27C512-25 - 512Kbit 64Kx8 CMOS EPROM 250ns | Microchip
MPN: 27C512-25 ✗ End of Life| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $4.95 | $4.95 |
| 10 | $4.45 | $44.50 |
| 100 | $3.95 | $395.00 |
| 500 | $3.55 | $1,775.00 |
| 1,000 | $3.2 | $3,200.00 |
Drop-in alternatives for 27C512-25 — 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:
27C512-20
✅ Drop-In ⚠️ 参数待验证✓ In Stock
$4.1 / Unit
View Datasheet →27C512-15FA
✅ Drop-In ⚠️ 参数待验证✓ In Stock
$1.65 / Unit
View Datasheet →27C512-10
✅ Drop-In ⚠️ 参数待验证✓ In Stock
$2.7 / Unit
View Datasheet →27C512L-15T
✅ Drop-In ⚠️ 参数待验证✓ In Stock
Contact for price
View Datasheet →27C512-25-X
✅ Drop-In ⚠️ 参数待验证✓ In Stock
$2.95 / Unit
View Datasheet →M27C512
✅ Drop-In📋 Reference alternative (not in catalog)
AT27C512R
✅ Drop-In📋 Reference alternative (not in catalog)
W27C512
✅ Drop-In📋 Reference alternative (not in catalog)
27C512-25 Maximum Ratings & Electrical Characteristics
| Memory Organization | 64K x 8 (524,288 bits) |
| Memory Type | CMOS EPROM (UV / OTP) |
| Maximum Access Time | 250 ns |
| Supply Voltage (Read Mode) | 5 V +/- 10% |
| Standby Current (CMOS) | 20 uA typical |
| Operating Mode | Asynchronous |
| Output Type | 3-state, common I/O |
| Pinout Standard | JEDEC-approved 28-pin |
| Package | DIP-28 |
| Mounting Type | Through Hole |
| Programming Method | High-voltage EPROM programming (Flashrite type) |
| Erase Method | UV (windowed variant) or not erasable (OTP variant) |
| Access Time Guarantee | Any byte in less than 250 ns |
| Technology | CMOS floating gate |
27C512-25 Pin Configuration
| Pin 1 | A15 — Address input bit 15 (highest order) |
| Pin 2 | A12 — Address input bit 12 |
| Pin 3 | A7 — Address input bit 7 |
| Pin 4 | A6 — Address input bit 6 |
| Pin 5 | A5 — Address input bit 5 |
| Pin 6 | A4 — Address input bit 4 |
| Pin 7 | A3 — Address input bit 3 |
| Pin 8 | A2 — Address input bit 2 |
| Pin 9 | A1 — Address input bit 1 |
| Pin 10 | A0 — Address input bit 0 |
| Pin 11 | D0 — Data output bit 0 |
| Pin 12 | D1 — Data output bit 1 |
| Pin 13 | D2 — Data output bit 2 |
| Pin 14 | GND — Ground reference |
| Pin 15 | D3 — Data output bit 3 |
| Pin 16 | D4 — Data output bit 4 |
| Pin 17 | D5 — Data output bit 5 |
| Pin 18 | D6 — Data output bit 6 |
| Pin 19 | D7 — Data output bit 7 |
| Pin 20 | /CE — Chip Enable (active low) |
| Pin 21 | A10 — Address input bit 10 |
| Pin 22 | /OE — Output Enable (active low) |
| Pin 23 | A11 — Address input bit 11 |
| Pin 24 | A9 — Address input bit 9 |
| Pin 25 | A8 — Address input bit 8 |
| Pin 26 | A13 — Address input bit 13 |
| Pin 27 | A14 — Address input bit 14 |
| Pin 28 | VCC — Power supply, 5V (read mode) |
Safe Operating Area (SOA) & Thermal Characteristics
No official SOA curve available for this digital IC. Always operate within absolute maximum ratings specified in the datasheet. Ensure adequate cooling and derate as needed.
