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Microchip Technology AT27C256R-45TU
- Part No.:
- AT27C256R-45TU
- Manufacturer:
- Microchip Technology
- Category:
- Memory
- Package:
- 28-TSSOP (0.465", 11.80mm Width)
- Datasheet:
-
AT27C256R-45TU.pdf
- Description:
- IC EPROM 256KBIT PARALLEL 28TSOP
- Quantity:
- Payment:
- Shipping:
Inventory:3,222
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Product details
Overview
AT27C256R-45TU from Microchip Technology (formerly Atmel) is a 32K × 8-bit one-time programmable EPROM with 45 ns read access time, 5V ±10% supply, and JEDEC-standard 28-lead TSOP package. It serves as nonvolatile firmware storage in microprocessor systems, enabling direct byte-access without WAIT states and supporting industrial temperature operation (–40°C to +85°C).
For engineers reviewing the AT27C256R-45TU datasheet, AT27C256R-45TU pinout, AT27C256R-45TU application, or AT27C256R-45TU equivalent, key selection criteria include verified 45 ns tACC timing, VPP-programmable OTP architecture, dual-line control (CE/OE), CMOS/TTL I/O compatibility, and TSOP-28 mechanical footprint compliance.
Technical Context
The AT27C256R-45TU implements a parallel-addressed OTP EPROM architecture with 15 address lines (A0–A14) and 8 bidirectional data outputs (O0–O7). Its two-line enable scheme (CE active-low, OE active-low) enables bus contention avoidance in shared-data-bus systems.
Programming uses Rapid™ algorithm at 100 µs/byte with 12.0 V ±0.5 V on A9 for product identification and 13.0 V ±0.25 V VPP during write cycles. Read-mode operation requires only 5V supply, with standby current ≤100 µA and active current ≤20 mA at 5 MHz.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Memory Size | 32K × 8-bit (262,144 bits), fixed OTP configuration - no erase capability, suitable for final firmware image storage. |
| Read Access Time | 45 ns max (tACC), enabling direct interface with 12–20 MHz microprocessors without wait-state insertion. |
| Supply Voltage | 5V ±10% - compatible with standard TTL/CMOS logic rails; no auxiliary voltage required for read mode. |
| Standby Current | ≤100 µA (ISB1, CMOS CE input) - supports low-power hold states in battery-backed or energy-sensitive systems. |
| Operating Temperature | –40°C to +85°C - qualified for industrial-grade embedded control, instrumentation, and motor drive applications. |
| VPP Programming Voltage | 13.0 V ±0.25 V - requires dedicated programming supply; not used during normal read operation. |
| ESD Protection | 2,000V HBM - enhances robustness during handling and board-level assembly in non-EPA environments. |
Pinout & Package
AT27C256R-45TU is housed in a 28-lead Thin Small Outline Package (TSOP, Type 1), 8.1 mm × 13.7 mm body, 0.55 mm pitch, JEDEC MO-153 compliant. Pin 1 index located at top-left corner with beveled edge marking.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| A0–A14 | Address Inputs | 15-bit parallel address bus; fully decoded to select one of 32,768 bytes - no internal address latching. |
| O0–O7 | Data Outputs | Tri-state CMOS/TTL-compatible outputs; driven only when CE = OE = low - high-impedance otherwise. |
| CE | Chip Enable | Active-low global device select; controls power state transition between active (≤20 mA) and standby (≤100 µA). |
| OE | Output Enable | Active-low output gate; allows multiple devices on same data bus by enabling/disabling drivers independently of CE. |
| VPP | Programming Supply | 13 V input required only during programming; must be applied simultaneously with or after VCC per datasheet safety rule. |
| VCC | Power Supply | +5V main supply; powers all logic and memory array during read and program modes. |
| GND | Ground Reference | Signal and power return; decoupling capacitor (0.1 µF ceramic) required adjacent to pin per layout guideline. |
| NC | No Connect | Pins 1 and 17 in PLCC variant are NC; TSOP variant has no NC pins - all 28 pins assigned per pinout diagram. |
Key Features
| Feature | Design Value |
|---|---|
| Rapid™ Programming Algorithm | 100 µs/byte typical programming time with auto-verify loop - reduces production programming cycle time vs. legacy EPROMs. |
