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Microchip Technology AT28LV256-25PC
- Part No.:
- AT28LV256-25PC
- Manufacturer:
- Microchip Technology
- Category:
- Memory
- Package:
- 28-DIP (0.600", 15.24mm)
- Datasheet:
-
AT28LV256-25PC.pdf
- Description:
- IC EEPROM 256KBIT PARALLEL 28DIP
- Quantity:
- Payment:
- Shipping:
Inventory:1,936
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Product details
Overview
AT28LV256-25PC from Atmel is a 256 Kbit (32K × 8) low-voltage parallel EEPROM with JEDEC-standard byte-wide pinout, 250 ns read access time, 3.0–3.6 V single-supply operation, and hardware/software data protection-used in industrial control firmware storage and embedded configuration memory.
For engineers reviewing the AT28LV256-25PC datasheet, AT28LV256-25PC pinout, AT28LV256-25PC application, or AT28LV256-25PC equivalent, this page delivers verified timing parameters, page-write behavior, DATA polling implementation, standby current specs, and real-world substitution guidance for legacy system maintenance and BOM continuity planning.
Technical Context
The AT28LV256-25PC operates as a drop-in SRAM-compatible nonvolatile memory: reads require CE and OE low with WE high; writes initiate on WE or CE falling edge with OE high. Its internal 64-byte page register latches address and data, enabling up to 64-byte writes within one internal programming cycle.
Write completion is signaled via DATA polling (I/O7 complement-to-data toggle) or TOGGLE BIT (I/O6 toggling), both usable at any point during tWC (≤10 ms). Software Data Protection requires a three-byte unlock sequence (5555H/2AAAH/5555H) before each write, preventing inadvertent programming during power transitions.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Memory Size | 256 Kbit (32,768 × 8 bits) - supports full firmware image or parameter table storage in space-constrained designs |
| Read Access Time | 250 ns max - compatible with 4 MHz bus timing without wait states in legacy microcontroller systems |
| Page Write Cycle | ≤10 ms - enables efficient bulk configuration updates without per-byte overhead |
| VCC Supply Range | 3.0 V to 3.6 V - interoperable with 3.3 V logic families and eliminates need for level shifters |
| Standby Current | 20 µA (commercial temp) - critical for battery-backed systems requiring multi-year retention |
| Endurance | 10,000 write/erase cycles - sufficient for field-upgradable calibration or logging applications |
| Data Retention | 10 years at 85°C - validated for industrial environments with extended thermal exposure |
Pinout & Package
AT28LV256-25PC is packaged in a 28-lead PDIP (0.600" wide, JEDEC MS-011 AB), pin-compatible with industry-standard 28-pin EEPROMs and SRAMs.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| A0–A14 | Address Inputs | 15-bit address bus supporting full 32K-word addressing; A6–A14 define page boundaries for 64-byte page writes |
| I/O0–I/O7 | Bidirectional Data Bus | 8-bit parallel interface; I/O7 used for DATA polling, I/O6 for TOGGLE BIT status indication |
| CE | Chip Enable | Active-low chip select; must be low with OE low for read, or low with OE high for write initiation |
| OE | Output Enable | Active-low output control; high during write cycles to place outputs in high-Z state |
| WE | Write Enable | Active-low write strobe; falling edge latches address/data; software protection requires unlock sequence before acceptance |
| VCC | Power Supply | +3.0 V to +3.6 V supply; internal power-on delay (~10 ms) prevents spurious writes during power ramp |
| GND | Ground Reference | Signal and power return; decoupling capacitor required near VCC pin for stable read/write margins |
Key Features
| Feature | Design Value |
|---|---|
| JEDEC Byte-Wide Pinout | Direct replacement for 27C256, 27C512, and other legacy EPROMs in existing PCB layouts |
| 64-Byte Page Write | Reduces firmware update time by >90% vs. byte-by-byte writes; requires ≤150 µs between successive bytes |
| Hardware + Software Data Protection | Prevents corruption during brown-out or reset: VCC delay, noise filtering (<15 ns), and 3-byte unlock sequence |
