DS1305E

Overview

The DS1305E is a serial alarm real-time clock (RTC) in a 20-pin TSSOP package, operating from 2.0V to 5.5V with a commercial temperature range of 0°C to +70°C. It provides binary-coded decimal (BCD) timekeeping for seconds through year, including leap-year compensation valid until 2100. The device includes 96 bytes of battery-backed NV RAM and two programmable time-of-day alarms. It supports SPI Modes 1 and 3 or standard 3-wire interfaces via the SERMODE pin. Key features include dual power supply pins for primary and backup sources, an optional trickle charger for rechargeable backups, and interface logic compatibility down to 3V.

Feature Summary

• Full BCD clock/calendar with leap-year correction up to 2100
• 96-byte battery-backed NV RAM for data storage
• Dual programmable time-of-day alarms with interrupt outputs
• Supports SPI (Modes 1/3) and standard 3-wire serial interfaces

Applications

• Systems requiring precise timekeeping with battery backup
• Data logging applications utilizing NV RAM
• Microcontroller-based devices needing scheduled interrupts
• Mixed-supply systems requiring 3V logic compatibility

Procurement Notes

Verify the specific suffix requirements for packaging and compliance. The base model DS1305E denotes the commercial temperature range in a tube package. Suffixes such as '+T&R' indicate lead-free/RoHS-compliant tape and reel packaging. Confirm that the selected variant matches the required operating temperature range and physical form factor for the target assembly process.

Selection Notes

Select the DS1305E for commercial temperature applications (0°C to +70°C). For industrial environments (-40°C to +85°C), choose the DS1305EN variant. Ensure the system design accommodates the dual power supply configuration if using a rechargeable backup source with the trickle charger. Verify that the microcontroller supports either SPI Mode 1/3 or the 3-wire interface protocol defined by the SERMODE pin connection.

Part Context

The DS1305E belongs to the Maxim Integrated DS1305 family of serial alarm RTCs. It shares core functionality with the DIP-16 version but offers a surface-mount 20-TSSOP footprint. The 'E' suffix specifically identifies the commercial temperature grade. This component is designed for low-power timekeeping where space efficiency and flexible serial communication are prioritized over high-speed data throughput.

Replacement Considerations

The DS1305EN serves as the direct industrial temperature replacement for the DS1305E within the same package. Other DS1305 variants share identical electrical characteristics but differ in temperature rating or packaging format.