ds1688/DS1691 3 volt/5 volt serialized real time clock with nv ram control ds1688/DS1691 030598 1/5 features incorporates industry standard ds1287 pc clock plus enhanced features: ? +3 or +5 volt operation ? 64bit silicon serial number ? 64bit 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 6 pf or 12.5 pf crystal ? 114 bytes user nvram ? auxiliary battery input ? ram clear input ? century register ? 32 khz output for power management ? 32bit v cc powered elapsed time counter ? 32bit v bat powered elapsed time counter ? 16bit power cycle counter ? compatible with existing bios for original ds1287 functions ? available as chip (ds1688) or standalone module with embedded battery and crystal (DS1691) ? timekeeping algorithm includes leap year compensa- tion valid up to 2100 ordering information part # description ds1688 rtc chip, 28pin dip ds1688s rtc chip, 28pin soic DS1691 rtc module; 28pin dip pin assignment v baux x1 x2 rclr ad0 ad1 ad2 ad3 ad4 ad5 ad6 ad7 pwr gnd cei ceo v cci v cco sqw v bat irq psel rd gnd wr ale cs ks v baux 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 v cci v cco sqw v bat irq psel rd gnd wr ale cs ks 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 ds1688 28pin dip (600 mil) ds1688s 28pin soic (330 mil) cei ceo v cci v cco sqw nc irq psel rd nc wr ale cs ks v baux 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 DS1691 28pin encapsu- lated package (740 mil) pin description x1 crystal input x2 crystal output rclr ram clear input ad0-ad7 mux'ed address/data bus pwr poweron interrupt output ks kickstart input cs rtc chip select input ale rtc address strobe wr rtc write data strobe rd rtc read data strobe v cco ram power supply output
ds1688/DS1691 030598 2/5 irq interrupt request output sqw square wave output v cci +3 or +5 volt main supply gnd ground v bat battery + supply v baux auxiliary battery supply psel +3 or +5 volt power select cei ram chip enable in ceo ram chip enable out description the ds1688/DS1691 is a real time clock (rtc) de- signed 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 protec- tion to an external sram. the ds1688 also incorpo- rates 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 64bit serial number as well as an addi- tional 64bit 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 num- ber can be used to electronically identify a system for purposes such as establishment of a network node ad- dress 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 cir- cuitry 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 trig- gered by one or either of these events, and can be used to turn on an external power supply. the pwr pin is un- der software control, so that when a task is complete, the system power can then be shut down. 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 war- ranty 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 real time clock is also used to retain ram data in the absence of v cc power through the v cco pin. the chip enable out- put 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 timeofday 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, selfcon- tained 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 cc is guaranteed. for a complete description of operating conditions, electrical characteristics, bus timing, and pin descrip- tions other than the sqw output, see the ds1689/ds1693 data sheet. signal description sqw (square wave output) the sqw output signal functions identical to the ds1689/ds1693 with an exception occurring at powerup. a 32 khz square wave will be output on this pin, t rec , after a powerup condition has been detected. this condition sets the fol- lowing 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.
ds1688/DS1691 030598 3/5 ds1688 28pin dip 1 c a b d h j k g e f dim min max 28pin pkg a in. 1.445 1.470 mm 36.70 37.34 b in. 0.530 0.550 mm 13.46 13.97 c in. 0.140 0.160 mm 3.56 4.06 d in. 0.600 0.625 mm 15.24 15.88 e in. 0.015 0.040 mm 0.38 1.02 f in. 0.120 0.145 mm 3.05 3.68 g in. 0.090 0.110 mm 2.29 2.79 h in. 0.625 0.675 mm 15.88 17.15 j in. 0.008 0.012 mm 0.20 0.30 k in. 0.015 0.022 mm 0.38 0.56
ds1688/DS1691 030598 4/5 ds1688s 28pin soic h b j k g c e a f d 08 deg. typ. dim min max 28pin pkg a in. 0.706 0.728 mm 17.93 18.49 b in. 0.338 0.350 mm 8.58 8.89 c in. 0.086 0.110 mm 2.18 2.79 d in. 0.020 0.050 mm 0.58 1.27 e in. 0.002 0.014 mm 0.05 0.36 f in. 0.090 0.124 mm 2.29 3.15 g in. mm h in. 0.460 0.480 mm 11.68 12.19 j in. 0.006 0.013 mm 0.15 0.33 k in. 0.014 0.020 mm 0.36 0.51 0.050 bsc 1.27
ds1688/DS1691 030598 5/5 DS1691 28pin 740 mil module a 28 114 15 c e f k d g b h j dim min max a in. mm b in. mm c in. mm d in. mm e in. mm f in. mm g in. mm h in. mm j in. mm k in. mm 1.520 38.61 1.540 39.12 0.695 17.65 0.740 18.80 0.350 8.89 0.375 9.52 0.100 2.54 0.130 3.30 0.015 0.38 0.030 0.76 0.110 2.79 0.140 3.56 0.090 2.29 0.110 2.79 0.590 14.99 0.630 16.00 0.008 0.20 0.012 0.30 0.015 0.38 0.021 0.53 28pin pkg 13 equal spaces at .100 .010 tna note: pins 2, 3, 19 and 23 are missing by design.
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