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Microchip Technology AT27C256R-55RI
- Part No.:
- AT27C256R-55RI
- Manufacturer:
- Microchip Technology
- Category:
- Memory
- Package:
- 28-SOIC (0.342", 8.69mm Width)
- Datasheet:
-
AT27C256R-55RI.pdf
- Description:
- IC EPROM 256KBIT PARALLEL 28SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:2,800
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Product details
Overview
AT27C256R-55RI from Microchip Technology (formerly Atmel) is a 256K-bit (32K × 8) one-time programmable EPROM designed for nonvolatile firmware storage in microprocessor systems. It delivers 55 ns read access time, operates on a single 5V ±10% supply, and supports industrial temperature range (–40°C to +85°C) in 28-lead SOIC package. Used for boot code, configuration data, and BIOS storage where reprogrammability is unnecessary but reliability and fast readout are critical.
For engineers reviewing the AT27C256R-55RI datasheet, AT27C256R-55RI pinout, AT27C256R-55RI application, or AT27C256R-55RI equivalent, key selection criteria include verified 55 ns tACC timing, industrial-grade standby current ≤100 µA, dual-line control (CE/OE), OTP security, and JEDEC-standard SOIC-28 footprint compatibility with legacy 27C256 designs.
Technical Context
The AT27C256R-55RI implements a CMOS-based OTP EPROM architecture with address decoding for 15-bit address space (A0–A14), 8-bit parallel data bus (O0–O7), and two independent enable controls (CE and OE) enabling flexible bus interface without contention. Its Rapid™ programming algorithm uses 100 µs/byte CE pulses at VPP = 13.0 V for reliable one-time write.
It features integrated product identification (Manufacturer ID = 0x1E, Device ID = 0x8C) accessed via A9 high-voltage mode (12.0 V), and includes ESD protection (2,000 V HBM) and latchup immunity (200 mA). The device requires no external clock and operates asynchronously with TTL/CMOS-compatible I/O levels.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Memory Size | 256 Kbit (32K × 8) - provides sufficient space for firmware images up to 32 KB in embedded boot ROM applications |
| Read Access Time (tACC) | 55 ns max - enables direct connection to 12–15 MHz microprocessors without wait states |
| Supply Voltage | 5 V ±10% - compatible with standard logic rails; eliminates need for auxiliary voltage regulators |
| Standby Current (ISB1) | 100 µA max - ensures ultra-low power retention during system sleep modes |
| Active Current (ICC) | 20 mA max at 5 MHz - supports sustained read bursts without thermal derating in compact PCB layouts |
| Operating Temperature | –40°C to +85°C - qualified for industrial control, motor drives, and factory automation environments |
| Programming Voltage (VPP) | 13.0 V ±0.25 V - requires dedicated programming hardware; prevents accidental writes during normal operation |
Pinout & Package
AT27C256R-55RI is packaged in a 28-lead SOIC (Small Outline Integrated Circuit), 0.330" wide, JEDEC MS-012 compliant, with 1.27 mm pitch and gull-wing leads. Pin 1 marked by index notch; pin 1 is A12 (not NC).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| A0–A14 | Address Inputs | 15-bit address bus selecting one of 32,768 bytes; TTL/CMOS compatible, driven directly from MPU address lines |
| O0–O7 | Data Outputs | 8-bit bidirectional data bus (output only); high-impedance when CE or OE inactive; drives standard TTL loads |
| CE | Chip Enable | Active-low global chip select; must be low before OE to avoid bus contention; controls VCC current draw |
| OE | Output Enable | Active-low output gate; allows multiple devices on same data bus; float timing tDF = 25 ns max |
| VPP | Programming Voltage | 13 V input required only during programming; must be applied simultaneously with or after VCC |
| VCC | Power Supply | +5 V supply; decoupling requires 0.1 µF ceramic capacitor placed within 5 mm of pins 14 and 28 |
| GND | Ground | Reference for all signals and supplies; shared return path for ICC and IPP currents |
Key Features
| Feature | Design Value |
|---|---|
| Rapid™ Programming Algorithm | 100 µs/byte typical programming time with auto-verify loop - reduces production programming cycle time by >5× vs. legacy EPROMs |
| Integrated Product ID Code | Manufacturer ID (0x1E) and Device ID (0x8C) accessible via A9 = 12 V - enables automated programmer validation and BOM traceability |
