DS1685EN-3/T&R

Real Time Clock Overview

The DS1685EN-3+T&R is a real-time clock (RTC) IC manufactured by Analog Devices Inc./Maxim Integrated. It operates within a voltage range of 2.7V to 3.7V and supports a multiplexed parallel interface. The device features a 242-byte battery-backed NV SRAM, Y2K compliance, and a 64-bit silicon serial number. It provides timekeeping with leap-year compensation valid through 2099. The component is housed in a 24-TSSOP package and functions within an operating temperature range of -40°C to +85°C.

Real Time Clock Feature Summary

• Multiplexed parallel bus interface for system integration
• 242 bytes of non-volatile RAM with dual-bank architecture
• Integrated power-control circuitry for wake-up and kickstart capabilities
• Y2K compliant with century register and leap-year logic

Real Time Clock Applications

• Embedded systems requiring persistent timekeeping
• Utility meters needing accurate date and time logging
• Security systems utilizing alarm and interrupt features
• Network hubs, bridges, and routers for timestamping

Real Time Clock Procurement Notes

Verify the specific suffix 'EN' confirms the industrial temperature grade (-40°C to +85°C) and 'T&R' indicates tape-and-reel packaging. Confirm RoHS compliance status via the '+' designation in the part number. Ensure the primary supply voltage aligns with the 2.7V to 3.7V operational limits specified for this variant.

Real Time Clock Selection Notes

Select this model when a multiplexed parallel interface is required rather than serial alternatives like I2C or SPI. The industrial temperature rating makes it suitable for harsh environments compared to commercial variants. Verify that the system design can accommodate the 24-pin TSSOP footprint and the necessary address/data bus lines for the parallel connection.

Real Time Clock Part Context

This component belongs to the DS1685/DS1687 family of 3V/5V Real-Time Clocks. It serves as a successor to earlier industry-standard PC RTCs such as the DS1285 and DS1385. The 'EN' suffix denotes the extended industrial temperature range, while the base DS1685 refers to the chip functionality encapsulated in various packages including TSSOP.

Real Time Clock Replacement Considerations

Public confirmed substitute part numbers: DS1685E-3+T&R (Commercial temp), DS1685S-3+T&R (SOIC package).

Real Time Clock FAQ

What crystal load capacitance options are supported?

The DS1685EN-3 supports operation with crystals having a specified load capacitance of either 6pF or 12.5pF, selectable via the Crystal-Select bit in Extended Control Register 4B.

How is the auxiliary battery function utilized?

The VBAUX pin allows for an auxiliary battery input which supports kickstart and wake-up features. It also serves as a backup source if the primary VBAT is absent or at a lower voltage.

Can the device trigger system power-on?

Yes, the PWR output pin can be activated by a time/date alarm or a key closure on the KS pin, allowing the RTC to control external system power supplies.