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Microchip Technology AT27C256R-70JU
- Part No.:
- AT27C256R-70JU
- Manufacturer:
- Microchip Technology
- Category:
- Memory
- Package:
- 32-LCC (J-Lead)
- Datasheet:
-
AT27C256R-70JU.pdf
- Description:
- IC EPROM 256KBIT PARALLEL 32PLCC
- Quantity:
- Payment:
- Shipping:
Inventory:2,375
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Product details
Overview
AT27C256R-70JU from Microchip Technology (formerly Atmel) is a 32K × 8-bit, one-time programmable EPROM used for firmware storage in microprocessor systems. It delivers 45ns read access time, operates on a single 5V ±10% supply, and supports industrial temperature range (–40°C to +85°C) in a 32-lead PLCC package with JEDEC-standard pinout.
For engineers reviewing the AT27C256R-70JU datasheet, AT27C256R-70JU pinout, AT27C256R-70JU application, or AT27C256R-70JU equivalent, this device serves as a low-power, high-reliability OTP memory solution for boot code, configuration data, and fixed algorithm storage where reprogrammability is not required but fast, deterministic read timing is critical.
Technical Context
The AT27C256R-70JU 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 pulses at VPP = 12.0V ±0.5V and VCC = 6.5V ±0.25V, verified per byte with up to 10 retries before failure declaration.
It features integrated product identification (manufacturer code 0x1E, device code 0x8C) accessed via A9 = 12.0V and A0 toggled - a hardware-level feature used by industry-standard programmers to auto-select voltage profiles and algorithms. ESD protection exceeds 2,000V and latchup immunity is rated at 200mA.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Memory size | 262,144 bits (32K × 8), sufficient for full microcontroller boot ROM or FPGA configuration bitstream |
| Read access time | 70 ns max (–70 speed grade), eliminates WAIT states in 5 MHz Z80/8086-class systems |
| VCC supply | 5 V ±10%, compatible with legacy TTL/CMOS logic rails without regulation overhead |
| Standby current | 100 µA max, enables low-power retention in battery-backed or intermittent-operation systems |
| Active current | 20 mA max at 5 MHz, supports sustained burst reads without thermal derating |
| Programming voltage | VPP = 12.0 V ±0.5 V, requires dedicated high-voltage supply during one-time programming only |
| Operating temperature | –40°C to +85°C, qualified for industrial control, instrumentation, and telecom infrastructure |
Pinout & Package
AT27C256R-70JU is housed in a 32-lead plastic J-leaded chip carrier (PLCC), JEDEC MS-016 variation AE compliant, with 11.5 mm × 14.0 mm body and 1.27 mm lead pitch. Pin 1 identifier is marked by a corner chamfer.
| 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; VOH ≥2.4 V at –400 µA, VOL ≤0.4 V at 2.1 mA |
| CE | Chip enable | Active-low primary selection; controls power state transition between standby (VIH) and active (VIL) |
| OE | Output enable | Active-low secondary control; gates output drivers independently of CE to prevent bus contention |
| VCC | Power supply | +5 V ±10% main supply; must be applied simultaneously with or before VPP during programming |
| VPP | Programming voltage | +12.0 V ±0.5 V input for OTP programming only; disconnected during normal read operation |
| GND | Ground reference | Signal and power return; requires local 0.1 µF ceramic decoupling per device |
| NC | No connect | Pins 1 and 17 in PLCC are unconnected; no internal bonding or electrical function |
Key Features
| Feature | Design Value |
|---|---|
| Rapid programming | 100 µs/byte typical pulse width enables <1 second full-device programming (32K bytes), reducing production test time |
| Integrated ID code | Manufacturer (0x1E) and device (0x8C) codes accessible via A9/VH and A0 toggle, enabling automated programmer recognition |
| Two-line control | Independent CE and OE pins allow flexible memory mapping and eliminate need for external bus transceivers |
| High-reliability process | 2,000 V HBM ESD rating and 200 mA latchup immunity ensure robustness in noisy industrial environments |
| Green packaging | Pb/halide-free PLCC package complies with RoHS Directive 2011/65/EU without performance trade-offs |
Applications
| Industrial PLC Firmware Storage | Legacy Microprocessor Boot ROM |
|---|---|
|
Use Scenario: Storing fixed ladder logic firmware and I/O configuration in programmable logic controllers deployed in factory automation. IC Role / Device Role / Timing Role: Nonvolatile boot memory providing deterministic 70 ns read latency to initialize CPU and peripherals at power-up. Use Value: Eliminates reliance on slow serial EEPROM or unreliable battery-backed SRAM; ensures repeatable startup behavior across temperature and voltage variations. |
Use Scenario: Hosting BIOS or monitor firmware in Z80-, 8086-, or 68000-based embedded systems where field updates are unnecessary. IC Role / Device Role / Timing Role: Primary read-only instruction store mapped into upper memory space, accessed via standard address/data bus. Use Value: Delivers sub-100 ns access without wait-state insertion, preserving maximum throughput in cycle-critical real-time execution. |
| Telecom Line Card Configuration | Medical Instrument Calibration Data |
|
Use Scenario: Holding hardware-specific initialization parameters and protocol stack constants on T1/E1 line interface cards operating in central office environments. IC Role / Device Role / Timing Role: Static configuration memory accessed once at card reset; supports JEDEC-standard PLCC socketing for field replacement. Use Value: Guarantees data integrity over 20+ year service life with zero write cycles, avoiding wear-out mechanisms inherent in flash or EEPROM. |
Use Scenario: Storing factory-calibrated sensor offset/gain coefficients and safety-critical lookup tables in Class II medical devices (e.g., infusion pumps, ECG monitors). IC Role / Device Role / Timing Role: Tamper-proof, nonvolatile data repository accessed during self-test sequence prior to clinical operation. Use Value: Meets IEC 62304 software lifecycle requirements for immutable configuration data; immune to accidental overwrite or corruption. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar OTP EPROM applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| AT27C256B-70JU | Successor revision with updated process; identical pinout, timing, and programming voltage; same 70 ns access spec | No functional change; qualifies as drop-in replacement per Microchip's migration notice | Select AT27C256B-70JU for new designs requiring long-term availability and latest fab process yield |
| MX27C256-70PC | 32-pin PDIP package; 70 ns access; same 32K×8 organization but lacks integrated ID code and rapid programming verification loop | Requires manual programmer setup; less suitable for automated high-volume programming lines | Choose MX27C256-70PC only when PLCC footprint is unavailable and manual programming is acceptable |
Compared with AT27C256R-70JU, the AT27C256B-70JU offers identical system-level compatibility with enhanced manufacturing support, while the MX27C256-70PC trades programmability intelligence and package form factor for legacy through-hole assembly flexibility.
