Component comparison · Last verified 2026-07-27
Choose DS1337+ when an 8-pin through-hole RTC with an external crystal and operation from a lower main supply is required. Choose DS3231S# when the design needs a factory-integrated crystal, temperature compensation and specified ppm accuracy. Both provide 400 kHz I2C and two alarms, but package, backup circuitry, timebase and temperature features make them non-interchangeable.
DS1337+ vs DS3231S# specifications
| Specification | DS1337+ | DS3231S# |
|---|---|---|
| Serial interface | I2C up to 400 kHz | I2C up to 400 kHz |
| Timebase | External 32.768 kHz crystal | Integrated crystal and TCXO |
| Timekeeping accuracy | Depends on the selected crystal, loading and layout | +/-2 ppm from 0 deg C to +40 deg C |
| Main supply range | 1.8 V to 5.5 V for accessible operation | 2.3 V to 5.5 V |
| Backup architecture | No dedicated VBAT input; timekeeping continues as VCC falls to 1.3 V | Dedicated VBAT input with automatic switchover |
| Time-of-day alarms | Two | Two |
| Digital temperature output | None | +/-3 deg C accuracy |
| Aging trim register | None | Available |
| Package / case | 8-pin narrow PDIP, 300 mil | 16-pin wide SOIC, 300 mil |
| Orderable temperature grade | Industrial, -40 deg C to +85 deg C | Commercial, 0 deg C to +70 deg C |
Key differences
External-crystal timing and integrated TCXO timing serve different requirements
DS1337+ depends on the chosen external crystal, effective load capacitance, layout and environment. DS3231S# integrates its crystal and a temperature-compensated oscillator, providing a defined ppm accuracy limit without a separate crystal network.
Power backup and monitoring features differ
DS1337+ has no dedicated VBAT pin and maintains time as VCC declines to its lower timekeeping threshold. DS3231S# automatically switches to a separate backup source and also exposes temperature data and an aging-trim register.
Package and temperature grades target different assemblies
DS1337+ is an industrial-temperature 8-pin PDIP orderable code. DS3231S# is a commercial-temperature 16-pin wide SOIC code, so neither the footprint nor the qualified ambient range is the same.
Can these parts be interchanged?
DS1337+ and DS3231S# are not footprint- or pin-compatible. The designs use different package sizes, oscillator architectures and backup-power connections despite sharing I2C, two alarms and common RTC concepts. Verify the PCB footprint, supply and battery design, firmware register behavior, accuracy budget, temperature grade and assembly process before selecting either device.
- 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
DS1337+ vs DS3231S# FAQ
What is the main timing difference between DS1337+ and DS3231S#?
DS1337+ requires an external 32.768 kHz crystal, so system accuracy depends on crystal and board conditions. DS3231S# integrates the crystal and a TCXO and specifies +/-2 ppm from 0 deg C to +40 deg C.
Can DS3231S# replace DS1337+ without changing the PCB?
No. DS1337+ uses an 8-pin narrow PDIP while DS3231S# uses a 16-pin wide SOIC, and their power-backup and oscillator connections differ.
Do both devices support I2C fast mode and alarms?
Yes. Both support I2C operation up to 400 kHz and provide two time-of-day alarms, but their register details and interrupt handling still need firmware review.
Which part is intended for a wider ambient temperature range?
The DS1337+ orderable code is specified for -40 deg C to +85 deg C. DS3231S# is the commercial 0 deg C to +70 deg C code; DS3231SN# is the industrial-temperature DS3231 variant.
Which part avoids external crystal selection and layout work?
DS3231S# integrates both the crystal and temperature-compensated oscillator. DS1337+ requires an external crystal with the specified load capacitance and careful oscillator layout.
Sources and verification
- Analog Devices DS1337 product page
- Analog Devices DS1337 datasheet
- Analog Devices DS3231 product page
- Analog Devices DS3231 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.
Request a component quote