Component comparison · Last verified 2026-07-27
Choose DS1307+ when a 5 V design needs automatic switchover to a dedicated backup battery and 56 bytes of battery-backed SRAM. Choose DS1337+ when a wider main-supply range, 400 kHz I2C and two programmable alarms matter more. Both use external crystals and 8-pin PDIP packages, but their supply architecture, pinout and feature maps are not interchangeable.
DS1307+ vs DS1337+ specifications
| Specification | DS1307+ | DS1337+ |
|---|---|---|
| Serial interface | I2C up to 100 kHz | I2C up to 400 kHz |
| Main supply range | 4.5 V to 5.5 V | 1.8 V to 5.5 V for accessible operation |
| Backup architecture | Dedicated VBAT input with automatic switchover | No dedicated VBAT input; timekeeping continues as VCC falls to 1.3 V |
| User SRAM | 56 bytes, battery backed | None |
| Time-of-day alarms | None | Two |
| Square-wave output | 1 Hz, 4.096 kHz, 8.192 kHz or 32.768 kHz | Programmable square wave with interrupt sharing |
| Timebase | External 32.768 kHz crystal | External 32.768 kHz crystal |
| Crystal load capacitance | 12.5 pF | 6 pF |
| Package / case | 8-pin narrow PDIP, 300 mil | 8-pin narrow PDIP, 300 mil |
| RTC I2C address | 1101000b (0x68) | 1101000b (0x68) |
Key differences
Backup power and retained memory are fundamentally different
DS1307+ has a dedicated VBAT pin, automatic supply switchover and 56 bytes of backed-up SRAM. DS1337+ has no dedicated battery input or user SRAM; its timekeeping circuit remains active while VCC falls to the specified lower timekeeping voltage.
DS1337+ adds alarms and a faster I2C limit
DS1337+ supports two time-of-day alarms and I2C fast mode up to 400 kHz. DS1307+ has no alarm registers and its SCL specification is limited to 100 kHz, although it does provide a selectable square-wave output.
The identical package outline does not mean identical pins
Both orderable codes use an 8-pin narrow PDIP, but pin 3 is VBAT on DS1307+ and an alarm interrupt output on DS1337+. Their crystal loading, control registers and power-fail behavior also differ.
Can these parts be interchanged?
DS1307+ and DS1337+ are not drop-in replacements even though both use an 8-pin narrow PDIP and the same I2C address. Pin 3, supply behavior, crystal load requirement, register map, alarm functions and retained-memory support differ. Review the schematic, crystal network, backup source, firmware, startup behavior and required bus speed before changing the BOM.
- 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
DS1307+ vs DS1337+ FAQ
What is the main difference between DS1307+ and DS1337+?
DS1307+ emphasizes automatic battery switchover and 56 bytes of battery-backed SRAM. DS1337+ instead provides two alarms, faster 400 kHz I2C and a wider accessible main-supply range, but no dedicated VBAT input or user SRAM.
Can DS1337+ directly replace DS1307+ in an 8-pin socket?
No. The package outline and I2C address match, but pin 3 has a different function and the power, crystal and register architectures differ. A board and firmware redesign is normally required.
Which part is better for a design that must retain small configuration data?
DS1307+ is the relevant option when the application needs its 56 bytes of battery-backed SRAM. DS1337+ does not provide user SRAM, so retained application data needs another memory device.
Which device supports programmable alarms?
DS1337+ provides two time-of-day alarms. DS1307+ has no alarm registers, although it can generate selectable square-wave frequencies from its SQW/OUT pin.
Do DS1307+ and DS1337+ use the same external crystal?
Both use a 32.768 kHz external crystal, but the specified load capacitance differs: 12.5 pF for DS1307+ and 6 pF for DS1337+. Recheck the crystal and PCB layout when changing devices.
Sources and verification
- Analog Devices DS1307 product page
- Analog Devices DS1307 datasheet
- Analog Devices DS1337 product page
- Analog Devices DS1337 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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