DS1338Z-33+

The Analog Devices DS1338Z-33+ 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 with automatic month-end adjustments including leap year correction valid up to 2100. The clock operates in 24-hour or 12-hour format with AM/PM indicator. A built-in power-sense circuit detects power failures and automatically switches to the backup battery supply, maintaining time and date operation. The programmable square-wave output provides frequency options for system timing needs.

The DS1338Z-33+ operates as an I2C real-time clock with three key subsystems: 1) Clock/Calendar Core: An internal oscillator driven by an external 32.768kHz crystal provides the timebase. The oscillator output is divided down to 1Hz for timekeeping. The BCD counters track seconds, minutes, hours, day, date, month, and year with automatic carry logic for all transitions including leap years. 2) NV SRAM: 56 bytes of SRAM are battery-backed through the VBAT pin. When VCC fails below VBAT, the internal power-switching circuit disconnects VCC and connects VBAT to the SRAM and clock, preserving data and timekeeping with typical 500nA battery current. 3) I2C Interface: The device acts as an I2C slave, responding to read/write commands for both the time registers (addresses 0x00-0x07) and the NV SRAM (addresses 0x08-0x3F).

• System timekeeping in embedded controllers and POS terminals
• Data logging timestamping in industrial equipment
• Battery-backed time reference in medical devices