Component comparison · Last verified 2026-07-27
Choose DS1302+ when the controller uses its dedicated 3-wire protocol, a wider main-supply range and the programmable trickle charger are useful. Choose DS1307+ for a standard I2C bus, automatic switchover to a backup battery, 56 bytes of retained SRAM and a square-wave output. Both are 8-pin PDIP RTCs with external crystals, but protocol, pins and power circuits differ.
DS1302+ vs DS1307+ specifications
| Specification | DS1302+ | DS1307+ |
|---|---|---|
| Serial interface | Dedicated 3-wire interface | I2C up to 100 kHz |
| Transfer modes | Single-byte and clock/RAM burst transfers | Addressed I2C single- or multibyte transfers |
| Main supply range | 2.0 V to 5.5 V | 4.5 V to 5.5 V |
| Backup architecture | Dual supplies with programmable trickle charger | Dedicated VBAT input with automatic switchover; no battery charging |
| Battery-backed user RAM | 31 bytes | 56 bytes |
| Square-wave output | None | 1 Hz, 4.096 kHz, 8.192 kHz or 32.768 kHz |
| Timebase | External 32.768 kHz crystal | External 32.768 kHz crystal |
| Crystal load capacitance | 6 pF | 12.5 pF |
| Package / case | 8-pin narrow PDIP, 300 mil | 8-pin narrow PDIP, 300 mil |
| Calendar support | Leap-year compensation valid through 2100 | Leap-year compensation valid through 2100 |
Key differences
The host protocols require different hardware and drivers
DS1302+ uses CE, I/O and SCLK signals with a device-specific 3-wire command format and burst modes. DS1307+ is an I2C slave using SDA and SCL, so MCU pins, bus sharing and firmware transactions are different.
The backup-source circuits follow different design assumptions
DS1302+ includes a programmable trickle charger for an appropriate rechargeable backup source. DS1307+ automatically switches to VBAT but does not charge it, making battery selection and protection requirements different.
Retained memory, output function and crystal loading differ
DS1302+ supplies 31 bytes of backed-up RAM and no square-wave output, while DS1307+ supplies 56 bytes and a selectable SQW/OUT signal. Their external crystal load specifications are also 6 pF and 12.5 pF respectively.
Can these parts be interchanged?
DS1302+ and DS1307+ are not drop-in replacements despite sharing an 8-pin narrow PDIP outline. Their serial protocols, signal assignments, backup-source circuits, crystal load requirements, RAM maps and output functions differ. Confirm the schematic, footprint pin mapping, battery chemistry, firmware driver, bus timing and oscillator components before redesigning around either RTC.
- Electrical ratings and operating conditions
- Package dimensions, footprint and pinout
- Interface, timing and firmware behavior
- Temperature and qualification grade
- Lifecycle status and current documentation revision
DS1302+ vs DS1307+ FAQ
What is the main interface difference between DS1302+ and DS1307+?
DS1302+ uses a dedicated 3-wire interface with CE, I/O and SCLK. DS1307+ is an I2C slave using SDA and SCL at up to 100 kHz, so the devices require different MCU connections and drivers.
Can DS1307+ directly replace DS1302+ in an 8-pin socket?
No. The package outline is the same, but the pin functions, serial protocol, crystal loading and backup-power circuits differ. A schematic and firmware change is required.
Which device provides more battery-backed RAM?
DS1307+ provides 56 bytes of battery-backed SRAM, while DS1302+ provides 31 bytes. Check the application's retained-data map before selecting a part.
Which RTC includes a trickle charger?
DS1302+ includes a programmable trickle charger intended for a suitable rechargeable backup source. DS1307+ automatically switches to VBAT but does not charge the connected battery.
Do DS1302+ and DS1307+ use the same crystal load capacitance?
No. Both use an external 32.768 kHz crystal, but DS1302+ specifies a 6 pF load and DS1307+ specifies 12.5 pF. Reusing the same crystal without review can affect timekeeping accuracy.
Sources and verification
- Analog Devices DS1302 product page
- Analog Devices DS1302 datasheet
- Analog Devices DS1307 product page
- Analog Devices DS1307 datasheet
This comparison supports preliminary selection and sourcing review. Similar specifications do not establish drop-in compatibility. Confirm the complete orderable code and current manufacturer documentation before design release or purchase.
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