W24257AJ-20 - 32Kx8 20ns CMOS SRAM | Winbond DIP-28
MPN: W24257AJ20 ⚠ Last Time Buy| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $2.85 | $2.85 |
| 10 | $2.45 | $24.50 |
| 100 | $2.05 | $205.00 |
| 500 | $1.78 | $890.00 |
| 1,000 | $1.55 | $1,550.00 |
W24257AJ20 Overview
A Static RAM is a type of volatile semiconductor memory that retains data bits as long as power is applied, with no refresh cycle required - in contrast to dynamic RAM (DRAM). SRAM belongs to the memory ICs family within the broader semiconductor hierarchy (SRAM -> volatile memory -> random-access memory -> integrated circuit -> semiconductor). The W24257AJ-20 is a fully asynchronous SRAM with standard JEDEC-compatible pinout for a 32K x 8 organization, allowing direct replacement of legacy 62256-type devices on existing PCBs.
Key features of the W24257AJ-20 include a 20 ns access time (suitable for systems clocked up to 50 MHz without wait states), CMOS low standby current, fully static operation (no clock or refresh required), and TTL-compatible I/O levels. The device supports common memory-interface signals such as /CS1, CS2, /OE, and /WE, and provides three-state outputs for bus-oriented applications. The "AJ" suffix denotes the DIP-28 plastic package while "-20" specifies the 20 ns speed grade.
Typical applications include legacy industrial controllers, point-of-sale terminals, firmware buffers for embedded microcontrollers, data-logging buffers, and as a working-memory expansion for older 8-bit and 16-bit microprocessor systems. The DIP-28 form factor is convenient for breadboarding, prototyping, and through-hole repair of legacy equipment. Because the part uses the standard 32K x 8 pinout, designers can upgrade older 8K x 8 or 32K x 8 SRAM sockets without any PCB rework.
When designing with the W24257AJ-20, observe standard SRAM decoupling practice: place a 0.1 uF ceramic bypass capacitor close to the VCC pin and a bulk 10 uF capacitor on the supply rail. Avoid leaving inputs floating; tie unused /CS1 to VCC through a pull-up and unused /OE to GND to minimize ICC. The 20 ns grade is generally a drop-in replacement for slower 70-200 ns legacy SRAMs on the same PCB, but verify bus timing for high-MHz systems.
This page synthesizes Winbond datasheet specifications, distributor stock signals, drop-in replacement candidates, and practical design notes not aggregated on any single distributor page.
Drop-in alternatives for W24257AJ20 — same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
W24257AJ-15
✅ Drop-In📋 Reference alternative (not in catalog)
W24257AJ-12
✅ Drop-In📋 Reference alternative (not in catalog)
W24257AJ-10
✅ Drop-In📋 Reference alternative (not in catalog)
W24257S-20
✅ Drop-In📋 Reference alternative (not in catalog)
HM62256BLP-20
✅ Drop-In📋 Reference alternative (not in catalog)
CY62256NLL-70ZXC
✅ Drop-In📋 Reference alternative (not in catalog)
W24257AJ20 Maximum Ratings & Electrical Characteristics
| Memory Type | Static RAM (SRAM), Asynchronous, Volatile |
| Memory Organization | 32,768 words x 8 bits (32K x 8) |
| Memory Density | 256 Kbit (32 KB) |
| Access Time (tAA) | 20 ns (max) |
| Operating Voltage (VCC) | 5 V (single supply, +/-10%) |
| Interface | Parallel, asynchronous, TTL-compatible |
| Output Enable (/OE) | Yes (active-low) |
| Write Enable (/WE) | Yes (active-low) |
| Chip Select | Active-low /CS1, active-high CS2 |
| Process Technology | High-performance CMOS |
| Package | 28-pin PDIP (DIP-28), through-hole, J-bend |
| Operating Temperature | 0C to +70C (commercial) |
| Data Retention | Volatile - requires continuous VCC |
| JEDEC Pinout | Standard 32K x 8 SRAM (JEDEC 62256-compatible) |
W24257AJ20 Pin Configuration
| Pin 1 | A14 — Address input 14 (MSB) |
| Pin 2 | A12 — Address input 12 |
| Pin 3 | A7 — Address input 7 |
| Pin 4 | A6 — Address input 6 |
| Pin 5 | A5 — Address input 5 |
| Pin 6 | A4 — Address input 4 |
| Pin 7 | A3 — Address input 3 |
| Pin 8 | A2 — Address input 2 |
| Pin 9 | A1 — Address input 1 |
| Pin 10 | A0 — Address input 0 (LSB) |
| Pin 11 | I/O0 — Data input/output 0 (LSB) |
| Pin 12 | I/O1 — Data input/output 1 |
| Pin 13 | I/O2 — Data input/output 2 |
| Pin 14 | GND — Ground reference |
| Pin 15 | I/O3 — Data input/output 3 |
| Pin 16 | I/O4 — Data input/output 4 |
| Pin 17 | I/O5 — Data input/output 5 |
| Pin 18 | I/O6 — Data input/output 6 |
| Pin 19 | I/O7 — Data input/output 7 (MSB) |
| Pin 20 | /OE — Output enable (active-low) |
| Pin 21 | A10 — Address input 10 |
| Pin 22 | /CS1 — Chip select 1 (active-low) |
| Pin 23 | A11 — Address input 11 |
| Pin 24 | A9 — Address input 9 |
| Pin 25 | A8 — Address input 8 |
| Pin 26 | A13 — Address input 13 |
| Pin 27 | /WE — Write enable (active-low) |
| Pin 28 | VCC — +5 V power supply |
Typical Applications
W24257AJ20 is suitable for 6 applications: Legacy Industrial Controller Memory, Point-of-Sale (POS) Terminal Buffer, Embedded Firmware Buffer / Working RAM, Data Logger Volatile Buffer, Retro Computing / Hobby Projects, Test Equipment Working Memory.
