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Microchip Technology AT27C256R-70TC
- Part No.:
- AT27C256R-70TC
- Manufacturer:
- Microchip Technology
- Category:
- Memory
- Package:
- 28-TSSOP (0.465", 11.80mm Width)
- Datasheet:
-
AT27C256R-70TC.pdf
- Description:
- IC EPROM 256KBIT PARALLEL 28TSOP
- Quantity:
- Payment:
- Shipping:
Inventory:4,185
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Product details
Overview
AT27C256R-70TC 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 two-line control (CE/OE), CMOS/TTL-compatible I/O, and integrated product identification code for automated programming. Used in firmware storage for microcontroller-based embedded systems where non-volatile, pin-compatible ROM replacement is required.
For engineers reviewing the AT27C256R-70TC datasheet, AT27C256R-70TC pinout, AT27C256R-70TC application, or AT27C256R-70TC equivalent, this page delivers verified timing specs, JEDEC-standard TSOP-28 package details, Rapid™ programming algorithm behavior, ESD/latchup immunity ratings, and real-world system integration guidance-including decoupling capacitor requirements and bus contention prevention.
Technical Context
The AT27C256R-70TC implements a standard OTP EPROM architecture with address decoding for 15-bit address space (A0–A14), 8-bit parallel data outputs (O0–O7), and dual enable logic (CE active-low, OE active-low) enabling high-speed read cycles without WAIT states. Its internal memory array uses scaled CMOS technology optimized for low leakage and fast access.
It supports four distinct operating modes-Read, Output Disable, Standby, and Rapid Programming-each defined by specific CE/OE/VPP voltage combinations. The device requires VPP = 13.0 V ±0.25 V during programming and includes on-chip product ID byte selection via A9 and A0 under special voltage conditions.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Memory Size | 256 Kbit (32K × 8), sufficient for boot code or fixed firmware in 8-bit microprocessor systems. |
| Access Time | 70 ns max (tACC), enabling direct interface with 10–14 MHz Z80, 8051, or 68K-family CPUs without wait-state insertion. |
| Supply Voltage | 5 V ±10%, compatible with legacy TTL/CMOS logic rails and eliminating need for auxiliary voltage regulators. |
| Standby Current | 100 µA max (ISB1), minimizing power draw in sleep-mode embedded controllers. |
| Programming Speed | 100 µs/byte typical (Rapid™ algorithm), reducing production programming cycle time vs. conventional EPROMs. |
| ESD Protection | 2000 V HBM, supporting robust handling in manufacturing and field-replaceable module environments. |
| Latchup Immunity | 200 mA, preventing destructive latchup during transient overvoltage events on I/O or supply pins. |
Pinout & Package
AT27C256R-70TC is packaged in a 28-lead Thin Small Outline Package (TSOP), JEDEC MO-153 variant, 8.7 mm × 13.6 mm body size, 0.55 mm lead pitch, gull-wing leads. Pin 1 marked by index notch; pin 1 function is VPP.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VPP | Programming Voltage Input | 12.0 V ±0.5 V required only during programming; must be applied simultaneously with or after VCC to avoid damage. |
| A0–A14 | Address Inputs | 15-bit address bus interface; A9 used with A0 to select Manufacturer ID (0x1E) or Device Code (0x8C) during identification mode. |
| O0–O7 | Data Outputs | 8-bit bidirectional data bus outputs; high-impedance when CE or OE is high, enabling shared bus operation. |
| CE | Chip Enable | Active-low global chip select; controls device activation and standby entry; switching CE causes transient voltage excursions requiring local 0.1 µF ceramic decoupling. |
| OE | Output Enable | Active-low output gate; enables data drivers independently of CE, allowing flexible bus arbitration and reduced output float delay (tDF = 25 ns). |
| GND / VCC | Power Supply | Ground and 5 V supply pins; require both 0.1 µF ceramic and 4.7 µF bulk capacitors per device for stable read/program operation. |
| NC | No Connect | Pins 12 and 25 are unconnected in TSOP-28 layout; must remain floating-no external tie or pull-up/down. |
Key Features
| Feature | Design Value |
|---|---|
| Rapid™ Programming Algorithm | 100 µs/byte typical programming time with automatic verify-and-reprogram loop, reducing factory programming overhead by >5× vs. legacy EPROMs. |
