27C512A-12I/SO - 512Kbit CMOS EPROM 120ns | Microchip Technology
MPN: 27C512A-12I/SO β End of Life| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $4.5 | $4.50 |
| 10 | $4.1 | $41.00 |
| 100 | $3.65 | $365.00 |
| 500 | $3.2 | $1,600.00 |
| 1,000 | $2.85 | $2,850.00 |
Drop-in alternatives for 27C512A-12I/SO 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:
27C512A-12/SO
β Drop-Inπ Reference alternative (not in catalog)
27C512A-15I/SO
β Drop-In β οΈ εζ°εΎ ιͺθ―π Reference alternative (not in catalog)
27C512A-20I/SO
β Drop-In β οΈ εζ°εΎ ιͺθ―π Reference alternative (not in catalog)
27C512A-12I/SO Maximum Ratings & Electrical Characteristics
| Memory Organization | 64K x 8 (512 Kbit) |
| Memory Type | CMOS EPROM (One-Time Programmable) |
| Maximum Access Time | 120 ns |
| Supply Voltage | 5 V (4.5 V to 5.5 V) |
| Active Current | 25 mA |
| Standby Current | 30 uA |
| Interface Type | Asynchronous |
| Output Type | 3-State, Common I/O |
| Address Lines | 15 (A0-A14) |
| Data Lines | 8 (DQ0-DQ7) |
| Operating Temperature | -40C to +85C (Industrial) |
| Package | 28-lead SOIC (SO), 330 mil |
| Mounting Type | Surface Mount |
| Auto ID Feature | Yes (aids automated programming) |
| Factory Programming | Available |
| Technology | CMOS (low power) |
| Temperature Grade | I (Industrial) |
27C512A-12I/SO 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 | DQ0 β Data input/output, bit 0 |
| Pin 12 | DQ1 β Data input/output, bit 1 |
| Pin 13 | DQ2 β Data input/output, bit 2 |
| Pin 14 | VSS β Ground |
| Pin 15 | DQ3 β Data input/output, bit 3 |
| Pin 16 | DQ4 β Data input/output, bit 4 |
| Pin 17 | DQ5 β Data input/output, bit 5 |
| Pin 18 | DQ6 β Data input/output, bit 6 |
| Pin 19 | DQ7 β Data input/output, bit 7 |
| 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 during programming |
| Pin 23 | A11 β Address input, bit 11 |
| Pin 24 | A9 β Address input, bit 9 (also used for Auto ID mode) |
| 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 Power supply, 5V (4.5V to 5.5V) |
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
27C512A-12I/SO is suitable for 6 applications: Legacy Embedded Controller Firmware Storage, Industrial Automation and PLC Equipment, Automotive Control Units (Industrial-Temperature Band), Telecommunications Line Cards and Network Hardware, Test and Measurement Equipment Repair, Character Generators and Fixed Lookup Tables.
Legacy Embedded Controller Firmware Storage
The 27C512A-12I/SO stores boot and application firmware in 8-bit microcontroller systems built around 5V buses such as the 8051, 68HC11, and Z80 families. Its 120 ns access time supports zero-wait-state operation at common legacy CPU clock rates, while the 64K x 8 organization directly matches the 64 KB address space of classic 8-bit architectures without bank switching. The 3-state common-I/O outputs connect directly to the processor data bus, and /E plus /OE controls allow clean bus handoff with other memory-mapped devices. Because it is OTP and non-volatile, firmware remains intact for the product's service life without battery backup, which is a key requirement for fielded legacy hardware where flash upgrades are not supported by the original design.
Recommended
Industrial Automation and PLC Equipment
Industrial controllers, PLC I/O modules, and motor-drive boards frequently specify the industrial temperature range that the 27C512A-12I/SO provides: -40C to +85C per Microchip's specification. Its 5V CMOS logic levels match the legacy industrial 5V backplane environment, and its 30 uA standby current reduces consumption in battery-backed or low-duty-cycle control cabinets. Lookup tables for sensor linearization, PID coefficients, and state-machine code reside permanently in the OTP array, immune to power interruptions and electrical noise common on factory floors. The device's asynchronous interface needs no clock or configuration, simplifying retrofits into existing card designs. When repairing long-service-life industrial equipment whose firmware is frozen, this EPROM keeps original hardware in service without board redesign.
Recommended
Automotive Control Units (Industrial-Temperature Band)
Automotive aftermarket ECUs, ignition controllers, and performance-tuning boards built in the 1990s commonly used 27C512-family EPROMs for fuel and ignition maps. The 27C512A-12I/SO covers the industrial band -40C to +85C, adequate for cabin-mounted electronics, and its 120 ns access time supports real-time lookup of calibration tables during engine cycles. Tuners program a single byte-wide 64K map into the OTP array; the 3-state outputs connect directly to the ECU data bus. Note that underhood locations exceeding +85C require a higher-grade device, so this part is best suited to interior-mounted controllers. For replacement or remanufacturing of these legacy units, the same 28-lead SOIC footprint accepts the full 27C512A speed family without PCB changes.