| Two-Line Control Architecture | Independent CE and OE inputs - permits partial decoding and memory-mapped I/O without external logic gates |
| High-Reliability Process | 2,000 V HBM ESD rating and 200 mA latchup immunity - ensures robustness in handling and board-level ESD events |
| JEDEC Standard Packages | SOIC-28 footprint matches industry-standard 27C256 replacements - enables drop-in upgrade without PCB redesign |
Applications
| Industrial PLC Firmware Storage | Legacy Embedded Boot ROM |
|---|---|
Use Scenario: Storing fixed ladder logic and I/O mapping tables in programmable logic controllers deployed in factory environments with wide temperature swings and electrical noise. IC Role / Device Role / Timing Role: Nonvolatile boot memory providing immediate instruction fetch upon power-up; 55 ns tACC ensures deterministic scan-cycle timing. Use Value: Eliminates reliance on slow serial EEPROM or external flash; guarantees zero-latency execution of safety-critical startup routines. |
Use Scenario: Holding immutable BIOS or bootloader code in legacy x86 or 68K-based industrial computers where firmware updates are rare and security against accidental overwrite is essential. IC Role / Device Role / Timing Role: Primary ROM device mapped to upper memory space; CE/OE dual-control prevents bus conflicts during DMA transfers. Use Value: OTP nature prevents field corruption; industrial temp rating ensures reliability across uncontrolled cabinet temperatures. |
| Automotive Instrument Cluster Calibration Data | Medical Device Configuration Memory |
Use Scenario: Storing calibrated sensor offsets and display lookup tables in automotive dashboards operating across –40°C to +85°C ambient conditions. IC Role / Device Role / Timing Role: Read-only configuration store accessed during power-on self-test; VPP isolation prevents unintended writes during vehicle cranking transients. Use Value: Immunity to radiation-induced bit flips and voltage glitches ensures calibration integrity over 15+ year service life. |
Use Scenario: Retaining FDA-approved device parameters (e.g., infusion pump flow rates, defibrillator energy settings) in Class II medical electronics requiring tamper-proof memory. IC Role / Device Role / Timing Role: Secure, nonvolatile parameter repository; OTP guarantee ensures configuration cannot be altered post-certification. Use Value: Meets IEC 62304 software lifecycle requirements for permanent configuration storage without runtime write capability. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar OTP EPROM applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| AT27C256R-55PI | Same die, PDIP-28 package (0.600" width) instead of SOIC-28; higher thermal resistance and larger footprint | Suitable for through-hole prototyping or legacy board repair; not recommended for new SMT designs | Select only if existing PCB layout uses PDIP socket or manual assembly is required |
| AM27C256-55DC | AMD second-source part; identical 55 ns timing and pinout, but lower ESD rating (1,500 V) and no integrated ID code | Lacks manufacturer/device ID verification - incompatible with automated programming equipment requiring ID handshake | Acceptable for cost-sensitive, low-volume builds where ID-based validation is not mandated |
Compared with AT27C256R-55RI, the AT27C256R-55PI offers identical electrical performance but requires through-hole assembly and lacks space efficiency, while AM27C256-55DC sacrifices programmability assurance and ESD robustness for marginal cost reduction - making AT27C256R-55RI optimal for new industrial SMT designs requiring traceability and reliability.
Availability
AT27C256R-55RI is available at Aetrix Electronics and suitable for industrial control systems, legacy embedded boot applications, and medical device configuration storage requiring stable component supply across extended product lifecycles.
Supply support for AT27C256R-55RI includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.
Manufacturer
Microchip Technology acquired Atmel in 2016 and maintains full support for the legacy AT27C series. The company specializes in secure, reliable microcontrollers and nonvolatile memory solutions for industrial and automotive markets.
The AT27C256R product line was developed to provide pin- and function-compatible OTP EPROM alternatives to aging 27C256 devices, emphasizing industrial temperature operation, rapid programming, and integrated identification for automated manufacturing.