| Integrated Product ID Code | Manufacturer ID (0x1E) and Device Code (0x8C) readable via A9/VH and A0 toggle - enables automated programmer recognition and algorithm selection. |
| Two-Line Control Architecture | Independent CE and OE enables flexible bus arbitration - supports interleaved access and partial-memory disable without external logic. |
| Industrial Temperature Range | –40°C to +85°C operation validated across full speed grade - eliminates derating concerns in factory automation and outdoor equipment. |
| JEDEC-Standard TSOP Package | 28-lead TSOP (Type 1) with 0.55 mm pitch - compatible with standard SMT reflow profiles and automated optical inspection (AOI) fiducials. |
Applications
| Industrial PLC Firmware Storage | Automotive Engine Control Unit (ECU) |
|---|---|
Use Scenario: Storing calibrated lookup tables and boot code in programmable logic controllers deployed in factory-floor environments with wide ambient temperature swings. IC Role / Device Role / Timing Role: Nonvolatile firmware ROM providing deterministic 45 ns read latency to ensure real-time I/O scan cycle integrity. Use Value: Eliminates WAIT states for 16-bit microcontrollers running at 16 MHz, maintaining <100 ns total instruction fetch overhead per opcode. | Use Scenario: Holding ignition timing maps and sensor calibration constants in engine management modules operating under hood temperatures up to +85°C. IC Role / Device Role / Timing Role: OTP EPROM acting as tamper-resistant, field-programmable code repository with guaranteed data retention >10 years. Use Value: Supports rapid ECU reprogramming at service centers using standardized 13 V VPP protocol without requiring UV erasure infrastructure. |
| Medical Diagnostic Equipment Boot ROM | Telecom Line Card Configuration Memory |
Use Scenario: Storing FPGA configuration bitstreams and safety-critical boot firmware in portable ultrasound and patient monitor systems. IC Role / Device Role / Timing Role: Power-on read-only memory delivering verified firmware within 500 ns of VCC stabilization, meeting IEC 62304 startup timing requirements. Use Value: 2,000V HBM ESD rating ensures reliability during clinical handling and ESD-prone hospital environments. | Use Scenario: Holding DSP initialization parameters and hardware revision identifiers in carrier-grade DSLAM and ONU line cards. IC Role / Device Role / Timing Role: Parallel-interface configuration store accessed during FPGA configuration handshake sequence prior to system clock enable. Use Value: Dual CE/OE control allows selective disabling of AT27C256R-45TU while other peripherals remain active on shared data bus. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar OTP EPROM applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| AM27C256B-45DC | Same 32K×8 OTP EPROM, 45 ns access, but in 28-pin PDIP (not TSOP); higher standby current (1 mA vs. 100 µA). | Preferred where through-hole assembly or socket-based prototyping is required; unsuitable for space-constrained SMT designs. | Select AM27C256B-45DC only if PDIP form factor and legacy socket compatibility outweigh TSOP density advantages. |
| MX27C256-45PC | Functionally identical 32K×8 OTP EPROM, 45 ns, but rated only for commercial temp range (0°C to 70°C); no automotive/industrial qualification. | Limited to office equipment or lab instruments with controlled ambient; fails qualification for industrial control or automotive under-hood use. | Choose MX27C256-45PC only for cost-sensitive commercial applications where extended temperature operation is unnecessary. |
Compared with AM27C256B-45DC and MX27C256-45PC, the AT27C256R-45TU uniquely combines TSOP-28 SMT packaging, industrial temperature rating, and 100 µA standby current - making it the sole option for compact, ruggedized, low-power embedded firmware storage.
Availability
AT27C256R-45TU is available at Aetrix Electronics and suitable for industrial PLCs, automotive ECUs, medical diagnostic boot systems, and telecom line card configuration requiring stable component supply across long production lifecycles.
