Datasheet

ManualsBrandsMAXIM INTEGRATED ManualsIntegrated Circuits (ICs)Timer IC t- real time clock Clock/calendar SOIC 8 N

GENERAL DESCRIPTION

The DS1307 serial real-time clock (RTC) is a low-

power, full binary-coded decimal (BCD) clock/calendar

plus 56 bytes of NV SRAM. Address and data are

transferred serially through an I

C, bidirectional bus.

The clock/calendar provides seconds, minutes, hours,

day, date, month, and year information. The end of

the month date is automatically adjusted for months

with fewer than 31 days, including corrections for leap

year. The clock operates in either the 24-hour or 12-

hour format with AM/PM indicator. The DS1307 has a

built-in power-sense circuit that detects power failures

and automatically switches to the backup supply.

Timekeeping operation continues while the part

operates from the backup supply.

TYPICAL OPERATING CIRCUIT

FEATURES

 Real-Time Clock (RTC) Counts Seconds,

Minutes, Hours, Date of the Month, Month, Day of

the week, and Year with Leap-Year

Compensation Valid Up to 2100

 56-Byte, Battery-Backed, General-Purpose RAM

with Unlimited Writes

 I

C Serial Interface

 Programmable Square-Wave Output Signal

 Automatic Power-Fail Detect and Switch Circuitry

 Consumes Less than 500nA in Battery-Backup

Mode with Oscillator Running

 Optional Industrial Temperature Range:

-40°C to +85°C

 Available in 8-Pin Plastic DIP or SO

 Underwriters Laboratories (UL) Recognized

PIN CONFIGURATIONS

SCL

SDA

BAT

GND

SQW/OUT

SCL

SDA

BAT

GND

SQW/OUT

PDIP (300 mils)SO (150 mils)

TOP VIEW

ORDERING INFORMATION

PART TEMP RANGE VOLTAGE (V)

PIN-PACKAGE TOP MARK*

DS1307+

0°C to +70°C

5.0

8 PDIP (300 mils)

DS1307

DS1307N+

-40°C to +85°C

5.0

8 PDIP (300 mils)

DS1307N

DS1307Z+

0°C to +70°C

5.0

8 SO (150 mils)

DS1307

DS1307ZN+

-40°C to +85°C

5.0

8 SO (150 mils)

DS1307N

DS1307Z+T&R

0°C to +70°C

5.0

8 SO (150 mils) Tape and Reel

DS1307

DS1307ZN+T&R

-40°C to +85°C

5.0

8 SO (150 mils) Tape and Reel

DS1307N

+Denotes a lead-free/RoHS-compliant package.

*A “+” anywhere on the top mark indicates a lead-free package. An “N” anywhere on the top mark indicates an industrial temperature range

device.

DS1307

CPU

SDA

SCL

GND

CRYSTAL

SQW/OUT

BAT

= t

DS1307

64 x 8, Serial, I

C Real-Time Clock

1 of

REV: 100208

Summary of content (14 pages)