Typical Applications
27C512-25 is suitable for 6 applications: Legacy Automotive ECU Firmware, Retro Computer and Arcade Board Repair, Industrial Machine Controller Firmware, Embedded System Prototyping and Firmware Development, Test and Measurement Equipment Firmware, Character Generator and Lookup Table Storage.
Legacy Automotive ECU Firmware
The 27C512-25 fits classic automotive engine control units from the late 1980s and 1990s, where the 64K x 8 organization matches typical calibration image sizes and the 250 ns access time satisfies era-correct 8-bit ECU processor bus timing without wait states. Its single 5V read supply integrates directly into the vehicle's regulated 5V logic rail, and the JEDEC 28-pin DIP socket format allows chip swaps without soldering. For ECU tuning, technicians program a fresh OTP or windowed device with modified fuel and ignition maps; per TunerCat guidance, a new known-type programmed EPROM is safer than erasing and reprogramming an original windowed chip. The 20 uA typical CMOS standby current keeps battery drain negligible when the ECU is powered down.
Recommended
Retro Computer and Arcade Board Repair
The 27C512-25 is a primary replacement device for repairing vintage home computers, game consoles, and arcade PCBs, where original masked ROMs or failing EPROMs must be substituted with a programmable equivalent. The JEDEC-standard 28-pin pinout drops into original ROM sockets on boards designed for the 27C512 footprint, and the 250 ns timing meets the clock rates of Z80, 6502, and 68000-family systems of the period. Because original EPROMs are 30-40 years old, bit rot and failed UV windows are common; programming a new 27C512-25 with a verified ROM image restores full functionality. The UV-window variant allows image correction during restoration, while OTP variants reduce cost for final builds.
Recommended
Industrial Machine Controller Firmware
Factory equipment from the 1990s - CNC controllers, PLC I/O boards, motor drive controllers, and robotic arm boards - commonly stores firmware and lookup tables in 27C512-family EPROMs. The 27C512-25's 5V-only read operation, 3-state common-I/O outputs, and +/-10% supply tolerance make it robust on industrial logic rails with moderate noise, and its non-volatile storage survives power loss indefinitely. When an original EPROM fails, the 27C512-25 programmed with the machine's firmware image returns the equipment to service without redesign. Using faster grades (27C512-20/-15FA) provides timing margin for controllers whose processor buses were marginal at original specifications, and the DIP-28 package suits socketed industrial boards designed for field firmware updates.
Recommended
Embedded System Prototyping and Firmware Development
During development of legacy-architecture embedded systems, the windowed (UV) 27C512 variant allows repeated erase-and-program cycles while debugging firmware, with each iteration programmed via a standard EPROM programmer using the family high-voltage programming algorithm. The 250 ns access time accommodates mainstream 8- and 16-bit prototype processors, and the 64K x 8 capacity holds typical monitor programs plus application code. Once firmware is frozen, an OTP 27C512-25 is programmed for the production build at lower unit cost. For teams wanting to eliminate UV erase cycles entirely, the pin-compatible Winbond W27C512 EEPROM provides electrical erasure in the same DIP-28 footprint, dramatically shortening development iteration time while preserving board compatibility.
Recommended
Test and Measurement Equipment Firmware
Bench instruments from the EPROM era - oscilloscopes, logic analyzers, spectrum analyzers, and programmable power supplies - store boot code, calibration constants, and Menus in 27C512-class devices. When an instrument's EPROM fails or a corrupted calibration image must be restored, the 27C512-25 programmed with a dump from a known-good unit provides an exact replacement. The 5V read supply, 250 ns access, and JEDEC 28-pin pinout match the original socket without board modification, and the low 20 uA standby current suits battery-backed portable instruments. Keeping a small stock of 27C512-25 devices plus verified firmware images is standard practice for laboratories maintaining legacy test fleets beyond vendor support lifetimes.
