DS1340, DS1340C

I²C RTC with Trickle Charger

I²C Real-Time Clock with Trickle Charger Offers Software Clock Calibration

Please check latest availability status for a specific part variant.


The DS1340 is a real-time clock (RTC)/calendar that is pin compatible and functionally equivalent to the ST M41T00, including the software clock calibration. The device additionally provides trickle-charge capability on the VBACKUP pin, a lower timekeeping voltage, and an oscillator STOP flag. Block access of the register map is identical to the ST device. Two additional registers, which are accessed individually, are required for the trickle charger and flag. The clock/calendar provides seconds, minutes, hours, day, date, month, and year information. A built-in power-sense circuit detects power failures and automatically switches to the backup supply. The device is programmed serially through an I²C bidirectional bus.
DS1340, DS1340C: Typical Operating Circuit DS1340, DS1340C: Typical Operating Circuit Enlarge+

Key Features

  • Enhanced Second Source for the ST M41T00
  • Completely Manages All Timekeeping Functions
    • RTC Counts Seconds, Minutes, Hours, Day, Date, Month, and Year
    • Software Clock Calibration
    • Oscillator Stop Flag
  • Low-Power Operation Extends Battery Backup Run Time
    • Low Timekeeping Voltage Down to 1.3V
    • Automatic Power-Fail Detect and Switch Circuitry
    • Trickle-Charge Capability
  • Three Operating Voltage Ranges (1.8V, 3V, and 3.3V) Supports Systems Using Legacy and Modern Power Buses
  • Surface-Mount Package with an Integrated Crystal (DS1340C) Saves Additional Space and Simplifies Design
  • Simple Serial Port Interfaces with Most Microcontrollers
    • Fast (400kHz) I2C Interface
  • 8-Pin µSOP or SO Package Minimizes Required Space
  • Underwriters Laboratories (UL®) Recognized


  • Medical Equipment
  • Point-of-Sale Equipment
  • Portable Instrumentation
  • Telecommunications

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

Part NumberInterfaceVSUPPLY
Time Keeping Current
Memory TypeTime of Day AlarmsIntegrated ResonatorFunctionsPackage/PinsBudgetary
typSee Notes
DS1340 I2C
SOIC (N)/8
SOIC (W)/16
$1.58 @1k
$2.75 @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.

Tools & Models

  • DS1340 IBIS Model
  • Product Reliability Reports: DS1340.pdf 
    Request Reliability Report for: DS1340C 
    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.

    Quality Management System >
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    Related Resources

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    • 64-Byte RAM for User Data Storage
    • Simple Serial Interface Connects to Most Microcontrollers