Supply support for AT27C256R-45TU 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 delivers cost-effective, pin-verified OTP EPROM solutions targeting firmware storage in resource-constrained industrial, automotive, and medical embedded systems where UV-erasable EPROMs are impractical.
FAQ
What is the maximum allowed VPP voltage during programming of the AT27C256R-45TU?
The AT27C256R-45TU requires VPP = 13.0 V ± 0.25 V during programming, with absolute maximum rating of +14.0 V on A9 and VPP pins. Exceeding 13.25 V risks over-stress and potential latent failure; the device's Rapid™ algorithm relies on precise VPP regulation to achieve 100 µs/byte programming. Always verify VPP stability with oscilloscope before initiating AT27C256R-45TU programming sequences.
Does the AT27C256R-45TU support read operations at 3.3V supply?
No, the AT27C256R-45TU is specified exclusively for 5V ±10% operation (4.5V to 5.5V). Its input thresholds (VIL ≤ 0.8V, VIH ≥ 2.0V) and output drive strength (VOL ≤ 0.4V at 2.1 mA) are designed for 5V TTL/CMOS compatibility. Attempting 3.3V read operation results in undefined outputs, excessive ICC, and potential latch-up - the AT27C256R-45TU does not meet 3.3V logic family specifications.
Can the AT27C256R-45TU be reprogrammed after initial programming?
No, the AT27C256R-45TU is a one-time programmable (OTP) EPROM. Its floating-gate memory cells undergo irreversible oxide breakdown during programming, preventing electrical erasure. Unlike UV-erasable EPROMs, the AT27C256R-45TU lacks a quartz window and cannot be reset - each byte written remains permanently stored unless physically destroyed.
What decoupling capacitors are required for stable AT27C256R-45TU operation?
The AT27C256R-45TU requires a 0.1 µF ceramic capacitor placed between VCC and GND, mounted as close as possible to the device's pins to suppress high-frequency transients during CE transitions. For multi-device EPROM arrays, add a 4.7 µF bulk electrolytic capacitor near the power entry point. These values are mandated in the "System Considerations" section of the AT27C256R-45TU datasheet to prevent non-conformance due to supply rail excursions.
How is the manufacturer and device identification code read from the AT27C256R-45TU?
The AT27C256R-45TU identification code is accessed by asserting CE = OE = VIL, setting A9 = 12.0 V ±0.5 V (VH), holding A1–A14 = VIL, and toggling A0: low (VIL) reads Manufacturer ID (0x1E), high (VIH) reads Device Code (0x8C). This two-byte code is electrically sensed by programmers to auto-select correct algorithms - no external hardware modification is needed to read the AT27C256R-45TU ID.
AT27C256R-45TU Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Microchip Technology
- Series:
- -
- Package/Case:
- 28-TSSOP (0.465", 11.80mm Width)
- Packaging:
- Tray
- 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:
- 45 ns
- Voltage - Supply:
- 4.5V ~ 5.5V
- Operating Temperature:
- -40°C ~ 85°C (TC)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 28-TSOP
AT27C256R-45TU FAQ
1.How can I place an order for AT27C256R-45TU through Aetrix?
Please submit a Request for Quotation (RFQ) for AT27C256R-45TU 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-45TU reliable?
The price and inventory of AT27C256R-45TU are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for AT27C256R-45TU is usually 5 days.
3.What payment methods are accepted for AT27C256R-45TU?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for AT27C256R-45TU transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for AT27C256R-45TU?
AT27C256R-45TU orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your AT27C256R-45TU 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-45TU?
For technical support, including AT27C256R-45TU datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your AT27C256R-45TU requirements.
6.How does Aetrix verify that AT27C256R-45TU is sourced from the original manufacturer or authorized distributors?
All AT27C256R-45TU 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-45TU meets industry standards.
7.What is the process for return or replacement of AT27C256R-45TU?
All AT27C256R-45TU units undergo pre-shipment inspection (PSI). If there is an issue with AT27C256R-45TU, 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-45TU part is unused and in its original packaging.
Return procedure for AT27C256R-45TU:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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