27C256T-15/SO - 256K 32Kx8 CMOS EPROM 150ns | Microchip Technology
부품 번호: 27C256T-15/SO ✗ 단종| 수량 | 단가 | 합계 |
|---|---|---|
| 1 | $2.95 | $2.95 |
| 10 | $2.65 | $26.50 |
| 100 | $2.35 | $235.00 |
| 500 | $2.1 | $1,050.00 |
| 1,000 | $1.9 | $1,900.00 |
27C256T-15/SO 개요
An EPROM (Erasable Programmable Read-Only Memory) is a non-volatile semiconductor memory that retains firmware or fixed data without power and can be erased with ultraviolet light when housed in a quartz-window package; the plastic SOIC variant is intended for one-time programming in production. Within the memory hierarchy it sits under Memory ICs, in the broader category of non-volatile parallel memory alongside EEPROM and flash, and remains common in legacy and industrial systems.
Key features include CMOS technology for low power consumption with 20 mA active current and 100 uA standby current, 150 ns maximum access time for asynchronous parallel interfacing, 3-state outputs, and Auto ID identification to aid automated programming equipment. Factory programming and auto-insertion-compatible plastic packages are supported.
The device uses CMOS process technology to achieve a low standby current of 100 uA, which is valuable in battery-backed or power-sensitive legacy designs. Access is fully asynchronous with /CE, /OE, and PGM control lines, and the 3-state outputs allow direct bus connection in microprocessor systems.
Typical applications include legacy firmware storage in industrial controllers, automotive ECUs and engine-management ROM sockets, telecommunications equipment, and retro-computing repair where a 27C256 socket must be populated with a surface-mount device.
Design consideration: since this is an EPROM, the programmed content cannot be electrically erased; verify firmware on a programmer before soldering, and respect the 4.5V to 5.5V VCC window and programming voltage requirements on VPP.
This page synthesizes distributor availability data, drop-in alternatives, and practical design notes not consolidated in the manufacturer datasheet. Pricing references are as of 2026-09-13.
드롭인 대체품: 27C256T-15/SO — 동일 패키지, 핀 호환. PCB 재작업이 필요한 다른 패키지 부품은 제외됩니다.
이 시리즈의 변형
다음과 드롭인 호환되는 동일 시리즈 모델: 27C256T-15/SO (동일 폼 팩터 및 풋프린트) — 차이점: Package, Memory Type, Mounting Type, Organization, Erase Method.
빠른 비교 도구 — 나란히 비교할 대체 부품을 선택하십시오:
27C256-15/SO
✅ 드롭인📋 참조 대체품 (카탈로그에 없음)
27C256T-15E/SO
✅ 드롭인📋 참조 대체품 (카탈로그에 없음)
27C256T-15I/SO
✅ 드롭인📋 참조 대체품 (카탈로그에 없음)
W27E257-15
✅ 드롭인📋 참조 대체품 (카탈로그에 없음)
AT27C256
✅ 드롭인📋 참조 대체품 (카탈로그에 없음)
27C256T-15/SO 사양
| 메모리 유형 | CMOS EPROM (non-volatile) |
| Memory Organization | 32K x 8 (256 Kbit) |
| Total Density | 262,144 bits |
| Maximum Access Time | 150 ns |
| Supply Voltage (VCC) | 4.5 V to 5.5 V |
| 인터페이스 | Parallel, asynchronous |
| 출력 유형 | 3-state outputs |
| Active Current | 20 mA |
| Standby Current | 100 uA |
| Technology | CMOS |
| Operation Mode | Asynchronous |
| Auto ID | Yes (automated programming identification) |
| 패키지 | 28-lead SOIC (SO), surface mount |
| 실장 유형 | Surface Mount |
27C256T-15/SO 핀 구성
| 핀 1 | VPP — Programming supply voltage |
| 핀 2 | A12 — Address input 12 (MSB) |
| 핀 3 | A7 — Address input 7 |
| 핀 4 | A6 — Address input 6 |
| 핀 5 | A5 — Address input 5 |
| 핀 6 | A4 — Address input 4 |
| 핀 7 | A3 — Address input 3 |
| 핀 8 | A2 — Address input 2 |
| 핀 9 | A1 — Address input 1 |
| 핀 10 | A0 — Address input 0 (LSB) |
| 핀 11 | O0 — Data output 0 (LSB) |
| 핀 12 | O1 — Data output 1 |
| 핀 13 | O2 — Data output 2 |
| 핀 14 | GND — Ground |
| 핀 15 | O3 — Data output 3 |
| 핀 16 | O4 — Data output 4 |
| 핀 17 | O5 — Data output 5 |
| 핀 18 | O6 — Data output 6 |
| 핀 19 | O7 — Data output 7 (MSB) |
| 핀 20 | /CE — Chip enable (active low) |
| 핀 21 | A10 — Address input 10 |
| 핀 22 | /OE — Output enable (active low) |
| 핀 23 | A11 — Address input 11 |
| 핀 24 | A9 — Address input 9 |
| 핀 25 | A8 — Address input 8 |
| 핀 26 | A13 — Address input 13 |
| 핀 27 | PGM — Program enable (active low) |
| 핀 28 | VCC — Power supply, 4.5V to 5.5V |
일반적인 애플리케이션
27C256T-15/SO 적합 용도: 6 애플리케이션s: Legacy Industrial Controller Firmware, Automotive ECU ROM Replacement, Retro-Computing and Arcade Board Repair, Telecommunications Equipment Firmware, Test and Measurement Instrument ROM, Embedded Security and Fixed-Code Storage.
