DS1746-70IND+

Real Time Clock Overview

The DS1746-70IND+ is a Y2K-compliant, nonvolatile timekeeping RAM integrating a real-time clock/calendar and 128k x 8 SRAM. It operates at 5V with a 70ns access time in a 32-pin EDIP package. The device features BCD-coded registers for century, year, month, date, day, hours, minutes, and seconds, including automatic leap year compensation valid to 2100. Clock registers reside in the top eight RAM locations and are double-buffered to prevent data corruption during updates. It includes integrated power-fail write protection, a lithium energy source, and a battery voltage-level indicator flag.

Real Time Clock Feature Summary

• Integrated NV SRAM, RTC, crystal, power-fail control circuit, and lithium energy source
• Y2K compliant with BCD-coded registers and automatic leap year compensation valid to 2100
• Double-buffered clock registers resident in the eight top RAM locations
• Power-fail write protection allows ±10% VCC supply tolerance

Real Time Clock Applications

• Industrial systems requiring precise timekeeping and nonvolatile data storage
• Embedded controllers needing Y2K compliance and battery-backed memory
• Equipment requiring automatic leap year correction and long-term data retention

Real Time Clock Procurement Notes

Verify the component matches the industrial temperature range (-40°C to +85°C) and 5V operating voltage. Confirm the 32-pin EDIP package type. Ensure the ordering suffix indicates lead-free/RoHS compliance. Check that the lithium energy source is electrically disconnected until first power application to retain freshness.

Real Time Clock Selection Notes

Select this part for applications requiring a full-function RTC with 128KB of nonvolatile memory in a single DIP module. Compare against other densities in the DS174xP family if pin compatibility is required but different storage capacities are needed. Ensure the system design accommodates the specific address mapping where clock registers occupy the highest RAM addresses.

Real Time Clock Part Context

This component belongs to the DS1746/DS1746P series of Y2K-compliant, nonvolatile timekeeping RAMs manufactured by Analog Devices Inc./Maxim Integrated. It is designed as a drop-in replacement for standard static RAM while providing integrated timekeeping capabilities. The 'IND' suffix denotes the industrial temperature grade, and the '+' suffix indicates RoHS compliance.

Real Time Clock Replacement Considerations

The DS1746-70IND+ is pin-for-pin compatible with other densities of the DS174xP timekeeping RAM family. Verify that any substitute maintains the same 128k x 8 capacity and 70ns access speed to ensure functional equivalence without board redesign.

Real Time Clock FAQ

How does the device handle data integrity during power loss?

The DS1746-70IND+ includes a power-fail circuit that deselects the device when VCC falls below the write protection point (VPF). This prevents unpredictable system operation and data loss. When VCC drops below the battery switch point (VSO), power switches to the internal lithium source.

What is the expected data retention period?

The device is guaranteed to retain data and keep time for over 10 years in the absence of power at 25°C with the internal clock oscillator running. Each unit ships with the lithium energy source disconnected to ensure full energy capacity upon first use.

How are clock registers accessed?

Clock registers are accessed identically to the static RAM and are resident in the eight top RAM locations (addresses 1FFF8h to 1FFFFh). They are double-buffered to avoid accessing incorrect data during clock update cycles.