DS1338C, DS1338U, DS1338Z

I²C RTC with 56-Byte NV RAM

Please check latest availability status for a specific part variant.


The DS1338 serial real-time clock (RTC) is a low-power, full binary-coded decimal (BCD) clock/calendar plus 56 bytes of NV SRAM. Address and data are transferred serially through an I²C interface. The clock/calendar provides seconds, minutes, hours, day, date, month, and year information. 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 24-hour or 12-hour format with AM/PM indicator. The DS1338 has a built-in power-sense circuit that detects power failures and automatically switches to the backup supply, maintaining time and date operation.
DS1338, DS1338C, DS1338U, DS1338Z: Block Diagram DS1338, DS1338C, DS1338U, DS1338Z: Block Diagram Enlarge+

Key Features

  • Completely Manages All Timekeeping Functions
    • RTC Counts Seconds, Minutes, Hours, Date of the Month, Month, Day of the Week, and Year with Leap-Year Compensation Valid Up to 2100
    • 56-Byte, Battery-Backed, General- Purpose RAM with Unlimited Writes
    • Programmable Square-Wave Output Signal
  • Surface-Mount Package with an Integrated Crystal (DS1338C) Saves Additional Space and Simplifies Design
  • Interfaces with Most Microcontrollers
    • I2C Serial Interface
  • Low-Power Operation Extends Battery Backup Run Time
    • Automatic Power-Fail Detect and Switch Circuitry
  • -40°C to +85°C Industrial Temperature Range Supports Operation in a Wide Range of Applications
  • Underwriters Laboratories (UL®) Recognized


  • Consumer Electronics (Set-Top Box, Digital Recording, Network Appliance)
  • Handhelds (GPS, POS Terminal)
  • Medical (Glucometer, Medicine Dispenser)
  • Office Equipment (Fax/Printer, Copier)
  • Other (Utility Meter, Vending Machine, Thermostat, Modem)
  • Telecommunications (Router, Switcher, Server)
Part NumberInterfaceVSUPPLY
Time Keeping Current
Memory TypeMemory Size
Time of Day AlarmsIntegrated ResonatorFunctionsPackage/PinsBudgetary
typSee Notes
DS1338 I2C
80012.5NV SRAM560-RTC
SOIC (N)/8
SOIC (W)/16
$1.50 @1k
$2.71 @1k
See All Timekeeping & Real-Time Clocks (76)
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.

Quality and Environmental Data

Request Reliability Report for: DS1338C  DS1338U  DS1338Z 
Lead-Free Package Tin (Sn) Whisker Reports

Additional Resources

RTC Calculator

Why on Earth Don’t You Include a Clock in Your Design?

CAD Symbols and Footprints

  • DS1338C-18#
  • DS1338C-3#
  • DS1338C-33#
  • DS1338C-33#T&R
  • DS1338U-18+
  • DS1338U-18+T&R
  • DS1338U-3+
  • DS1338U-3+T&R
  • DS1338U-33+
  • DS1338U-33+T&R
  • DS1338Z-18+
  • DS1338Z-18+T&R
  • DS1338Z-3+
  • DS1338Z-3+T&R
  • DS1338Z-33+
  • DS1338Z-33+T&R
  • Device   Fab Process   Technology   Sample size   Rejects   FIT at 25°C   FIT at 55°C  

    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.

    Quality Management System >
    Environmental Management System >


    Related Resources

    Low-Current, Real-Time Clock with I2C Interface and Power Management

    • Increases Battery Life
    • Provides Flexible Configurability
    • Saves Board Space

    Low-Current, Real-Time Clock with I2C Interface

    • Increases Battery Life
    • Provides Flexible Configurability
    • Saves Board Space