December 2004 AS7C251MNTD18A ® 2.5V 1M x 18 Pipelined SRAM with NTDTM Features • • • • • • • • • Organization: 1,048,576 words × 18 bits NTD™architecture for efficient bus operation Fast clock speeds to 166 MHz Fast clock to data access: 3.5/3.8 ns Fast OE access time: 3.5/3.8 ns Fully synchronous operation Asynchronous output enable control Available in 100-pin TQFP package Individual byte write and global write • • • • • • Clock enable for operation hold Multiple chip enables for easy expansion 2.5V core power supply Self-timed write cycles Interleaved or linear burst modes Snooze mode for standby operation Logic block diagram 20 A[19:0] D Address register burst logic Q 20 CLK D Q Write delay addr. registers CE0 CE1 CE2 20 CLK R/W Control logic BWa BWb CLK LBO ZZ DQ [a,b] Write Buffer ADV / LD CLK 18 D 1M x 18 SRAM array 18 Data Q input register 18 CLK 18 18 CLK CEN CLK Output register OE 18 OE DQ [a,b] Selection guide -166 -133 Units 6 7.5 ns Maximum clock frequency 166 133 MHz Maximum clock access time 3.5 3.8 ns Maximum operating current 290 270 mA Maximum standby current 85 75 mA Maximum CMOS standby current (DC) 40 40 mA Minimum cycle time 12/23/04, v.2.2 Alliance Semiconductor P. 1 of 18 Copyright © Alliance Semiconductor. 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AS7C251MNTD18A ® 16 Mb 2.5V Synchronous SRAM products list1,2 Org 1MX18 512KX32 512KX36 1MX18 512KX32 512KX36 1MX18 512KX32 512KX36 1MX18 512KX32 512KX36 1MX18 512KX32 512KX36 Part Number AS7C251MPFS18A AS7C25512PFS32A AS7C25512PFS36A AS7C251MPFD18A AS7C25512PFD32A AS7C25512PFD36A AS7C251MFT18A AS7C25512FT32A AS7C25512FT36A AS7C251MNTD18A AS7C25512NTD32A AS7C25512NTD36A AS7C251MNTF18A AS7C25512NTF32A AS7C25512NTF36A Mode PL-SCD PL-SCD PL-SCD PL-DCD PL-DCD PL-DCD FT FT FT NTD-PL NTD-PL NTD-PL NTD-FT NTD-FT NTD-FT Speed 166/133 MHz 166/133 MHz 166/133 MHz 166/133 MHz 166/133 MHz 166/133 MHz 7.5/8.5/10 ns 7.5/8.5/10 ns 7.5/8.5/10 ns 166/133 MHz 166/133 MHz 166/133 MHz 7.5/8.5/10 ns 7.5/8.5/10 ns 7.5/8.5/10 ns 1 Core Power Supply: VDD = 2.5V + 0.125V 2 I/O Supply Voltage: VDDQ = 2.5V + 0.125V PL-SCD PL-DCD FT NTD1-PL NTD-FT : : : : : Pipelined Burst Synchronous SRAM - Single Cycle Deselect Pipelined Burst Synchronous SRAM - Double Cycle Deselect Flow-through Burst Synchronous SRAM Pipelined Burst Synchronous SRAM with NTDTM Flow-through Burst Synchronous SRAM with NTDTM 1. NTD: No Turnaround Delay. NTDTM is a trademark of Alliance Semiconductor Corporation. All trademarks mentioned in this document are the property of their respective owners. 12/23/04, v.2.2 Alliance Semiconductor P. 2 of 18 AS7C251MNTD18A ® Pin assignment 91 90 89 88 87 86 85 84 83 82 81 TQFP 14 x 20mm 80 79 78 77 76 75 74 73 72 71 70 69 68 67 66 65 64 63 62 61 60 59 58 57 56 55 54 53 52 51 A NC NC VDDQ VSSQ NC DQPa DQa7 DQa6 VSSQ VDDQ DQa5 DQa4 VSS NC VDD ZZ DQa3 DQa2 VDDQ VSSQ DQa1 DQa0 NC NC VSSQ VDDQ NC NC NC LBO A A A A A1 A0 NC NC VSS VDD NC NC A A A A A A A 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 VDDQ VSSQ NC NC DQb0 DQb1 VSSQ VDDQ DQb2 DQb3 NC VDD NC VSS DQb4 DQb5 VDDQ VSSQ DQb6 DQb7 DQPb NC VSSQ VDDQ NC NC NC 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 92 NC NC NC 100 99 98 97 96 95 94 93 A A CE0 CE1 NC NC BWb BWa CE2 VDD VSS CLK R/W CEN OE ADV/LD A A A A 100-pin TQFP - top view 12/23/04, v.2.2 Alliance Semiconductor P. 3 of 18 AS7C251MNTD18A ® Functional description The AS7C251MNTD18A family is a high performance CMOS 16-Mbit synchronous Static Random Access