28-03-2014, 02:58 PM
DS1307 64 x 8, Serial, I2C Real-Time Clock
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.
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
DETAILED DESCRIPTION
The DS1307 is a low-power clock/calendar with 56 bytes of battery-backed SRAM. The clock/calendar provides
seconds, minutes, hours, day, date, month, and year information. The date at the end of the month is automatically
adjusted for months with fewer than 31 days, including corrections for leap year. The DS1307 operates as a slave
device on the I C bus. Access is obtained by implementing a START condition and providing a device identification
code followed by a register address. Subsequent registers can be accessed sequentially until a STOP condition is
executed. When VCC falls below 1.25 x VBAT, the device terminates an access in progress and resets the device
address counter. Inputs to the device will not be recognized at this time to prevent erroneous data from being
written to the device from an out-of-tolerance system. When VCC falls below VBAT, the device switches into a low-
current battery-backup mode. Upon power-up, the device switches from battery to VCC when VCC is greater than
VBAT +0.2V and recognizes inputs when VCC is greater than 1.25 x VBAT. The block diagram in Figure 1 shows the
main elements of the serial RTC.