1 of 10 111899 features 10 years minimum data retention in the absence of external power data is automatically protected during power loss directly replaces 8k x 8 volatile static ram or eeprom unlimited write cycles low-power cmos jedec standard 28-pin dip package read and write access times as fast as 70 ns lithium energy source is electrically disconnected to retain freshness until power is applied for the first time full 10% v cc operating range (ds1225ad) optional 5% v cc operating range (ds1225ab) optional industrial temperature range of -40c to +85c, designated ind pin assignment 28-pin encapsulated package 720-mil extended pin description a0-a12 - address inputs dq0-dq7 - data in/data out ce - chip enable we - write enable oe - output enable v cc - power (+5v) gnd - ground nc - no connect description the ds1225ab and ds1225ad are 65,536-bit, fully static, nonvolatile srams organized as 8192 words by 8 bits. each nv sram has a self-contained lithium energy source 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. the nv srams can be used in place of existing 8k x 8 srams directly conforming to the popular bytewide 28-pin dip standard. the devices also match the pinout of the 2764 eprom and the 2864 eeprom, allowing direct substitution while enhancing performance. there is no limit on the number of write cycles that can be executed and no additional support circuitry is required for microprocessor interfacing. ds1225ab/ad 64k nonvolatile sram www.dalsemi.com 15 13 27 a7 a5 a3 a2 a1 a0 dq0 dq1 gnd dq2 vcc we nc 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 a6 a4 nc
ds1225ab/ad 2 of 10 read mode the ds1225ab and ds1225ad 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 13 address inputs (a 0 -a 12 ) defines which of the 8192 bytes of data is to be accessed. valid data will be available to the eight data output drivers within t acc (access time) after the last address input signal is stable, providing that ce and oe access times are also satisfied. if ce and oe access times are not satisfied, then data access must be measured from the later-occurring signal and the limiting parameter is either t co for ce or t oe for oe rather than address access. write mode the ds1225ab and ds1225ad execute a write cycle whenever the 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 the 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 contention. 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 ds1225ab provides full functional capability for v cc greater than 4.75 volts and write protects by 4.5 volts. the ds1225ad 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 support 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, the 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 ds1225ab and 4.5 volts for the ds1225ad. freshness seal each ds1225 is shipped from dallas semiconductor with the lithium energy source disconnected, guaranteeing full energy capacity. when v cc is first applied at a level of greater than v tp , the lithium energy source is enabled for battery backup operation.
ds1225ab/ad 3 of 10 absolute maximum ratings* voltage on any pin relative to ground -0.3v to +7.0v operating temperature 0c to 70c; -40c to +85c for ind parts storage temperature -40c to +70c; -40c to +85c for ind parts soldering temperature 260c for 10 seconds ? 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. recommended dc operating conditions (t a : see note 10) parameter symbol min typ max units notes ds1225ab power supply voltage v cc 4.75 5.0 5.25 v ds1225ad power supply voltage v cc 4.50 5.0 5.5 v logic 1 v ih 2.2 v cc v logic 0 v il 0.0 +0.8 v (v cc =5v 5% for ds1225ab) (t a : see note 10) dc electrical characteristics (v cc =5v 10% for ds1225ad) parameter symbol min typ max units notes input leakage current i il -1.0 +1.0 a i/o leakage current ce > v ih < v cc i io -1.0 +1.0 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 5.0 10.0 ma standby current ce =v cc -0.5v i ccs2 3.0 5.0 ma operating current t cyc =200 ns (commercial) i cc01 75 ma operating current t cyc =200 ns (industrial) i cc01 85 ma write protection voltage (ds1225ab) v tp 4.50 4.62 4.75 v write protection voltage (ds1225ad) v tp 4.25 4.37 4.5 v capacitance (t a =25c) parameter symbol min typ max units notes input capacitance c in 510pf input/output capacitance c i/o 510pf