Memory (SRAM) organized as 1,048,576 words × 18 bits and incorporates a LATE LATE Write. This variation of the 16Mb+ synchronous SRAM uses the No Turnaround Delay (NTD™) architecture, featuring an enhanced write operation that improves bandwidth over pipelined burst devices. In a normal pipelined burst device, the write data, command, and address are all applied to the device on the same clock edge. If a read command follows this write command, the system must wait for two 'dead' cycles for valid data to become available. These dead cycles can significantly reduce overall bandwidth for applications requiring random access or read-modify-write operations. NTD™ devices use the memory bus more efficiently by introducing a write latency which matches the two-cycle pipelined or one-cycle flow-through read latency. Write data is applied two cycles after the write command and address, allowing the read pipeline to clear. With NTD™, write and read operations can be used in any order without producing dead bus cycles. Assert R/W low to perform write cycles. Byte write enable controls write access to specific bytes, or can be tied low for full 18 bit writes. Write enable signals, along with the write address, are registered on a rising edge of the clock. Write data is applied to the device two clock cycles later. Unlike some asynchronous SRAMs, output enable OE does not need to be toggled for write operations; it can be tied low for normal operations. Outputs go to a high impedance state when the device is de-selected by any of the three chip enable inputs. In pipelined mode, a two cycle deselect latency allows pending read or write operations to be completed. Use the ADV (burst advance) input to perform burst read, write and deselect operations. When ADV is high, external addresses, chip select, R/W pins are ignored, and internal address counters increment in the count sequence specified by the LBO control. Any device operations, including burst, can be stalled using the CEN=1, the clock enable input. The AS7C251MNTD18A operates with a 2.5V ± 5% power supply for the device core (VDD). These devices are available in a 100-pin TQFP package. TQFP capacitance Parameter Input capacitance I/O capacitance Symbol CIN* CI/O* Test conditions VIN = 0V VOUT = 0V Min - Max 5 7 Unit pF pF * Guaranteed not tested TQFP thermal resistance Description Thermal resistance (junction to ambient)1 Thermal resistance (junction to top of case)1 Conditions Test conditions follow standard test methods and procedures for measuring thermal impedance, per EIA/JESD51 1–layer Symbol θJA 4–layer θJA Typical 40 22 θJC 8 Units °C/W °C/W °C/W 1 This parameter is sampled 12/23/04, v.2.2 Alliance Semiconductor P. 4 of 18 AS7C251MNTD18A ® Signal descriptions Signal I/O Properties Description CLK I CLOCK CEN I SYNC Clock enable. When de-asserted high, the clock input signal is masked. A, A0, A1 Clock. All inputs except OE, LBO, and ZZ are synchronous to this clock. I SYNC Address. Sampled when all chip enables are active and ADV/LD is asserted. I/O SYNC Data. Driven as output when the chip is enabled and OE is active. CE0, CE1, CE2 I SYNC Synchronous chip enables. Sampled at the rising edge of CLK, when ADV/LD is asserted. Are ignored when ADV/LD is high. ADV/LD I SYNC Advance or Load. When sampled high, the internal burst address counter will increment in the order defined by the LBO input value. When low, a new address is loaded. R/W I SYNC A high during LOAD initiates a READ operation. A low during LOAD initiates a WRITE operation. Is ignored when ADV/LD is high. BW[a,b] I SYNC Byte write enables. Used to control write on individual bytes. Sampled along with WRITE command and BURST WRITE. OE I ASYNC Asynchronous output enable. I/O pins are not driven when OE is inactive. LBO I STATIC Selects Burst mode. When tied to VDD or left floating, device follows interleaved Burst order. When driven Low, device follows linear Burst order. This signal is internally pulled High. ZZ I ASYNC Snooze. Places device in low power mode; data is retained. Connect to GND if unused. NC - - DQ[a,b] No connects. Snooze Mode SNOOZE MODE is a low current, power-down mode in which the device is deselected and current is reduced to ISB2. The duration of SNOOZE MODE is dictated by the length of time the ZZ is in a High state. The ZZ pin is an asynchronous, active high input that causes the device to enter SNOOZE MODE. When the ZZ pin becomes a logic High, ISB2 is guaranteed after the time tZZI is met. After entering SNOOZE MODE, all inputs except ZZ is disabled and all outputs go to High-Z. Any operation pending when entering SNOOZE MODE is not guaranteed to successfully complete. Therefore, SNOOZE MODE (READ or WRITE) must not be initiated until valid pending operations are completed. Similarly, when exiting SNOOZE MODE during tPUS, only a DESELECT or READ cycle should be given while the SRAM is transitioning out of SNOOZE MODE. 12/23/04, v.2.2 Alliance Semiconductor P. 5 of 18 AS7C251MNTD18A ® Burst order Interleaved burst order (LBO = 1) Linear burst order (LBO = 0) A1A0 A1A0 A1A0 A1A0 Starting address 0 0 0 1 1 0 1 1 A1A0 A1A0 A1A0 A1A0 Starting Address 0 0 0 1 1 0 1 1 First increment 0 1 0 0 1 1 1 0 First increment 0 1 1 0 1 1 0 0 Second increment 1 0 1 1 0 0 0 1 Second increment 1 0 1 1 0 0 0 1 Third increment 1 1 1 0 0 1 0 0 Third increment 1 1 0 0 0 1 1 0 Synchronous truth table[5,6,7,8,9,11] CE0 CE1 CE2 ADV/LD R/W BWn OE CEN Address source CLK Operation DQ H X X L X X X L NA L to H DESELECT Cycle High-Z X X H L X X X L NA L to H DESELECT Cycle High-Z X L X L X X X L NA L to H DESELECT Cycle High-Z X X X H X X X L NA L to H CONTINUE DESELECT Cycle High-Z L H L L H X L L READ Cycle (Begin Burst) Q X X X H X X L L READ Cycle (Continue Burst) Q L H L L H X H L X X X H X X H L L H L L L L X L X X X H X L X L L H L L L H X L X X X H X H X L X X X X X X X H External L to H Next L to H External L to H NOP/DUMMY READ (Begin Burst) High-Z Next L to H External L to H Next L to H DUMMY READ (Continue Burst) L to H 1,10 2 High-Z 1,2,10 D 3 WRITE CYCLE (Continue Burst) D 1,3,10 High-Z 2,3 WRITE ABORT (Continue Burst) High-Z 1,2,3, 10 INHIBIT CLOCK - 4 Current L to H Key: X = Don’t Care, H = HIGH, L = LOW. BWn = H means all byte write signals (BWa, BWb, BWc, and BWd) are HIGH. BWn = L means one or more byte write signals are LOW. Notes: 1 CONTINUE BURST cycles, whether READ or WRITE, use the same control inputs. The type of cycle performed (READ or WRITE) is chose in the initial BEGIN BURST cycle. A CONINUE DESELECT cycle can only be entered if a DESELECT CYCLE is executed first. 2 DUMMY READ and WRITE ABORT cycles can be considered NOPs because the device performs no external operation. A WRITE ABORT means a WRITE command is given, but no operation is performed. 3 OE may be wired LOW to minimize the number of control signal to the SRAM. The device will automatically turn off the output drivers during a WRITE cycle. OE may be used when the bus turn-on and turn-off times do not meet an application’s requirements. 