1 of 11 022101 features integrated nv sram, real time clock, crystal, power-fail control circuit and lithium energy source clock registers are accessed identically to the static ram. these registers are resident in the eight top ram locations. totally nonvolatile with over 10 years of operation in the absence of power bcd coded year, month, date, day, hours, minutes, and seconds with leap year compensation valid up to 2100 power-fail write protection allows for 10% v cc power supply tolerance ds1644 only (dip module) ? upward compatible with the ds1643 timekeeping ram to achieve higher ram density ? standard jedec bytewide 32k x 8 static ram pinout DS1644P only (powercap ? module board) ? surface mountable package for direct connection to powercap containing battery and crystal ? replaceable battery (powercap) ? power-fail output ? pin-for-pin compatible with other densities of ds164xp timekeeping ram pin assignment pin description a0-a14 - address input ce - chip enable oe - output enable we - write enable v cc - +5v gnd - ground dq0-dq7 - data input/output nc - no connection pfo - power-fail output (DS1644P only) x1, x2 - crystal connection v bat - battery connection 15 ds1644/DS1644P nonvolatile timekeeping ram www.dalsemi.com 13 27 28-pin encapsulated package (720-mil extended) a7 a5 a3 a2 a1 a0 dq0 dq1 gnd dq2 vcc we a 13 a 8 a 9 a 11 oe a 10 ce dq7 dq6 dq5 dq3 dq4 1 2 3 4 5 6 7 8 9 10 11 12 14 28 26 25 24 23 22 21 20 19 18 17 16 a12 a 6 a4 a14 1 nc 2 3 nc nc pfo v cc we oe ce dq7 dq6 dq5 dq4 dq3 dq2 dq1 dq0 gnd 4 5 6 7 8 9 10 11 12 13 14 15 16 17 nc a 14 33 32 31 30 29 28 27 26 25 24 23 22 21 20 19 18 a 13 a 12 a 11 a 10 a 9 a 8 a 7 a 6 a 5 a 4 a 3 a 2 a 1 a 0 34 nc x1 gnd v bat x2 34-pin powercap module board (uses ds9034pcx powercap) a12
ds1644/DS1644P 2 of 11 ordering information ds1644 28-pin dip module *DS1644P 34-pin powercap module board *ds9034pcx (power cap) required; must be ordered separately description the ds1644 is a 32k x 8 nonvolatile static ram with a full function real time clock, which are both accessible in a byte-wide format. the nonvolatile timekeeping ram is function equivalent to any jedec standard 32k x 8 sram. the device can also be easily substituted for rom, eprom and eeprom, providing read/write nonvolatility and the addition of the real time clock function. the real time clock information resides in the eight uppermost ram locations. the rtc registers contain year, month, date, day, hours, minutes, and seconds data in 24-hour bcd format. corrections for the day of the month and leap year are made automatically. the rtc clock registers are double-buffered to avoid access of incorrect data that can occur during clock update cycles. the double-buffered system also prevents time loss as the timekeeping countdown continues unabated by access to time register data. the ds1644 also contains its own power-fail circuitry, which deselects the device when the v cc supply is in an out-of- tolerance condition. this feature prevents loss of data from unpredictable system operation brought on by low v cc as errant access and update cycles are avoided. packages the ds1644 is available in two packages (28-pin dip and 34-pin powercap module). the 28-pin dip style module integrates the crystal, lithium energy source, and silicon all in one package. the 34-pin powercap module board is designed with contacts for connection to a separate powercap (ds9034pcx) that contains the crystal and battery. this design allows the powercap to be mounted on top of the DS1644P after the completion of the surface-mount process. mounting the powercap after the surface mount process prevents damage to the crystal and battery due to the high temperatures required for solder reflow. the powercap is keyed to prevent reverse insertion. the powercap module board and powercap are ordered separately and shipped in separate containers. the part number for the powercap is ds9034pcx. clock operations - reading the clock while the double-buffered register structure reduces the chance of reading incorrect data, internal updates to the ds1644 clock registers should be halted before clock data is read to prevent reading of data in transition. however, halting the internal clock register updating process does not affect clock accuracy. updating is halted when a 1 is written into the read bit, the 7th most significant bit in the control register. as long as a 1 remains in that position, updating is halted. after a halt is issued, the registers reflect the count, that is day, date, and time that was present at the moment the halt command was issued. however, the internal clock registers of the double-buffered system continue to update so that the clock accuracy is not affected by the access of data. all of the ds1644 registers are updated simultaneously after the clock status is reset. updating is within a second after the read bit is written to 0.
