DS1307 real-time clock pinout

The DS1307 is a 5 V I²C real-time clock with an external 32.768 kHz crystal and 56 bytes of battery-backed SRAM.

SO-8 · 150 mil

8 contacts Current package

Analog Devices / Maxim Integrated ·

Top view. Start at the package pin-1 index and follow the numbered leads.

Supply input · Power

Primary device supply. Place the bypass capacitor close to this pin.

Analog Devices / Maxim DS1307 Rev. 5, pp. 1–8.

Pin	Signal	Direction	Function
1	X1 Oscillator input	Oscillator input	Connect one side of a 32.768 kHz, 12.5 pF load crystal.
2	X2 Oscillator output	Oscillator output	Connect the other side of the crystal. For a suitable external 32.768 kHz drive at X1, leave X2 open.
3	VBAT Supply input	Supply input	Backup supply input. Ground it when no backup source is used.
4	GND Supply return	Supply return	Connect to the common ground plane or bench return.
5	SDA Bidirectional	Bidirectional	Open-drain I²C data. The bus needs a pull-up to its logic rail.
6	SCL Input	Input	I²C clock. Connect to the host clock line with its bus pull-up.
7	SQW/OUT Open drain	Open drain	Optional square wave or static logic output. Pull up when used.
8	VCC Supply input	Supply input	Primary device supply. Place the bypass capacitor close to this pin.

Fixed 7-bit address 0x68. Calendar fields are binary-coded decimal. I²C access is disabled below the main-supply power-fail threshold.

Parameter	Limit	Conditions and source
Main supply4.5–5.5 V	4.5–5.5 V	Recommended operating range. Analog Devices / Maxim DS1307 Rev. 5, pp. 1–8.
Backup supply2.0–3.5 V	2.0–3.5 V	Separate from the 5 V main supply. Analog Devices / Maxim DS1307 Rev. 5, pp. 1–8.
I²C clock100 kHz maximum	100 kHz maximum	Standard mode. The 2.2 V minimum input high permits a compatible lower-voltage pull-up rail. Analog Devices / Maxim DS1307 Rev. 5, pp. 1–8.
Crystal load12.5 pF	12.5 pF	32.768 kHz nominal. The DS1307 includes the oscillator load capacitance. Analog Devices / Maxim DS1307 Rev. 5, pp. 1–8.

This reference covers the 8-lead PDIP and narrow 8-lead SO versions. Both use the same lead numbering.

DS1307 manufacturer documentation· Analog Devices / Maxim DS1307 Rev. 5, pp. 1–8.