4 If an INHIBIT CLOCK command occurs during a READ operation, the DQ bus will remain active (Low-Z). If it occurs during a WRITE cycle, the bus will remain in High-Z. No WRITE operations will be performed during the INHIBIT CLOCK cycle. 5 BWa enables WRITEs to byte “a” (DQa pins); BWb enables WRITEs to byte “b” (DQb pins); BWc enables WRITEs to byte “c” (DQc pins); BWd enables WRITEs to byte “d” (DQd pins). 6 All inputs except OE and ZZ must meet setup and hold times around the rising edge (LOW to HIGH) of CLK. 7 Wait states are inserted by setting CEN HIGH. 8 This device contains circuitry that will ensure that the outputs will be in High-Z during power-up. 9 The device incorporates a 2-bit burst counter. Address wraps to the initial address every fourth BURST CYCLE. 10 The address counter is incremented for all CONTINUE BURST cycles. 11 ZZ pin is always Low in this truth table. 12/23/04, v.2.2 1 WRITE CYCLE (Begin Burst) External L to H NOP/WRITE ABORT (Begin Burst) Next Notes Alliance Semiconductor P. 6 of 18 AS7C251MNTD18A ® State diagram for NTD SRAM Burst Read Read Read Ds el Re ad Dsel d ea Dsel el Ds ite Wr Burst Write Burst Dsel W rit e Burst Dsel R Write Read Write Write Burst Read Burst Write Burst Absolute maximum ratings Parameter Symbol Min Max Unit VDD, VDDQ –0.3 +3.6 V Input voltage relative to GND (input pins) VIN –0.3 VDD + 0.3 V Power supply voltage relative to GND Input voltage relative to GND (I/O pins) VIN –0.3 VDDQ + 0.3 V Power dissipation PD – 1.8 W DC output current IOUT – 50 mA Storage temperature Tstg –65 +150 oC Temperature under bias (junction) Tbias –65 +150 o C Stresses greater than those listed under Absolute Maximum Ratings may cause permanent damage to the device. This is a stress rating only, and functional operation of the device at these or any other conditions outside those indicated in the operational sections of this specification is not implied. Exposure to absolute maximum rating conditions may affect reliability. Recommended operating conditions Parameter Symbol Min Nominal Max Unit Supply voltage for inputs VDD 2.375 2.5 2.625 V Supply voltage for I/O VDDQ 2.375 2.5 2.625 V Vss 0 0 0 V Ground supply 12/23/04, v.2.2 Alliance Semiconductor P. 7 of 18 AS7C251MNTD18A ® DC electrical characteristics Parameter Sym Conditions Min Max Unit current† |ILI| VDD = Max, 0V < VIN < VDD -2 2 µA Output leakage current |ILO| OE ≥ VIH, VDD = Max, 0V < VOUT < VDDQ -2 2 µA Input high (logic 1) voltage VIH Address and control pins 1.7* VDD+0.3 V I/O pins 1.7* VDDQ+0.3 V Input low (logic 0) voltage VIL Address and control pins -0.3** 0.7 V I/O pins -0.3** 0.7 V Output high voltage VOH IOH = –4 mA, VDDQ = 2.375V 1.7 – V Output low voltage VOL IOL = 8 mA, VDDQ = 2.625V – 0.7 V Input leakage † LBO and ZZ pins have an internal pull-up or pull-down, and input leakage = ±10 µA. *V max < VDD +1.5V for pulse width less than 0.2 X t IH CYC ** VIL min = -1.5 for pulse width less than 0.2 X tCYC IDD operating conditions and maximum limits Parameter Operating power supply current1 Sym ICC ISB Standby power supply current Conditions CE0 < VIL, CE1 > VIH, CE2 < VIL, f = fMax, IOUT = 0 mA, ZZ < VIL All VIN ≤ 0.2V or > VDD – 0.2V, Deselected, f = fMax, ZZ < VIL -166 -133 Unit 290 270 mA 85 75 ISB1 Deselected, f = 0, ZZ < 0.2V, all VIN ≤ 0.2V or ≥ VDD – 0.2V 40 40 ISB2 Deselected, f = fMax, ZZ ≥ VDD – 0.2V, all VIN ≤ VIL or ≥ VIH 40 40 mA 1 ICC given with no output loading. ICC increases with faster cycle times and greater output loading. 