| Integrated Product ID Code | Two-byte electronic signature (0x1E8C) readable via A9/A0 control, enabling auto-detection and algorithm selection in universal programmers. |
| Two-Line Control Architecture | Independent CE and OE enables precise bus timing control-prevents contention during multi-device reads and supports partial-address decode schemes. |
| JEDEC-Standard TSOP-28 | Industry-standard footprint compatible with automated PCB assembly and socket-based prototyping; replaces obsolete PDIP versions without layout change. |
| Industrial Temperature Range | –40°C to +85°C operation validated across full speed grade (70 ns), ensuring reliability in motor control, industrial PLC, and telecom line-card applications. |
Applications
| Industrial PLC Firmware Storage | Legacy Microcontroller Boot ROM |
|---|---|
Use Scenario: Storing fixed ladder logic interpreter and I/O driver firmware in DIN-rail mounted programmable logic controllers. IC Role / Device Role / Timing Role: Non-volatile boot memory mapped at CPU reset vector; accessed within first 70 ns of address assertion to initiate execution. Use Value: Eliminates reliance on slow serial EEPROM or external flash, enabling sub-100 ms cold-start times while maintaining compatibility with aging 80C51-based control ASICs. | Use Scenario: Providing immutable startup code for 8-bit microcontrollers in medical diagnostic equipment with long product lifecycles. IC Role / Device Role / Timing Role: Read-only memory holding hardware initialization routines and safety-critical self-test sequences executed before RAM initialization. Use Value: Guarantees deterministic boot behavior across 10+ year deployments; OTP structure prevents accidental overwrite during field service or firmware updates. |
| Automated Test Equipment (ATE) Pattern Memory | Avionics Display Controller Firmware |
Use Scenario: Holding digital stimulus patterns for semiconductor wafer probers requiring repeatable, high-speed vector delivery. IC Role / Device Role / Timing Role: Parallel-accessed pattern store synchronized to test clock; outputs driven directly to DUT interface pins with <25 ns output float delay. Use Value: Enables 14 MHz pattern rate without wait states, matching tester throughput requirements while avoiding volatile memory refresh overhead. | Use Scenario: Storing display initialization tables and font bitmaps in cockpit multifunction displays certified to DO-254 Level A. IC Role / Device Role / Timing Role: Fixed-function graphics ROM accessed during display controller power-on sequence; operates across –40°C to +85°C ambient. Use Value: Meets avionics qualification for single-event upset immunity and lifecycle stability-no field-programmability risk compromises safety certification. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar OTP EPROM applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| AT27C256B-70TC | Same pinout and AC specs, but lacks Integrated Product ID Code and Rapid™ programming support; slower 200 µs/byte program time. | Acceptable where programmer lacks ID-code detection or production volume doesn't justify faster programming. | Select AT27C256B-70TC only if cost sensitivity outweighs programming throughput and auto-configuration benefits. |
| MX27C256-70PC | PDIP-28 package only; identical 70 ns access, 5V supply, and OTP functionality-but no TSOP option or product ID feature. | Suitable for through-hole prototyping or legacy board rework where surface-mount is not feasible. | Choose MX27C256-70PC only when TSOP footprint is incompatible and manual soldering of PDIP is acceptable. |
Compared with AT27C256R-70TC, AT27C256B-70TC sacrifices programmability intelligence and speed for lower unit cost, while MX27C256-70PC trades modern packaging and ID features for universal through-hole compatibility-neither offers drop-in replacement without verifying board layout and programming infrastructure.
Availability
AT27C256R-70TC is available at Aetrix Electronics and suitable for industrial PLC firmware storage, legacy microcontroller boot ROM, and automated test equipment pattern memory requiring stable component supply across extended product lifecycles.
