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Microchip Technology AT27C256R-70PA
- Part No.:
- AT27C256R-70PA
- Manufacturer:
- Microchip Technology
- Category:
- Memory
- Package:
- 28-DIP (0.600", 15.24mm)
- Datasheet:
-
AT27C256R-70PA.pdf
- Description:
- IC EPROM 256KBIT PARALLEL 28DIP
- Quantity:
- Payment:
- Shipping:
Inventory:3,022
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Product details
Overview
AT27C256R-70PA from Microchip Technology (formerly Atmel) is a 256K-bit (32K × 8) one-time programmable EPROM designed for nonvolatile firmware storage in microprocessor systems. It features 45 ns read access time, 5V ±10% single-supply operation, and automotive-grade temperature range (–40°C to +125°C). Used in engine control units and industrial PLCs where reliable boot code retention is required.
For engineers reviewing the AT27C256R-70PA datasheet, AT27C256R-70PA pinout, AT27C256R-70PA application, or AT27C256R-70PA equivalent, key selection criteria include read timing (tACC = 70 ns), standby current (≤100 µA), VPP programming voltage (12.0 V), JEDEC-standard 28-pin PDIP package, and OTP reliability for unmodified firmware deployment.
Technical Context
The AT27C256R-70PA implements a CMOS-based OTP EPROM architecture with dual-line control (CE/OE) enabling bus contention avoidance in shared-memory systems. Its address space spans A0–A14 (15-bit), supporting 32,768 bytes with byte-wide parallel outputs O0–O7.
It uses Rapid™ programming with 100 µs/byte typical pulse width at VPP = 12.0 V and VCC = 6.5 V, and includes integrated product identification (Manufacturer ID = 0x1E, Device ID = 0x8C) accessed via A9 high-voltage mode and A0 toggle.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Memory Size | 256 Kbit (32K × 8) - supports full 8-bit data bus interface without multiplexing |
| Read Access Time | 70 ns max - ensures compatibility with 10–14 MHz microprocessor buses without wait states |
| Supply Voltage | 5 V ±10% - operates from standard logic rail; no auxiliary voltage required for read mode |
| Standby Current | 100 µA max - enables low-power hold state during processor sleep or reset |
| Programming Voltage | VPP = 12.0 V ±0.5 V - requires dedicated programming supply; not used during normal read operation |
| Operating Temp | –40°C to +125°C - qualified for under-hood automotive and harsh industrial environments |
| ESD Protection | 2,000 V HBM - withstands handling and board-level ESD events without latchup or parametric shift |
Pinout & Package
AT27C256R-70PA is supplied in a 28-lead, 0.600" wide plastic dual inline package (PDIP), per JEDEC MS-011 AB. Pin 1 is index-marked; pins 1 and 28 are VPP and VCC respectively. NC pins are absent - all 28 pins serve defined functions.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| A0–A14 | Address Inputs | 15-bit address bus; selects one of 32,768 memory locations |
| O0–O7 | Data Outputs | True TTL/CMOS-compatible bidirectional data bus (output only in read mode) |
| CE | Chip Enable | Active-low global enable; disables outputs and reduces current to standby level when high |
| OE | Output Enable | Active-low output gate; allows CE-controlled power-down while maintaining bus isolation |
| VPP | Programming Supply | 12 V input required only during programming; must be applied simultaneously with or after VCC |
| VCC | Power Supply | +5 V main supply; powers logic and memory array during read and program modes |
| GND | Ground Reference | Common return path for VCC, VPP, and I/O; decoupling capacitor required per datasheet |
Key Features
| Feature | Design Value |
|---|---|
| Rapid™ Programming Algorithm | 100 µs/byte typical - cuts firmware update time vs. legacy EPROMs; supports automated production programming |
| Integrated Product ID Code | Manufacturer ID 0x1E / Device ID 0x8C - enables auto-detection and algorithm selection in universal programmers |
| Two-Line Control (CE/OE) | Independent chip and output gating - eliminates bus contention in multi-device memory maps |
| Automotive Temperature Range | –40°C to +125°C - validated for extended thermal cycling in powertrain and chassis modules |
| 200 mA Latchup Immunity | Withstands transient overcurrent events without destructive latchup - improves system robustness in noisy environments |
Applications
| Engine Control Unit (ECU) | Industrial Programmable Logic Controller (PLC) |
|---|---|
Use Scenario: Stores calibrated fuel injection lookup tables and real-time diagnostic firmware in gasoline/diesel powertrain systems. IC Role / Device Role / Timing Role: Nonvolatile boot ROM providing deterministic startup code execution within 70 ns of address assertion. Use Value: Ensures fail-safe boot sequence even after battery disconnect; OTP prevents accidental corruption during field updates. | Use Scenario: Holds ladder logic runtime firmware and I/O configuration data in factory-floor automation controllers. IC Role / Device Role / Timing Role: Static memory mapped at fixed address space; accessed by 8-bit microcontroller during scan cycle initialization. Use Value: Eliminates reliance on external EEPROM or flash; 100 µA standby draw extends backup battery life during power loss. |
| Avionics Display Processor | Medical Infusion Pump Controller |
Use Scenario: Stores display font glyphs and safety-critical UI state machine code in cockpit multifunction displays. IC Role / Device Role / Timing Role: Read-only instruction/data store; accessed synchronously with video refresh timing to avoid frame jitter. Use Value: 70 ns tACC guarantees pixel data availability before horizontal sync; OTP prevents unauthorized firmware modification. | Use Scenario: Retains dosage calibration constants and regulatory-compliant alarm logic in Class II infusion devices. IC Role / Device Role / Timing Role: Secure firmware repository; verified at power-on via checksum against stored ID codes (0x1E/0x8C). Use Value: Meets IEC 62304 software safety requirements; 2,000 V ESD rating protects against clinical environment static discharge. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar OTP EPROM applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| AT27C256R-70PC | Same die, identical specs, but in commercial temp range (0°C to +70°C) and same 28P6 PDIP package | Not rated for automotive thermal cycling; unsuitable for under-hood use | Select AT27C256R-70PA when operating ambient exceeds 70°C or requires AEC-Q100 alignment |
| MX27C256AP-70 | Functionally compatible 256K OTP EPROM; 70 ns access, 5V supply, but lacks integrated ID code and Rapid™ programming | Requires external programmer setup; no auto-ID support increases programming setup time | Choose AT27C256R-70PA when production line efficiency and verification traceability are critical |
Compared with AT27C256R-70PC, the AT27C256R-70PA adds automotive qualification and extended thermal margin; versus MX27C256AP-70, it delivers faster programming, built-in ID verification, and higher ESD/latchup immunity - directly impacting manufacturing yield and field reliability.
