DS1688S+ Datasheet DS1688S+, DS1691, DS1688 | P1-P3

DS1688/DS1691

3V/5V Serialized Real-Time Clocks

with NV RAM Control

1 of 3 REV: 112205

GENERAL DESCRIPTION

The DS1688/DS1691 are real-time clocks

(RTCs) designed as successors to the industry

standard DS1285, DS1385, DS1485, and

DS1585 PC real-time clocks. These devices

provide the industry standard DS1285 clock

function with the new feature of either +3.0V 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.

PIN CONFIGURATIONS

FEATURES

Incorporates Industry Standard DS1287 PC

Clock Plus Enhanced Features:

 +3V 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 V

Powered Elapsed Time

Counter

 32-Bit V

BAT

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

ORDERING INFORMATION

PART TEMP RANGE VOLTAGE (V) PIN-PACKAGE TOP MARK*

DS1688S

0C to +70C

3 to 5

28 SO (0.330)

DS1688S

DS1688S+

0C to +70C

3 to 5

28 SO (0.330)

DS1688S

DS1691

0C to +70C

3 to 5

28 EDIP (0.740)

DS1691

+ Denotes a lead(Pb)-free/RoHS-compliant device.

+ A “+” anywhere on the top mark denotes a lead(Pb)-free/RoHS-compliant device.

www.maxim-ic.com

TOP VIEW

DS1688/DS1691

2 of 3

DETAILED DESCRIPTION

Each DS1688/DS1691 is individually manufactured with a unique 64-bit serial number as well as an

additional 64-bit customer-specific ROM or serial number. The serial number is programmed and tested

at Dallas to ensure that no two devices are alike. The serial number can be used to electronically identify

a system for purposes such as establishment of a network node address or for maintenance tracking.

Customers can reserve blocks of available numbers from Dallas Semiconductor.

The serialized RTCs also incorporate power-control circuitry, which allows the system to be powered on

via an external stimulus, such as a keyboard or by a time and date (wake up) alarm. The PWR output pin

can be triggered by one or either of these events, and can be used to turn on an external power supply.

The PWR pin is under software control, so that when a task is complete, the system power can then be

shut down.

The DS1688/DS1691 incorporate a power-on elapsed time counter, a power-on cycle counter, and a

battery powered continuous counter. These three counters provide valuable information for maintenance

and warranty requirements.

Automatic backup and write protection for an external SRAM is provided through the V

CCO

and CEO

pins. The lithium energy source used to permanently power the RTC is also used to retain RAM data in

the absence of V

power through the V

CCO

pin. The chip enable output to RAM (CEO) is controlled

during power transients to prevent data corruption.

The DS1688 is a clock/calendar chip with the features described above. An external crystal and battery

are the only components required to maintain time-of-day and memory status in the absence of power.

The DS1691 incorporates the DS1688 chip, a 32.768kHz crystal, and a lithium battery in a complete, self-

contained timekeeping module. The entire unit is fully tested at Dallas Semiconductor such that a

minimum of 10 years of timekeeping and data retention in the absence of V

is guaranteed.

For a complete description of operating conditions, electrical characteristics, bus timing, and pin

descriptions other than the SQW output, refer to the DS1689/DS1693 data sheet, available online at

www.maxim-ic.com/DS1689

S1688/DS1691

PIN DESCRIPTION

SO EDIP

NAME FUNCTION

1 1 V

BAUX

Auxiliary Battery Supply

2, 3 — X1, X2 Crystal Input, Crystal Output

4 4

RCLR

Active-Low RAM Clear Input

5–12 5–12 AD0–AD7 Muxed Address/Data Bus

13 13

PWR

Active-Low Power-On Interrupt Output

14, 19 14 GND Ground

15 15

Active-Low Kickstart Input

16 16

Active-Low Chip Select Input

17 17 ALE Address Strobe

18 18

Active-Low Write Data Strobe

20 20

Active-Low Read Data Strobe

21 21 PSEL +3V or +5V Power Select

22 22

IRQ

Active-Low Interrupt Request Output

23 — V

BAT

Battery + Supply

24 24 SQW

Square-Wave Output. This signal functions identical to the

DS1689/DS1693 with an exception occurring at power-up. A

32kHz square wave is output on this pin, t

REC

, after a power-up

condition has been detected. This condition sets the following

bits, enabling the 32kHz output: DV1 = 1, SQWE = 1, and E32K

= 1. The square wave is output on this pin if either SQWE = 1 or

E32K = 1.

25 25 V

CCO

RAM Power-Supply Output

26 26 V

CCI

+3V or +5V Main Supply

27 27

CEO

Active-Low RAM Chip Enable Out

28 28

CEI

Active-Low RAM Chip Enable In

—

2, 3, 19,

N.C. No Connection

PACKAGE INFORMATION

For the latest package outline information and land patterns, go to www.maxim-ic.com/packages.

PACKAGE TYPE PACKAGE CODE DOCUMENT NO.

28 SO F28+3 21-0251

28 PDIP P28-6 21-0044

28 EDIP MDP28-2 21-0241

3 of 3

Maxim/Dallas Semiconductor cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim/Dallas Semiconductor product. No

circuit patent licenses are implied. Maxim/Dallas Semiconductor reserves the right to change the circuitry and specifications without notice at any time.

Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600

The Maxim logo is a registered trademark of Maxim Integrated Products, Inc. The Dallas logo is a registered trademark of Dallas Semiconductor Corporation.

P1-P3

DS1688S+

Mfr. #:

Buy DS1688S+

Manufacturer:

Maxim Integrated

Description:

Real Time Clock

Lifecycle:

New from this manufacturer.

Delivery:

DHL FedEx Ups TNT EMS

Payment:

T/T Paypal Visa MoneyGram Western Union

DS1688S+

DS1688S+

Products related to this Datasheet