1 of 8 features ? 5 years minimum data retention in the absence of external power ? data is automatically protected during power loss ? unlimited write cycles ? low - power cmos operation ? read and write access times of 70 ns ? lithium energy so urce is electrically disconnected to retain freshness until power is applied for the first time ? full 10% v cc operating range (ds1270y) ? optional 5% v cc operating range (ds1270ab) ? optional industrial temperature range of - 40 c to +85 c, designated ind pin assignment pin description a0 ? a20 - address inputs dq0 - dq7 - data in/data out ce - chip enable we - write enable oe - out put enable v cc - power (+5v) gnd - ground nc - no connect description the ds1270 16m nonvolatile srams are 16,777,216 - bit, fully static nonvolatile srams organized as 2,097,152 words by 8 bits. each nv sram has a self - contained lithium energy sou rce and control circuitry which constantly monitors v cc for an out - of - tolerance condition. when such a condition occurs, the lithium energy source is automatically switched on and write protection is unconditionally enabled to prevent data corruption. ther e is no limit on the number of write cycles which can be executed and no additional support circuitry is required for microprocessor interfacing. ds1270y/ab 16m nonvolatile sram www.maxim - ic.com 13 1 2 3 4 5 6 7 8 9 10 11 12 14 35 36 - pin encapsulated package 740- mil ext ended a18 a14 a7 a6 a5 a4 a3 a2 a0 a1 v cc a19 nc a15 a17 we a13 a8 a9 a11 oe a10 dq7 ce 36 34 33 32 31 30 29 28 27 26 25 23 24 a20 a16 a12 nc dq0 dq1 15 16 22 21 d q6 dq5 17 18 gnd dq2 dq3 dq4 19 20 19 - 561 5 ; rev 11/1 0
ds1270y/ab 2 of 8 read mode the ds1270 devices execute a read cycle whenever we (write enable) is inactive (high) and ce (chip enable) and oe (output enable) are active (low). the unique address specified by the 21 address inputs (a 0 - a 20 ) defines which of the 2,097,152 bytes of data is accessed. valid data will be av ailable to the eight data output drivers within t acc (access time) after the last address input signal is stable, providing that ce and oe (output enable) access times are also satisfied. if oe and ce access times are not satisfied, then data access must be measured from the later - occurring signal ( ce or oe ) and the limiting parameter is either t co for ce or t oe for oe rather than t acc . write mode the ds1270 devices execute a write cycle whenever we and ce signals are active (low) after address inputs are stable. the later - occurring falling edge of ce or we will determine the start of the write cycle. the write cycle is terminated by the earlier rising edge of ce or we . all address inputs must be kept valid throughout t he write cycle. we must return to the high state for a minimum recovery time (t wr ) before another cycle can be initiated. the oe control signal should be kept inactive (high) during write cycles to avoid bus conten tion. however, if the output drivers are enabled ( ce and oe active) then we will disable the outputs in t odw from its falling edge. data retention mode the ds1270ab provides full - functional ca pability for v cc greater than 4.75 volts and write protects by 4.5 volts. the ds1270y provides full - functional capability for v cc greater than 4.5 volts and write protects by 4.25 volts. data is maintained in the absence of v cc without any additional suppo rt circuitry. the nonvolatile static rams constantly monitor v cc . should the supply voltage decay, the nv srams automatically write protect themselves, all inputs become don?t care, and all outputs become high - impedance. as v cc falls below approximately 3. 0 volts, a power switching circuit connects the lithium energy source to ram to retain data. during power - up, when v cc rises above approximately 3.0 volts, the power switching circuit connects external v cc to ram and disconnects the lithium energy source. normal ram operation can resume after v cc exceeds 4.75 volts for the ds1270ab and 4.5 volts for the ds1270y. freshness seal each ds1270 device is shipped from maxim with its lithium energy source disconnected, guaranteeing full energ y capacity. when v cc is first applied at a level greater than v tp , the lithium energy source is enabled for battery backup operation.
