27C512QC-55 - 512Kbit 64Kx8 CMOS UV EPROM 55ns | Macronix
MPN: 27C512QC-55 β End of Life| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $6.5 | $6.50 |
| 10 | $5.85 | $58.50 |
| 100 | $5.2 | $520.00 |
| 500 | $4.68 | $2,340.00 |
| 1,000 | $4.22 | $4,220.00 |
Drop-in alternatives for 27C512QC-55 β same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Quick Comparison Tool β Select alternative parts for side-by-side comparison:
27C512QC-45
β Drop-In β οΈ εζ°εΎ ιͺθ―π Reference alternative (not in catalog)
27C512QC-70
β Drop-In β οΈ εζ°εΎ ιͺθ―π Reference alternative (not in catalog)
27C512QC-90
β Drop-In β οΈ εζ°εΎ ιͺθ―π Reference alternative (not in catalog)
27C512-20
β Drop-Inβ In Stock
$4.1 / Unit
View Datasheet β27C512-25-X
β Drop-Inβ In Stock
$2.95 / Unit
View Datasheet β27C512-15FA
β Drop-Inβ In Stock
$1.65 / Unit
View Datasheet βM27C512
β Drop-Inπ Reference alternative (not in catalog)
27C512QC-55 Maximum Ratings & Electrical Characteristics
| Memory Organization | 512K-bit (64K x 8) |
| Memory Type | CMOS UV EPROM |
| Access Time | 55 ns |
| Supply Voltage (Read) | Single +5 V |
| Programming Voltage (VPP) | +12.5 V |
| Family Speed Grades | 45/55/70/90/100/120/150 ns |
| Operation | Totally static |
| Interface Compatibility | Completely TTL compatible |
| Address Bus | A0 to A14 (15 lines) |
| Data Bus | D0 to D7 (8 lines, bidirectional 3-state) |
| Package | 28-pin ceramic DIP with quartz window (QC) |
| Erase Method | Ultraviolet light through quartz window |
| Mounting Type | Through Hole |
27C512QC-55 Pin Configuration
| Pin 1 | A15 β Address input bit 15 |
| Pin 2 | A12 β Address input bit 12 |
| Pin 3 | A7 β Address input bit 7 |
| Pin 4 | A6 β Address input bit 6 |
| Pin 5 | A5 β Address input bit 5 |
| Pin 6 | A4 β Address input bit 4 |
| Pin 7 | A3 β Address input bit 3 |
| Pin 8 | A2 β Address input bit 2 |
| Pin 9 | A1 β Address input bit 1 |
| Pin 10 | A0 β Address input bit 0 |
| Pin 11 | D0 β Data input/output bit 0 (3-state) |
| Pin 12 | D1 β Data input/output bit 1 (3-state) |
| Pin 13 | D2 β Data input/output bit 2 (3-state) |
| Pin 14 | GND β Ground reference |
| Pin 15 | D3 β Data input/output bit 3 (3-state) |
| Pin 16 | D4 β Data input/output bit 4 (3-state) |
| Pin 17 | D5 β Data input/output bit 5 (3-state) |
| Pin 18 | D6 β Data input/output bit 6 (3-state) |
| Pin 19 | D7 β Data input/output bit 7 (3-state) |
| Pin 20 | E β Chip enable (active low) |
| Pin 21 | A10 β Address input bit 10 |
| Pin 22 | OE/VPP β Output enable (active low) / programming voltage +12.5V |
| Pin 23 | A11 β Address input bit 11 |
| Pin 24 | A9 β Address input bit 9 |
| Pin 25 | A8 β Address input bit 8 |
| Pin 26 | A13 β Address input bit 13 |
| Pin 27 | A14 β Address input bit 14 |
| Pin 28 | VCC β +5V power supply |
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
27C512QC-55 is suitable for 6 applications: Legacy Embedded Firmware Storage, Retro-Computing and Arcade Board Restoration, Industrial Controller Boot Code, Telecommunications Equipment Character Storage, Test and Measurement Instrument Firmware, Educational and Development Platforms.
Legacy Embedded Firmware Storage
The 27C512QC-55 stores boot code and application firmware in 8-bit and 16-bit microprocessor systems where a 64K x 8 non-volatile code space is required. Its 55 ns access time supports zero-wait-state fetch at common legacy CPU clock rates, while TTL-compatible 3-state outputs connect directly to the processor bus. The quartz window allows engineers to erase with UV light and reprogram during development, making it well suited to firmware iteration before committing to OTP parts. Because it is totally static and draws minimal standby current from the single +5V rail, it fits battery-backed industrial controllers. One consideration: at end of life, plan a last-time-buy or qualify a pin-compatible substitute for long-term production.
Recommended
Retro-Computing and Arcade Board Restoration
Vintage computers, game consoles, and arcade PCBs from the 1980s and 1990s rely on 27C512-class EPROMs for game code and BIOS images. The 27C512QC-55 matches the JEDEC 28-pin DIP socket, +5V supply, and 55 ns timing expected by these boards, allowing direct replacement of corrupted or dead ROMs. Community repair guides note that used EPROMs frequently fail programming, so fresh windowed parts like this one are preferred. The quartz window enables repeated re-burning when testing ROM hacks or patched images. Use a verified ROM dump, confirm checksum after programming, and verify the board speed grade - faster grades always substitute safely into slower sockets.
