DS1338Z-33

Real Time Clock Overview

The DS1338Z-33+ is a low-power serial real-time clock (RTC) and calendar integrated circuit manufactured by Analog Devices Inc./Maxim Integrated. It features full binary-coded decimal (BCD) timekeeping with leap-year compensation valid up to the year 2100. The device includes 56 bytes of battery-backed NV SRAM for general-purpose data storage. Communication occurs via an I²C serial interface supporting standard (100 kHz) and fast mode (400 kHz). It operates within a supply voltage range of 3.0V to 5.5V on VCC and 1.3V to 3.7V on VBAT, maintaining timekeeping during power failures through automatic switching. The component is housed in an 8-pin SOIC package.

Real Time Clock Feature Summary

• Full BCD clock/calendar with automatic month-end adjustments and leap-year correction valid until 2100
• 56-byte battery-backed NV SRAM with unlimited write cycles
• Built-in power-fail detect and switch circuitry for seamless transition to backup supply
• Programmable square-wave output signal at 1Hz, 4.096kHz, 8.192kHz, or 32.768kHz

Real Time Clock Applications

• Handheld devices such as GPS units and POS terminals
• Consumer electronics including set-top boxes and digital recorders
• Office equipment like fax machines, printers, and copiers
• Medical devices such as glucometers and medicine dispensers
• Telecommunications infrastructure including routers, switches, and servers

Real Time Clock Procurement Notes

Verify that the ordering suffix matches the required specifications. The '+' suffix indicates a lead-free/RoHS-compliant device. Confirm the package type corresponds to the 'Z' designation (8-SOIC, 0.150 inch width). Ensure the temperature range requirement aligns with the industrial specification (-40°C to +85°C). Cross-reference the manufacturer part number with authorized distributors to confirm current availability status.

Real Time Clock Selection Notes

Select the DS1338Z-33+ when a nominal 3.3V supply voltage is utilized, as indicated by the '-33' suffix specifying a typical VCC of 3.3V. This variant differs from the -18 and -3 versions primarily in its recommended operating voltage range. Ensure the design accommodates an external 32.768kHz crystal with a 12.5pF load capacitance, as this model does not integrate the oscillator crystal unlike the DS1338C series. Verify I²C bus pull-up resistor values are appropriate for the desired clock speed.

Real Time Clock Part Context

The DS1338Z-33+ belongs to the DS1338 family of serial RTCs. The 'Z' suffix denotes the 8-pin SOIC package, while the '33' indicates the specific voltage variant optimized for 3.3V operation. Other variants include the DS1338Z-18+ (1.8V), DS1338Z-3+ (3.0V), and the DS1338U series which utilizes an 8-pin µSOP package. The DS1338C series integrates the crystal internally but uses a different 16-pin package.

Real Time Clock Replacement Considerations

Direct pin-compatible replacements within the same package include the DS1338Z-18+ and DS1338Z-3+, provided the system voltage supports their respective operating ranges. For applications requiring an integrated crystal, the DS1338C series offers similar functionality but requires a 16-pin SOIC footprint. No other direct substitutes are documented in the provided datasheet.