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Microchip Technology AT27C256R-45JU
- Part No.:
- AT27C256R-45JU
- Manufacturer:
- Microchip Technology
- Category:
- Memory
- Package:
- 32-LCC (J-Lead)
- Datasheet:
-
AT27C256R-45JU.pdf
- Description:
- IC EPROM 256KBIT PARALLEL 32PLCC
- Quantity:
- Payment:
- Shipping:
Inventory:999
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Product details
Overview
AT27C256R-45JU from Microchip Technology (formerly Atmel) is a 32K × 8-bit, one-time programmable EPROM with 45ns read access time, 5V ±10% supply operation, and JEDEC-standard 32-lead PLCC packaging. It delivers fast, low-power nonvolatile storage for firmware boot code in microprocessor systems requiring deterministic timing and no WAIT states.
For engineers reviewing the AT27C256R-45JU datasheet, AT27C256R-45JU pinout, AT27C256R-45JU application, or AT27C256R-45JU equivalent, this device serves as a legacy-compatible OTP memory solution for industrial control, embedded instrumentation, and automotive ECU boot ROM where reprogrammability is not required but reliability and speed are critical.
Technical Context
The AT27C256R-45JU implements a CMOS-based OTP EPROM architecture with dual-line control (CE/OE), enabling bus contention avoidance in shared-memory systems. Its rapid programming algorithm uses 100µs/byte CE pulses at VPP = 12.0V and VCC = 6.5V, followed by verify cycles - all executed without external high-voltage generators.
It features integrated product identification (manufacturer code 0x1E, device code 0x8C) readable via A9 = 12.0V and A0 toggling, supporting automated programming equipment recognition. The device operates across -40°C to +85°C with 2,000V HBM ESD protection and 200mA latchup immunity, meeting industrial reliability requirements.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Memory size | 32K × 8-bit (262,144 bits) - supports full firmware image storage for 8-bit/16-bit MCUs without external paging logic |
| Read access time | 45ns max - eliminates WAIT states on 5MHz Z80, 8086, and 68000-based systems |
| Supply voltage | 5V ±10% - compatible with standard TTL/CMOS logic rails; no auxiliary voltage required in read mode |
| Active current | 20mA max at 5MHz - enables low-thermal-load integration in dense PCB layouts |
| Standby current | 100µA max - supports power-sensitive applications during processor sleep modes |
| Programming voltage | VPP = 12.0V ±0.5V - requires dedicated programming hardware; not supported in-system |
| Operating temperature | -40°C to +85°C - qualified for industrial-grade embedded control environments |
Pinout & Package
AT27C256R-45JU is supplied in a 32-lead plastic J-leaded chip carrier (PLCC), JEDEC MS-016 variation AE compliant, with 1.27mm pitch and 14.86mm × 12.32mm body dimensions. Pin 1 identifier located at top-left corner (notch side).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| A0–A14 | Address inputs | 15-bit address bus interface; selects one of 32,768 bytes; TTL/CMOS-compatible thresholds |
| O0–O7 | Data outputs | 8-bit bidirectional data bus output; active-low OE-controlled; VOH ≥2.4V @ -400µA |
| CE | Chip enable | Primary device select; must be low for read or program; controls VPP path during programming |
| OE | Output enable | Secondary output gate; allows CE-driven standby while maintaining bus isolation |
| VPP | Programming voltage | 12.0V input during programming only; must be applied simultaneously with or after VCC |
| VCC | Power supply | 5V ±10% main supply; powers core logic and I/O buffers in read/standby modes |
| GND | Ground reference | Signal and power return; requires local 0.1µF ceramic decoupling per device |
| NC | No connect | Pins 1 and 17 in PLCC package - physically present but internally unconnected; must remain floating |
Key Features
| Feature | Design Value |
|---|---|
| Rapid programming algorithm | 100µs/byte typical programming time with auto-verify loop - reduces production programming cycle time by >5× vs conventional EPROMs |
| Integrated product ID code | Manufacturer ID (0x1E) and device ID (0x8C) accessible via A9/VH and A0 toggle - enables automatic algorithm selection in universal programmers |
| Two-line control architecture | Independent CE and OE pins - permits flexible memory mapping and prevents bus contention during partial decode |
| High-reliability process | 2,000V HBM ESD rating and 200mA latchup immunity - ensures robustness in noisy industrial environments |
| Green packaging option | Pb/halide-free PLCC (JU suffix) - complies with RoHS Directive 2011/65/EU without derating performance |
Applications
| Industrial PLC Firmware Storage | Automotive ECU Boot ROM |
|---|---|
Use Scenario: Storing fixed startup firmware for programmable logic controllers operating in factory-floor environments with wide temperature swings and electrical noise. IC Role / Device Role / Timing Role: Nonvolatile boot memory providing deterministic 45ns read access to initialization code for 8051 or ColdFire-based controllers. Use Value: Eliminates boot latency from mass storage; withstands 85°C ambient and 200mA transient currents without corruption. |
Use Scenario: Holding immutable bootloader code in engine control units where field updates are prohibited and failure modes must be strictly controlled. IC Role / Device Role / Timing Role: One-time programmable ROM ensuring firmware integrity; CE/OE dual-control prevents accidental overwrites during CAN diagnostics. Use Value: Guarantees zero risk of runtime corruption; 2,000V ESD protection survives vehicle-level ISO 10605 testing. |
| Medical Instrument Bootloader | Legacy Computer BIOS Storage |
Use Scenario: Securing certified boot routines in Class II medical devices where regulatory validation requires immutable firmware images. IC Role / Device Role / Timing Role: OTP EPROM storing FDA-cleared initialization sequences; accessed directly by x86-compatible reset vector logic. Use Value: Meets IEC 62304 software lifecycle requirements for "no change after release"; no flash wear-out concerns. |
Use Scenario: Replacing obsolete 27C256 EPROMs in retro-computing restoration projects and industrial PC motherboards. IC Role / Device Role / Timing Role: Drop-in replacement for 27C256 with identical pinout and 45ns timing - supports original ISA bus timing budgets. Use Value: Maintains compatibility with vintage 1980s–1990s system designs without layout modification or timing recalculations. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar OTP EPROM applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| AT27C256R-45PU | Same die, 28-lead PDIP package (0.600" width); 45ns access; identical DC/AC specs | Through-hole assembly; larger footprint; no lead coplanarity concerns | Select for legacy wave-soldered boards or prototyping where PLCC socketing is unavailable |
| MX27C256 (Macronix) | 45ns access; same 32K×8 organization; requires VPP = 12.5V; slightly higher ICC (25mA) | Second-source availability; different ID code structure; not pin-identical in PLCC variant | Use when long-term supply continuity is prioritized over Atmel-specific programming tool support |
Compared with AT27C256R-45PU and MX27C256, the AT27C256R-45JU offers superior board-area efficiency in surface-mount designs and guaranteed compatibility with Atmel-certified programming algorithms, making it optimal for new industrial PCBs where space and toolchain alignment matter.