Legacy Industrial Controller Firmware
The 27C256T-15/SO stores boot firmware and fixed lookup tables in legacy PLC and industrial controllers that still use 27C256 sockets. Its 150 ns access time is compatible with 8-bit and 16-bit microprocessor buses from the 1980s and 1990s, and the 100 uA CMOS standby current suits equipment that must retain code through power cycles without a battery. Because the 28-lead SOIC footprint matches the original design, failing through-hole or socketed parts can be replaced with a surface-mount device on an adapter or a matching SOIC footprint. Content programmed in production cannot be altered in the field, which is an advantage where firmware integrity and tamper-resistance are required, but demands rigorous pre-programming verification.
추천
Automotive ECU ROM Replacement
Engine-control units of the 1990s era commonly used 27C256 EPROMs for fuel and ignition maps. The 27C256T-15/SO provides the same 32K x 8 organization and 150 ns access timing required by these ECUs, with 4.5V to 5.5V operation matching the automotive 5V regulator rail and 3-state outputs interfacing directly to the MCU bus. For repair and remapping work, choose the industrial (27C256T-15I/SO) or extended (27C256T-15E/SO) temperature grades when the underhood environment exceeds commercial limits. As a one-time-programmable device, each calibration revision requires a new part, so electrically erasable substitutes such as the W27E257-15 are popular during development, with the OTP EPROM used for the final production fit.
추천
Retro-Computing and Arcade Board Repair
Vintage PC, console, and arcade motherboards rely on 27C256 EPROMs for BIOS and game code, and replacement parts are the primary repair path as originals fail or are lost. The 27C256T-15/SO matches the original 150 ns speed grade, and the minuszerodegrees replacement guide confirms that 150 ns devices are suitable for IBM 5155/5160/5162/5170 motherboards, where access time acts as a maximum rating. The 28-lead SOIC package suits boards converted to surface mount or fitted with SOIC sockets. Programmers with Auto ID support automatically identify the device, simplifying batch programming of replacement ROMs for collectors and repair shops restoring large quantities of boards.
추천
Telecommunications Equipment Firmware
Older telecom line cards, modems, and PBX modules used 27C256 EPROMs for code storage, and field-service organizations still need replacements to keep installed bases running. The device's asynchronous parallel interface, 3-state outputs, and 20 mA active current fit directly into these 5V bus-based designs without glue-logic changes. The SOIC surface-mount package supports automated rework on modern assembly lines repairing surface-mount cards, and tape-and-reel packaging (the T suffix) supports pick-and-place placement during volume refurbishment. Because telecom deployments often run for decades, stocking a lifecycle-stable replacement such as this EOL-class EPROM or its pin-compatible industrial variant protects long-term serviceability of the installed base.
추천
Test and Measurement Instrument ROM
Older oscilloscopes, logic analyzers, and bench instruments from the 1990s store self-test and operating firmware in 27C256 EPROMs, and instrument repair often requires replacement parts with exact timing. The 27C256T-15/SO delivers the 150 ns maximum access time expected by these designs, and its 100 uA standby current keeps battery-backed memory subsystems within budget. In repair workflows, the instrument firmware image is recovered from a donor unit or archived dump, programmed into the EPROM with verification, and soldered or socketed in place of the failed device. Since the plastic SOIC cannot be erased, service centers typically program spares in batches and store them as serialized inventory for field swap-outs.
