DS1305E/T&R

Real Time Clock Overview

The DS1305E/T&R is a serial alarm real-time clock (RTC) manufactured by Analog Devices Inc./Maxim Integrated, packaged in a 20-TSSOP (0.173", 4.40mm width) tape and reel format. It provides binary coded decimal (BCD) timekeeping for seconds, minutes, hours, date, month, day of week, and year with leap-year compensation valid to 2100. The device includes 96 bytes of battery-backed NV RAM and two programmable time-of-day alarms. It operates on a supply voltage of 2V to 5.5V with a maximum timekeeping current of 25.3µA at 2V and 81µA at 5V. The component supports SPI Modes 1 and 3 or standard 3-wire interfaces and functions within a commercial temperature range of 0°C to +70°C.

Real Time Clock Feature Summary

• Dual power supply pins (VCC1, VCC2) and battery input (VBAT) support primary, backup, and trickle-charge configurations.
• Two programmable time-of-day alarms with interrupt outputs (INT0, INT1) and maskable fields.
• Supports direct SPI (Modes 1 and 3) or standard 3-wire serial interface with burst mode access.
• Includes 96-byte battery-backed NV RAM for data storage.

Real Time Clock Applications

• Systems requiring precise calendar and timekeeping with low-power standby modes.
• Data logging devices utilizing the integrated NV RAM for non-volatile storage.
• Microcontroller-based systems needing scheduled interrupts via dual alarm outputs.
• Mixed-supply environments using the VCCIF pin for 3V logic compatibility.

Real Time Clock Procurement Notes

Verify the specific ordering suffix against the manufacturer's datasheet to confirm temperature grade and package type. The 'E' designation indicates the commercial temperature range (0°C to +70°C), while 'EN' denotes the industrial range (-40°C to +85°C). Ensure the T&R suffix matches the required tape and reel packaging specifications for automated assembly processes.

Real Time Clock Selection Notes

Select the DS1305E/T&R when a commercial temperature range is sufficient for the application environment. Confirm that the system design accommodates the 20-pin TSSOP footprint and utilizes either SPI or 3-wire serial protocols. Consider the trickle charger register configuration if a rechargeable backup source such as a supercapacitor is employed for continuous operation during primary power loss.

Real Time Clock Part Context

The DS1305 series comprises serial alarm RTCs available in various packages including 16-DIP and 20-TSSOP. The DS1305E variant specifically refers to the commercial temperature grade version housed in the 20-TSSOP package. This part number represents a subset of the broader DS1305 family, distinguished by its operating temperature limits and surface-mount packaging configuration.

Real Time Clock Replacement Considerations

The DS1305EN+T&R serves as a functional substitute offering identical electrical characteristics but extended to the industrial temperature range (-40°C to +85°C). Verify that the higher temperature rating aligns with the environmental requirements of the target application before substitution.