DS1688/DS1691
3V/5V Serialized Real-Time Clocks
with NV RAM Control
www.maxim-ic.com
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.
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
CC
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
PIN-PACKAGE
28 SO (0.330″)
28 SO (0.330″)
28 EDIP (0.740″)
TOP MARK*
DS1688S
DS1688S
DS1691
PIN CONFIGURATIONS
TOP VIEW
ORDERING INFORMATION
PART
DS1688S
DS1688S+
DS1691
TEMP RANGE
0°C to +70°C
0°C to +70°C
0°C to +70°C
VOLTAGE (V)
3 to 5
3 to 5
3 to 5
+
Denotes a lead-free/RoHS-compliant device.
+
A “+” anywhere on the top mark denotes a lead-free/RoHS-compliant device.
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REV: 112205
DALLAS [ DALLAS SEMICONDUCTOR ]
