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| DS1688/DS1691 DS1688/DS1691 3 Volt/5 Volt Serialized Real Time Clock with NV RAM Control FEATURES Incorporates industry standard DS1287 PC clock plus enhanced features: PIN ASSIGNMENT VBAUX X1 X2 RCLR AD0 AD1 AD2 AD3 AD4 AD5 AD6 AD7 PWR GND 1 2 3 4 5 6 7 8 9 10 11 12 13 14 28 27 26 25 24 23 22 21 20 19 18 17 16 15 CEI CEO VCCI VCCO SQW VBAT IRQ PSEL RD GND WR ALE CS KS VBAUX X1 X2 RCLR AD0 AD1 AD2 AD3 AD4 AD5 AD6 AD7 PWR GND 1 2 3 4 5 6 7 8 9 10 11 12 13 14 28 27 26 25 24 23 22 21 20 19 18 17 16 15 CEI CEO VCCI VCCO SQW VBAT IRQ PSEL RD GND WR ALE CS KS * +3 or +5 volt operation * 64-bit Silicon serial number * 64-bit customer specific ROM or additional serial number available control circuitry supports system power on from date/time alarm or key closure battery backup and write protection to external SRAM 12.5 pF crystal * Power * Automatic * Crystal select bit allows RTC to operate with 6 pF or * 114 bytes user NVRAM * Auxiliary battery input * RAM clear input * Century register * 32 KHz 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 functions existing BIOS for original DS1287 DS1688 28-PIN DIP (600 MIL) VBAUX NC NC RCLR AD0 AD1 AD2 AD3 AD4 AD5 AD6 AD7 PWR GND 1 2 3 4 5 6 7 8 9 10 11 12 13 14 28 27 26 25 24 23 22 21 20 19 18 17 16 15 DS1688S 28-PIN SOIC (330 MIL) CEI CEO VCCI VCCO SQW NC IRQ PSEL RD NC WR ALE CS KS DS1691 28-PIN ENCAPSULATED PACKAGE (740 MIL) * Available as chip (DS1688) or stand-alone module with embedded battery and crystal (DS1691) PIN DESCRIPTION X1 X2 RCLR AD0-AD7 PWR KS CS ALE WR RD VCCO - - - - - - - - - - - Crystal Input Crystal Output RAM Clear Input Mux'ed Address/Data Bus Power-on Interrupt Output Kickstart Input RTC Chip Select Input RTC Address Strobe RTC Write Data Strobe RTC Read Data Strobe RAM Power Supply Output * Timekeeping algorithm includes leap year compensation valid up to 2100 ORDERING INFORMATION PART # DS1688 DS1688S DS1691 DESCRIPTION RTC Chip, 28-pin DIP RTC Chip, 28-pin SOIC RTC Module; 28-pin DIP 030598 1/5 DS1688/DS1691 IRQ SQW VCCI GND VBAT VBAUX PSEL CEI CEO - - - - - - - - - Interrupt Request Output Square Wave Output +3 or +5 Volt Main Supply Ground Battery + Supply Auxiliary Battery Supply +3 or +5 Volt Power Select RAM Chip Enable In RAM Chip Enable Out The DS1688/DS1691 incorporates 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 VCCO and CEO pins. The lithium energy source used to permanently power the real time clock is also used to retain RAM data in the absence of VCC power through the VCCO 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 32.768 KHz 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 VCC is guaranteed. For a complete description of operating conditions, electrical characteristics, bus timing, and pin descriptions other than the SQW output, see the DS1689/DS1693 data sheet. 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 +5.0 volt 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 NVSRAM, power on elapsed timer, and power cycle counter. 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 insure 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. Blocks of available numbers from Dallas Semiconductor can be reserved by the customer. The serialized RTC's 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. SIGNAL DESCRIPTION SQW (Square Wave Output) - The SQW output signal functions identical to the DS1689/DS1693 with an exception occurring at power-up. A 32 KHz square wave will be output on this pin, tREC, after a power-up condition has been detected. This condition sets the following bits enabling the 32 KHz output; DV1=1, SQWE=1, and E32K=1. The square wave will be output on this pin if either SQWE=1 or E32K=1. 030598 2/5 DS1688/DS1691 DS1688 28-PIN DIP PKG DIM B D A IN. MM B IN. MM 1 A C IN. MM D IN. MM E IN. MM F IN. MM C G IN. MM H IN. MM J IN. MM K IN. MM 28-PIN MIN 1.445 36.70 0.530 13.46 0.140 3.56 0.600 15.24 0.015 0.38 0.120 3.05 0.090 2.29 0.625 15.88 0.008 0.20 0.015 0.38 MAX 1.470 37.34 0.550 13.97 0.160 4.06 0.625 15.88 0.040 1.02 0.145 3.68 0.110 2.79 0.675 17.15 0.012 0.30 0.022 0.56 F K G E J H 030598 3/5 DS1688/DS1691 DS1688S 28-PIN SOIC K G PKG DIM A IN. MM B IN. MM C IN. MM D IN. MM E IN. MM F IN. MM G IN. MM C H IN. MM E A J IN. MM K IN. MM 0.460 11.68 0.006 0.15 0.014 0.36 0.480 12.19 0.013 0.33 0.020 0.51 28-PIN MIN 0.706 17.93 0.338 8.58 0.086 2.18 0.020 0.58 0.002 0.05 0.090 2.29 0.050 1.27 MAX 0.728 18.49 0.350 8.89 0.110 2.79 0.050 1.27 0.014 0.36 0.124 3.15 BSC B F 0-8 deg. typ. J D H 030598 4/5 DS1688/DS1691 DS1691 28-PIN 740 MIL MODULE 28 15 PKG DIM A IN. MM B IN. MM 1 A 14 C IN. MM D IN. MM E IN. MM F C E IN. MM 28-PIN MIN 1.520 38.61 0.695 17.65 0.350 8.89 0.100 2.54 0.015 0.38 0.110 2.79 0.090 2.29 0.590 14.99 0.008 0.20 0.015 0.38 MAX 1.540 39.12 0.740 18.80 0.375 9.52 0.130 3.30 0.030 0.76 0.140 3.56 0.110 2.79 0.630 16.00 0.012 0.30 0.021 0.53 G IN. MM F H IN. MM J IN. MM D K 13 EQUAL SPACES AT .100 .010 TNA G K IN. MM NOTE: PINS 2, 3, 19 AND 23 ARE MISSING BY DESIGN. J H B 030598 5/5 |
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