The 1338 is a serial real-time clock (RTC) device that consumes ultra-low power and provides a full binary-coded decimal (BCD) clock/calendar with 56 bytes of battery backed Non-Volatile Static RAM. The clock/calendar provides seconds, minutes, hours, day, date, month, and year information. The clock operates in either the 24-hour or 12-hour format with AM/PM indicator. The end of the month date is automatically adjusted for months with fewer than 31 days, including corrections for leap year. Access to the clock/calendar registers is provided by an I2C interface capable of operating in fast I2C mode. Built-in Power-sense circuitry detects power failures and automatically switches to the backup supply, maintaining time and date operation.


  • Real-Time Clock (RTC) counts seconds, minutes, hours, day, date, month, and year with leap-year compensation valid up to 2100
  • 56-Byte battery-backed Non Volatile RAM for data storage
  • Fast mode I2C Serial interface
  • Automatic power-fail detect and switch circuitry
  • Programmable square-wave output
  • Packaged in 8-pin MSOP, 8-pin SOIC, or 16-pin SOIC (surface-mount package with an integrated crystal)
  • Industrial temperature range (-40°C to +85°C)


Title language Type Format File Size Date
Datasheets & Errata
star 1338 Datasheet Datasheet PDF 427 KB
Errata# : UEN-13-01 Datasheet Errata PDF 421 KB
1338B-31 Datasheet Datasheet PDF 541 KB
Application Notes & White Papers
AN-828 Termination - LVPECL Application Note PDF 322 KB
AN-844 Termination - AC Coupling Clock Receivers Application Note PDF 170 KB
AN-845 Termination - LVCMOS Application Note PDF 146 KB
AN-842 Thermal Considerations in Package Design and Selection Application Note PDF 495 KB
AN-840 Jitter Specifications for Timing Signals Application Note PDF 442 KB
AN-838 Peak-to-Peak Jitter Calculations Application Note PDF 115 KB
AN-839 RMS Phase Jitter Application Note PDF 233 KB
AN-815 Understanding Jitter Units Application Note PDF 565 KB
AN-827 Application Relevance of Clock Jitter Application Note PDF 1.15 MB
AN-805 Recommended Ferrite Beads Application Note PDF 121 KB
PCN# : A2003-01 Add Greatek Taiwan as an Alternate Assembly Location on Select Packages Product Change Notice PDF 113 KB
PDN#: CQ-19-04 Product Discontinuance Notice Product Discontinuation Notice PDF 1010 KB
PCN# : A1602-01(R1) Add Greatek Taiwan as Alternate Assembly Product Change Notice PDF 611 KB
PCN# : A1602-01 Add Greatek Taiwan as Alternate Assembly Product Change Notice PDF 611 KB
PDN# : CQ-14-08 Manufacturing Discontinunce PDN Product Discontinuation Notice PDF 486 KB
PCN# : A1403-03 Gold wire to Copper wire Product Change Notice PDF 42 KB
PCN# : W1101-02R4 Fab 4 to TSMC Product Change Notice PDF 70 KB
PCN# : W1101-02R3 Fab 4 to TSMC Product Change Notice PDF 71 KB
PCN# : W1101-02R2 Fab 4 to TSMC Product Change Notice PDF 67 KB
PCN# : A1208-01R1 Gold to Copper Wire Product Change Notice PDF 254 KB
PCN# : A1208-06 Changed of Assembly Location and Crystal Product Change Notice PDF 1.06 MB
PCN# : A1204-01R1 Revised Notification to Remove Selective Devices from TSSOP-16 Product Change Notice PDF 332 KB
IDT Clock Generation Overview Overview PDF 1.83 MB
Real Time Clocks Product Brief PDF 441 KB