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Microchip Technology AT28BV256-20PC
- Part No.:
- AT28BV256-20PC
- Manufacturer:
- Microchip Technology
- Category:
- Memory
- Package:
- 28-DIP (0.600", 15.24mm)
- Datasheet:
-
AT28BV256-20PC.pdf
- Description:
- IC EEPROM 256KBIT PARALLEL 28DIP
- Quantity:
- Payment:
- Shipping:
Inventory:4,921
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Product details
Overview
AT28BV256-20PC from Atmel is a 256 Kbit (32K × 8) parallel EEPROM with JEDEC-standard byte-wide pinout, 2.7–3.6 V single-supply operation, 200 ns read access time, and hardware/software data protection-used in industrial control firmware storage and embedded configuration memory.
For engineers reviewing the AT28BV256-20PC datasheet, AT28BV256-20PC pinout, AT28BV256-20PC application, or AT28BV256-20PC equivalent, key selection criteria include page-write capability (64-byte burst), CMOS standby current (20 µA), DATA polling/Toggle Bit write-completion detection, and industrial temperature range support (−40°C to +85°C).
Technical Context
The AT28BV256-20PC implements a static RAM-compatible interface with dual-line chip enable (CE) and output enable (OE) control to prevent bus contention. Its internal 64-byte page register latches address and data during write cycles, enabling background bus release while internal timing completes programming.
Write operations support both byte and page modes, with software data protection requiring a three-step unlock sequence before each write. End-of-write detection is implemented via DATA Polling on I/O7 (complement-to-data) and Toggle Bit behavior on I/O6, both usable at any point during tWC (10 ms max).
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Memory Size | 256 Kbit (32,768 × 8 bits); supports full byte-addressable nonvolatile storage without external refresh. |
| Read Access Time | 200 ns maximum; enables direct replacement of SRAM in legacy 8-bit microcontroller systems. |
| Page Write Cycle | 10 ms maximum; allows up to 64 bytes per write with automatic internal timing-no external wait-state logic required. |
| VCC Supply Range | 2.7 V to 3.6 V; compatible with 3.3 V logic families and battery-backed systems operating down to 2.7 V. |
| Standby Current | 20 µA (CMOS); enables low-power retention in always-on industrial monitoring nodes. |
| Endurance | 10,000 write/erase cycles; sufficient for field-updatable calibration tables and infrequent configuration changes. |
| Data Retention | 10 years at 85°C; validated for long-life deployment in unattended equipment. |
Pinout & Package
AT28BV256-20PC is supplied in a 28-lead plastic dual in-line package (PDIP), 0.600" wide (package code 28P6), with JEDEC-standard byte-wide pinout and no internal pull-ups or special power sequencing requirements.
| 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 writes. |
| I/O0–I/O7 | Bidirectional Data Bus | True bidirectional 8-bit data path; I/O7 used for DATA Polling, I/O6 for Toggle Bit status reporting. |
| CE | Chip Enable | Active-low device select; must be low with OE low and WE high for read; inhibits writes when high. |
| OE | Output Enable | Active-low output control; places I/O pins in high-impedance state when high-prevents bus conflicts during shared-memory access. |
| WE | Write Enable | Active-low write strobe; initiates byte or page write on falling edge; combined with CE for robust noise immunity (15 ns filter). |
| VCC | Power Supply | 2.7–3.6 V supply; includes internal VCC power-on delay (~10 ms) to prevent spurious writes during power ramp. |
| GND | Ground Reference | Signal and power ground reference; decoupling capacitor recommended within 1 cm of VCC pin. |
Key Features
| Feature | Design Value |
|---|---|
| Automatic Page Write | Latches up to 64 bytes internally, freeing address/data bus immediately after initiation-enables concurrent host CPU operations during 10 ms programming. |
| DATA Polling & Toggle Bit | Dual, real-time write-completion detection methods (I/O7 complement, I/O6 toggle) eliminate need for fixed delays or external timers in firmware. |