FAQ
What is the maximum read access time specified for AT27C256R-55RI?
The AT27C256R-55RI has a maximum read access time (tACC) of 55 ns under industrial temperature conditions (–40°C to +85°C) and VCC = 5 V ±10%. This value is guaranteed across the full operating range and is measured from address valid to valid data output with both CE and OE asserted low. The "-55" suffix explicitly denotes this speed grade.
Does AT27C256R-55RI support in-system programming?
No, AT27C256R-55RI does not support in-system programming. It is a one-time programmable (OTP) EPROM requiring external UV-erasable or high-voltage programming equipment. Programming necessitates VPP = 13.0 V applied to pin 1, simultaneous with VCC, and is performed off-board using certified programmers such as BP Microsystems or Xeltek units.
What package type is used by AT27C256R-55RI?
AT27C256R-55RI uses a 28-lead SOIC (Small Outline Integrated Circuit) package, 0.330" wide, per JEDEC MS-012. It is surface-mount compatible with standard reflow profiles and has gull-wing leads spaced at 1.27 mm pitch. Pin 1 is located at the index notch end and corresponds to A12.
Can AT27C256R-55RI be used as a direct replacement for older AT27C256 versions?
Yes, AT27C256R-55RI is functionally and pin-compatible with earlier AT27C256 variants (e.g., AT27C256-55PC) in SOIC-28 configuration. It retains identical pinout, timing, and electrical specifications while adding Rapid™ programming and integrated ID code - making it a validated drop-in upgrade for legacy designs.
What is the purpose of the VPP pin on AT27C256R-55RI?
The VPP pin on AT27C256R-55RI supplies 13.0 V programming voltage during OTP write operations. It is unused during normal read mode (connected to VCC) and must never float. During programming, VPP must be applied simultaneously with or after VCC and removed simultaneously with or before VCC to prevent latchup or data corruption.
AT27C256R-55RI Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Microchip Technology
- Series:
- -
- Package/Case:
- 28-SOIC (0.342", 8.69mm Width)
- Packaging:
- Tube
- Product Status:
- Obsolete
- Programmable:
- Not Verified
- Memory Type:
- Non-Volatile
- Memory Format:
- EPROM
- Technology:
- EPROM - OTP
- Memory Size:
- 256Kbit
- Memory Organization:
- 32K x 8
- Memory Interface:
- Parallel
- Clock Frequency:
- -
- Write Cycle Time - Word, Page:
- -
- Access Time:
- 55 ns
- Voltage - Supply:
- 4.5V ~ 5.5V
- Operating Temperature:
- -40°C ~ 85°C (TC)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 28-SOIC
AT27C256R-55RI FAQ
1.How can I place an order for AT27C256R-55RI through Aetrix?
Please submit a Request for Quotation (RFQ) for AT27C256R-55RI on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.
2.Are the price and stock information for AT27C256R-55RI reliable?
The price and inventory of AT27C256R-55RI are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for AT27C256R-55RI is usually 5 days.
3.What payment methods are accepted for AT27C256R-55RI?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for AT27C256R-55RI transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for AT27C256R-55RI?
AT27C256R-55RI orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your AT27C256R-55RI order is processed, you will receive an email with the shipment details and tracking number.
Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.
5.How can I obtain technical support or documentation for AT27C256R-55RI?
For technical support, including AT27C256R-55RI datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your AT27C256R-55RI requirements.
6.How does Aetrix verify that AT27C256R-55RI is sourced from the original manufacturer or authorized distributors?
All AT27C256R-55RI products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that AT27C256R-55RI meets industry standards.
7.What is the process for return or replacement of AT27C256R-55RI?
All AT27C256R-55RI units undergo pre-shipment inspection (PSI). If there is an issue with AT27C256R-55RI, returns or replacements are accepted under the following conditions:
1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.
2.The issue is reported within 90 days of delivery.
3.The AT27C256R-55RI part is unused and in its original packaging.
Return procedure for AT27C256R-55RI:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
AT27C256R-55RI Tags
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