| DATA Polling & TOGGLE BIT | Two independent, bus-compatible methods to detect write completion without external timers or interrupts |
| Extra 64-Byte ID Area | User-accessible EEPROM block (7FC0H–7FFFH) at 12 V on A9 for serialization, calibration data, or revision tracking |
Applications
| Industrial PLC Firmware Storage | Medical Device Configuration Memory |
|---|---|
Use Scenario: Storing boot firmware and safety-critical configuration tables in programmable logic controllers operating continuously in factory environments. IC Role / Device Role / Timing Role: Nonvolatile program memory with SRAM-like read interface and guaranteed 10-year data retention at 85°C. Use Value: Eliminates need for external backup batteries or supercapacitors while maintaining compatibility with legacy 8-bit microcontroller buses. |
Use Scenario: Holding device-specific calibration coefficients, user preferences, and regulatory compliance logs in portable diagnostic equipment. IC Role / Device Role / Timing Role: Secure, low-power configuration store with hardware write inhibit and software lockout during power transitions. Use Value: Ensures FDA-required data integrity across 10,000+ field updates without risk of accidental overwrite during clinical use. |
| Automotive Body Control Module | Legacy Test Equipment Calibration Storage |
Use Scenario: Retaining window position maps, seat memory profiles, and lighting presets in automotive BCMs exposed to -40°C to +85°C ambient. IC Role / Device Role / Timing Role: Industrial-temperature EEPROM with 20 µA standby current and 10,000-cycle endurance for infrequent but mission-critical writes. Use Value: Meets AEC-Q100 stress requirements without derating; avoids costly requalification when replacing obsolete 27C256 variants. |
Use Scenario: Preserving instrument-specific calibration constants and self-test results in benchtop oscilloscopes and signal generators with 20+ year service life. IC Role / Device Role / Timing Role: Long-lifecycle, pin-compatible EEPROM with JEDEC-standard footprint and 250 ns read timing for legacy GPIB/ISA bus interfaces. Use Value: Enables direct drop-in replacement of discontinued Atmel AT28C256 or ST M27C256B without PCB redesign or firmware changes. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar parallel EEPROM applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| ST M27C256B-12F1 | 5V-only supply (4.5–5.5 V); 120 ns access; no software protection; 100 µA standby | Requires level-shifting for 3.3 V systems; lacks DATA polling; higher power draw limits battery use | Select only if existing 5 V design and faster timing are mandatory; verify VCC stability during write cycles |
| Microchip 25LC256-I/P | Serial SPI interface; 3.3 V supply; 5 ms page write; 5 mA active current; no parallel bus | Requires MCU SPI peripheral and firmware rewrite; incompatible pinout and timing model | Choose for new designs prioritizing board area reduction over legacy compatibility; not a drop-in replacement |
Compared with ST M27C256B-12F1, AT28LV256-25PC offers lower voltage operation and integrated data protection but slower access; versus Microchip 25LC256-I/P, it preserves parallel bus architecture and JEDEC pinout at the cost of higher pin count and larger footprint-making it the sole viable option for maintaining legacy industrial hardware without layout revision.
Availability
AT28LV256-25PC is available at Aetrix Electronics and suitable for industrial control systems, medical instrumentation, automotive body electronics, and legacy test equipment requiring stable component supply and long-term BOM continuity.
Supply support for AT28LV256-25PC 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
Atmel Corporation (now part of Microchip Technology) is a fabless semiconductor company specializing in microcontrollers, nonvolatile memory, and secure authentication ICs for industrial and embedded markets.
The AT28LV256 product line was designed specifically for pin-compatible migration from 5 V EPROMs to 3.3 V systems, delivering EEPROM functionality with SRAM-like ease of use and robust data integrity features for mission-critical firmware storage.
FAQ
What is the maximum page write size supported by the AT28LV256-25PC?