추천
Embedded Security and Fixed-Code Storage
Applications that must store fixed identifiers, encryption keys, or boot constants benefit from the inherently immutable nature of a programmed EPROM: unlike flash or EEPROM, a soldered-in 27C256T-15/SO cannot be electrically rewritten, providing a simple hardware-level tamper barrier without extra security circuitry. The 32K x 8 capacity holds code plus fixed tables comfortably, the 4.5V to 5.5V supply matches standard industrial 5V rails, and the 150 ns access time meets typical 8-bit MCU bus timing. Designers should treat program content as permanent - any revision means a new programmed device - and should protect pin 1 (VPP) and the /PGM line on the PCB so that in-system programming attempts are physically prevented.
추천
추천 제품 요약
엔지니어링 참조 데이터: 27C256T-15/SO — 비교, 설계 지침 및 규정 준수 정보.
선택 가이드
대체품과의 비교
| 파라미터 | 이 제품 | 27C256-15/SO | 27C256T-15I/SO | W27E257-15 | AT27C256 |
|---|---|---|---|---|---|
| Package | 28-lead SOIC | 28-lead SOIC - same | 28-lead SOIC - same | 28-pin (SOIC/DIP) - same footprint | 28-pin (SOIC/DIP/PLCC) - SOIC same footprint |
| Brand | Microchip Technology (Fairchild legacy listing) | Microchip Technology | Microchip Technology | Winbond | Microchip Technology (Atmel) |
| Memory Organization | 32K x 8 (256 Kbit) | 32K x 8 | 32K x 8 | 32K x 8 | 32K x 8 |
| Maximum Access Time | 150 ns | 150 ns | 150 ns | 150 ns | Faster grades available (55-150 ns) |
| Supply Voltage | 4.5 V to 5.5 V | 4.5 V to 5.5 V | 4.5 V to 5.5 V | 4.5 V to 5.5 V | 4.5 V to 5.5 V |
| Erase Method | UV erase / OTP in plastic SOIC | UV erase / OTP in plastic SOIC | UV erase / OTP in plastic SOIC | Electrical erase (EEPROM) | OTP or windowed UV erase |
| Lifecycle Status | EOL (secondary market) | EOL (secondary market) | EOL (secondary market) | EOL (secondary market) | EOL (secondary market) |
주요 차별점
- Surface-mount 28-lead SOIC packaging for legacy sockets (vs 27C256-15/SO)
- Standard commercial temperature grade at lowest cost (vs 27C256T-15I/SO)
- Immutable UV/OTP EPROM behavior versus electrically erasable substitutes (vs W27E257-15)
- Exact original speed grade match (vs AT27C256)
설계 노트
The 27C256T-15/SO in a plastic SOIC package is one-time programmable - there is no quartz window for UV erasure. Program and fully verify the firmware image in an external programmer (which can use Auto ID to identify the device) BEFORE assembly; a single bit error after reflow means scrapping the board or hot-air rework. Keep pin 1 (VPP) and pin 27 (PGM) routed to non-user-accessible points in security-sensitive designs so in-system programming is impossible.
Connect every VCC (pin 28) and GND (pin 14) with a 0.1 uF ceramic decoupling capacitor placed within a few millimeters of the package. Tie unused control lines properly: /CE (pin 20) and /OE (pin 22) must be actively driven or pulled up; leaving them floating can place outputs in undefined high-impedance states or increase active current beyond the 20 mA datasheet figure. Keep address lines short and equalized where bus timing approaches the 150 ns access budget.
The 150 ns maximum access time is a worst-case figure; the CPU address-to-data setup must satisfy t_ACC plus output-enable delays. When retrofitting this part into designs that originally used a faster grade, verify the timing margin: per the minuszerodegrees replacement guide, access time is a maximum rating, so a faster 27C256 always works where a 150 ns part was designed - but a 150 ns part in a faster socket is not guaranteed. If in doubt, qualify the faster 27C256 variants as second sources.
규정 준수 정보
This is a legacy EOL part; RoHS status is not clearly stated in verified distributor data (some broker listings reference RoHS stock). Obtain a certificate of conformance from the seller if compliance is mandatory.
