I²C
Fixed 7-bit address 0x68. Calendar fields are binary-coded decimal. I²C access is disabled below the main-supply power-fail threshold.
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.
PDIP-8 · 300 mil 8 contacts
SO-8 · 150 mil
8 contacts Current package−40 to +85 °C.
SO-8 · 150 mil pinout
2 · X2
Connect the other side of the crystal. For a suitable external 32.768 kHz drive at X1, leave X2 open.
All 8 pins
| 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. |
Signal assignments
Electrical limits
| 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. |
Models and documents
This reference covers the 8-lead PDIP and narrow 8-lead SO versions. Both use the same lead numbering.
- DS1307Z+
- 0 to +70 °C.
- DS1307Z+T&R
- 0 to +70 °C, tape and reel.
- DS1307ZN+
- −40 to +85 °C.
- DS1307ZN+T&R
- −40 to +85 °C, tape and reel.
- DS1307 manufacturer documentation· Analog Devices / Maxim DS1307 Rev. 5, pp. 1–8.