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Microchip Technology AT27C256R-70RU
- Part No.:
- AT27C256R-70RU
- Manufacturer:
- Microchip Technology
- Category:
- Memory
- Package:
- 28-SOIC (0.342", 8.69mm Width)
- Datasheet:
-
AT27C256R-70RU.pdf
- Description:
- IC EPROM 256KBIT PARALLEL 28SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:1,636
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Product details
Overview
AT27C256R-70RU from Microchip Technology (formerly Atmel) is a 32K × 8-bit one-time programmable EPROM (OTP EPROM) optimized for fast read access and low-power embedded firmware storage. It operates on a single 5V ±10% supply, delivers 70 ns address-to-output delay (tACC), draws ≤100 µA standby current, and supports industrial temperature range (–40°C to +85°C). It is used in microcontroller boot code storage where non-volatility, pin-compatible legacy replacement, and elimination of WAIT states are critical.
For engineers reviewing the AT27C256R-70RU datasheet, AT27C256R-70RU pinout, AT27C256R-70RU application, or AT27C256R-70RU equivalent, key selection criteria include verified 70 ns read timing, 28-lead SOIC (28R) green package compliance, rapid 100 µs/byte programming, CMOS/TTL I/O compatibility, and dual-line control (CE/OE) architecture for bus contention management.
Technical Context
The AT27C256R-70RU implements a parallel-addressed OTP EPROM architecture with 15 address lines (A0–A14) and 8 bidirectional data outputs (O0–O7), controlled exclusively by CE and OE signals-no write enable or byte-select logic. Its internal rapid programming algorithm uses 13.0 V VPP and 6.5 V VCC during programming, with strict sequencing requirements (VCC applied before/with VPP).
It features integrated product identification (Manufacturer ID = 0x1E, Device ID = 0x8C) accessed via A9 high-voltage mode (11.5–12.5 V), enabling automated programmer recognition. Absolute maximum ratings include –2.0 V to +7.0 V on all pins except A9 (–2.0 V to +14.0 V) and VPP (–2.0 V to +14.0 V), with 2,000 V HBM ESD protection and 200 mA latchup immunity.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Memory Size | 32K × 8 bits (262,144-bit OTP EPROM) |
| Read Access Time (tACC) | 70 ns max - enables direct interface with 14 MHz Z80 or 8 MHz 8086 without WAIT states |
| Supply Voltage | 5 V ±10% - single-rail operation compatible with legacy 5V logic families |
| Standby Current (ISB1) | 100 µA max - supports low-power hold modes in battery-backed systems |
| Active Current (ICC) | 20 mA max at 5 MHz - defines power budget for sustained read bursts |
| Programming Speed | 100 µs/byte typical - reduces firmware update time in production programming |
| Operating Temperature | –40°C to +85°C - qualified for industrial-grade embedded control environments |
| Package | 28-lead SOIC (28R), Pb/halide-free - RoHS-compliant surface-mount footprint |
Pinout & Package
AT27C256R-70RU is supplied in a 28-lead plastic gull-wing small outline integrated circuit (SOIC) package per JEDEC MS-012, body width 0.330", lead pitch 1.27 mm. Dimensions: 18.0–18.5 mm length × 11.7–12.5 mm width × 2.39–2.79 mm height.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| A0–A14 | Address Inputs | 15-bit address bus interface; latched on CE/OE assertion for memory location selection |
| O0–O7 | Data Outputs | 8-bit bidirectional data bus; high-impedance when CE=VIH or OE=VIH |
| CE | Chip Enable | Primary device select; must be VIL for read/program; controls VCC current draw and output drive |
| OE | Output Enable | Secondary output gate; allows CE-controlled standby while permitting data reads without bus contention |
| VPP | Programming Voltage | 13.0 V input required only during programming; must be sequenced after VCC and decoupled with 0.1 µF capacitor |
| VCC | Power Supply | 5 V ±10% main supply; powers logic and output drivers; requires 0.1 µF ceramic + 4.7 µF bulk decoupling |
| GND | Ground Reference | Signal and power return path; shared with system ground plane for noise control |
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 conventional EPROMs |
| Integrated Product ID Code | Manufacturer ID (0x1E) and Device ID (0x8C) readable via A9 high-voltage mode - enables automatic algorithm selection in universal programmers |
| Two-Line Control Architecture | Dedicated CE and OE inputs - eliminates need for external bus transceivers or glue logic in microprocessor bus interfaces |
| CMOS/TTL Input/Output Compatibility | VIL ≤0.8 V, VIH ≥2.0 V, VOL ≤0.4 V, VOH ≥2.4 V - interoperable with both 5V CMOS and bipolar TTL systems without level shifters |
| Green (Pb/Halide-Free) Packaging | RoHS-compliant 28R SOIC package - meets environmental compliance requirements for industrial and medical equipment |
Applications
| Industrial PLC Firmware Storage | Legacy Microprocessor Boot ROM |
|---|---|
Use Scenario: Storing fixed ladder logic and I/O configuration in programmable logic controllers deployed in factory automation cabinets. IC Role / Device Role / Timing Role: Non-volatile boot memory providing deterministic 70 ns read latency to ensure real-time scan cycle timing integrity. Use Value: Eliminates WAIT states on 80C188EB-based controllers, maintaining 100 µs scan cycle budgets without CPU clock scaling. | Use Scenario: Holding BIOS and peripheral initialization code in retro-computing restoration projects using Z80 or 8086-based S-100 bus systems. IC Role / Device Role / Timing Role: Pin-compatible OTP EPROM replacement for obsolete 27256 devices, retaining original board layout and timing margins. Use Value: Enables drop-in replacement with identical 28-pin SOIC footprint and verified 70 ns tACC, avoiding PCB redesign. |
| Medical Device Calibration Data | Automotive ECU Configuration ROM |