Recommended
Industrial Controller Boot Code
Programmable logic controllers, motor drives, and instrumentation often hold initialization and diagnostic code in a 64K x 8 EPROM. The 27C512QC-55 offers the wide temperature tolerance of a hermetic ceramic cerdip package, high immunity to data corruption in electrically noisy factory environments, and a simple parallel bus interface with TTL levels. The 55 ns access time covers address decoding through 74-series logic without penalty. Field-service technicians can erase the windowed device under UV and re-burn updated firmware without soldering changes. Designers should add a pull-up on chip enable to prevent bus contention during power-up sequencing and keep address lines short to preserve the 55 ns timing margin.
Recommended
Telecommunications Equipment Character Storage
Legacy telecom line cards, modems, and PBX boards used 27C512 EPROMs for character tables, dialing code sets, and firmware. The 27C512QC-55's single +5V operation integrates directly into telecom backplane power schemes, and its totally static CMOS core avoids clock-related noise in sensitive analog front ends. With a 55 ns access time, table lookups complete within a single processor cycle. The UV-erasable ceramic package suits equipment that undergoes periodic field firmware updates by swapping pre-programmed devices. When maintaining such systems, keep spare programmed devices on hand, since erase-and-program cycles are limited and lamp aging affects erase consistency across production lots.
Recommended
Test and Measurement Instrument Firmware
Bench instruments such as oscilloscope front panels, function generators, and data loggers stored operating firmware and lookup tables in 27C512 EPROMs. The 27C512QC-55 provides deterministic 55 ns access for microcoded state machines, TTL-compatible outputs that directly drive legacy bus transceivers, and stable data retention without refresh. Its ceramic windowed package lets calibration engineers revise firmware during instrument refurbishment. The single +5V supply simplifies retrofit into aging power rails. For instruments with 12-16 MHz CPUs, confirm the 55 ns timing meets the CPU cycle budget including decode delays; otherwise select the 27C512QC-45 grade, which substitutes pin-for-pin with an 18% faster access time.
Recommended
Educational and Development Platforms
EPROM-based development boards remain a practical teaching tool for computer architecture courses because students can observe the full program-erase-verify cycle. The 27C512QC-55's quartz window demonstrates UV erasure physically, its 12.5V VPP programming illustrates early non-volatile memory physics, and its JEDEC 28-pin footprint fits standard breadboard adapters and universal programmers. The 64K x 8 map is large enough for meaningful programs yet simple to navigate in a hex editor. Because the device is static and TTL compatible, it connects to common 8-bit trainers without glue-logic complexity. Budget for a UV eraser and programmer, and note that erase cycles should be limited to preserve long-term reliability.
Recommended
Recommended Products Summary
Engineering reference data for 27C512QC-55 β comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | 27C512QC-45 | 27C512-20 | 27C512-25-X | 27C512-15FA | M27C512 |
|---|---|---|---|---|---|---|
| Package | 28-pin ceramic DIP with quartz window (QC) | 28-pin ceramic DIP with quartz window - same | DIP-28 - same pinout | DIP-28 - same pinout | DIP-28 - same pinout | DIP-28 (UV/OTP variants) - same JEDEC pinout |
| Brand | Macronix International | Macronix International | Macronix International | Macronix International | Macronix International | STMicroelectronics |
| Organization | 64K x 8 (512 Kbit) | 64K x 8 | 64K x 8 | 64K x 8 | 64K x 8 | 64K x 8 (65536 x 8) |
| Access Time | 55 ns | 45 ns | 200 ns | 250 ns | 150 ns | [DATA_NEEDED] |
| Read Supply Voltage | Single +5 V | Single +5 V | Single +5 V | Single +5 V | Single +5 V | Single +5 V |
| Programming Voltage (VPP) | +12.5 V | +12.5 V | +12.5 V | +12.5 V | +12.5 V | [DATA_NEEDED] |
| Erasability | UV via quartz window | UV via quartz window | [DATA_NEEDED] | [DATA_NEEDED] | [DATA_NEEDED] | UV or OTP ranges offered |
| I/O Compatibility | TTL compatible, static | TTL compatible, static | TTL compatible, static | TTL compatible, static | TTL compatible, static | TTL compatible |
Key Differentiators
- Faster access in same ceramic windowed package (vs 27C512QC-70)
- UV-erasable and reprogrammable for development (vs M27C512 (OTP variants))
- Cross-brand pin compatibility widens sourcing (vs M27C512)
Design Notes
Verify the 55 ns access time against your processor timing budget, including address decoder propagation (e.g., 74HC138 delay) and bus transceiver delays. Estimated: a 12 MHz 80C31 with ALE-based addressing leaves roughly 83 ns per cycle; subtracting decoder and latch delays of 20-30 ns leaves little margin over the 55 ns ROM access, so choose the 27C512QC-45 grade if measured margin is under 10 ns. Always validate at worst-case VCC (-5%) and maximum temperature.
Decouple VCC with a 0.1 uF ceramic capacitor placed within 10 mm of pin 28. Although CMOS EPROMs draw low standby current, output drivers switching 8 data lines can cause supply transients during zero-wait-state instruction fetch. Pull the chip enable pin high through a 10 kOhm resistor during power-up so the 3-state outputs stay off until the CPU bus is initialized, preventing bus contention with RAM or peripherals sharing the data bus.
Program only with VPP at +12.5V per the 27C512 algorithm - applying higher programming voltages permanently damages the cell array. Ensure the UV erasure window is covered with an opaque label in the field; ambient fluorescent light and direct sunlight will slowly erase data over months of exposure. Used or unmarked EPROMs frequently fail programming or have partially erased cells, so verify a blank read of FF hex in every location before programming production devices.
Compliance Information
Legacy ceramic cerdip EPROM predating RoHS; provided web data does not state compliance status. Ceramic packaging historically used leaded glass seals - confirm with manufacturer for RoHS-restricted applications.
