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1 of 16 note: some revisions of this device may incorporate deviations from published specifications known as errata. multipl e revisions of any device may be simultaneously available through various sales channels. for information about device errata, click here: www.maxim - ic.com/errata . 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. ? centu ry byte register (i.e., y2k compliant) ? totally nonvolatile with over 10 years of operation in the absence of power ? bcd - coded century, year, month, date, day, hours, minutes, and seconds with automatic leap year compensation valid up to the year 2100 ? batter y voltage - level indicator flag ? power - fail write protection allows for 10% v cc power supply tolerance ? lithium energy source is electrically disconnected to retain freshness until power is applied for the first time ? dip module only standard jedec byte - wide 128k x 8 static ram pinout ? powercap module board only surface mountable package for direct connection to powercap containing battery and crystal replaceable battery (powercap) power - on reset output pin - for - pin compatible with other densities of ds174xp tim ekeeping ram ? also available in industrial temperature range: - 40c to +85c ? underwriters laborator ies (ul) r ecognized pin configurations encapsulated dip n.c. 13 1 2 3 4 5 6 7 8 9 10 11 12 14 31 a14 a7 a5 a4 a3 a2 a1 a0 dq1 dq0 v cc a15 n.c. we a13 a8 a9 a11 oe a10 ce dq7 dq5 dq6 32 30 29 28 27 26 25 24 23 22 21 19 20 a16 a12 a6 dq2 gnd 15 16 18 17 dq4 dq3 maxim ds1746 top view 1 n.c. 2 3 a15 a16 rst v cc 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 n.c. a14 33 32 31 30 29 28 27 26 25 24 23 22 21 20 19 18 a13 a12 a11 a10 a9 a8 a7 a6 a5 a4 a3 a2 a1 a0 34 n.c. x1 gnd v bat x2 powercap module board (uses ds9034pcx + or ds9034i - pcx + powercap) maxim ds1746p we 19 - 5503; rev 3 /1 2 ds1746/ds1746p y2k - compliant, nonvolatile timekeeping rams
ds1746/ds1746p y2k - compliant, nonvolatile timekeeping rams 2 of 16 pin description pin name function pdip powercap 1, 30 1, 33, 34 n.c. no con nection 2 3 a16 address input 3 32 a14 4 30 a12 5 25 a7 6 24 a6 7 23 a5 8 22 a4 9 21 a3 10 20 a2 11 19 a1 12 18 a0 23 28 a10 25 29 a11 26 27 a9 27 26 a8 28 31 a13 31 2 a15 13 16 dq0 data input/output 14 15 dq1 15 14 dq2 17 13 dq3 18 12 dq4 19 11 dq5 20 10 dq6 21 9 dq7 16 17 gnd ground 22 8 ce active - low chip enable input 24 7 oe active - low output enable input 29 6 we active - low write - enable input 32 5 v cc power - supply input 4 rst active - low power - fail output, open drain. requires a pullup resistor for proper operation. x1, x2, v bat crystal connection, v bat battery connection. ul recognized to ensure against reverse charging when used with a lithium battery. www.maxim - ic.com/qa/info/ul/
ds1746/ds1746p y2k - compliant, nonvolatile timekeeping rams 3 of 16 ordering information part voltage range (v) temp range pin - package top mark ? ds1746 - 70+ 5.0 0c to +70c 32 edip (0.740a) ds1746+070 ds1746 - 70ind+ 5.0 - 40c to +85c 32 edip (0.740a) ds1746+070 ind ds1746p - 70+ 5.0 0c to +70c 34 powercap* ds1746p+70 ds1746p - 70ind+ 5.0 - 40c to +85c 34 powercap* ds1746p+070 ind ds1746w - 120+ 3.3 0c to +70c 32 edip (0.740a) ds1746w+120 ds1746w - 120ind+ 3.3 - 40c to +85c 32 edip (0.740a) ds1746w+120 ind ds1746wp - 120+ 3.3 0c to +70c 34 powercap* ds1746wp+120 ds1746wp - 120ind+ 3.3 - 40c to +85c 34 powercap* ds1746wp+120 ind + denotes a lead(pb) - free/rohs - compliant package. the top mark will include a + symbol on lead - free devices. * ds9034 - pcx + or ds9034i - pcx+ required (must be ordered separately). ? an ind anywhere on the top mark denotes an industrial temperature grade device. description the ds1746 is a full - function, year - 2000- compliant (y2kc), real - time clock/calendar (rtc) and 128k x 8 nonvolatile static ram. user access to all registers within the ds1746 is accomplished with a byte - wide interface as shown in figure 1. the rtc information and control bits reside in the eight uppermost ram locations. the rtc registers contain century, year, month, date, day, hours, m inutes, and seconds data in 24 - hour binary - coded decimal (bcd) format. corrections for the date of each 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 up date cycles. the double - buffered system also prevents time loss as the timekeeping countdown continues unabated by access to time register data. the ds1746 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.