| Hardware + Software Protection | VCC power-on delay, noise-filtered WE/CE inputs, and mandatory 3-byte unlock sequence prevent accidental writes during power transitions or EMI events. |
| Extra 64-Byte ID Area | Dedicated user-accessible EEPROM block (7FC0H–7FFFH) enabled by 12 V on A9-supports unique device serialization or firmware version tracking. |
| JEDEC Byte-Wide Pinout | Direct drop-in compatibility with industry-standard 28-pin parallel EEPROM footprints (e.g., 28C256), simplifying board-level upgrades. |
Applications
| Industrial PLC Configuration Storage | Medical Device Calibration Memory |
|---|---|
Use Scenario: Storing runtime-configurable I/O mapping and alarm thresholds in programmable logic controllers deployed in factory automation cabinets. IC Role / Device Role / Timing Role: Nonvolatile configuration register holding persistent settings across cold power cycles; accessed via 8-bit microcontroller bus during boot and runtime reconfiguration. Use Value: 20 µA standby current extends backup battery life; 10,000-cycle endurance accommodates quarterly calibration updates over 10+ year product lifetime. | Use Scenario: Retaining sensor offset/gain coefficients and patient-specific therapy parameters in portable infusion pumps and diagnostic monitors. IC Role / Device Role / Timing Role: Secure, tamper-resistant parameter store accessed only during device initialization or clinician-initiated recalibration-protected by software data protection sequence. Use Value: Hardware write inhibit (CE high/OE low/WE high) prevents corruption during brown-out conditions; 10-year data retention ensures compliance with medical device regulatory shelf-life requirements. |
| Telecom Line Card Firmware | Automotive Body Control Module (BCM) |
Use Scenario: Holding boot loader patches and field-upgradable protocol stacks in carrier-grade DSLAM line cards operating in temperature-controlled central offices. IC Role / Device Role / Timing Role: Parallel EEPROM interfaced to 8051 or ARM7-based management MCU; provides fast 200 ns reads for rapid boot execution and page writes for secure firmware updates. Use Value: 200 ns access time matches SRAM-like timing budgets; page write reduces update time vs. byte-by-byte writes-critical for minimizing service interruption windows. | Use Scenario: Storing seat/mirror position presets, lighting profiles, and door lock configurations in automotive BCMs exposed to under-hood thermal cycling. IC Role / Device Role / Timing Role: Industrial-grade (−40°C to +85°C) nonvolatile memory mapped into microcontroller address space; retains user preferences through ignition cycles and battery disconnects. Use Value: Qualified for industrial temperature range and 10-year data retention-meets AEC-Q100 stress test expectations for passenger compartment electronics. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar parallel EEPROM applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| ST M28W256F | 256 Kbit, 2.7–3.6 V, 250 ns access, 10 ms page write-but lacks software data protection and Toggle Bit detection. | Requires external write-protection logic or firmware polling delay; not suitable where robust power-fail write safety is mandated. | Select when cost sensitivity outweighs need for integrated write-safety features and faster 200 ns access is not required. |
| Microchip 25LC256 | 256 Kbit SPI EEPROM, 2.5–5.5 V, 5 MHz interface-serial architecture, no parallel bus interface or JEDEC pinout. | Requires SPI controller and different PCB layout; incompatible with existing 28-pin DIP footprint and 8-bit address/data bus designs. | Select only for new designs prioritizing pin count reduction and board space savings over legacy bus compatibility. |
Compared with ST M28W256F and Microchip 25LC256, the AT28BV256-20PC uniquely combines 200 ns read speed, JEDEC-standard parallel pinout, integrated software/hardware write protection, and dual-status detection-making it the only drop-in solution for upgrading legacy SRAM-based systems with nonvolatile storage without redesigning timing or protection logic.
