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Microchip Technology AT27C256R-90RI
- Part No.:
- AT27C256R-90RI
- Manufacturer:
- Microchip Technology
- Category:
- Memory
- Package:
- 28-SOIC (0.342", 8.69mm Width)
- Datasheet:
-
AT27C256R-90RI.pdf
- Description:
- IC EPROM 256KBIT PARALLEL 28SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:3,026
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Product details
Overview
AT27C256R-90RI from Microchip Technology (formerly Atmel) is a 32K × 8-bit one-time programmable EPROM with 45 ns read access time, 5V ±10% supply, and industrial temperature range (–40°C to +85°C). It features dual-line control (CE/OE), CMOS/TTL-compatible I/O, and Rapid™ programming at 100 µs/byte - enabling firmware storage in microcontroller boot systems without wait states.
For engineers reviewing the AT27C256R-90RI datasheet, AT27C256R-90RI pinout, AT27C256R-90RI application, or AT27C256R-90RI equivalent, key selection criteria include verified 45 ns tACC timing, VPP = 12.0 V programming voltage, 100 µA max standby current, JEDEC-standard 28-lead SOIC package, and OTP reliability for fixed-code embedded firmware.
Technical Context
The AT27C256R-90RI implements a CMOS-based OTP EPROM architecture with address decoding for 32K × 8-bit organization, supporting asynchronous parallel read access via A0–A14 address inputs and O0–O7 data outputs. Its two-control-line interface (CE and OE) enables bus contention avoidance in shared-memory systems.
Programming uses a dedicated VPP pin (12.0 ± 0.5 V) with Rapid™ algorithm requiring 100 µs CE pulses and verification loops per byte. Product identification is implemented via A9 high-voltage sensing (11.5–12.5 V) and A0 toggling to select manufacturer (0x1E) or device code (0x8C) bytes.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Memory Size | 256 Kbit (32K × 8) - supports full 8-bit microprocessor data bus without banking. |
| Read Access Time | 45 ns max - eliminates WAIT states on 5 MHz Z80, 8051, or 68K-based systems. |
| Supply Voltage | 5 V ±10% - compatible with standard TTL/CMOS logic rails; no auxiliary supplies needed. |
| Standby Current | 100 µA max - enables low-power retention in battery-backed or intermittent operation. |
| Active Current | 20 mA max at 5 MHz - supports sustained read bursts without thermal derating. |
| Programming Voltage | VPP = 12.0 ± 0.5 V - requires external high-voltage source; not 5 V-only programmable. |
| ESD Protection | 2,000 V HBM - meets industrial handling requirements without additional protection circuitry. |
| Latchup Immunity | 200 mA - prevents destructive latchup during transient overvoltage events. |
Pinout & Package
AT27C256R-90RI is packaged in a 28-lead SOIC (package code "R", JEDEC MS-012AB), 0.330" wide, with 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 (32K depth); TTL/CMOS compatible; driven by MPU address lines. |
| O0–O7 | Data Outputs | 8-bit bidirectional data bus; high-impedance when CE or OE inactive; drives standard TTL loads. |
| CE | Chip Enable | Active-low chip select; enables internal decode and output drivers only when asserted. |
| OE | Output Enable | Active-low output gate; controls data bus drive independently of CE for bus sharing. |
| VPP | Programming Voltage | 12 V input during programming only; must be applied simultaneously with or after VCC. |
| VCC | Power Supply | +5 V supply; powers all logic and memory array; requires 0.1 µF ceramic decoupling. |
| GND | Ground | Signal and power reference; connects to system ground plane for noise immunity. |
| NC | No Connect | Pins 16 and 17 in SOIC are unconnected; must remain floating (no tie to VCC/GND). |
Key Features
| Feature | Design Value |
|---|---|
| Rapid™ Programming Algorithm | 100 µs/byte typical - reduces production programming time vs. legacy EPROMs; includes auto-verify loop. |
| Integrated Product ID Code | Manufacturer ID (0x1E) and Device ID (0x8C) readable via A9/A0 control - enables automated programmer recognition. |
| Dual-Line Control (CE/OE) | Independent chip and output enable - allows interleaved memory access and avoids bus contention in multi-device systems. |
| Industrial Temperature Range | –40°C to +85°C - qualified for use in motor control, PLC, and factory automation environments. |
| JEDEC-Standard SOIC Package | 28-lead, 0.330" wide - ensures compatibility with standard PCB footprints and reflow profiles. |
| CMOS/TTL I/O Compatibility | VIL ≤ 0.8 V, VIH ≥ 2.0 V - interoperates directly with both 5 V CMOS and bipolar TTL logic families. |
Applications
| Industrial PLC Firmware Storage | Legacy Microcontroller Boot ROM |
|---|---|
Use Scenario: Storing fixed ladder logic and I/O mapping firmware in programmable logic controllers deployed in factory environments. IC Role / Device Role / Timing Role: Non-volatile boot memory providing deterministic 45 ns read access to initialization code for 8051 or 80C188-based controllers. Use Value: Eliminates reliance on slow serial EEPROM or external flash; ensures fast, repeatable startup under temperature cycling and EMI stress. | Use Scenario: Holding immutable BIOS or monitor code in retro-computing or instrumentation systems using Z80 or 68000 CPUs. IC Role / Device Role / Timing Role: Parallel-addressed OTP EPROM serving as primary instruction store with no software overhead for memory management. Use Value: Guarantees code integrity across decades; immune to accidental overwrite unlike UV-erasable EPROMs or flash. |
| Automotive Body Control Module | Medical Diagnostic Equipment Bootloader |
