DS1685S-3

Real Time Clock Overview

The DS1685S-3+ is a real-time clock (RTC) integrated circuit manufactured by Analog Devices Inc./Maxim Integrated. It operates on a single +3V supply within the 0°C to +70°C temperature range and is housed in a 24-pin SOIC package. The device provides timekeeping with a calendar function, supporting both 12-hour and 24-hour formats, and includes date alarm capabilities. It features 242 bytes of battery-backed nonvolatile RAM and incorporates a 64-bit silicon serial number. Key electrical parameters include a maximum timing current of 2mA at 3V, with backup battery voltage requirements between 2.5V and 3.7V.

Real Time Clock Feature Summary

• Integrated 242-byte battery-backed NVSRAM for user data retention
• Y2K compliant with leap-year compensation valid through 2099
• Power-control circuitry supports system power-on via date/time alarm or key closure
• Includes a 32kHz square-wave output for power management activities

Real Time Clock Applications

• Embedded systems requiring precise timekeeping
• Utility meters for billing and operational logging
• Security systems needing event timestamping
• Network hubs, bridges, and routers for synchronization

Real Time Clock Procurement Notes

Verify that the specific order suffix corresponds to the Tape & Reel packaging variant if automated surface-mount assembly is required. Confirm the lead-free/RoHS compliance status indicated by the '+' designation matches environmental regulations for the target deployment region. Ensure the primary VCC supply is strictly limited to the 3V specification to prevent device damage.

Real Time Clock Selection Notes

Select this component when a parallel multiplexed bus interface is preferred over serial protocols like I2C or SPI. The DS1685S-3+ is suitable for designs requiring direct hardware wake-up capabilities from a low-power state. Verify that the host processor can manage the address/data demultiplexing signals (ALE/CS) required for bus communication.

Real Time Clock Part Context

This part belongs to the DS1685 family, which serves as a successor to industry-standard PC clocks such as the DS1287. While the base DS1685 chip requires external components, the 'S' suffix denotes the standalone encapsulated SOIC package version. The '-3' indicates the specific voltage grade optimized for 3V operation, distinguishing it from the 5V variants in the same series.

Real Time Clock Replacement Considerations

Direct pin-compatible replacements within the same voltage grade include other members of the DS1685 family with identical package footprints. Cross-voltage substitutions require careful evaluation of the VCC operating limits and power-fail trip points.