DS1685E-5/T&R

Real Time Clock Overview

The DS1685E-5+T&R is a real-time clock (RTC) IC manufactured by Analog Devices Inc./Maxim Integrated, packaged in a 24-pin TSSOP. It operates at +5V with a supply range of 4.5V to 5.5V and supports an operating temperature range of 0°C to +70°C. The device features a multiplexed address/data bus interface, providing timekeeping capabilities including calendar functions valid through 2099 with leap-year compensation. It includes 242 bytes of battery-backed NV SRAM, a 64-bit silicon serial number, and power-control circuitry for system wake-up via alarm or key closure.

Real Time Clock Feature Summary

• Multiplexed bidirectional address/data bus interface for standard PC clock compatibility
• 242 bytes of non-volatile RAM divided into two banks (114 bytes base + 128 bytes extended)
• Integrated power-control circuitry enabling system power-on via date/time alarm or kickstart input
• 32.768kHz square-wave output available on the SQW pin for power management

Real Time Clock Applications

• Embedded systems requiring precise timekeeping
• Utility meters needing long-term data retention
• Security systems with alarm logging requirements
• Network hubs, bridges, and routers

Real Time Clock Procurement Notes

Verify that the specific orderable part number matches the required package and voltage variant. The 'E' suffix indicates the TSSOP package, while '+T&R' denotes lead-free/RoHS compliance and tape-and-reel packaging. Confirm the industrial temperature grade if operation outside the commercial 0°C to +70°C range is required, as this model is specified for commercial temperatures only.

Real Time Clock Selection Notes

Select this component when a multiplexed parallel interface is preferred over serial alternatives like I2C or SPI. Ensure the design accommodates the 24-pin TSSOP footprint and provides appropriate external crystal components (6pF or 12.5pF load capacitance). Verify that the system power supply remains stable above 4.5V for full accessibility and that backup battery connections are made to VBAT or VBAUX pins for continuous operation during power loss.

Real Time Clock Part Context

This device belongs to the DS1685/DS1687 family, designed as successors to industry-standard DS1285/DS1287 PC clocks. The DS1685E variant specifically refers to the chip-only version in a TSSOP package, distinct from the DS1687 which integrates the crystal and battery in an EDIP package. The '5' designation confirms +5V operation, whereas '-3' variants support +3V logic levels.

Real Time Clock Replacement Considerations

Direct replacements within the same family include DS1685S-5+T&R (SOIC package) or DS1685Q-5+T&R (PLCC package) for different form factors. For industrial temperature grades (-40°C to +85°C), consider DS1685EN-5+T&R. Cross-family replacements may require interface adaptation if moving from multiplexed parallel to serial RTCs.