ds1746/ds1746p y2k - compliant, nonvolatile timekeeping rams 4 of 16 figure 1 . block diagram packa ges the ds1746 is available in two packages (32 - pin dip and 34 - pin powercap module). the 32 - 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 c onnection to a separate powercap (ds9034pcx) that contains the crystal and battery. this design allows the powercap to be mounted on top of the ds1746p 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 p art 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 ds1746 clock registers should be halted before clock data is re ad 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 one is written into the read bit, bit 6 of the century register (see table 2). as long as a one 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 current 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 ds1746 registers are updated simultaneously after the internal clock register updating process has been re - enabled. updating is within a second after th e read bit is written to zero. the read bit must be a zero for a minimum of 500 s to ensure the external registers will be updated.
ds1746/ds1746p y2k - compliant, nonvolatile timekeeping rams 5 of 16 table 1 . truth table v cc ce oe we mode dq power v cc >v pf v ih x x deselect high - z standby v il x v i l write data in active v il v il v ih read data out active v il v ih v ih read high - z active v so ds1746/ds1746p y2k - compliant, nonvolatile timekeeping rams 6 of 16 table 2 . register map address data function range b7 b6 b5 b4 b3 b2 b1 b0 1ffff 10 year year year 00 - 99 1fffe x x x 10 month month month 01 - 12 1fffd x x 10 date date date 01 - 31 1fffc bf ft x x x day day 01 - 07 1fffb x x 10 hour hour hour 00 - 23 1fffa x 10 minutes minutes minutes 00 - 59 1fff9 osc 10 seconds seconds seconds 00 - 59 1fff8 w r 10 century century century 00 - 39 osc = stop bit r = read bit ft = frequency test w = write bit x = see note bf = battery flag note: a ll indicated x bits are not used but must be set to 0 during a write cycle to ensure proper clock operation. retrieving data from ram or clock the ds1746 is in the read mode whenever oe (output enable) is low, 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 an d states are satisfied. if ce or oe access times and states 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 indeter minate until the next address access. writing data to ram or clock the ds1746 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 transition of we , or ce . the addresses must be hel d 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 ds afterward. in a typical application, the o e 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 inp uts. a low transition on we will then disable the output t wez after we goes active.
ds1746/ds1746p y2k - compliant, nonvolatile timekeeping rams 7 of 16 data - retention mode the 5v device is fully accessible and data can be written or read only when v cc is greater than v pf . however, when v cc is below the power - fail point, v pf , (point at which write protection occurs) the internal clock registers and sram are blocked from any access. at this time the power fail reset output signal ( rst) is driven active and will remain active until v cc returns to nominal levels. when v cc fall s below the battery switch point v so (battery supply level), device power is switched from the v cc pin to the backup battery. rtc operation and sram data are maintained from the battery until v cc is returned to nominal levels. the 3.3v device is fully acce ssible and data can be written or read only when v cc is greater than v pf . when v cc falls below the power fail point, v pf , access to the device is inhibited. at this time the power fail reset output signal ( rst ) is driven active and will remain active until v cc returns to nominal levels. if v pf is less than v so , the device power is switched from v cc to the backup supply (v bat ) when v cc drops below v pf . if v pf is greater than v so , the device power is switched from v cc to the backup supply (v bat ) when v cc drop s below v so . rtc operation and sram data are maintained from the battery until v cc is returned to nominal levels. the rst signal is an open drain output and requires a pull up. except for the rst , all control, data, and address signals must be powered down when v cc is powered down. battery longevity the ds1746 has a lithium power source that is designed to provide energy for clock activity, and clock and ram data retention when the v cc supply is not present. the capability of this internal power supply is sufficient to power the ds1746 continuously for the life of the equipment in which it is installed. for specification purposes, the life expectancy is 10 years at 25 c with the internal clock oscillator running in the absence of v cc power. each ds1746 is s hipped from maxim with its lithium energy source disconnected, guaranteeing full energy capacity. when v cc is first applied at a level greater than v pf , the lithium energy source is enabled for battery backup operation. actual life expectancy of the ds1746 will be much longer than 10 years since no lithium battery energy is consumed when v cc is present. battery monitor the ds1746 constantly monitors the battery voltage of the internal battery. the battery flag bit (bit 7) of the day register is used to ind icate the voltage level range of the battery. this bit is not writable and should always be a one when read. if a zero is ever present, an exhausted lithium energy source is indicated and both the contents of the rtc and ram are questionable.