Recommended
Character Generator and Lookup Table Storage
The 27C512-25 serves as a fixed lookup store for font/character generators, video ROMs, sine and coefficient tables, and state-machine microcode in legacy digital designs. Its asynchronous 250 ns access makes address-to-data lookup deterministic - no controller or refresh logic is needed - and the 64K x 8 array holds large character sets or high-resolution tables. The 3-state outputs with common I/O allow multiple ROMs to share a data bus under /CE and /OE control, enabling banked table selection in designs needing more than 64K entries. Because contents are hard-programmed, data integrity is immune to software corruption, a key reason table ROMs persisted in commercial designs even after EEPROM availability.
Recommended
Recommended Products Summary
Engineering reference data for 27C512-25 — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | 27C512-20 | M27C512 | AT27C512R | W27C512 |
|---|---|---|---|---|---|
| Package | DIP-28 | DIP-28 - same | DIP-28 (also PLCC32 variants) | DIP-28 (also PLCC32, TSOP) | DIP-28 (also PLCC32) |
| Brand | Microchip Technology | Microchip Technology | STMicroelectronics | Microchip Technology (Atmel) | Winbond |
| Access Time | 250 ns | 200 ns | [DATA_NEEDED] speed-grade dependent | 45 ns (fastest grade) | 45/70/90/120 ns |
| Memory Organization | 64K x 8 (512 Kbit) | 64K x 8 | 64K x 8 (512 Kbit) | 64K x 8 (524,288 bits) | 64K x 8 |
| Memory Technology | CMOS UV/OTP EPROM | CMOS UV/OTP EPROM | UV EPROM and OTP EPROM | OTP EPROM | EEPROM (electrically erasable) |
| Standby Current (typical) | 20 uA | [DATA_NEEDED] | [DATA_NEEDED] | [DATA_NEEDED] | [DATA_NEEDED] |
| Supply Voltage (Read) | 5 V +/- 10% | 5 V +/- 10% | 5 V single supply | 5 V single supply | 5 V single supply |
| Lifecycle Status | Obsolete | Obsolete | Obsolete / last-time-buy stock | Obsolete | Obsolete |
| Pinout Standard | JEDEC 28-pin EPROM | JEDEC 28-pin EPROM - same | JEDEC 28-pin EPROM - same | JEDEC 28-pin EPROM - same | JEDEC 28-pin EPROM - same |
Key Differentiators
- True 250 ns speed grade availability (vs AT27C512R)
- UV erasable variant availability (vs AT27C512R)
- CMOS low standby power (vs M27C512)
Design Notes
Never erase and reprogram an unknown EPROM type. As TunerCat's EPROM guidance warns, programming voltage and algorithm differ between 27-series types, and applying the wrong algorithm can damage the device permanently. For board repair, purchase a fresh known-type programmed device (such as the 27C512-25) instead of reusing an unidentified windowed chip. Also verify whether your device is UV or OTP before attempting erase cycles - OTP devices are destroyed by reprogramming attempts.
The 27C512-25 reads from a single 5V supply with +/-10% tolerance (4.5V to 5.5V). Decouple VCC with a 0.1 uF ceramic capacitor close to pin 28 and GND pin 14. Programming requires elevated voltages on VPP/control pins per the family programming algorithm; ensure the programmer socket adapter routes these only during programming mode. In systems with marginal 5V rails, the +/-10% tolerance absorbs noise, but brownout during programming corrupts images - verify supply stability with an EPROM programmer self-test.
Verify /CE and /OE access timing against the host CPU bus before substituting grades. The 27C512-25 guarantees 250 ns address-to-output access; faster CPUs need the 27C512-20, -15FA, or -10 grades. Because faster devices are always safe drop-ins for slower sockets, standardizing on a faster grade (e.g., 27C512-15FA) across a repair fleet maximizes substitution flexibility. Unused address inputs must not float - tie A14/A15 per the board design, since floating address pins cause nondeterministic data output.
Compliance Information
Compliance data not present in retrieved sources. Legacy DIP-28 EPROMs of this era are typically non-RoHS (tin-lead finish); verify with supplier before RoHS-restricted deployments.
