DS1307 64 x 8, Serial, I

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PIN DESCRIPTION

PIN

NAME

FUNCTION

1

X1

2

X2

Connections for Standard 32.768kHz Quartz Crystal. The internal oscillator circuitry is

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.

Note: For more information on crystal selection and crystal layout considerations, refer to

Application Note 58: Crystal Considerations with Dallas Real-Time Clocks.

3

Backup Supply Input for Any Standard 3V Lithium Cell or Other Energy Source. Battery

voltage must be held between the minimum and maximum limits for proper operation.

DS1307 for more than 10 years in the absence of power at +25°C.

UL recognized to ensure against reverse charging current when used with a lithium

battery. Go to: www.maxim-ic.com/qa/info/ul/.

4

GND

Ground

5

SDA

Serial Data Input/Output. SDA is the data input/output for the I

SDA pin is open drain and requires an external pullup resistor. The pullup voltage can be

6

SCL

Serial Clock Input. SCL is the clock input for the I

data movement on the serial interface. The pullup voltage can be up to 5.5V regardless of

7

SQW/OUT

Square Wave/Output Driver. When enabled, the SQWE bit set to 1, the SQW/OUT pin

outputs one of four square-wave frequencies (1Hz, 4kHz, 8kHz, 32kHz). The SQW/OUT

pin is open drain and requires an external pullup resistor. SQW/OUT operates with either

8

Primary Power Supply. When voltage is applied within normal limits, the device is fully

accessible and data can be written and read. When a backup supply is connected to the

function continues unaffected by the lower input voltage.

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

code followed by a register address. Subsequent registers can be accessed sequentially until a STOP condition is

address counter. Inputs to the device will not be recognized at this time to prevent erroneous data from being

main elements of the serial RTC.