ds1746/ds1746p y2k - compliant, nonvolatile timekeeping rams 8 of 16 absolute maxi mum ratings voltage range on any pin relative to ground 5.5v version .... .. - 0.3v to +6.0v 3.3v version.. - 0.3v to +4.6v storage temperature range edip ........................................... ........ ..... . - 40c to +85c powercap ................................................................................................................ ... - 55c to +125c lead temperature (soldering, 10s) . ............................ ........................................................... . +260c note: edip is hand or wave - soldered only. soldering temperature (reflow, powercap)...................................................................................... +260 c th is is a stress rating only and functional operation of the device at these or any other condition above those indicated in th e operation sections of this specification is not implied. exposure to absolute maximum rating conditions for extended periods of t ime may affect reliability. operating range range temp range v cc commercial 0c to +70c, noncondensing 3.3v 10% or 5v 10% industrial - 40c to +85c, noncondensing 3.3v 10% or 5v 10% recommended dc operating conditions (t a = over the operating rang e) parameter symbol min typ max units notes logic 1 voltage all inputs v cc = 5v 10% v cc = 3.3v 10% v ih 2.2 v cc + 0.3v v 1 v ih 2.0 v cc + 0.3v v 1 logic 0 voltage all inputs v cc = 5v 10% v cc = 3.3v 10% v il - 0.3 0.8 v 1 v il - 0.3 0.6 v 1 dc electrical characteristics (v cc = 5.0v 10%, t a = over the operating range.) parameter symbol min typ max units notes active supply current icc 85 ma 2, 3 , 10 ttl st andby current ( ce = v ih ) icc 1 6 ma 2, 3 cmos standby current ( ce v cc - 0.2v) icc 2 4 ma 2, 3 input leakage current (any input) i il - 1 +1 a output leakage current (any output) i ol - 1 +1 a output logic 1 voltage (i out = - 1.0 ma) v oh 2.4 1 output logic 0 voltage (i out = +2.1 ma) v ol 0.4 1 write protection voltage v pf 4.25 4.50 v 1 battery switchover voltage v so v bat 1, 4
ds1746/ds1746p y2k - compliant, nonvolatile timekeeping rams 9 of 16 dc electrical characteristics (v cc = 3.3v 10% , t a = over the operating range.) parameter symbol min typ max units notes active supply current icc 30 ma 2, 3 , 10 ttl standby current ( ce = v ih ) icc 1 2 ma 2, 3 cmos standby current ( ce v cc - 0.2v) icc 2 2 ma 2, 3 input leakage cu rrent (any input) i il - 1 +1 a output leakage current (any output) i ol - 1 +1 a output logic 1 voltage (i out = - 1.0 ma) v oh 2.4 1 output logic 0 voltage (i out = +2.1 ma) v ol 0.4 1 write protection voltage v pf 2.80 2.97 v 1 battery switchov er voltage v so v bat or v pf v 1, 4 ac characteristics read cycle (5v) (v cc = 5.0v 10%, t a = over the operating range.) parameter symbol min typ max units notes read cycle time t rc 70 ns address access time t aa 70 ns ce to dq low - z t cel 5 ns ce access time t cea 70 ns ce data off time t cez 25 ns oe to dq low - z t oel 5 ns oe access time t oea 35 ns oe data off time t oez 25 ns output hold from address t oh 5 ns
ds1746/ds1746p y2k - compliant, nonvolatile timekeeping rams 10 of 16 ac characteristics read cycle (3.3v) (v cc = 3.3v 10%, t a = 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 to dq low - z t cel 5 ns ce access time t cea 120 ns ce data off time t cez 40 ns oe to dq low - z t oel 5 ns oe access time t oea 100 ns oe data off time t oez 35 ns output hold from address t oh 5 ns read cycle timing diagram t rc t cea t oea t cel t oel t oh t oez t aa valid dq0-dq7 oe ce a0-a16 t cez valid
ds1746/ds1746p y2k - compliant, nonvolatile timekeeping rams 11 of 16 ac characteristics write cycle (5v) (v cc = 5.0v 10%, t a = over the operating range.) parameter symbol min typ max units notes write cycle time t wc 70 ns address setup time t as 0 ns we pulse width t wew 50 ns ce pulse width t cew 60 ns data setup time t ds 30 ns data hold time t dh1 0 ns 8 data hold time t dh2 0 ns 9 we data off time t wez 25 ns write recovery time t wr1 5 ns 8 write recovery time t wr2 5 ns 9 ac characteristics write cycle (3.3v) (v cc = 3.3v 10%, t a = over the operating range.) parameter symbol min typ max units notes write cycle time t wc 120 ns address setup time t as 0 120 ns we pulse width t wew 100 ns ce pulse width t cew 110 ns ce and ce2 pulse width t cew 110 ns data setup time t ds 80 ns data hold time t dh1 0 ns 8 data hold time t dh2 0 ns 9 we data off time t wez 40 ns write recovery time t wr1 5 ns 8 write recov ery time t wr2 10 ns 9
