DS1270W 3.3V 16Mb Nonvolatile SRAM www.maxim-ic.com FEATURES § § § § § § § PIN ASSIGNMENT Five 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 as fast as 100ns Lithium energy source is electrically disconnected to retain freshness until power is applied for the first time Optional industrial (IND) temperature range of -40°C to +85°C NC A20 A18 A16 A14 A12 A7 A6 A5 A4 A3 36 35 34 33 32 31 30 29 28 27 26 25 VCC A19 NC A15 A17 WE A13 A8 A9 A11 OE A2 1 2 3 4 5 6 7 8 9 10 11 12 A1 13 24 CE A0 DQ0 14 23 15 DQ7 DQ6 DQ1 16 22 21 DQ2 17 20 DQ4 GND 18 19 DQ3 A10 DQ5 36-Pin Encapsulated Package 740mil Extended PIN DESCRIPTION A0–A20 DQ0–DQ7 CE WE OE VCC GND NC - Address Inputs - Data In/Data Out - Chip Enable - Write Enable - Output Enable - Power (+3.3V) - Ground - No Connect DESCRIPTION The DS1270W 16Mb nonvolatile (NV) SRAMs are 16,777,216-bit, fully static, NV SRAMs organized as 2,097,152 words by 8 bits. Each NV SRAM has a self-contained lithium energy source and control circuitry that constantly monitors VCC 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. There is no limit on the number of write cycles that can be executed, and no additional support circuitry is required for microprocessor interfacing. 1 of 8 110602 DS1270W 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 (A0–A20) defines which of the 2,097,152 bytes of data is accessed. Valid data will be available to the eight data output drivers within tACC (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 tCO for CE or tOE for OE rather than tACC. 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 the write cycle. WE must return to the high state for a minimum recovery time (tWR) 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 tODW from its falling edge. DATA-RETENTION MODE The DS1270W provides full-functional capability for VCC greater than 3.0V and write protects by 2.8V. Data is maintained in the absence of VCC without any additional support circuitry. The nonvolatile static RAMs constantly monitor VCC. 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 VCC falls below approximately 2.5V, a power-switching circuit connects the lithium energy source to RAM to retain data. During power-up, when VCC rises above approximately 2.5V, the power-switching circuit connects external VCC to RAM and disconnects the lithium energy source. Normal RAM operation can resume after VCC exceeds 3.0V. FRESHNESS SEAL Each DS1270 device is shipped from Dallas Semiconductor with its lithium energy source disconnected, guaranteeing full energy capacity. When VCC is first applied at a level greater than VTP, the lithium energy source is enabled for battery backup operation. 2 of 8 DS1270W ABSOLUTE MAXIMUM RATINGS* Voltage on Any Pin Relative to Ground Operating Temperature Range Storage Temperature Range Soldering Temperature * -0.3V to +4.6V 0°C to 70°C (-40°C to +85°C for IND parts) -40°C to +70°C (-40°C to +85°C for IND parts) +260°C 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 PARAMETER (TA: See Note 10) SYMBOL MIN TYP MAX UNITS Power-Supply Voltage VCC 3.0 3.3 3.6 V Logic 1 Input Voltage VIH 2.2 VCC V Logic 0 Input Voltage VIL 0.0 +0.4 V DC ELECTRICAL CHARACTERISTICS PARAMETER Input Leakage Current (TA: See Note 10; VCC = 3.3V ± 0.3V) SYMBOL IIL MIN -4.0 I/O Leakage Current IIO -4.0 Output Current at 2.2V IOH -1.0 mA Output Current at 0.4V IOL 2.0 mA TYP MAX +4.0 UNITS +4.0 mA ICCS1 150 300 mA Standby Current CE = VCC - 0.2V ICCS2 100 200 mA Operating Current ICCO1 50 mA Write Protection Voltage VTP 3.0 V 2.8 2.9 CAPACITANCE NOTES mA Standby Current CE = 2.2V PARAMETER NOTES (TA = +25°C) SYMBOL MIN TYP MAX UNITS Input Capacitance CIN 20 40 pF Input/Output Capacitance CI/O 20 40 pF 3 of 8 NOTES DS1270W (TA: See Note 10; VCC = 3.3V ± 0.3V) AC ELECTRICAL CHARACTERISTICS PARAMETER Read Cycle Time Access Time SYMBOL tRC DS1270W-100 DS1270W-150 MIN MIN MAX 100 MAX UNITS ns 150 tACC 100 150 ns NOTES OE to Output Valid tOE 50 70 ns CE to Output Valid tCO 100 150 ns OE or CE to Output Active tCOE Output High-Z from Deselection tOD Output Hold from Address Change tOH 5 5 ns Write Cycle Time tWC 100 150 ns Write Pulse Width tWP 75 100 ns Address Setup Time tAW 0 0 ns Write Recovery Time tWR1 tWR2 5 20 5 20 ns ns 12 13 Output High-Z from WE tODW ns 5 Output Active from WE tOEW 5 5 ns 5 Data Setup Time tDS 40 60 ns 4 Data Hold Time tDH1 tDH2 0 20 0 20 ns ns 12 13 5 5 35 35 35 TIMING DIAGRAM: READ CYCLE SEE NOTE 1 4 of 8 35 ns 5 ns 5 3 DS1270W TIMING DIAGRAM: WRITE CYCLE 1 TIMING DIAGRAM: WRITE CYCLE 2 SEE NOTES 2, 3, 4, 6, 7, 8 AND 13 5 of 8 DS1270W POWER-DOWN/POWER-UP CONDITION SEE NOTE 11 POWER-DOWN/POWER-UP TIMING (TA: See Note 10) PARAMETER SYMBOL MIN TYP MAX UNITS NOTES VCC Fail Detect to CE and WE Inactive tPD 1.5 ms 11 VCC Slew from VTP to 0V tF 150 ms VCC Slew from 0V to VTP tR 150 ms VCC Valid to CE and WE Inactive tPU 2 ms VCC Valid to End of Write Protection tREC 125 ms (TA = 25°C) PARAMETER Expected Data-Retention Time SYMBOL MIN tDR 5 TYP MAX UNITS NOTES 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 = VIH or VIL. If OE = VIH during write cycle, the output buffers remain in a high-impedance state. 3. tWP is specified as the logical AND of CE and WE . tWP is measured from the latter of CE or WE going low to the earlier of CE or WE going high. 4. tDS is measured from the earlier of CE or WE going high. 5. These parameters are sampled with a 5pF 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 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. 6 of 8 DS1270W 9. Each DS1270 has a built-in switch that disconnects the lithium source until VCC is first applied by the user. The expected tDR is defined as accumulative time in the absence of VCC 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 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 VCC. 12. tWR1 and tDH1 are measured from WE going high. 13. tWR2 and tDH2 are measured from CE going high. 14. DS1270 modules are recognized by Underwriters Laboratory (U.L.â) under file E99151. DC TEST CONDITIONS AC TEST CONDITIONS Outputs Open Cycle = 200ns for operating current All voltages are referenced to ground Output Load: 100pF + 1TTL Gate Input Pulse Levels: 0 to 2.7V Timing Measurement Reference Levels Input: 1.5V Output: 1.5V Input Pulse Rise and Fall Times: 5ns ORDERING INFORMATION DS1270W - SSS - III Operating Temperature Range blank: 0°C to +70°C IND: -40°C to +85°C Access Speed 100: 100ns 150: 150ns 7 of 8 DS1270W DS1270W NONVOLATILE SRAM 36-PIN, 740MIL EXTENDED MODULE, LONG PKG 8 of 8 36-PIN DIM MIN MAX A IN. MM 2.080 52.83 2.100 53.34 B IN. MM 0.720 18.29 0.740 18.80 C IN. MM 0.395 10.03 0.405 10.29 D IN. MM 0.180 4.57 0.210 5.33 E IN. MM 0.015 0.38 0.025 0.63 F IN. MM 0.120 3.05 0.150 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