ds1270y/ab 3 of 8 absolute maximum ratings voltage on any pin relative to ground - 0.3v to +6.0v operating temperature range commercial: 0c to + 70c industrial: - 40c to +85c storage temperature - 40c to +85c lead temperature (soldering, 10 s ) +260 c note: edip is wave or hand soldered only. 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 ext ended periods of time may affect reliability. recommended dc operating conditions ( t a : see note 10 ) parameter symbol min typ max units notes ds1270ab power supply voltage v cc 4.75 5.0 5.25 v ds1270y power supply voltage v cc 4.5 5. 0 5.5 v logic 1 input voltage v ih 2.2 v cc v logic 0 input voltage v il 0 +0.8 v dc electrical (v cc =5v 5% for ds1270ab) characteristics ( t a : see note 10 ) (v cc =5v 10% for d s1270y) parameter symbol min typ max units notes input leakage current i il - 4.0 +4.0 a i/o leakage current i io - 4.0 +4.0 a output current @ 2.4v i oh - 1.0 ma output current @ 0.4v i ol 2.0 ma standby current ce =2.2v i ccs1 1.0 1.5 ma standby current ce =v cc - 0.5v i ccs2 100 250 a operating current i cco1 85 ma write protection voltage (ds1270ab) v tp 4.50 4.62 4.75 v write protection voltage (ds1270y) v tp 4.25 4.37 4.5 v capacitance ( t a = + 25 c) parameter symbol min typ max units notes input capacitance c in 20 40 pf output capacitance c i/o 20 40 pf
ds1270y/ab 4 of 8 ac electrical (v cc =5v 5% for ds1270ab) characteristics ( t a : see note 10 ) (v cc =5v 10% for ds1270y) parameter symbol ds1270ab - 70 ds1270y - 70 units notes min max read cycle time t rc 70 ns access time t acc 70 ns oe to output valid t oe 35 ns ce to output valid t co 70 ns oe or ce to output active t coe 5 ns 5 output high z from deselection t od 25 ns 5 output hold from address ch ange t oh 5 ns write cycle time t wc 70 ns write pulse width t wp 55 ns 3 address setup time t aw 0 ns write recovery time t wr1 t wr2 5 15 ns ns 12 13 output high z from we t odw 25 ns 5 output active from we t oew 5 ns 5 data setup time t ds 30 ns 4 data hold time t dh1 t dh2 0 10 ns ns 12 13 timing diagram: read cycle see note 1
ds1270y/ab 5 of 8 timing di agram: write cycle 1 timing diagram: write cycle 2 see notes 2, 3, 4, 6, 7, 8 and 13
ds1270y/ab 6 of 8 power - down/power - up condition see note 11 power - down/power - up timing ( t a : see note 10) parameter symbol min typ max uni ts notes v cc fail detect to ce and we inactive t pd 1.5 s 11 v cc slew from v tp to 0v t f 150 s v cc slew from 0v to v tp t r 150 s v cc valid to ce and we inactive t pu 2 ms v cc valid to end of write protection t rec 125 ms ( t a = + 25 c) parameter symbol min typ max units notes expected data r etention time t dr 5 years 9 warning: under no circumstance are negative undershoots, of any amplitude, allowed when device is in battery backup mode. notes: 1. we is high for a read cycle. 2. oe = v ih or v il . if oe = v ih during write cycle, the output buffers remain in a high - impedance state. 3. t wp is specified as the logical and of ce and we . t wp is measured from the latter of ce or we going low to the earlier of ce or we going high. 4. t ds is measured from the earlier of ce or we going high. 5. these parameters are sampled with a 5 pf load and are not 100% tested. 6. if the ce low transition occurs simultaneously with or latter than the we low transition, the output buffers remain in a high - impedance state during this period. 7. if the ce high transition occurs prior to or simultaneously with the we high transition, the output buffers remain in high - impedance state during this period.
ds1270y/ab 7 of 8 8. if we is low or the we low trans ition occurs prior to or simultaneously with the ce low transition, the output buffers remain in a high - impedance state during this period. 9. each ds1270 has a built - in switch that disconnects the lithium source until the user first ap plies v cc . the expected t dr is defined as accumulative time in the absence of v cc starting from the time power is first applied by the user. this parameter is assured by component selection, process control, and design. it is not measured directly during p roduction testing. 10. all ac and dc electrical characteristics are valid over the full operating temperature range. for commercial products, this range is 0 c to 70 c. for industrial products (ind), this range is - 40 c to +85 c. 11. in a power - down condition the voltage on any pin may not exceed the voltage on v cc . 12. t wr1 and t dh1 are measured from we going high. 13. t wr2 and t dh2 are measured f rom ce going high. 14. ds1270 modules are recognized by underwriters laborator ies (u l ) under file e99151. dc test conditions ac test conditions outputs open output load: 100 pf + 1ttl gate cycle = 200ns for operating current input pulse levels: 0.0 to 3.0 volts all voltages are referenced to ground timing measurement reference levels input: 1.5v output: 1.5v input pulse rise and fall times: 5 ns ordering information part temp range supply tolerance pin - package speed grade (ns) ds1270ab - 70# 0c to +70c 5v 5% 36 740 edip 70 ds1270ab - 70ind# - 40c to +8 5c 5v 5% 36 740 edip 70 ds1270y - 70# 0c to +70c 5v 10% 36 740 edip 70 ds1270y - 70ind# - 40c to +85c 5v 10% 36 740 edip 70 #denotes a rohs - compli ant device that may include lead(pb) that is exempt under the rohs requirements. package information for the latest package outline information an d land patterns, 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 outline no. land pattern no. 36 e dip mdt 36#2 ? 21- 0245
ds1270y/ab 8 of 8 revision history revision date description pages changed 11/10 updated the storage information, soldering temperature, and lead temperature information in the absolute maximum ratings section; removed the - 100 min/max information from the ac electrical characteristics table; updated the ordering information tabl e (removed - 10 0 parts and leaded - 7 0 parts); replaced the package outline drawing with the package information table 1, 3, 4, 7
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