Availability
AT27C256R-70JU is available at Aetrix Electronics and suitable for industrial control, legacy computing, telecom infrastructure, and medical instrumentation requiring stable component supply across extended product lifecycles.
Supply support for AT27C256R-70JU 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 supply chain responsibility for legacy Atmel memory products including the AT27C series.
The AT27C256R belongs to Atmel's OTP EPROM product line, designed specifically for cost-sensitive, high-reliability embedded systems where firmware immutability, fast read performance, and industrial temperature operation are mandatory.
FAQ
What is the maximum operating temperature range for the AT27C256R-70JU?
The AT27C256R-70JU is rated for industrial temperature operation from –40°C to +85°C. This range is validated per JEDEC JESD22-A108 and applies to all DC and AC specifications including read access time (70 ns), standby current (100 µA max), and output drive capability. The AT27C256R-70JU does not support automotive-grade temperature ranges; for –40°C to +125°C operation, Microchip recommends the AT27C256R-70AU variant in PDIP package.
Can the AT27C256R-70JU be reprogrammed after initial programming?
No, the AT27C256R-70JU is a one-time programmable (OTP) EPROM. Its floating-gate memory cells undergo irreversible oxide breakdown during the 12 V VPP programming step, permanently altering threshold voltage. Once programmed, data cannot be erased or rewritten. The AT27C256R-70JU is intended for applications where firmware or calibration data remains fixed throughout the product's lifetime.
What decoupling capacitors are required for stable operation of the AT27C256R-70JU?
The AT27C256R-70JU requires two decoupling capacitors: a 0.1 µF high-frequency ceramic capacitor placed directly between VCC and GND pins, as close to the device as possible, and a 4.7 µF bulk electrolytic capacitor located near the power entry point of the board. These values are specified in the "System considerations" section of the AT27C256R-70JU datasheet to suppress transient voltage excursions during CE switching and stabilize VCC under array-level loading.
Does the AT27C256R-70JU support standard microprocessor bus timing?
Yes, the AT27C256R-70JU fully supports standard microprocessor bus timing with CE and OE control lines. Its tACC (70 ns), tCE (70 ns), and tOE (30 ns) parameters meet or exceed timing requirements for 5 MHz Z80, 8086, and 68000 systems. The AT27C256R-70JU also provides TTL/CMOS-compatible input thresholds (VIL ≤0.8 V, VIH ≥2.0 V) and output drive (VOH ≥2.4 V, VOL ≤0.4 V), ensuring direct interfacing without level-shifting circuitry.
How is the integrated product identification code accessed on the AT27C256R-70JU?
The AT27C256R-70JU identification code is accessed by applying VH = 12.0 V ±0.5 V to pin A9 while holding A1–A14 low, then toggling A0: low (VIL) reads the manufacturer ID (0x1E), high (VIH) reads the device ID (0x8C). This mode is entered with CE = OE = VIL and VCC = 6.5 V ±0.25 V. The AT27C256R-70JU ID code is used by automated programmers to validate part identity and select correct programming algorithms before initiating write operations.
AT27C256R-70JU 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:
- 70 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-70JU FAQ
1.How can I place an order for AT27C256R-70JU through Aetrix?
Please submit a Request for Quotation (RFQ) for AT27C256R-70JU 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-70JU reliable?
The price and inventory of AT27C256R-70JU are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for AT27C256R-70JU is usually 5 days.
3.What payment methods are accepted for AT27C256R-70JU?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for AT27C256R-70JU transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for AT27C256R-70JU?
AT27C256R-70JU orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your AT27C256R-70JU 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-70JU?
For technical support, including AT27C256R-70JU datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your AT27C256R-70JU requirements.
6.How does Aetrix verify that AT27C256R-70JU is sourced from the original manufacturer or authorized distributors?
All AT27C256R-70JU 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-70JU meets industry standards.
7.What is the process for return or replacement of AT27C256R-70JU?
All AT27C256R-70JU units undergo pre-shipment inspection (PSI). If there is an issue with AT27C256R-70JU, 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-70JU part is unused and in its original packaging.
Return procedure for AT27C256R-70JU:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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