DS17485S-5/T&R

Real Time Clock Overview

The DS17485S-5/T&R is a real-time clock (RTC) IC from the DS17x85 series, designed as a successor to the DS12885. It features a multiplexed byte-wide interface and provides timekeeping for seconds through year with leap-year compensation through 2099. The device includes 4096 bytes of battery-backed NV SRAM and 114 bytes of general-purpose RAM. It supports +5V operation (4.5V to 5.5V) with automatic power-fail detection and switching to backup supplies at VBAT or VBAUX. Key features include a silicon serial number, programmable square-wave output, and system power-on control via alarm or kickstart.

Real Time Clock Feature Summary

• Multiplexed byte-wide address/data bus interface
• 4096 bytes extended battery-backed NV SRAM plus 114 bytes general-purpose RAM
• Automatic power-fail detect and switch circuitry
• 64-bit silicon serial number

Real Time Clock Applications

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

Real Time Clock Procurement Notes

Verify component status as obsolete; direct replacement is DS17485S-5+T&R. Confirm RoHS compliance requirements as original units are non-compliant. Ensure supply chain sources provide valid datasheets matching Analog Devices/Maxim Integrated specifications. Check for availability in tape-and-reel packaging formats.

Real Time Clock Selection Notes

Select this part for applications requiring parallel interface RTCs with large nonvolatile memory. Verify voltage compatibility (+5V nominal) against system rails. Ensure external 32.768kHz crystal load capacitance matches the device's 6pF or 12.5pF selectable options. Confirm package type (SOIC-24) fits PCB layout constraints.

Real Time Clock Part Context

Part of the DS17x85 family, succeeding the industry-standard DS12885. Manufactured by Analog Devices Inc./Maxim Integrated. Available in SOIC package variants. The 'S' denotes SOIC package, '5' indicates +5V operation, and '/T&R' specifies tape-and-reel packaging.

Real Time Clock Replacement Considerations

Direct substitute: DS17485S-5+T&R. Verify pinout and register compatibility before integration.

Real Time Clock FAQ

How does the device handle primary power failure?

A precision temperature-compensated circuit monitors VCC. If VCC falls below the power-fail trip point (VPF), the device automatically switches to the higher of VBAT or VBAUX backup supplies.

What is the function of the KS pin?

The KS (Kickstart) pin is an active-low input that can trigger system power-on when VCC is removed, provided VBAUX is present and the auxiliary-battery-enable bit is set.

Can the oscillator be driven externally?

Yes, an external 32.768kHz oscillator signal can be connected to the X1 pin, leaving the X2 pin unconnected.