ds1644/DS1644P 3 of 11 ds1644 block diagram figure 1 ds1644 truth table table 1 v cc ce oe we mode dq power v ih x x deselect high-z standby x x x deselect high-z standby v il xv il write data in active v il v il v ih read data out active 5v 10% v il v ih v ih read high-z active <4.5v >v bat x x x deselect high-z cmos standby ds1644/DS1644P 4 of 11 clock accuracy (dip module) the ds1644 is guaranteed to keep time accuracy to within 1 minute per month at 25 c. the rtc is calibrated at the factory by dallas semiconductor using nonvolatile tuning elements, and does not require additional calibration. for this reason, methods of field clock calibration are not available and not necessary. clock accuracy is also effected by the electrical environment and caution should be taken to place the rtc in the lowest level emi section of the pcb layout. for additional information please see application note 58. clock accuracy (powercap module) the ds1644 and ds9034pcx are each individually tested for accuracy. once mounted together, the module will typically keep time accuracy to within 1.53 minutes per month (35 ppm) at 25c. clock accuracy is also effected by the electrical environment and caution should be taken to place the rtc in the lowest level emi section of the pcb layout. for additional information please see application note 58. ds1644 register map - bank1 table 2 data address b 7 b 6 b 5 b 4 b 3 b 2 b 1 b 0 function 7fff - - - - - - - - year 00-99 7ffe x x x - - - - - month 01-12 7ffd xx------date 01-31 7ffc x ft x x x - - - day 01-07 7ffb x x - - - - - - hour 00-23 7ffa x-------minutes00-59 7ff9 osc ------- seconds 00-59 7ff8 w rxxxxxxcontrola osc = stop bit r = read bit ft = frequency test w = write bit x = unused note: all indicated ?x? bits are not dedicated to any particular function and can be used as normal ram bits.
ds1644/DS1644P 5 of 11 retrieving data from ram or clock the ds1644 is in the read mode whenever we (write enable) is high, and ce (chip enable) is low. the device architecture allows ripple-through access to any of the address locations in the nv sram. valid data will be available at the dq pins within t aa after the last address input is stable, providing that the ce and oe access times and states are satisfied. if ce or oe access times are not met, valid data will be available at the latter of chip enable access (t cea ) or at output enable access time (t oea ). the state of the data input/output pins (dq) is controlled by ce and oe . if the outputs are activated before t aa , the data lines are driven to an intermediate state until t aa . if the address inputs are changed while ce and oe remain valid, output data will remain valid for output data hold time (t oh ) but will then go indeterminate until the next address access. writing data to ram or clock the ds1644 is in the write mode whenever we and ce are in their active state. the start of a write is referenced to the latter occurring high to low transition of we or ce . the addresses must be held valid throughout the cycle. ce or we must return inactive for a minimum of t wr prior to the initiation of another read or write cycle. data in must be valid t ds prior to the end of write and remain valid for t dh afterward. in a typical application, the oe signal will be high during a write cycle. however, oe can be active provided that care is taken with the data bus to avoid bus contention. if oe is low prior to we transitioning low the data bus can become active with read data defined by the address inputs. a low transition on we will then disable the outputs t wez after we goes active. data retention mode when v cc is within nominal limits (v cc > 4.5 volts) the ds1644 can be accessed as described above with read or write cycles. however, when v cc is below the power-fail point v pf (point at which write protection occurs) the internal clock registers and ram are blocked from access. this is accomplished internally by inhibiting access via the ce signal. at this time the power-fail output signal ( pfo ) will be driven active low and will remain active until v cc returns to nominal levels. when v cc falls below the level of the internal battery supply, power input is switched from the v cc pin to the internal battery and clock activity, ram, and clock data are maintained from the battery until v cc is returned to nominal level.