Availability
AT27C256R-45JU is available at Aetrix Electronics and suitable for industrial PLCs, automotive ECUs, medical instrument bootloaders, and legacy computer restoration projects requiring stable component supply and long-lifecycle support.
Supply support for AT27C256R-45JU 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 technical and manufacturing continuity for legacy Atmel memory products. The company specializes in secure, reliable microcontrollers and nonvolatile memory solutions for industrial and automotive markets.
The AT27C256R belongs to Atmel's OTP EPROM product line, designed specifically for applications demanding firmware immutability, deterministic timing, and high-temperature reliability - particularly in safety-critical and long-lifecycle embedded systems.
FAQ
What is the maximum operating temperature range for the AT27C256R-45JU?
The AT27C256R-45JU is rated for industrial operation from -40°C to +85°C. This range is validated per JEDEC JESD22-A108 and applies to both read and standby modes. Programming must occur at TA = 25°C ±5°C, as specified in the AC programming characteristics table. The AT27C256R-45JU does not support automotive-grade (-40°C to +125°C) operation - that capability is reserved for the AT27C256R-45AU variant.
Can the AT27C256R-45JU be programmed in-circuit?
No, the AT27C256R-45JU cannot be programmed in-circuit. It requires VPP = 12.0V ±0.5V applied externally during programming, which is incompatible with standard 5V system rails. Programming must be performed using a dedicated EPROM programmer that supports the rapid 100µs CE-pulse algorithm and product ID verification. The AT27C256R-45JU has no internal charge pump or ISP capability.
What decoupling capacitors are required for stable operation of the AT27C256R-45JU?
Each AT27C256R-45JU requires a 0.1µF high-frequency ceramic capacitor placed between VCC and GND, mounted as close as possible to the device pins. For arrays of multiple AT27C256R-45JU devices, a 4.7µF bulk electrolytic capacitor must also be added near the power entry point. These values are specified in the "System considerations" section and prevent transient-induced non-conformance during CE switching.
Does the AT27C256R-45JU support byte-level programming?
Yes, the AT27C256R-45JU supports byte-level programming via its rapid algorithm: each address is programmed individually with a 100µs CE pulse, then verified before advancing. The device does not support page or sector programming - every byte must be addressed and verified separately. This ensures precise firmware image control but increases total programming time linearly with data size.
How is the product identification code read from the AT27C256R-45JU?
The AT27C256R-45JU product identification code is read by setting A9 to VH = 12.0V (while holding A1–A14 low), then toggling A0: low (VIL) returns the manufacturer ID (0x1E), and high (VIH) returns the device ID (0x8C). All other address lines must be held low, and VCC must be at 6.5V ±0.25V. This mode is defined in Table 5-1 as "Product identification" and requires a high-voltage capable test setup.
AT27C256R-45JU Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Microchip Technology
- Series:
- -
- Package/Case:
- 32-LCC (J-Lead)
- Packaging:
- Tube
- Product Status:
- Active
- Programmable:
- 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:
- 45 ns
- Voltage - Supply:
- 4.5V ~ 5.5V
- Operating Temperature:
- -40°C ~ 85°C (TC)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 32-PLCC (13.97x11.43)
AT27C256R-45JU FAQ
1.How can I place an order for AT27C256R-45JU through Aetrix?
Please submit a Request for Quotation (RFQ) for AT27C256R-45JU 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-45JU reliable?
The price and inventory of AT27C256R-45JU are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for AT27C256R-45JU is usually 5 days.
3.What payment methods are accepted for AT27C256R-45JU?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for AT27C256R-45JU transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for AT27C256R-45JU?
AT27C256R-45JU orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your AT27C256R-45JU 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-45JU?
For technical support, including AT27C256R-45JU datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your AT27C256R-45JU requirements.
6.How does Aetrix verify that AT27C256R-45JU is sourced from the original manufacturer or authorized distributors?
All AT27C256R-45JU 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-45JU meets industry standards.
7.What is the process for return or replacement of AT27C256R-45JU?
All AT27C256R-45JU units undergo pre-shipment inspection (PSI). If there is an issue with AT27C256R-45JU, 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-45JU part is unused and in its original packaging.
Return procedure for AT27C256R-45JU:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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