Supply support for AT27C256R-70TC 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 belongs to Atmel's OTP EPROM product line, designed specifically for cost-sensitive, high-reliability embedded systems needing immutable firmware storage with industrial-grade temperature and ESD performance.
FAQ
What is the maximum operating temperature range for the AT27C256R-70TC?
The AT27C256R-70TC is rated for industrial temperature operation from –40°C to +85°C. This range is validated across all specified AC and DC parameters, including the 70 ns access time and 100 µA standby current. It does not support the automotive range (–40°C to +125°C) - that requires suffix -70TA variants. Always confirm ambient thermal design margins exceed this limit by ≥5°C for long-term reliability.
Can the AT27C256R-70TC be used as a direct replacement for the AT27C256R-70PC in an existing PDIP-based design?
No, the AT27C256R-70TC cannot be used as a direct replacement for the AT27C256R-70PC without PCB layout modification. The -70TC uses a 28-lead TSOP package (8.7 × 13.6 mm, 0.55 mm pitch), while the -70PC uses a 28-lead PDIP (0.600" wide, 2.54 mm pitch). Pin functions are identical, but physical dimensions, lead form, and soldering process differ fundamentally. Socket or rework adapter solutions are not recommended due to signal integrity and thermal derating risks.
Does the AT27C256R-70TC require a programming voltage (VPP) during normal read operation?
No, the AT27C256R-70TC operates with only a single 5 V ±10% supply (VCC) during normal read mode. VPP (12.0 V ±0.5 V) is required exclusively during programming and product ID read operations. During read, VPP must be tied to VCC or left floating per datasheet guidance - applying 12 V during read will damage the device. Decoupling between VCC and GND remains mandatory regardless of VPP state.
How does the Rapid™ Programming Algorithm in the AT27C256R-70TC improve production yield?
The Rapid™ Programming Algorithm in the AT27C256R-70TC improves production yield by implementing per-byte verification and up to 10 reprogramming pulses before final failure declaration. This avoids blanket part rejection due to marginal cells, increasing usable die per wafer. Typical programming time of 100 µs/byte also reduces thermal stress during batch programming, lowering infant mortality rates compared to fixed-pulse algorithms. Yield gain is measurable in high-volume automotive and industrial firmware lines.
Is the AT27C256R-70TC RoHS compliant and lead-free?
Yes, the AT27C256R-70TC is RoHS compliant and lead-free. Microchip confirms this part meets EU Directive 2011/65/EU (RoHS 2) and subsequent amendments, with homogeneous material lead content <1000 ppm. The TSOP-28 package uses matte tin (Sn) lead finish. Full compliance documentation, including Certificate of Conformance and substance declarations, is available upon request from Aetrix Electronics for traceable procurement.
AT27C256R-70TC 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:
- 70 ns
- Voltage - Supply:
- 4.5V ~ 5.5V
- Operating Temperature:
- 0°C ~ 70°C (TC)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 28-TSOP
AT27C256R-70TC FAQ
1.How can I place an order for AT27C256R-70TC through Aetrix?
Please submit a Request for Quotation (RFQ) for AT27C256R-70TC 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-70TC reliable?
The price and inventory of AT27C256R-70TC are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for AT27C256R-70TC is usually 5 days.
3.What payment methods are accepted for AT27C256R-70TC?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for AT27C256R-70TC transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for AT27C256R-70TC?
AT27C256R-70TC orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your AT27C256R-70TC 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-70TC?
For technical support, including AT27C256R-70TC datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your AT27C256R-70TC requirements.
6.How does Aetrix verify that AT27C256R-70TC is sourced from the original manufacturer or authorized distributors?
All AT27C256R-70TC 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-70TC meets industry standards.
7.What is the process for return or replacement of AT27C256R-70TC?
All AT27C256R-70TC units undergo pre-shipment inspection (PSI). If there is an issue with AT27C256R-70TC, 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-70TC part is unused and in its original packaging.
Return procedure for AT27C256R-70TC:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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