Use Scenario: Storing calibration tables and safety-critical configuration data in body control units operating at –40°C to +85°C. IC Role / Device Role / Timing Role: Read-only memory holding static vehicle-specific parameters accessed during power-on self-test (POST). Use Value: Meets AEC-Q100-relevant reliability (2,000 V ESD, 200 mA latchup) without requiring redundant error correction. | Use Scenario: Hosting bootloader firmware in FDA-class II diagnostic devices where firmware tampering must be physically impossible. IC Role / Device Role / Timing Role: One-time-programmable ROM ensuring bootloader authenticity and preventing field modification of critical startup routines. Use Value: Provides hardware-enforced immutability - no software patch, update, or malware can alter stored code post-programming. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar OTP EPROM applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| AM27C256B-90DC | Same 32K×8 OTP EPROM, 45 ns access, but uses 28-pin PDIP (not SOIC); VPP = 12.5 V. | Requires PCB layout change for through-hole mounting; lacks SOIC thermal performance. | Select if legacy through-hole assembly is required and board space permits larger footprint. |
| MX27C256-90PC | Functionally identical timing and pinout, but manufactured by Macronix; same 28-pin SOIC, 45 ns, 5 V supply. | No functional or layout impact; validated drop-in replacement per distributor cross-reference. | Preferred for second-source assurance where Atmel/Microchip supply continuity is constrained. |
Compared with AM27C256B-90DC, AT27C256R-90RI offers surface-mount compatibility and better thermal dissipation; versus MX27C256-90PC, it provides original Atmel qualification data and long-term documentation support - critical for medical and industrial certifications.
Availability
AT27C256R-90RI is available at Aetrix Electronics and suitable for industrial PLC firmware storage, legacy microcontroller boot ROM, and automotive body control module applications requiring stable component supply across extended product lifecycles.
Supply support for AT27C256R-90RI 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 legacy Atmel memory products including the AT27C256R series.
The AT27C256R product line was designed for reliable, low-power, one-time programmable firmware storage in industrial, automotive, and embedded systems where code immutability and deterministic timing are mandatory.
FAQ
What is the maximum allowed VPP voltage for programming the AT27C256R-90RI?
The AT27C256R-90RI requires VPP = 12.0 ± 0.5 V during programming, with absolute maximum rating of +14.0 V. Exceeding 12.5 V risks oxide damage and premature failure. The AT27C256R-90RI datasheet specifies VID (A9 identification voltage) tolerance as 11.5–12.5 V, confirming this window applies to all VPP-related operations including programming and ID read.
Can the AT27C256R-90RI operate with a 3.3 V supply?
No, the AT27C256R-90RI is specified only for 5 V ±10% operation (4.5–5.5 V). Its input thresholds (VIL ≤ 0.8 V, VIH ≥ 2.0 V) and output drive levels (VOH ≥ 2.4 V at –400 µA) assume 5 V rail compliance. Using 3.3 V violates DC operating conditions and will result in undefined read behavior and failed programming verification.
Is the AT27C256R-90RI pin-compatible with the AT27C256R-90PI?
Yes - both AT27C256R-90RI and AT27C256R-90PI share identical 28-pin SOIC (R) and 28-pin PDIP (P) packages respectively, but differ only in temperature grade (industrial –40°C to +85°C for both) and package type. Pin functions, numbering, and electrical characteristics are identical; only mechanical mounting differs.
Does the AT27C256R-90RI support in-system programming?
No, the AT27C256R-90RI requires external high-voltage (12 V) programming equipment and cannot be programmed in-circuit without dedicated VPP routing and isolation. Its Rapid™ algorithm mandates precise VPP timing and voltage control, making true in-system programming impractical without custom hardware support.
What decoupling capacitance is required for stable AT27C256R-90RI operation?
The AT27C256R-90RI requires a minimum 0.1 µF ceramic capacitor between VCC and GND, placed as close as possible to the device pins. For systems with multiple EPROMs, a 4.7 µF bulk electrolytic capacitor is also recommended near the power entry point to suppress ripple-induced timing violations during simultaneous read accesses.
AT27C256R-90RI 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:
- 90 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-90RI FAQ
1.How can I place an order for AT27C256R-90RI through Aetrix?
Please submit a Request for Quotation (RFQ) for AT27C256R-90RI 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-90RI reliable?
The price and inventory of AT27C256R-90RI are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for AT27C256R-90RI is usually 5 days.
3.What payment methods are accepted for AT27C256R-90RI?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for AT27C256R-90RI transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for AT27C256R-90RI?
AT27C256R-90RI orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your AT27C256R-90RI 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-90RI?
For technical support, including AT27C256R-90RI datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your AT27C256R-90RI requirements.
6.How does Aetrix verify that AT27C256R-90RI is sourced from the original manufacturer or authorized distributors?
All AT27C256R-90RI 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-90RI meets industry standards.
7.What is the process for return or replacement of AT27C256R-90RI?
All AT27C256R-90RI units undergo pre-shipment inspection (PSI). If there is an issue with AT27C256R-90RI, 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-90RI part is unused and in its original packaging.
Return procedure for AT27C256R-90RI:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
AT27C256R-90RI Tags
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