12/23/04, v.2.2 Alliance Semiconductor P. 8 of 18 AS7C251MNTD18A ® Timing characteristics over operating range -166 Parameter -133 Notes1 Sym Min Max Min Max Unit Clock frequency FMAX – 166 – 133 MHz Cycle time tCYC 6 – 7.5 – ns Clock access time tCD – 3.5 – 3.8 ns Output enable low to data valid tOE – 3.5 – 3.8 ns Clock high to output low Z tLZC 0 – 0 – ns 2, 3, 4 Data output invalid from clock high tOH 1.5 – 1.5 – ns 2 Output enable low to output low Z tLZOE 0 – 0 – ns 2, 3, 4 Output enable high to output high Z tHZOE – 3.5 – 3.8 ns 2, 3, 4 Clock high to output high Z tHZC – 3.5 – 3.8 ns 2, 3, 4 Output enable high to invalid output tOHOE 0 – 0 – ns Clock high pulse width tCH 2.4 – 2.4 – ns 5 Clock low pulse width tCL 2.3 – 2.4 – ns 5 Address and Control setup to clock high tAS 1.5 – 1.5 – ns 6 Data setup to clock high tDS 1.5 – 1.5 – ns 6 Write setup to clock high tWS 1.5 – 1.5 – ns 6, 7 Chip select setup to clock high tCSS 1.5 – 1.5 – ns 6, 8 Address hold from clock high tAH 0.5 – 0.5 – ns 6 Data hold from clock high tDH 0.5 – 0.5 – ns 6 Write hold from clock high tWH 0.5 – 0.5 – ns 6, 7 Chip select hold from clock high tCSH 0.5 – 0.5 – ns 6, 8 Clock enable setup to clock high tCENS 1.5 – 1.5 – ns 6 Clock enable hold from clock high tCENH 0.5 – 0.5 – ns 6 ADV setup to clock high tADVS 1.5 – 1.5 – ns 6 ADV hold from clock high tADVH 0.5 – 0.5 – ns 6 1 See “Notes” on page 15 Snooze Mode Electrical Characteristics Description Current during Snooze Mode ZZ active to input ignored ZZ inactive to input sampled ZZ active to SNOOZE current ZZ inactive to exit SNOOZE current 12/23/04, v.2.2 Conditions Symbol ZZ > VIH ISB2 tPDS tPUS tZZI tRZZI Alliance Semiconductor Min Max Units 40 mA cycle cycle cycle cycle 2 2 2 0 P. 9 of 18 AS7C251MNTD18A ® Key to switching waveforms Rising input don’t care Falling input Undefined Timing waveform of read cycle tCH tCL tCYC CLK tCES tCEH CEN tAS Address tAH A1 A2 A3 tWS tWH R/W tWS tWH BWn tCSH CE0,CE2 CE1 tADVS tADVH ADV/LD OE tOE tLZOE Dout tHZOE Q(A1) tHLZC Q(A2Y‘10) Q(A2) Q(A2Y‘11) Q(A2Y‘01) Read Q(A1) 12/23/04, v.2.2 DSEL Read Q(A2) Continue Read Q(A2Y‘01) Continue Read Q(A2Y‘10) Continue Read Q(A2Y‘11) Alliance Semiconductor Q(A3) Inhibit Clock Read Q(A3) Continue Read Q(A3Y‘01) P. 10 of 18 AS7C251MNTD18A ® Timing waveform of write cycle tCH tCL tCYC CLK tCES tCEH CEN tAS Address tAH A1 A2 A3 R/W BWn tCSH CE0,CE2 CE1 tADVS tADVH ADV/LD OE tDS D(A1) Din tHZOE Dout Q(n-2) D(A3) D(A2Y‘01) D(A2Y‘10) D(A2Y‘11) Q(n-1) Write D(A1) 12/23/04, v.2.2 tDH D(A2) DSEL Write D(A2) Continue Write D(A2Y‘01) Continue Write D(A2Y‘10) Continue Write D(A2Y‘11) Alliance Semiconductor Inhibit Clock Write D(A3) Continue Write D(A3Y‘01) P. 11 of 18 AS7C251MNTD18A ® Timing waveform of read/write cycle tCH tCL tCYC CLK tCENS tCENH CEN CE1 tCSS tCSH CE0, CE2 tADVS tADVH ADV/LD tWS tWH tWS tWH tAS tAH R/W BWn ADDRESS A1 A3 A2 A4 A6 A5 A7 tCD tDS tDH D/Q D(A1) tLZC D(A2) D(A2Ý01) tOH tOE Q(A3) Q(A4) tHZC Q(A4Ý01) D(A5) Q(A6) tHZOE tLZOE OE Command Write D(A1) Write D(A2) Burst Write D(A2Ý01) Read Q(A3) Read Q(A4) Burst Read Q(A4Ý01) Write D(A5) Read Q(A6) Write D(A7) DSEL Note: Ý = XOR when LBO = high/no connect. Ý = ADD when LBO = low. BW[a:d] is don’t care. 12/23/04, v.2.2 Alliance Semiconductor P. 12 of 18 AS7C251MNTD18A ® NOP, stall and deselect cycles CLK CEN CE1 CE0, CE2 ADV/LD R/W BWn Address A2 A1 Q(A1) D/Q Command Read Q(A1) Burst