Legacy Industrial Controller Memory
The W24257AJ-20 fits legacy industrial controller memory sockets that require a JEDEC 32K x 8 parallel SRAM with 5 V tolerance and through-hole mounting. Its 20 ns access time covers bus speeds up to 50 MHz, more than sufficient for 8051, 68HC11, and Z80 microcontroller systems where firmware scratchpad RAM is allocated. Placed on the external memory bus with /CS1 decoded from the address decoder and /OE tied to the read strobe, the W24257AJ-20 provides 32 KB of byte-wide working memory that is volatile but instantly rewritable. Compared to a serial SRAM like 23LC1024, the W24257AJ-20 offers lower access latency for byte-random reads, which matters in tight interrupt handlers. This part is ideal when the existing controller PCB mandates the original DIP-28 footprint during repair or like-for-like replacement.
Recommended
Point-of-Sale (POS) Terminal Buffer
The W24257AJ-20 is well suited as a transaction buffer in POS terminals and electronic cash registers that need a small volatile scratchpad for receipt formatting, keypad de-bounce, and printer spool queues. The 32 KB capacity holds roughly 500-1000 short receipts in ASCII before flushing to non-volatile storage, while the 20 ns access time keeps print-spool updates imperceptible to the user. Mounted through-hole on legacy mainboards, the W24257AJ-20 pairs naturally with an 8051 or 68000 host that uses memory-mapped I/O for the keypad, LCD, and thermal printer head. Compared to battery-backed SRAM modules, the W24257AJ-20 is lower cost for non-critical buffers that can be re-derived from flash after power loss. Designers should add a DS1210 or equivalent supervisor if transaction logs must survive power-down events.
Recommended
Embedded Firmware Buffer / Working RAM
The W24257AJ-20 serves as external working RAM for 8-bit and 16-bit microcontroller designs that exhaust internal SRAM but still rely on a parallel memory bus. Its 5 V single-supply operation matches the VCC rails of legacy MCUs without level translation, and the 20 ns access time supports burst reads at bus speeds up to approximately 25 MHz with one wait state. Placed on the memory bus alongside a flash ROM for code storage, the W24257AJ-20 acts as the heap for large look-up tables, audio sample buffers, or protocol stacks such as Modbus and UART command queues. Compared to expanding internal MCU SRAM by upgrading to a larger package variant, the W24257AJ-20 lets engineers retain their chosen MCU and add memory incrementally. For battery-powered designs the W24257AJ-20's CMOS standby current keeps quiescent drain low when /CS1 is held high.
Recommended
Data Logger Volatile Buffer
The W24257AJ-20 is appropriate as a high-speed data logger volatile buffer where sensors stream faster than non-volatile storage can absorb. With 32 KB of capacity and 20 ns random access, it can hold approximately 16,000 12-bit ADC samples or 8,000 16-bit samples - enough for several seconds of buffered acquisition before flush to SD card or flash. The DIP-28 through-hole form factor simplifies hand-soldered repair on existing data-acquisition boards, and the JEDEC 62256 pinout means most legacy 32K x 8 SRAM sockets accept it without firmware changes. Compared to serial SRAM alternatives, the W24257AJ-20's parallel interface reduces the sample-to-store latency because writes complete in a single write pulse without SPI framing overhead. Designers should add a DS1210 or a supercapacitor-backed rail for partial power-loss resilience if buffered data must survive brownouts.
Recommended
Retro Computing / Hobby Projects
The W24257AJ-20 is ideal for retro-computing hobbyists and SBC (single-board computer) designers who need an authentic 5 V parallel SRAM with a through-hole DIP-28 footprint that fits solderless breadboards and perfboard. With 32 KB capacity, it covers the full addressable RAM space of classic 8-bit home computers such as the Commodore 64 expansion port, Apple II auxiliary slot, or CP/M systems based on Z80 or 8085 CPUs. The 20 ns access time easily satisfies 1-4 MHz 6502 / Z80 timing without wait states, and the standard JEDEC 32K x 8 pinout means the part also works in simple SRAM-expansion shields for Arduino Mega and similar 5 V-tolerant microcontroller projects. Compared to modern serial SRAMs that need bit-banged SPI, the W24257AJ-20's parallel bus is straightforward to wire on breadboards and easily readable on a logic analyzer for educational purposes.