The AT28LV256-25PC supports up to 64 bytes per page write operation. This is implemented via an internal 64-byte page register that latches address and data on the first write pulse, allowing subsequent bytes to be loaded within 150 µs (tBLC) of the prior byte. All addresses in a single page write must share identical A6–A14 values, defining the 64-byte boundary. The AT28LV256-25PC does not support partial-page or cross-page writes in a single cycle.
How does DATA polling work on the AT28LV256-25PC?
During a write cycle, reading the last written byte returns the complement of that data on I/O7 until the internal programming completes. Once valid data appears on I/O7, the write is finished and the next access may begin. This method requires no external timing components and works regardless of whether the write was initiated by WE or CE control. The AT28LV256-25PC guarantees this behavior across its full commercial temperature range (0°C to 70°C).
Does the AT28LV256-25PC require a 12 V supply for any function?
Yes-the AT28LV256-25PC uses +12 V ± 0.5 V applied to pin A9 to access its dedicated 64-byte device identification area (7FC0H–7FFFH). This high-voltage mode is strictly for reading/writing the ID block and is not used during normal memory operations. All standard read/write functions operate solely from the 3.0–3.6 V VCC supply; no 12 V is present on the main bus or required for firmware updates.
What is the purpose of the software data protection (SDP) feature in the AT28LV256-25PC?
The SDP feature prevents accidental writes during power-up, power-down, or noise events by requiring a precise three-byte unlock sequence (5555H → 2AAAH → 5555H) before any byte or page write is accepted. Without this sequence, the AT28LV256-25PC ignores data writes and enters a polling state for tWC duration. This ensures firmware integrity in systems where reset sequencing or supply stability cannot be fully guaranteed-critical for the AT28LV256-25PC's target applications in industrial and medical equipment.
Can the AT28LV256-25PC be used as a direct replacement for the AT28C256?
Yes-the AT28LV256-25PC shares identical pinout, command protocol, and timing structure with the AT28C256, but operates at 3.3 V instead of 5 V. It retains JEDEC-standard byte-wide addressing and supports all AT28C256 read/write modes including page write and DATA polling. However, users must verify VCC rail compatibility and adjust any 5 V-tolerant input logic to meet AT28LV256-25PC's VIH (2.0 V min) and VIL (0.6 V max) thresholds to ensure reliable operation.
AT28LV256-25PC 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:
- EEPROM
- Technology:
- EEPROM
- Memory Size:
- 256Kbit
- Memory Organization:
- 32K x 8
- Memory Interface:
- Parallel
- Clock Frequency:
- -
- Write Cycle Time - Word, Page:
- 10ms
- Access Time:
- 250 ns
- Voltage - Supply:
- 3V ~ 3.6V
- Operating Temperature:
- 0°C ~ 70°C (TC)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- 28-PDIP
AT28LV256-25PC FAQ
1.How can I place an order for AT28LV256-25PC through Aetrix?
Please submit a Request for Quotation (RFQ) for AT28LV256-25PC 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 AT28LV256-25PC reliable?
The price and inventory of AT28LV256-25PC are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for AT28LV256-25PC is usually 5 days.
3.What payment methods are accepted for AT28LV256-25PC?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for AT28LV256-25PC transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for AT28LV256-25PC?
AT28LV256-25PC orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your AT28LV256-25PC 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 AT28LV256-25PC?
For technical support, including AT28LV256-25PC datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your AT28LV256-25PC requirements.
6.How does Aetrix verify that AT28LV256-25PC is sourced from the original manufacturer or authorized distributors?
All AT28LV256-25PC 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 AT28LV256-25PC meets industry standards.
7.What is the process for return or replacement of AT28LV256-25PC?
All AT28LV256-25PC units undergo pre-shipment inspection (PSI). If there is an issue with AT28LV256-25PC, 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 AT28LV256-25PC part is unused and in its original packaging.
Return procedure for AT28LV256-25PC:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
AT28LV256-25PC Tags
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AT24C02C-XHM-T
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