DS17485S-3+

Real Time Clock Overview

The DS17485S-3+ is a real-time clock (RTC) IC from the DS17x85 family, designed as a successor to the DS12885. It provides timekeeping for seconds, minutes, hours, day, date, month, and year with leap-year compensation through 2099. The device features a multiplexed byte-wide interface and includes 114 bytes of general-purpose NV SRAM plus 4096 bytes of extended battery-backed NV SRAM. It supports optional +3.0V or +5.0V operation, with power-fail detection switching to backup supplies. Key enhancements include a 64-bit silicon serial number, SMI recovery stack, and power-control circuitry for system wake-up.

Real Time Clock Feature Summary

• Multiplexed byte-wide interface with 114 bytes user NV SRAM and 4096 bytes extended NV RAM
• Optional +3.0V or +5.0V VCC operation with automatic power-fail detection and switch
• 64-bit unique silicon serial number and SMI recovery stack
• Power-control circuitry enabling system power-on via date/time alarm or kickstart input

Real Time Clock Applications

• Embedded Systems
• Utility Meters
• Security Systems
• Network Hubs, Bridges, and Routers

Real Time Clock Procurement Notes

Verify the specific suffix 'S' indicates the SOIC package and '-3' denotes the +3.0V voltage range variant. Confirm RoHS compliance status (+ suffix typically indicates lead-free). Check current availability as this component may be subject to limited supply or end-of-life notices depending on the distributor. Ensure the design supports the required multiplexed bus timing for the selected voltage.

Real Time Clock Selection Notes

Select the DS17485S-3+ when a 4KB extended NV RAM capacity is required alongside standard RTC functions. Choose the -3 suffix for designs operating strictly at +3.0V; use -5 for +5.0V systems. The SOIC package is suitable for surface-mount assembly. Verify that the application can accommodate the multiplexed address/data bus interface rather than a simpler serial interface.

Real Time Clock Part Context

This part belongs to the DS17x85 series, which succeeded the industry-standard DS12885. Unlike the DS17487 module, the DS17485S-3+ is a bare die in an SOIC package requiring external crystal and battery connections. It shares the same core functionality and register map as other DS17x85 variants but differs in package type and voltage rating.

Real Time Clock Replacement Considerations

Direct replacements within the same family include the DS17485S-5+ for +5V applications. For legacy compatibility, the DS12885 is the predecessor, though it lacks the enhanced NV RAM and serial number features. No cross-family direct pin-compatible substitutes are documented.