Q(A1Ý01) STALL Q(A1Ý01) Burst Q(A1Ý10) A3 D(A2) Q(A1Ý10) DSEL Burst DSEL Write D(A2) Burst NOP D(A2Ý01) Burst D(A2Ý10) Write NOP D(A3) Note: Ý = XOR when LBO = high/no connect; Ý = ADD when LBO = low. OE is low. 12/23/04, v.2.2 Alliance Semiconductor P. 13 of 18 AS7C251MNTD18A ® Timing waveform of snooze mode CLK tPUS ZZ setup cycle ZZ recovery cycle ZZ tZZI Isupply ISB2 tRZZI All inputs (except ZZ) Deselect or Read Only Deselect or Read Only Normal operation Cycle Dout 12/23/04, v.2.2 High-Z Alliance Semiconductor P. 14 of 18 AS7C251MNTD18A ® AC test conditions • Output load: see Figure B, except for tLZC, tLZOE, tHZOE, tHZC, see Figure C. • Input pulse level: GND to 2.5V. See Figure A. Thevenin equivalent: • Input rise and fall time (measured at 0.25V and 2.25V): 2 ns. See Figure A. • Input and output timing reference levels: 1.25V. +2.5V +2.5V Z0 = 50Ω 90% 90% 10% GND 50Ω DOUT VL = VDDQ/2 30 pF* 10% Figure A: Input waveform Figure B: Output load (A) 319Ω/1667Ω DOUT 5 pF* 353Ω/1538Ω GND *including scope and jig capacitance Figure C: Output load(B) Notes: 1) For test conditions, see “AC test conditions”, Figures A, B, C 2) This parameter measured with output load condition in Figure C. 3) This parameter is sampled, but not 100% tested. 4) tHZOE is less than tLZOE and tHZC is less than tLZC at any given temperature and voltage. 5) tCH measured high above VIH and tCL measured as low below VIL 6) This is a synchronous device. All addresses must meet the specified setup and hold times for all rising edges of CLK. All other synchronous inputs must meet the setup and hold times with stable logic levels for all rising edges of CLK when chip is enabled. 7) Write refers to R/W and BW[a,b]. 8) Chip select refers to CE0, CE1, and CE2. 12/23/04, v.2.2 Alliance Semiconductor P. 15 of 18 AS7C251MNTD18A ® Package dimensions 100-pin quad flat pack (TQFP) A1 A2 b c D E e Hd He L L1 α Hd D TQFP Min Max 0.05 0.15 1.35 1.45 0.22 0.38 0.09 0.20 13.90 14.10 19.90 20.10 0.65 nominal 15.85 16.15 21.80 22.20 0.45 0.75 1.00 nominal 0° 7° Dimensions in millimeters b e He E α c L1 A1 A2 L 12/23/04, v.2.2 Alliance Semiconductor P. 16 of 18 AS7C251MNTD18A ® Ordering information Package &Width TQFP x18 –166 MHz –133 MHz AS7C251MNTD18A-166TQC AS7C251MNTD18A-133TQC AS7C251MNTD18A-166TQI AS7C251MNTD18A-133TQI Note: Add suffix ‘N’ to the above part number for Lead Free Parts (Ex. AS7C251MNTD18A-166TQCN) Part numbering guide AS7C 25 1M NTD 18 A –XXX TQ C/I X 1 2 3 4 5 6 7 8 9 10 1. Alliance Semiconductor SRAM prefix 2. Operating voltage: 25 = 2.5V 3. Organization: 1M 4. NTD™ = No Turn-Around Delay. Pipelined mode 5. Organization: 18 = x 18 6. Production version: A = first production version 7. Clock speed (MHz) 8. Package type: TQ = TQFP 9. Operating temperature: C = commercial (0° C to 70° C); I = industrial (-40° C to 85° C) 10. N = Lead free part 12/23/04, v.2.2 Alliance Semiconductor P. 17 of 18 AS7C251MNTD18A ® ® Alliance Semiconductor Corporation 2575, Augustine Drive, Santa Clara, CA 95054 Tel: 408 - 855 - 4900 Fax: 408 - 855 - 4999 www.alsc.com Copyright © Alliance Semiconductor All Rights Reserved Part Number: AS7C251MNTD18A Document Version: v.2.2 © Copyright 2003 Alliance Semiconductor Corporation. All rights reserved. Our three-point logo, our name and Intelliwatt are trademarks or registered trademarks of Alliance. All other brand and product names may be the trademarks of their respective companies. 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