ds1644/DS1644P 6 of 11 absolute maximum ratings* voltage on any pin relative to ground -0.3v to +7.0v storage temperature -40c to +85c soldering temperature 260c for 10 seconds (dip package) (see note 7) see ipc/jedec standard j-std-020a for surface mount devices *this is a stress rating only and functional operation of the device at these or any other conditions above those indicated in the operation sections of this specification is not implied. exposure to absolute maximum rating conditions for extended periods of time may affect reliability. operating range range temperature v cc commercial 0c to +70c 5v 10% recommended dc operating conditions (over the operating range) parameter symbol min typ max units notes supply voltage v cc 4.5 5.5 v 1 logic 1 voltage all inputs v ih 2.2 v cc +0.3 v logic 0 voltage all inputs v il -0.3 0.8 v dc electrical characteristics (over the operating range) parameter symbol min typ max units notes average v cc power supply current i cc1 75 ma 3 ttl standby current ( ce =v ih ) i cc2 6ma3 cmos standby current ( ce =v cc - 0.2v) i cc3 4.0 ma 3 input leakage current (any input) i il -1 +1 a output leakage current i ol -1 +1 a output logic 1 voltage (i out = -1.0 ma) v oh 2.4 v output logic 0 voltage (i out = +2.1 ma) v ol 0.4 v write protection voltage v pf 4.0 4.5 v
ds1644/DS1644P 7 of 11 ac electrical characteristics (over the operating range) parameter symbol min typ max units notes read cycle time t rc 120 ns address access time t aa 120 ns ce access time t cea 120 ns ce data off time t cez 40 ns output enable access time t oea 100 ns output enable data off time t oez 40 ns output enable to dq low-z t oel 5ns ce to dq low-z t cel 5ns output hold from address t oh 5ns write cycle time t wc 120 ns address setup time t as 0ns ce pulse width t cew 100 ns address hold from end of write t ah1 t ah2 5 30 ns ns 5 6 write pulse width t wew 75 ns we data off time t wez 40 ns we or ce inactive time t wr 10 ns data setup time t ds 85 ns data hold time high t dh1 t dh2 0 15 ns ns 5 6 ac test conditions input levels: 0v to 3v transition times: 5 ns capacitance (t a = 25 c) parameter symbol min typ max units notes capacitance on all pins (except dq) c i 7pf capacitance on dq pins c dq 10 pf ac electrical characteristics (power-up/down timing) (over the operating range) parameter symbol min typ max units notes ce or we at v ih before power down t pd 0 s v pf (max) to v pf (min) v cc fall time t f 300 s v pf (min) to v so v cc fall time t fb 10 s v so to v pf (min) v cc rise time t rb 1 s v pf (min) to v pf (max) v cc rise time t r 0 s power-up t rec 15 35 ms expected data retention time (oscillator on) t dr 10 years 4
ds1644/DS1644P 8 of 11 ds1644 read cycle timing ds1644 write cycle timing
ds1644/DS1644P 9 of 11 power-down/power-up timing notes: 1. all voltages are referenced to ground. 2. typical values are at 25 c and nominal supplies. 3. outputs are open. 4. data retention time is at 25 c and is calculated from the date code on the device package. the date code xxyy is the year followed by the week of the year in which the device was manufactured. for example, 9225 would mean the 25 th week of 1992. output load 5. t ah1 , t dh1 are measured from we going high. 6. t ah2 , t dh2 are measured from ce going high. 7. real-time clock modules (dip) can be successfully processed through conventional wave-soldering techniques as long as temperatures as long as temperature exposure to the lithium energy source contained within does not exceed +85 c. post solder cleaning with water washing techniques is acceptable, provided that ultrasonic vibration is not used. in addition, for the powercap version: a. dallas semiconductor recommends that powercap module bases experience one pass through solder reflow oriented with the label side up (?live - bug?). b. hand soldering and touch-up: do not touch or apply the soldering iron to leads for more than 3 (three) seconds. to solder, apply flux to the pad, heat the lead frame pad and apply solder. to remove the part, apply flux, heat the lead frame pad until the solder reflows and use a solder wick to remove solder.
ds1644/DS1644P 10 of 11 ds1644 28-pin package pkg 28-pin dim min max a in. mm 1.470 37.34 1.490 37.85 b in. mm 0.715 18.16 0.740 18.80 c in. mm 0.335 8.51 0.365 9.27 d in. mm 0.075 1.91 0.105 2.67 e in. mm 0.015 0.38 0.030 0.76 f in. mm 0.140 3.56 0.180 4.57 g in. mm 0.090 2.29 0.110 2.79 h in. mm 0.590 14.99 0.630 16.00 j in. mm 0.010 0.25 0.018 0.45 k in. mm 0.015 0.38 0.025 0.64 DS1644P pkg inches dim min nom max a 0.920 0.925 0.930 b 0.980 0.985 0.990 c - - 0.080 d 0.052 0.055 0.058 e 0.048 0.050 0.052 f 0.015 0.020 0.025 g 0.025 0.027 0.030 note: for the powercap version: a. dallas semiconductor recommends that powercap module bases experience one pass through solder reflow oriented with the label side up (?live - bug?). b. hand soldering and touch - up: do not touch or apply the soldering iron to leads for more than 3 (three) seconds. to solder, apply flux to the pad, heat the lead frame pad and apply solder. to remove the part, apply flux, heat the lead frame pad until the solder reflows and use a solder wick to remove solder.
ds1644/DS1644P 11 of 11 DS1644P with ds9034pcx attached pkg inches dim min nom max a 0.920 0.925 0.930 b 0.955 0.960 0.965 c 0.240 0.245 0.250 d 0.052 0.055 0.058 e 0.048 0.050 0.052 f 0.015 0.020 0.025 g 0.020 0.025 0.030 recommended powercap module land pattern pkg inches dim min nom max a - 1.050 - b - 0.826 - c - 0.050 - d - 0.030 - e - 0.112 -
|