ds1225ab/ad 4 of 10 (v cc =5v 5% for ds1225ab) (t a : see note 10) ac electrical characteristics (v cc =5v 10% for ds1225ad) ds1225ab-70 ds1225ad-70 ds1220ab-85 ds1220ad-85 parameter symbol min max min max units notes read cycle time t rc 70 85 ns access time t acc 70 85 ns oe to output valid t oe 35 45 ns ce to output valid t co 70 85 ns oe or ce to output active t coe 5 5ns5 output high z from deselection t od 25 30 ns 5 output hold from address change t oh 5 5ns write cycle time t wc 70 85 ns write pulse width t wp 55 65 ns 3 address setup time t aw 00 ns write recovery time t wr1 t wr2 0 10 0 10 ns ns 12 13 output high z from we t odw 25 30 ns 5 output active from we t oew 5 5ns5 data setup time t ds 30 35 ns 4 data hold time t dh1 t dh2 0 10 0 10 ns ns 12 13
ds1225ab/ad 5 of 10 ac electrical characteristics (cont?d) ds1225ab- 150 ds1225ad- 150 ds1220ab-200 ds1220ad-200 parameter symbol min max min max units notes read cycle time t rc 150 200 ns access time t acc 150 200 ns oe to output valid t oe 70 100 ns ce to output valid t co 150 200 ns oe or ce to output active t coe 5 5ns5 output high z from deselection t od 35 35 ns 5 output hold from address change t oh 5 5ns write cycle time t wc 150 200 ns write pulse width t wp 100 100 ns 3 address setup time t aw 00 ns write recovery time t wr1 t wr2 0 10 0 10 ns ns 12 13 output high z from we t odw 35 35 ns 5 output active from we t oew 5 5ns5 data setup time t ds 60 80 ns 4 data hold time t dh1 t dh2 0 10 0 10 ns ns 12 13
ds1225ab/ad 6 of 10 read cycle see note 1 write cycle 1 see notes 2, 3, 4, 6, 7, 8 and 12 write cycle 2 see notes 2, 3, 4, 6, 7, 8 and 13
ds1225ab/ad 7 of 10 power-down/power-up condition see note 11 power-down/power-up timing (t a : see note 10) parameter symbol min typ max units notes ce at v ih before power-down t pd 0 s 11 v cc slew from v tp to 0 v t f 300 s v cc slew from 0 v to v tp t r 300 s ce at v ih after power-up t rec 2 125 ms (t a = 25c) parameter symbol min typ max units notes expected data retention time t dr 10 years 9 warning: under no circumstance are negative undershoots, of any amplitude, allowed when device is in battery backup mode.
ds1225ab/ad 8 of 10 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 are 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 later 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 a high-impedance state during this period. 8. if we is low or the we low transition occurs prior to or simultaneously with the ce low transition, the output buffers remain in a high-impedance state during this period. 9. each ds1225ab and each ds1225ad has a built-in switch that disconnects the lithium source until v cc is first applied by the user. 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. 10. all ac and dc electrical characteristics are valid over the full operating temperature range. for commercial products, this range is 0c to 70c. for industrial products (ind), this range is -40c to +85c. 11. in a power down condition the voltage on any pin may not exceed the voltage on v cc . 12. t wr1 , t dh1 are measured from we going high. 13. t wr2 , t dh2 are measured from ce going high. 14. ds1225ab and ds1225ad modules are recognized by underwriters laboratory (u.l. ? ) under file e99151. dc test conditions outputs open all voltages are referenced to ground ac test conditions output load: 100 pf + 1ttl gate input pulse levels: 0 - 3.0v timing measurement reference levels input: 1.5v output: 1.5v input pulse rise and fall times: 5ns
ds1225ab/ad 9 of 10 ordering information
ds1225ab/ad 10 of 10 ds1225ab/ad nonvolatile sram, 28-pin, 720-mil extended module pkg 28-pin dim min max a in. mm 1.520 38.61 1.540 39.12 b in. mm 0.695 17.65 0.720 18.29 c in. mm 0.395 10.03 0.415 10.54 d in. mm 0.100 2.54 0.130 3.30 e in. mm 0.017 0.43 0.030 0.76 f in. mm 0.120 3.05 0.160 4.06 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 0.008 0.20 0.012 0.30 k in. mm 0.015 0.38 0.021 0.53
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