ds1746/ds1746p y2k - compliant, nonvolatile timekeeping rams 12 of 16 write cycle timing diagram, write - enable controlled t wc t wr1 t ds t as t wez t dh1 data input dq0-dq7 we ce a0-a16 data output t wew valid write cycle timing diagram, chip - enable controlled t wc t wr2 t ds t dh2 t as data input we ce a0-a16 t cew valid dq0-dq7
ds1746/ds1746p y2k - compliant, nonvolatile timekeeping rams 13 of 16 power - up/down ac characteristics 5v (v cc = 5.0v 10%, t a = ov er the operating range.) parameter symbol min typ max units notes ce or we at v h before power - down t pd 0 s v cc fall time: v pf(max) to v pf(min) t f 300 s v cc fall time: v pf(min) to v so t fb 10 s v cc ri se time: v pf(min) to v pf(max) t r 0 s power - up recover time t rec 35 ms expected data - retention time (oscillator on) t dr 10 years 5, 6 power - up/down timing (5v device)
ds1746/ds1746p y2k - compliant, nonvolatile timekeeping rams 14 of 16 power - up/down characteristics 3.3v (v cc = 3.3v 10%, t a = over the oper ating range.) parameter symbol min typ max units notes ce or we at v h , before power - down t pd 0 s v cc fall time: v pf(max) to v pf(min) t f 300 s v cc rise time: v pf(min) to v pf(max) t r 0 s v pf to rst high t rec 35 ms expected data - retention time (oscillator on) t dr 10 years 5, 6 power - up/down waveform timing (3.3v device) capacitance (t a = +25c) parameter symbol min typ max units notes capacitance on all input pins c in 14 pf capacitance on all output pins c o 10 pf
ds1746/ds1746p y2k - compliant, nonvolatile timekeeping rams 15 of 16 ac test conditions output load: 50pf + 1ttl gate input pulse levels: 0 to 3.0v timing measurement reference levels: input: 1.5v output: 1.5v input pulse rise and fall times: 5ns notes : 1) voltages are referenced to ground. 2) typical values are at +25 c and nominal supplies. 3) outputs are open. 4) battery switchover occurs at the lower of either the battery terminal voltage or v pf . 5) data - retention time is at +25 c. 6) each ds1746 has a built - in switch that disc onnects the lithium source until v cc is first applied by the user. the expected t dr is defined for dip modules and assembled powercap modules as a cumulative time in the absence of v cc starting from the time power is first applied by the user. 7) rtc 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 ultra - sonic vibration is not used. in addition, for the powercap: a) maxim 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 seconds. to solder, apply flux to the pad, heat the lead frame pad, and apply solder. to remove the part, apply flux, heat the l ead frame pad until the solder reflows, and use a solder wick to remove solder. 8) t wr1 , t dh1 are measured from we going high. 9) t wr2 , t dh2 are measured from ce going high. 10) t wc = 200ns. package information for the latest package outline information and land pa tterns, go to www.maxim - ic.com/packages . note that a +, #, or - in the package code indicates rohs status only. package drawings may show a different suffix character, but the drawing pertains to the package regardless of rohs status. package type package code document no. land pattern no. 32 edip mdf32+1 21- 0245 34 pwrcp pc2+6 21- 0246
ds1746/ds1746p y2k - compliant, nonvolatile timekeeping rams 16 of 16 maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a maxim product. no cir cuit patent licenses are implied. maxim reserves the right to change the circuitry and specifications without notice at any time. maxim integrated products, 120 san gabriel drive, sunnyvale, ca 94086 408 - 737 - 7600 ? 201 2 maxim integrated products maxim is a registered trademark of maxim integrated products. revision history revision date description pages changed 080508 added ul recognition information and weblink to the pin description table; corrected the top mark for C 70 part numbers in the ordering information table; update d the write timing diagrams to show t wr as specified by ram vendors 2, 3, 10, 12 9/10 updated the ordering information table top mark information ; updated the absolute maximum ratings section to include the storage temperature range and lead and soldering temperatures for edip and powercap packages; added note 10 to the i cc parameter in the dc electrical characteristics tables (for 5.0v and 3.3v) and the notes section; updated the package information table 3, 8, 9, 15 3/12 updated the absolute maximum rat ings section to add the 5v and 3.3v voltage range 8

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