DS1685QN-5+

Real Time Clock Overview

The DS1685QN-5+ is a real-time clock (RTC) and nonvolatile RAM device manufactured by Analog Devices Inc./Maxim Integrated. It operates at +5V with an industrial temperature range of -40°C to +85°C, housed in a 28-pin PLCC package. The component integrates a multiplexed address/data bus interface, 242 bytes of battery-backed NV SRAM, and a 64-bit silicon serial number. Key features include Y2K compliance, leap-year compensation through 2099, power-on control via alarm or kickstart, and a 32kHz square-wave output for power management.

Real Time Clock Feature Summary

• Multiplexed bidirectional address/data bus interface compatible with standard PC clock architectures
• 242 bytes of user-accessible nonvolatile RAM divided into two banks (114 bytes base + 128 bytes extended)
• Integrated power-control circuitry enabling system wake-up from date/time alarms or external key closures
• Y2K compliant timekeeping algorithm with automatic leap-year compensation valid through 2099

Real Time Clock Applications

• Embedded systems requiring precise timekeeping and nonvolatile data storage
• Utility meters needing reliable calendar functions and memory retention
• Security systems utilizing alarm-based power activation
• Network hubs, bridges, and routers for timestamping and configuration retention

Real Time Clock Procurement Notes

Verify the specific ordering suffix 'QN' corresponds to the -40°C to +85°C industrial temperature grade and PLCC package. Confirm RoHS compliance status as indicated by the '+' suffix. Ensure auxiliary battery connections are properly configured if utilizing kickstart or wake-up features, as these require VBAUX presence.

Real Time Clock Selection Notes

Select this part when a multiplexed bus interface is required rather than SPI or I2C. The +5V voltage rating distinguishes it from the -3 variant. Consider the PLCC package constraints for PCB layout. Verify that the host system can support the address/data multiplexing timing requirements defined in the datasheet.

Real Time Clock Part Context

This component belongs to the DS1685/DS1687 family, serving as a successor to industry-standard DS1285/DS1287 RTCs. It combines traditional clock/calendar functionality with enhanced features like silicon serial numbers and advanced power management. The 'QN' designation specifically identifies the industrial temperature range and plastic leaded chip carrier packaging within the broader product line.

Real Time Clock Replacement Considerations

Direct replacements must match the multiplexed bus interface and 28-pin PLCC form factor. The DS1685Q-5+ serves as the commercial temperature equivalent. Legacy DS1287 devices may be functionally compatible but lack the enhanced NV RAM and serial number features.