DS1305+

Overview

The DS1305+ is a serial alarm real-time clock (RTC) manufactured by Analog Devices Inc./Maxim Integrated, housed in a 16-DIP package. It provides binary coded decimal (BCD) timekeeping for seconds, minutes, hours, date, month, and year, with leap-year compensation valid through 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 a standard 3-wire interface via the SERMODE pin. Operating voltage ranges from 2.0V to 5.5V on primary and backup supplies, with timekeeping current ranging from 25.3µA at 2V to 81µA at 5V. The commercial temperature range is 0°C to +70°C.

Feature Summary

• Full BCD clock/calendar with leap-year compensation up to 2100
• 96-byte battery-backed NV RAM for data storage
• Dual power supply pins (VCC1, VCC2) with optional trickle charger output
• Supports SPI (Modes 1/3) or 3-wire serial interface

Applications

• Systems requiring precise timekeeping with battery backup
• Microcontroller-based devices needing non-volatile data storage
• Applications utilizing SPI or 3-wire serial communication protocols

Procurement Notes

Verify the specific package variant required, as the DS1305 family includes DIP and TSSOP options. Confirm that the commercial temperature grade (0°C to +70°C) meets system requirements; industrial grades (-40°C to +85°C) are available under different part numbers such as DS1305N. Ensure the serial interface mode (SPI vs. 3-wire) aligns with the host microcontroller's capabilities before procurement.

Selection Notes

Select the DS1305+ when a 16-pin DIP package is necessary for through-hole mounting. Compare against the DS1305E+ if surface-mount technology (TSSOP-20) is preferred for space-constrained designs. Verify that the 96-byte NV RAM capacity suffices for application data needs, as other RTC models may offer larger memory sizes. Ensure the host system can support the required serial protocol configuration via the SERMODE pin.

Part Context

The DS1305+ belongs to the DS1305 series of serial alarm real-time clocks. It is distinct from the DS1306 and DS1307, which utilize different interfaces (I2C/SPI vs. primarily I2C) and package types. The '+' suffix indicates a lead-free/RoHS-compliant package version. The device is designed to maintain time and date using either a primary supply or a backup source like a lithium battery or supercapacitor.

Replacement Considerations

For direct package and feature replacement, consider the DS1305E+ (TSSOP-20) if surface mount is acceptable. For industrial temperature range requirements, the DS1305N (DIP-16) or DS1305EN+ (TSSOP-20) are verified alternatives within the same series.