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Status
Part Number	Status	Replacement	Explanation
DS1688	This product is No Longer Available. See Ordering Information for recommended replacements.	DS1685	There is no direct replacement. The DS1685 has 242 bytes of RAM.
DS1691	This product is No Longer Available. See Ordering Information for recommended replacements.	DS17885	There is no direct replacement. The DS17x85 has 2K, 4K, and 8K bytes extended RAM.

Data Sheet

FULL DATA SHEET (PDF, 100kB) Download   E-Mail

Description

The DS1688/DS1691 is a real-time clock (RTC) designed as a successor to the industry standard DS1285, DS1385, DS1485, and DS1585 PC real time clocks. This device provides the industry standard DS1285 clock function with the new feature of either +3.0 or +5.0V operation and automatic backup and write protection to an external SRAM. The DS1688 also incorporates a number of enhanced features including a silicon serial number, power on/off control circuitry, 114 bytes of user NV SRAM, power on elapsed timer, and power cycle counter.

Key Features

Incorporates industry standard DS1287 PC clock plus enhanced features: +3 or +5V operation 64-bit Silicon serial number 64-bit customer specific ROM or additional serial number available Power control circuitry supports system power on from date/time alarm or key closure Automatic battery backup and write protection to external SRAM Crystal select bit allows RTC to operate with 6pF or 12.5pF crystal 114 bytes user NV RAM Auxiliary battery input RAM clear input Century register 32kHz output for power management 32-bit VCC powered elapsed time counter 32-bit VBAT powered elapsed time counter 16-bit power cycle counter Compatible with existing BIOS for original DS1287 functions Available as IC (DS1688) or stand-alone module with embedded battery and crystal (DS1691) Timekeeping algorithm includes leap year compensation valid up to 2100 Underwriters Laboratories (UL®) Recognized

Application Notes

Application Note 58: Crystal Considerations with Dallas Real-Time Clocks (RTCs) - DS1688 Application Note 499: Using the Multiplex Bus RTC Extended Features - DS1688, DS1691 Application Note 504: Design Considerations for Dallas Semiconductor Real-Time Clocks - DS1688, DS1691 Application Note 505: Lithium Coin-Cell Batteries: Predicting an Application Lifetime - DS1688 Application Note 701: Using the DS32kHz with Dallas Real-Time Clocks - DS1688 Application Note 1145: Interface a Multiplexed-Bus Real-Time Clock to a µP With Separate Address and Data Buses - DS1688, DS1691 Application Note 3778: Problems and Solutions for Adjusting to Changes in Daylight Saving Time - DS1688, DS1691

Design Guides

Real-Time Clocks (PDF)

Reliability Reports

Reliability Report: DS1688.pdf DS1691.pdf Underwriters Laboratories (UL®) Recognized

Software/Models

none

Ordering Information

Notes: Other options and links for purchasing parts are listed at: http://www.maxim-ic.com/sales. Didn't Find What You Need? Ask our applications engineers. Expert assistance in finding parts, usually within one business day. Part number suffixes: T or T&R = tape and reel;+ = RoHS/lead-free;# = RoHS/lead-exempt. More: SeeFull Data Sheet or Part Naming Conventions. * Some packages have variations, listed on the drawing. "PkgCode/Variation" tells which variation the product uses. Note that "+", "#", "-" in the part number suffix describes RoHS status. Package drawings may show a different suffix character.

Devices: 1-4 of 4

DS1688	Free Sample	Buy	Status	Recommended Replacement	Package: TYPE PINS FOOTPRINT   DRAWING CODE/VAR *	Temp	RoHS/Lead-Free? Materials Analysis
DS1688		N/A	No Longer Available	DS1685 There is no direct replacement. The DS1685 has 242 bytes of RAM.	PDIP(W);28 pin;593 mm² Outline Drawing: 21-0044 (PDF) Land Pattern: Not Applicable Use pkgcode/variation: P28-3*	0°C to +70°C	RoHS/Lead-Free: No Materials Analysis
DS1688S		N/A	No Longer Available	DS1685S-5+	SOIC(W);28 pin;235 mm² Outline Drawing: 21-0251 (PDF) Land Pattern: 90-0255 (PDF) Use pkgcode/variation: F28-2*	0°C to +70°C	RoHS/Lead-Free: No Materials Analysis
DS1688S+		N/A	No Longer Available	DS1685S-5+	SOIC(W);28 pin;235 mm² Outline Drawing: 21-0251 (PDF) Land Pattern: 90-0255 (PDF) Use pkgcode/variation: F28+2*	0°C to +70°C	RoHS/Lead-Free: Lead Free Materials Analysis
DS1691	Free Sample	Buy	Status	Recommended Replacement	Package: TYPE PINS FOOTPRINT   DRAWING CODE/VAR *	Temp	RoHS/Lead-Free? Materials Analysis
DS1691		N/A	No Longer Available	DS17885 There is no direct replacement. The DS17x85 has 2K, 4K, and 8K bytes extended RAM.	EDIP;28 pin;626 mm² Outline Drawing: 21-0241 (PDF) Land Pattern: Not Available Use pkgcode/variation: MDP28-2*	0°C to +70°C	RoHS/Lead-Free: No Materials Analysis

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