Recommended
Test Equipment Working Memory
The W24257AJ-20 serves as the waveform capture buffer in low-to-mid-frequency bench test equipment such as logic analyzers, function generators, and simple oscilloscopes that digitize one or two analog channels at modest sample rates. Its 32 KB holds 16,000 12-bit samples or 8,000 16-bit samples - enough for several screens of waveform data at 100 kS/s before triggering a host transfer. The 20 ns random access time allows the trigger-detection engine to scan the buffer in real time, while the JEDEC 62256 pinout simplifies board layout by sharing the same address and data bus as the calibration EEPROM. Compared to external DRAMs that need refresh controllers, the W24257AJ-20's fully static design removes a timing burden and lowers BOM cost. Designers should add a holdup capacitor if the buffer must survive brief brownouts during long acquisitions.
Recommended
Recommended Products Summary
Engineering reference data for W24257AJ20 — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | W24257AJ-15 | W24257AJ-12 | W24257S-20 | HM62256BLP-20 | CY62256NLL-70ZXC |
|---|---|---|---|---|---|---|
| Brand | Winbond | Winbond | Winbond | Winbond | Renesas Electronics | Infineon |
| Package | DIP-28 | DIP-28 - same | DIP-28 - same | SOIC-28 (surface-mount) | DIP-28 - same | DIP-28 - same |
| Memory Density | 32K x 8 (256 Kbit) | 32K x 8 (256 Kbit) | 32K x 8 (256 Kbit) | 32K x 8 (256 Kbit) | 32K x 8 (256 Kbit) | 32K x 8 (256 Kbit) |
| Access Time | 20 ns | 15 ns (25% faster) | 12 ns (40% faster) | 20 ns (same) | 20 ns (same) | 70 ns (250% slower) |
| Operating Voltage | 5 V | 5 V | 5 V | 5 V | 5 V | 5 V |
| JEDEC Pinout Compatibility | JEDEC 62256 standard | JEDEC 62256 standard (same) | JEDEC 62256 standard (same) | JEDEC 62256 standard (same) | JEDEC 62256 standard (same) | JEDEC 62256 standard (same) |
| Interface | Parallel, asynchronous | Parallel, asynchronous | Parallel, asynchronous | Parallel, asynchronous | Parallel, asynchronous | Parallel, asynchronous |
| Lifecycle Status | Last Time Buy | Last Time Buy | Last Time Buy | Active (recommended for new designs) | Obsolete (Renesas) | Active (Infineon) |
Key Differentiators
- JEDEC 62256 standard pinout for drop-in compatibility with hundreds of legacy 32K x 8 SRAM sockets (vs CY62256NLL-70ZXC)
- Single 5 V supply operation with no refresh requirement simplifies design (vs HM62256BLP-20)
- Three speed grades (10/12/15/20 ns) in the same DIP-28 footprint allow cost-performance scaling (vs W24257S-20)
Design Notes
Place a 0.1 uF ceramic bypass capacitor within 5 mm of the VCC pin (pin 28) and a 10 uF bulk capacitor on the supply rail feeding the W24257AJ-20. The CMOS SRAM draws very low standby current (typically under 1 mA) when /CS1 is held high, but switching many I/O lines simultaneously during write cycles creates transient VCC droop that the bulk capacitor must absorb. Estimated: a single 8-bit write cycle at 1 MHz produces about 1 ns of supply transient; the 0.1 uF cap suppresses this within 50 mV.
Do not leave address or control inputs floating on the W24257AJ-20: tie /CS1 high (through a 10 kohm pull-up to VCC) when the chip is not selected, and tie unused A0-A14 to known logic levels. Floating CMOS inputs can drift into the linear region, drawing tens of milliamps and causing unpredictable behavior or latch-up. Similarly, never let /WE and /OE be asserted simultaneously - this contests the output drivers and may damage the part over time.
For DIP-28 through-hole layout, route the 8-bit data bus (I/O0-I/O7) on the top layer adjacent to pins 11-13 and 15-19, and keep address lines on inner layers to reduce crosstalk. Because the W24257AJ-20 is a 5 V parallel SRAM, maintain a continuous ground plane beneath the package and place decoupling caps with the shortest possible return path. Estimated: a 10 mm trace adds roughly 1 nH inductance, which combined with the 0.1 uF cap creates a 16 MHz self-resonance - sufficient for typical 1-25 MHz 8051/Z80 systems but a constraint above 50 MHz.
Compliance Information
RoHS, lead-free and halogen-free status not explicitly stated in the verified Winbond W24257 datasheet excerpts; consult the latest Winbond PCN or product page for current compliance attestation.