Recommended
Telecommunications Line Cards and Network Hardware
Telecom line cards, modems, and early networking equipment relied on EPROM-resident code and DSP coefficient tables. The 27C512A-12I/SO's 64K x 8 array holds complete bootstrap code for line-card processors, and its 120 ns access time keeps power-up initialization fast enough for hot-peak traffic requirements. The 25 mA active current is modest across dense shelves containing dozens of cards, and 30 uA standby current suits redundant cards held powered but idle. Its 3-state outputs share the card bus with RAM and peripheral controllers, with /OE timing preventing contention during handoff. For maintaining installed-base telecom racks whose firmware cannot change, this OTP EPROM provides an exact, permanent substitute for discontinued silicon.
Recommended
Test and Measurement Equipment Repair
Oscilloscopes, spectrum analyzers, and bench instruments from the 5V EPROM era store their operating firmware in 27C512-class devices. Repair technicians use the 27C512A-12I/SO to replace corrupted or damaged firmware devices, restoring instruments whose manufacturers no longer supply parts. The device's Auto ID feature aids automated programmers in correctly setting the programming algorithm, reducing the risk of misprogramming during repair. Its industrial temperature rating and CMOS low power suit bench and field instruments alike. Because instrument firmware is fixed and validated, the OTP nature of the part is actually an advantage in repair work: the programmed content cannot be accidentally altered by electrical transients, and the 28-lead SOIC footprint matches the original socket or soldered position directly.
Recommended
Character Generators and Fixed Lookup Tables
Applications such as video character generators, barcode decoders, audio effect tables, and function generators store pure constant data in the 27C512A-12I/SO. Its 65,536-byte capacity holds a full 8x16 font set with multiple code pages, or waveform/sinewave tables with fine resolution. The 120 ns access time allows direct memory-mapped table lookups at video pixel rates when paired with a counter-driven address bus, and the asynchronous interface means no read latency beyond propagation delay. The 3-state outputs permit multiple table devices to share a data bus with simple address decoding. Because table content never changes after characterization, one-time programming carries no lifecycle penalty, and the permanent, non-volatile storage survives years of continuous power cycling.
Recommended
Recommended Products Summary
Engineering reference data for 27C512A-12I/SO β comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | 27C512A-12/SO | 27C512A-15I/SO | 27C512A-20I/SO |
|---|---|---|---|---|
| Package | 28-lead SOIC (SO) | 28-lead SOIC (SO) - same | 28-lead SOIC (SO) - same | 28-lead SOIC (SO) - same |
| Brand | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| Access Time | 120 ns | 120 ns | 150 ns | 200 ns |
| Organization | 64K x 8 | 64K x 8 | 64K x 8 | 64K x 8 |
| Operating Temperature | -40C to +85C | 0C to +70C | -40C to +85C | -40C to +85C |
| Supply Voltage | 4.5V to 5.5V | 4.5V to 5.5V | 4.5V to 5.5V | 4.5V to 5.5V |
| Active / Standby Current | 25 mA / 30 uA | 25 mA / 30 uA | 25 mA / 30 uA | 25 mA / 30 uA |
| Programming Type | OTP (One-Time Programmable) | OTP | OTP | OTP |
Key Differentiators
- Industrial temperature rating for harsh environments (vs 27C512A-12/SO)
- Fastest speed grade in the SOIC industrial family (vs 27C512A-15I/SO)
- CMOS low standby power versus NMOS-era 27512 parts (vs 27C512A-20I/SO)
Design Notes
Never assert /E and /OE on overlapping devices simultaneously - bus contention between the EPROM and a second memory-mapped device can exceed output current ratings. Sequence /OE at least one address-settling time after /E, and keep the /OE trace short to minimize reflected glitches. For mixed 3.3V/5V systems, note that this part drives true 5V output levels, which exceed the absolute maximum of many 3.3V-only inputs; use a level shifter or series resistor network rather than relying on 5V-tolerant claims.
Place 0.1 uF ceramic decoupling capacitors within 5 mm of the VCC (pin 28) and VSS (pin 14) pins to suppress supply transients during address transitions, when CMOS core current peaks. Since the 28-lead SOIC is a surface-mount EPROM, program the device before reflow if your programmer only supports socketed parts, or use a ZIF fixture for post-assembly programming via test pads on A9 and control lines required for Auto ID verification.
The most common failure mode with the 27C512A is substituting a slower speed grade without re-verifying CPU timing: moving from 120 ns to 150 ns or 200 ns parts adds up to 80 ns of address-to-output delay, which can corrupt instruction fetches marginally only at temperature extremes. Recalculate your worst-case access budget (address valid to data valid plus decoder delay) at +85C before using -15 or -20 grades. Also verify the programmer supports the 27C512A algorithm - older programmers set for NMOS 27512 may over-program CMOS parts.
Compliance Information
Legacy EOL part; current distributor listings do not state RoHS/REACH status. Verify compliance by date code with Microchip before use in new RoHS-required designs.
