Low-Current, SPI-Compatible Real-Time Clock

Save Board Space with TDFN Package and Ability to Drive Surface-Mount Crystals

Please check latest availability status for a specific part variant.


The DS1347 SPI-compatible real-time clock (RTC) contains a real-time clock/calendar and 31 x 8 bits of static random-access memory (SRAM). The real-time clock/calendar provides seconds, minutes, hours, day, date, month, year, and century information. A time/date programmable polled ALARM is included in the device. The end-of-the-month date is automatically adjusted for months with fewer than 31 days, including corrections for leap year. The clock operates in either the 24hr or 12hr format with an active-low AM/PM indicator. The device operates with a supply voltage of +2V to +5.5V, are available in the ultra-small 8-pin TDFN package, and work over the -40°C to +85°C industrial temperature range.
DS1346, DS1347: Typical Operating Circuit DS1346, DS1347: Typical Operating Circuit Enlarge+

Key Features

  • Completely Manages All Timekeeping Functions
    • RTC Counts Seconds, Minutes, Hours, Day of Week, Date of Month, Month, Year, and Century
    • Leap-Year Compensation
    • 31 x 8-Bit SRAM for Scratchpad Data Storage
    • Programmable Time/Date Polled ALARM Function
    • Uses Standard 32.768kHz Watch Crystal
  • Low-Power Operation Extends Battery Life
    • Low Timekeeping Current (400nA at 2V)
    • +2V to +5.5V Wide Operating Voltage Range
  • Standard Serial Port Interfaces with Most Microcontrollers
    • SPI (Mode 1 or 3) Interface: 4MHz at 5V, 1MHz at 2V
    • Single-Byte or Multiple-Byte (Burst Mode) Data Transfer for Read or Write of Clock Registers or SRAM
  • 3mm x 3mm x 0.8mm, 8-Pin TDFN Package Minimizes Required Space
    • No External Crystal Bias Resistors or Capacitors Required


  • Battery-Powered Products
  • Fax Machines
  • Intelligent Instruments
  • Point-of-Sale Equipment
  • Portable Instruments

See parametric specs for Timekeeping & Real-Time Clocks (78)

Part NumberInterfaceVSUPPLY
Time Keeping Current
Memory TypeMemory Size
Time of Day AlarmsFunctionsPackage/PinsBudgetary
typSee Notes
DS1347 SPI2.0 to 5.535012.5SRAM311RTC
$1.47 @1k

Pricing Notes:
This pricing is BUDGETARY, for comparing similar parts. Prices are in U.S. dollars and subject to change. Quantity pricing may vary substantially and international prices may differ due to local duties, taxes, fees, and exchange rates. For volume-specific and version-specific prices and delivery, please see the price and availability page or contact an authorized distributor.
Product Reliability Reports: DS1347.pdf 
Device   Fab Process   Technology   Sample size   Rejects   FIT at 25°C   FIT at 55°C   Material Composition  

Note : The failure rates are summarized by technology and mapped to the associated material part numbers. The failure rates are highly dependent on the number of units tested.

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Related Resources

±5ppm, I2C Real-Time Clock with Integrated MEMS Oscillator

  • Highly Accurate RTC with Integrated MEMS Resonator Completely Manages All Timekeeping Functions
  • 64-Byte RAM for User Data Storage
  • Simple Serial Interface Connects to Most Microcontrollers