL

2.0 µs

tPZ ; DAT

SDA Off Stable Time After Falling of SCL

2.0 µs

Rising Time of SCL and SDA (Input)

1000 ns

Falling Time of SCL and SDA (Input)

300 ns

tSP

Spike Width that can be Removed

50 ns

with Input Filter

) For detailed information refer to “USAGES, 1.2 Transmission System of I2C bus.”

• VDD≥2.0V (supports standard mode I2C bus)

SCL

SDA(IN)

SDA(OUT)

S Sr P

LOW

tHD;STA tHDH;DAT

Start condition

tSU;DAT

tPL;DAT

Stop condition

tHIGH

tHDL;DAT

tPZ;DAT

tHD;STA tSP

tSU;STA

tSU;STO

Repeated start condition

RS5C372B

Unless otherwise specified : VSS=0V, Topt=–40 to +85˚C, Crystal=32.768kHz or 32.000kHz

I/O conditions: V

IH=0.8×VDD, VIL=0.2×VDD, VOL=0.2×VDD, CL=50pF

Symbol Item Conditions MIN. TYP. MAX. Unit

fSCL SCL Clock Frequency 0 400 kHz

tLOW SCL Clock “L” Time 1.3 µs

tHIGH SCL Clock “H” Time 0.6 µs

tHD ; STA Start Condition Hold Time 0.6 µs

tSU ; STO Stop Condition Setup Time 0.6 µs tSU ; STA Start Condition Setup Time 0.6 µs

tSU ; DAT Data Setup Time 100 ns tHDH ; DAT “H” Data Hold Time 0 ns tHDL ; DAT “L” Data Hold Time 35 ns

tPL

; DAT

SDA “L” Stable Time After Falling of SCL

0.9 µs

tPZ ; DAT

SDA Off Stable Time After Falling of SCL

0.9 µs

Rising Time of SCL and SDA (Input)

300 ns

Falling Time of SCL and SDA (Input)

300 ns

tSP

Spike Width that can be Removed

50 ns

with Input Filter

) For detailed information refer to “USAGES, 1.2 Transmission System of I2C bus.”

• VDD≥2.5V (supports fast mode I2C bus)

SCL

SDA(IN)

SDA(OUT)

S Sr P

LOW

tHD;STA tHDH;DAT

Start condition

tSU;DAT

tPL;DAT

Stop condition

tHIGH

tHDL;DAT

tPZ;DAT

tHD;STA tSP

tSU;STA

tSU;STO

Repeated start condition

RS5C372A/B

GENERAL DESCRIPTION

1. Interfacing with the CPU

The RS5C372A/B read /write data over I2C bus interface via 2-wires: SDA (data) and SCL (clock). Since the output of the I/O pin of SDA is open drain, data interfacing with a CPU with different supply voltage is possible by applying pull-up resistor on the circuit board. The maximum clock frequency of 400kHz of SCL enables data transfer in I

bus fast mode.

2. Clock function

The clock function of the RS5C372A/B allows write/read data from lower two digits of the dominical year to seconds to and from the CPU. When lower two digits of the dominical year are multiples of 4, the year is recognized as a leap year automatically. Up to the year 2099 leap years will be automatically recognized.

3. Alarm function

RS5C372A

The RS5C372A has an alarm function that outputs an interrupt signal from INTRA or INTRB output pins to the CPU when the day of the week, hour or minute corresponds to the setting. These two systems of alarms (Alarm_A, Alarm_B), each may output interrupt signal separately at a specified time. The alarm may be selectable between on and off for each day of the week, thus allowing outputting alarm everyday or on a specific day of the week. The Alarm_A is output from the INTRA pin while the Alarm_B is output from either the INTRA or the INTRB pins. Polling is possible separately for each alarm function.

RS5C372B

The RS5C372B has an alarm function that outputs an interrupt signal from INTR output pin to the CPU when the day of the week, hour or minute corresponds to the setting. These two systems of alarms (Alarm_A, Alarm_B), each may output interrupt signal separately at a specified time. The alarm may be selectable between on and off for each day of the week, thus allowing outputting alarm everyday or on a specific day of the week. Polling is possible separately for each alarm function.

4. High precision time trimming function

The RS5C372A/B have an internal oscillation circuit capacitance CG and CD so that an oscillation circuit may be configured simply by externally connecting a crystal. Either 32.768kHz or 32.000kHz may be selected as a crystal oscillator by setting the internal register appropriately. The RS5C372A/B incorporate a time trimming circuit that adjusts gain or loss of the clock from the CPU up to approx. ±189ppm (±194ppm when 32.000kHz crystal is used) by approximately 3ppm steps to correct discrepancy in oscillation frequency. (Error after correction: ±1.5ppm: 25˚C) Thus by adjusting frequencies for each system,

· Clock display is possible at much higher precision than conventional real-time clock while using a crystal with broader fluctuation in precision.

· Even seasonal frequency fluctuation may be corrected by adjusting seasonal clock error.

) The year 2000 is a leap year while the year 2100 is not.

RS5C372A/B

· For those systems that have temperature detection precision of clock function may be increased by correcting clock error according to temperature fluctuations.

5. Oscillation halt sensing

The oscillation halt sensing function uses a register to store oscillation halt information. This function may be used to determine if the RS5C372A/B supply power has been booted from 0V and if it has been backed up. This function is useful for determining if clock data is valid or invalid.

6. Periodic interrupt

RS5C372A

The RS5C372A can output periodic interrupt pulses in addition to alarm function from the INTRA and INTRB pins. This frequency may be selected from 2Hz (every 0.5 seconds), 1Hz (every second), 1/60Hz (every minute), 1/3600Hz (every hour) and monthly (1st of month). Output wave form for periodic interrupt may be selected from regular pulse waveform (2Hz and 1Hz) and waveforms (every second, every minute, every hour and every month) that are appropriate for CPU level interrupt. Outputs may be selected either INTRA or INTRB. The RS5C372A/B has polling function that monitors pin status in the register.

RS5C372B

The RS5C372B can output periodic interrupt pulses in addition to alarm function from the INTR pin. This frequency may be selected from 2Hz (every 0.5 seconds), 1Hz (every second), 1/60Hz (every minute), 1/3600Hz (every hour) and monthly (1st of month). Output wave form for periodic interrupt may be selected from regular pulse waveform (2Hz and 1Hz) and waveforms (every second, every minute, every hour and every month) that are appropriate for CPU level interrupt. Periodic Interrupt outputs from INTR. The RS5C372B has polling function that monitors pin status in the register.

7. 32-kHz clock output

RS5C372A

The RS5C372A may output oscillation frequency from the INTRB pin. This clock output is set for output by default, which is set to on or off by setting the register.

RS5C372B

The RS5C372B may output oscillation frequency from the 32KOUT pin. This clock output is set for output by default, which is set to on or off by setting the register. The 32KOUT pin is CMOS push-pull output terminal.

Note

The year-digit counter of RS5C372A/B counts only lower two digits of a year and no counter is supplied for upper two digits. When you are going to use this product in a system that must cope with “2000 year problem” which shall be corrected by software.

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