PAGE 1
DS1307 64 x 8, Serial, I C Real-Time Clock 2 GENERAL DESCRIPTION FEATURES The DS1307 serial real-time clock (RTC) is a lowpower, full binary-coded decimal (BCD) clock/calendar plus 56 bytes of NV SRAM. Address and data are 2 transferred serially through an I C, bidirectional bus. The clock/calendar provides seconds, minutes, hours, day, date, month, and year information. The end of the month date is automatically adjusted for months with fewer than 31 days, including corrections for leap year.
PAGE 2
DS1307 64 x 8, Serial, I C Real-Time Clock ABSOLUTE MAXIMUM RATINGS Voltage Range on Any Pin Relative to Ground .................................................................................... -0.5V to +7.0V Operating Temperature Range (Noncondensing) Commercial ................................................................................................................................ 0°C to +70°C Industrial ........................................................................................
PAGE 3
2 DS1307 64 x 8, Serial, I C Real-Time Clock AC ELECTRICAL CHARACTERISTICS (VCC = 4.5V to 5.5V; TA = 0°C to +70°C, TA = -40°C to +85°C.) PARAMETER SCL Clock Frequency Bus Free Time Between a STOP and START Condition Hold Time (Repeated) START Condition SYMBOL CONDITIONS MIN TYP MAX UNITS 100 kHz fSCL 0 tBUF 4.7 µs 4.0 µs tHD:STA (Note 4) LOW Period of SCL Clock tLOW 4.7 µs HIGH Period of SCL Clock tHIGH 4.0 µs Setup Time for a Repeated START Condition tSU:STA 4.
PAGE 4
2 DS1307 64 x 8, Serial, I C Real-Time Clock TIMING DIAGRAM SDA tBUF tLOW tHD:STA tR tF SCL tHD:STA STOP tSU:STA tHIGH START tSU:STO SU:DAT tHD:DAT Figure 1.
PAGE 5
2 DS1307 64 x 8, Serial, I C Real-Time Clock TYPICAL OPERATING CHARACTERISTICS (VCC = 5.0V, TA = +25°C, unless otherwise noted.) ICCS vs. VCC 120 IBAT vs. VBAT V BAT=3.0V V CC = 0V 400 SQW=32kHz 110 350 100 SUPPLY CURRENT (uA SUPPLY CURRENT (nA 90 300 80 70 250 60 50 SQW off 200 40 30 150 20 10 100 0 1.0 2.0 3.0 VCC (V) 4.0 IBAT vs. Temperature VBACKUP (V) 3.0 3.5 SQW/OUT vs. Supply Voltage V CC=0V, V BAT=3.0 325.0 32768.5 SQW=32kHz 32768.
PAGE 6
2 DS1307 64 x 8, Serial, I C Real-Time Clock PIN DESCRIPTION PIN NAME 1 X1 2 X2 3 VBAT FUNCTION Connections for Standard 32.768kHz Quartz Crystal. The internal oscillator circuitry is designed for operation with a crystal having a specified load capacitance (CL) of 12.5pF. X1 is the input to the oscillator and can optionally be connected to an external 32.768kHz oscillator. The output of the internal oscillator, X2, is floated if an external oscillator is connected to X1.
PAGE 7
2 DS1307 64 x 8, Serial, I C Real-Time Clock OSCILLATOR CIRCUIT The DS1307 uses an external 32.768kHz crystal. The oscillator circuit does not require any external resistors or capacitors to operate. Table 1 specifies several crystal parameters for the external crystal. Figure 1 shows a functional schematic of the oscillator circuit. If using a crystal with the specified characteristics, the startup time is usually less than one second.
PAGE 8
2 DS1307 64 x 8, Serial, I C Real-Time Clock CLOCK AND CALENDAR The time and calendar information is obtained by reading the appropriate register bytes. Table 2 shows the RTC registers. The time and calendar are set or initialized by writing the appropriate register bytes. The contents of the time and calendar registers are in the BCD format. The day-of-week register increments at midnight. Values that correspond to the day of week are user-defined but must be sequential (i.e.
PAGE 9
2 DS1307 64 x 8, Serial, I C Real-Time Clock CONTROL REGISTER The DS1307 control register is used to control the operation of the SQW/OUT pin. BIT 7 OUT BIT 6 0 BIT 5 0 BIT 4 SQWE BIT 3 0 BIT 2 0 BIT 1 RS1 BIT 0 RS0 Bit 7: Output Control (OUT). This bit controls the output level of the SQW/OUT pin when the square-wave output is disabled. If SQWE = 0, the logic level on the SQW/OUT pin is 1 if OUT = 1 and is 0 if OUT = 0.
PAGE 10
2 DS1307 64 x 8, Serial, I C Real-Time Clock I2C DATA BUS 2 The DS1307 supports the I C protocol. A device that sends data onto the bus is defined as a transmitter and a device receiving data as a receiver. The device that controls the message is called a master. The devices that are controlled by the master are referred to as slaves. The bus must be controlled by a master device that generates the serial clock (SCL), controls the bus access, and generates the START and STOP conditions.
PAGE 11
2 DS1307 64 x 8, Serial, I C Real-Time Clock Figure 3. Data Transfer on I2C Serial Bus SDA MSB R/W DIRECTION BIT ACKNOWLEDGEMENT SIGNAL FROM RECEIVER ACKNOWLEDGEMENT SIGNAL FROM RECEIVER SCL 1 START CONDITION 2 6 7 8 9 1 2 3-7 ACK 8 9 ACK REPEATED IF MORE BYTES ARE TRANSFERED STOP CONDITION OR REPEATED START CONDITION Depending upon the state of the R/W bit, two types of data transfer are possible: 1. Data transfer from a master transmitter to a slave receiver.
PAGE 12
2 DS1307 64 x 8, Serial, I C Real-Time Clock The DS1307 can operate in the following two modes: 1. Slave Receiver Mode (Write Mode): Serial data and clock are received through SDA and SCL. After each byte is received an acknowledge bit is transmitted. START and STOP conditions are recognized as the beginning and end of a serial transfer. Hardware performs address recognition after reception of the slave address and direction bit (see Figure 4).
PAGE 13
2 DS1307 64 x 8, Serial, I C Real-Time Clock 1101000 0 A XXXXXXXX XXXXXXXX A XXXXXXXX S - Start Sr - Repeated Start A - Acknowledge (ACK) P - Stop A - Not Acknowledge (NACK) A Sr 1101000 Slave to master 1 A A XXXXXXXX Master to slave S Figure 6. Data Read (Write Pointer, Then Read)—Slave Receive and Transmit A ...
PAGE 14
2 DS1307 64 x 8, Serial, I C Real-Time Clock REVISION HISTORY REVISION DATE 100208 Moved the Typical Operating Circuit and Pin Configurations to first page. PAGES CHANGED 1 Removed the leaded part numbers from the Ordering Information table. 1 Added an open-drain transistor to SQW/OUT in the block diagram (Figure 1). Added the pullup voltage range for SDA, SCL, and SQW/OUT to the Pin Description table and noted that SQW/OUT can be left open if not used.