DS1687:3V/5V Real-Time Clock

The DS1685/DS1687 are real-time clocks (RTCs) designed as successors to the industry-standard DS1285,DS1385, DS1485, and DS1585 PC RTCs. These devices provide the industry-standard DS1285 clock function with either +3.0V or +5.0V operation. The DS1685 also incorporates a number of enhanced features including a silicon serial number, power-on/off control circuitry, 242 bytes of user NV SRAM, and 32.768kHz output for sustaining power management activities. The DS1685/DS1687 power-control circuitry allows the system to be powered on by 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 DS1685 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 DS1687 incorporates the DS1685 chip, a 32.768kHz crystal, and a lithium battery in a complete, self-contained timekeeping EDIP. 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 VCC is guaranteed.

Key Features
  • Y2K Compliant
  • +3V or +5V Operation
  • 64-Bit Silicon Serial Number
  • Power-Control Circuitry Supports System Power-On from Date/Time Alarm or Key Closure
  • 32kHz Output for Power Management
  • Crystal-Select Bit Allows RTC to Operate with 6pF or 12.5pF Crystal
  • SMI Recovery Stack
  • 242 Bytes Battery-Backed NV RAM
  • Auxiliary Battery Input
  • RAM Clear Input
  • Century Register
  • Date Alarm Register
  • Compatible with Existing BIOS for Original DS1287 Functions
  • Available as Chip (DS1685) or Stand-Alone Encapsulated DIP (EDIP) with Embedded Battery and Crystal (DS1687)
  • Timekeeping Algorithm Includes Leap-Year Compensation Valid Through 2099
DS1685, DS1687: Typical Operating Circuit
DS1685, DS1687: Typical Operating Circuit
Applications/Uses
  • Embedded Systems
  • Network Hubs, Switches, Routers
  • Security Systems
  • Utility Meters
DataSheet
titleDownload file
DS1685-DS1687 Data SheetDS1685-DS1687.pdf
Parametrics
Part NumberInterfaceVSUPPLY
(V)
Time Keeping Current
(nA)
CL
(pF)
Memory TypeMemory Size
(Bytes)
Time of Day AlarmsFunctionsPackage/PinsBudgetary
Price
typSee Notes
DS1685Multiplexed3
5
4006
12.5
NV SRAM2421RTCPDIP(W)/24
PLCC/28
SOIC(W)/24
TSSOP/24
$2.94 @1k
DS1687--EDIP/24$7.20 @1k
Quality and Environmental Data
Ordering Information
Part NumberNotesStatusRecommended ReplacementPackageTempRoHS
DS1687-33VNo Longer AvailableDS1685SN-5+EDIP,;24 pin;544.6 mm²0°C to +70°CSee data sheet
DS1687-3+ActiveEDIP,;24 pin;544.6 mm²0°C to +70°CLead Free
DS1687-3+C01No Longer AvailableEDIP,;24 pin;544.6 mm²0°C to +70°CLead Free
DS1687-3INDNo Longer AvailableDS1687-3IND+EDIP,;24 pin;544.6 mm²-40°C to +85°CSee data sheet
DS1687-3IND+ActiveEDIP,;24 pin;544.6 mm²-40°C to +85°CLead Free
DS1687-55VNo Longer AvailableDS1687-5+EDIP,;24 pin;544.6 mm²0°C to +70°CSee data sheet
DS1687-5+ActiveEDIP,;24 pin;544.6 mm²0°C to +70°CLead Free
DS1687-5INDNo Longer AvailableDS1687-5IND+EDIP,;24 pin;544.6 mm²-40°C to +85°CSee data sheet
DS1687-5IND+ActiveEDIP,;24 pin;544.6 mm²-40°C to +85°CLead Free
DS1685-DS1687.pdf DS1687
Tips for Writing Bulletproof Real-Time Clock Control Code DS3234
Problems and Solutions for Adjusting to Changes in Daylight Saving Time DS17887
Interface a Multiplexed-Bus Real-Time Clock to a µP With Separate Address and Data Buses DS17887
Using Multiplexed Bus Clocks with a Microcontroller DS17887
Design Considerations for Maxim Real-Time Clocks DS3234
Using the Multiplex Bus RTC Extended Features DS17887
DS1685/87 and DS17X85/87 Accessing Extended User RAM DS17887
DS1687.pdf DS1687
DS1685-DS1687.pdf DS1685