Use Scenario: Storing factory-calibrated sensor offset/gain coefficients in portable ultrasound transducer modules. IC Role / Device Role / Timing Role: Tamper-proof, radiation-tolerant firmware storage accessed during power-on self-test (POST) sequence. Use Value: 2,000 V ESD protection and –40°C to +85°C operation ensure reliability in handheld clinical environments with frequent static discharge events. | Use Scenario: Holding engine mapping tables and CAN protocol stack initialization parameters in Tier-1 automotive body control modules. IC Role / Device Role / Timing Role: Read-only configuration store accessed during cold start before CAN communication initialization. Use Value: 100 µA max standby current minimizes battery drain during vehicle sleep mode, extending parasitic draw below 20 µA threshold. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar OTP EPROM applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| AT27C256R-70PU | Same die, identical AC/DC specs, but in 28-lead PDIP (28P6) package instead of SOIC | Through-hole mounting; no reflow compatibility; higher profile; suitable for prototyping or legacy through-hole boards | Select when mechanical fit or hand-soldering is required; not for automated SMT assembly |
| AT27C256R-70TU | Same die, identical timing and electrical specs, but in 28-lead TSOP (28T) package | Thinner profile (1.20 mm max height), smaller footprint (13.4 × 8.0 mm), better thermal dissipation for dense layouts | Select for space-constrained designs requiring lowest profile and highest board density |
Compared with AT27C256R-70PU (PDIP) and AT27C256R-70TU (TSOP), the AT27C256R-70RU (SOIC) offers optimal balance of SMT manufacturability, thermal performance, and legacy board compatibility - its 0.330" width matches common 28-pin socket footprints while supporting full reflow profiles.
Availability
AT27C256R-70RU is available at Aetrix Electronics and suitable for industrial PLC firmware storage, legacy microprocessor boot ROM, and medical device calibration data applications requiring stable component supply across extended product lifecycles.
Supply support for AT27C256R-70RU 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 EPROM products including the AT27C256R series.
The AT27C256R product line was designed specifically for cost-sensitive, high-reliability embedded systems requiring non-volatile firmware storage with guaranteed read timing and long-term data retention - targeting industrial control, instrumentation, and retro-computing markets.
FAQ
What is the maximum operating temperature range for the AT27C256R-70RU?
The AT27C256R-70RU is rated for industrial temperature operation from –40°C to +85°C. This range is confirmed in the "Operating Modes" and "Ordering Information" sections of the official datasheet (0014M–EPROM–12/07), and applies specifically to the RU suffix variant in the 28R SOIC package. It does not support the automotive range (–40°C to +125°C), which is designated by the 'A' suffix (e.g., AT27C256R-70RA).
Does the AT27C256R-70RU require a separate programming voltage during normal operation?
No. The AT27C256R-70RU requires only a single 5 V ±10% supply (VCC) for normal read operation. The 13.0 V VPP programming voltage is needed exclusively during programming and must be applied only after VCC is stable, with strict sequencing per datasheet Section 15. During read mode, VPP is tied to VCC and draws no additional current beyond ICC and ISB specifications.
Is the AT27C256R-70RU pin-compatible with the original AT27C256B or AT27C256?
Yes. The AT27C256R-70RU maintains identical pinout, timing, and DC characteristics with the earlier AT27C256 and AT27C256B versions. All share the same 28-pin SOIC (28R) pin configuration, address/data/control signal mapping, and functional behavior - making it a direct drop-in replacement for legacy designs without layout changes.
What decoupling capacitors are required for stable operation of the AT27C256R-70RU?
The AT27C256R-70RU requires two decoupling capacitors: a 0.1 µF high-frequency ceramic capacitor placed between VCC and GND as close to the device as possible, plus a 4.7 µF bulk electrolytic capacitor near the power entry point of the EPROM array. These values are specified in Section 3 ("System Considerations") of the datasheet to suppress transient excursions during CE switching and stabilize supply rail ripple.
How is the Integrated Product Identification Code accessed on the AT27C256R-70RU?
The Integrated Product Identification Code is accessed by setting A9 to 11.5–12.5 V (VID), holding A1–A14 low (VIL), and toggling A0 between VIL (to read Manufacturer ID = 0x1E) and VIH (to read Device ID = 0x8C), with CE and OE both low. This mode is detailed in Section 17 of the datasheet and is used by industry-standard programmers to auto-detect device type and select correct algorithms.
AT27C256R-70RU 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:
- 70 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-70RU FAQ
1.How can I place an order for AT27C256R-70RU through Aetrix?
Please submit a Request for Quotation (RFQ) for AT27C256R-70RU 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-70RU reliable?
The price and inventory of AT27C256R-70RU are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for AT27C256R-70RU is usually 5 days.
3.What payment methods are accepted for AT27C256R-70RU?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for AT27C256R-70RU transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for AT27C256R-70RU?
AT27C256R-70RU orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your AT27C256R-70RU 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-70RU?
For technical support, including AT27C256R-70RU datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your AT27C256R-70RU requirements.
6.How does Aetrix verify that AT27C256R-70RU is sourced from the original manufacturer or authorized distributors?
All AT27C256R-70RU 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-70RU meets industry standards.
7.What is the process for return or replacement of AT27C256R-70RU?
All AT27C256R-70RU units undergo pre-shipment inspection (PSI). If there is an issue with AT27C256R-70RU, 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-70RU part is unused and in its original packaging.
Return procedure for AT27C256R-70RU:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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