Availability
AT27C256R-70PA is available at Aetrix Electronics and suitable for engine control units, industrial PLCs, avionics displays, and medical infusion pumps requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for AT27C256R-70PA 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 developed to deliver cost-effective, high-reliability OTP EPROMs for automotive and industrial firmware storage where reprogrammability is unnecessary and data integrity is paramount.
FAQ
What is the maximum read access time specified for AT27C256R-70PA?
The AT27C256R-70PA has a maximum read access time (tACC) of 70 ns under industrial and automotive operating conditions. This value is guaranteed across the full –40°C to +125°C temperature range and with VCC = 5V ±10%. The 70 ns rating ensures compatibility with microcontrollers running up to ~12 MHz without insertion of wait states during memory fetch cycles. This parameter is measured from address valid to valid data at the O0–O7 outputs with both CE and OE asserted low.
Does AT27C256R-70PA require a programming voltage during normal operation?
No, AT27C256R-70PA does not require VPP during normal read operation. VPP = 12.0 V is needed only during programming or product ID read mode. In standard read mode, the device operates from a single 5V ±10% supply (VCC), with VPP tied to VCC or left floating (though datasheet recommends connecting VPP to VCC if unused). Applying 12 V to VPP outside programming mode may cause excessive current draw or damage.
How is the Integrated Product Identification Code accessed on AT27C256R-70PA?
The Integrated Product Identification Code on AT27C256R-70PA is accessed by setting A9 to 12.0 V (VID = 11.5–12.5 V), holding A1–A14 low, and toggling A0: low selects the Manufacturer ID (0x1E), high selects the Device ID (0x8C). Both IDs appear on O7–O0 during a standard read cycle with CE and OE low. This feature enables automatic device recognition in programming equipment and avoids manual part selection errors.
What decoupling capacitors are required for stable operation of AT27C256R-70PA?
Per the AT27C256R-70PA datasheet, a 0.1 µF ceramic capacitor must be placed between VCC and GND, mounted as close as possible to the device pins. For systems with multiple EPROMs or high-noise environments, a 4.7 µF bulk electrolytic capacitor is also recommended between VCC and GND near the power entry point. These values suppress transient voltage excursions during CE switching and ensure stable VCC regulation during rapid output transitions.
Is AT27C256R-70PA pin-compatible with other speed grades in the same package?
Yes, AT27C256R-70PA is pin-compatible with all other AT27C256R variants in the 28P6 PDIP package (e.g., AT27C256R-45PA, AT27C256R-90PA), including identical pinout, voltage levels, and control signal definitions. Speed grade differences affect only tACC, tCE, and tOE timing parameters - not pin function or electrical interface. This allows drop-in replacement for timing margin validation or cost optimization without PCB revision.
AT27C256R-70PA Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Microchip Technology
- Series:
- -
- Package/Case:
- 28-DIP (0.600", 15.24mm)
- 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 ~ 125°C (TC)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- 28-PDIP
AT27C256R-70PA FAQ
1.How can I place an order for AT27C256R-70PA through Aetrix?
Please submit a Request for Quotation (RFQ) for AT27C256R-70PA 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-70PA reliable?
The price and inventory of AT27C256R-70PA are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for AT27C256R-70PA is usually 5 days.
3.What payment methods are accepted for AT27C256R-70PA?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for AT27C256R-70PA transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for AT27C256R-70PA?
AT27C256R-70PA orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your AT27C256R-70PA 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-70PA?
For technical support, including AT27C256R-70PA datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your AT27C256R-70PA requirements.
6.How does Aetrix verify that AT27C256R-70PA is sourced from the original manufacturer or authorized distributors?
All AT27C256R-70PA 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-70PA meets industry standards.
7.What is the process for return or replacement of AT27C256R-70PA?
All AT27C256R-70PA units undergo pre-shipment inspection (PSI). If there is an issue with AT27C256R-70PA, 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-70PA part is unused and in its original packaging.
Return procedure for AT27C256R-70PA:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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