Availability
AT28BV256-20PC is available at Aetrix Electronics and suitable for industrial PLCs, medical calibration systems, telecom line cards, and automotive body control modules requiring stable component supply and long-term lifecycle support.
Supply support for AT28BV256-20PC 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 security ICs for embedded systems.
The AT28BV256 product line was designed for high-reliability, battery-voltage parallel EEPROM applications in industrial, medical, and telecom equipment requiring robust write protection and JEDEC-compatible pinouts.
FAQ
What is the maximum page write size supported by the AT28BV256-20PC?
The AT28BV256-20PC supports a maximum page write size of 64 bytes. This is enabled by its internal 64-byte page register, which latches address and data during write initiation. All bytes written in a single page operation must reside on the same page, defined by address bits A6–A14. The AT28BV256-20PC enforces this via internal logic that halts data acceptance if A6–A14 change mid-page write.
Does the AT28BV256-20PC require a 12 V supply for normal operation?
No, the AT28BV256-20PC operates from a single 2.7 V to 3.6 V supply for all standard read/write functions. The 12 V requirement applies only to accessing the optional 64-byte device identification area (7FC0H–7FFFH), where A9 must be raised to 12.0 V ± 0.5 V. This high-voltage mode is strictly for factory programming or secure serialization-not for routine operation of the AT28BV256-20PC.
How does DATA Polling work on the AT28BV256-20PC during a write cycle?
During a write cycle, reading the last written byte from the AT28BV256-20PC returns the bitwise complement of that data on I/O7. Once the internal programming completes, true data appears on all outputs including I/O7. This allows firmware to poll I/O7 in a loop without fixed delays-reducing latency and eliminating guesswork in timing-critical applications using the AT28BV256-20PC.
Can the AT28BV256-20PC be used as a direct replacement for older 28C256 EEPROMs?
Yes, the AT28BV256-20PC uses a JEDEC-approved byte-wide pinout identical to the 28C256 and shares the same 28-pin PDIP footprint (28P6). It operates at lower voltage (2.7–3.6 V vs. 4.5–5.5 V), offers faster 200 ns access, and adds software data protection-but retains full read/write command compatibility. No PCB changes are needed when upgrading from 28C256 to AT28BV256-20PC.
What is the purpose of the extra 64 bytes of EEPROM in the AT28BV256-20PC?
The extra 64 bytes (addresses 7FC0H–7FFFH) serve as a dedicated device identification area. They can be programmed with unique serial numbers, calibration data, or firmware version stamps using a 12 V pulse on A9. This area is electrically isolated from main memory and retains data independently-providing traceability and anti-counterfeiting capability without consuming main array space in the AT28BV256-20PC.
AT28BV256-20PC 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:
- 200 ns
- Voltage - Supply:
- 2.7V ~ 3.6V
- Operating Temperature:
- 0°C ~ 70°C (TC)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- 28-PDIP
AT28BV256-20PC FAQ
1.How can I place an order for AT28BV256-20PC through Aetrix?
Please submit a Request for Quotation (RFQ) for AT28BV256-20PC 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 AT28BV256-20PC reliable?
The price and inventory of AT28BV256-20PC are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for AT28BV256-20PC is usually 5 days.
3.What payment methods are accepted for AT28BV256-20PC?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for AT28BV256-20PC transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for AT28BV256-20PC?
AT28BV256-20PC orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your AT28BV256-20PC 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 AT28BV256-20PC?
For technical support, including AT28BV256-20PC datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your AT28BV256-20PC requirements.
6.How does Aetrix verify that AT28BV256-20PC is sourced from the original manufacturer or authorized distributors?
All AT28BV256-20PC 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 AT28BV256-20PC meets industry standards.
7.What is the process for return or replacement of AT28BV256-20PC?
All AT28BV256-20PC units undergo pre-shipment inspection (PSI). If there is an issue with AT28BV256-20PC, 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 AT28BV256-20PC part is unused and in its original packaging.
Return procedure for AT28BV256-20PC:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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