DS1643P-85+

Real Time Clock Overview

The DS1643P-85+ is a nonvolatile timekeeping RAM integrating an 8K x 8 static RAM, real-time clock (RTC), crystal, and lithium energy source. It operates at 5.0V with access times of 85ns or 100ns. The RTC provides BCD-coded year, month, date, day, hours, minutes, and seconds with leap year compensation valid to 2100. Clock registers reside in the top eight RAM locations and are double-buffered. The device features power-fail write protection for ±10% VCC tolerance and electrically disconnects the lithium source until first power application.

Real Time Clock Feature Summary

• Integrated NV SRAM, RTC, Crystal, Power-Fail Control, and Lithium Energy Source
• BCD-Coded Time/Date with Leap Year Compensation Valid Up to 2100
• Power-Fail Write Protection Allows for ±10% VCC Power Supply Tolerance
• Lithium Energy Source Electrically Disconnected Until First Power Application

Real Time Clock Applications

• Systems requiring byte-wide 8K x 8 RAM with integrated timekeeping
• Applications substituting ROM, EPROM, or EEPROM sockets with read/write nonvolatility
• Surveillance systems needing persistent calendar and clock data

Real Time Clock Procurement Notes

Verify compatibility with the required PowerCap module (DS9034PCX or DS9034I-PCX+), which must be ordered separately. Confirm that the surface-mountable package design allows for post-reflow mounting of the PowerCap to protect the battery and crystal from soldering temperatures. Ensure the system design accommodates the open-drain PFO output requiring a pullup resistor.

Real Time Clock Selection Notes

Select the DS1643P-85+ when a surface-mountable RTC module is required instead of the through-hole DIP version. This part requires the separate DS9034PCX PowerCap for battery and crystal functionality. Choose this over the -100+ variant if 85ns access time is sufficient. Verify that the operating temperature range of 0°C to +70°C meets system requirements.

Real Time Clock Part Context

The DS1643P-85+ is part of the DS164XP family of nonvolatile timekeeping RAMs. It is functionally equivalent to JEDEC standard 8K x 8 SRAM but includes RTC capabilities in the upper memory addresses. The 'P' suffix denotes the PowerCap module board package, distinct from the EDIP DIP module. It is pin-for-pin compatible with other densities in the DS164XP series.

Real Time Clock Replacement Considerations

Public confirmed substitute part numbers: None identified.