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Microchip Technology AT28HC256E-70SU
- Part No.:
- AT28HC256E-70SU
- Manufacturer:
- Microchip Technology
- Category:
- Memory
- Package:
- 28-SOIC (0.295", 7.50mm Width)
- Datasheet:
-
AT28HC256E-70SU.pdf
- Description:
- IC EEPROM 256KBIT PAR 28SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:4,523
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Product details
Overview
AT28HC256E-70SU from Microchip Technology is a 256-Kbit (32,768 × 8) parallel EEPROM with 70 ns read access time, single 5V ±10% supply, JEDEC-approved byte-wide pinout, and industrial temperature range (–40°C to +85°C). It supports automatic 1–64-byte page writes, hardware/software data protection, and DATA Polling for write completion detection - used in embedded control firmware storage, industrial PLC configuration memory, and legacy system BIOS backup.
For engineers reviewing the AT28HC256E-70SU datasheet, AT28HC256E-70SU pinout, AT28HC256E-70SU application, or AT28HC256E-70SU equivalent, key selection criteria include 70 ns read timing, 3 ms or 10 ms page write cycle, CMOS/TTL compatibility, JEDEC-standard 28-pin SOIC package, and software data protection enable/disable sequences.
Technical Context
The AT28HC256E-70SU implements a static RAM-compatible parallel 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 operations, freeing the bus for concurrent tasks.
Write completion is verified via DATA Polling on I/O7 (complement-to-data during write, true data after completion) or Toggle Bit behavior on I/O6. Hardware protection includes VCC sense (<3.8 V inhibits write), 5 ms power-on delay, and noise filtering (<15 ns pulses ignored).
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Memory Size | 256 Kbit (32,768 × 8) - provides sufficient nonvolatile storage for firmware images, calibration tables, or device configuration in resource-constrained systems. |
| Read Access Time | 70 ns - enables direct replacement of SRAM in legacy 8-bit microcontroller systems without timing redesign. |
| Page Write Cycle | 3 ms or 10 ms max - selectable via part variant; fast 3 ms option reduces system wait time during field updates. |
| Supply Voltage | 5 V ±10% - compatible with standard TTL/CMOS logic rails and eliminates need for auxiliary voltage regulators. |
| Operating Temperature | –40°C to +85°C - qualified for industrial automation, motor drives, and outdoor instrumentation environments. |
| Endurance | 100,000 write cycles - supports frequent reprogramming in test equipment, programmable logic controllers, and calibration-critical devices. |
| Data Retention | 10 years - ensures long-term reliability of stored parameters without battery backup or refresh circuitry. |
| Standby Current | 3 mA - minimizes quiescent power in always-on industrial nodes where low-power sleep modes are unavailable. |
Pinout & Package
AT28HC256E-70SU is supplied in a 28-lead Small Outline Integrated Circuit (SOIC) package with JEDEC-standard byte-wide pinout and RoHS-compliant green packaging.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| A0–A14 | Address Inputs | 15-bit address bus supporting full 32,768-word addressing; A6–A14 define page boundaries for 64-byte page writes. |
| I/O0–I/O7 | Bidirectional Data Bus | 8-bit parallel data path; I/O7 used for DATA Polling, I/O6 for Toggle Bit status indication during write cycles. |
| CE | Chip Enable | Active-low chip select; must be low with OE low and WE high for read access; controls device selection in multi-chip memory maps. |
| OE | Output Enable | Active-low output gate; allows high-impedance tri-state control independent of CE to resolve bus contention in shared-data-bus architectures. |
| WE | Write Enable | Active-low write strobe; falling edge latches address/data; initiates byte or page write when CE is low and OE is high. |
| VCC | Power Supply | +5 V ±10% main supply; powers core logic and I/O buffers; internally monitored for hardware write inhibition below 3.8 V. |
| GND | Ground Reference | Signal and power return path; decoupling capacitor placement near Pin 14 critical for stable 70 ns read timing. |
Key Features
| Feature | Design Value |
|---|---|
| Automatic Page Write | Internal 64-byte latch and timer eliminate external sequencing logic - simplifies host MCU firmware for bulk parameter updates. |
| DATA Polling & Toggle Bit | Dual asynchronous write-complete detection methods allow flexible polling strategies without fixed delays - improves real-time system responsiveness. |
| Hardware Write Protection | VCC sensing, 5 ms power-on delay, and noise filtering prevent spurious writes during brown-out or EMI events - enhances field reliability in electrically noisy plants. |
| Software Data Protection | Three-step command sequence (AAh/55h/A0h) enables/disables write lock per JEDEC-standard protocol - supports secure firmware update workflows. |
| Device Identification Area | 64-byte reserved EEPROM block (7FC0h–7FFFh) accessible at 12 V on A9 - enables unique serialization, calibration traceability, or manufacturing lot tracking. |
Applications
| Industrial PLC Configuration Storage | Legacy Embedded System BIOS Backup |
|---|---|
Use Scenario: Storing ladder logic programs, I/O mapping tables, and alarm thresholds in programmable logic controllers deployed in factory-floor environments. IC Role / Device Role / Timing Role: Nonvolatile configuration memory accessed via 8-bit parallel bus; 70 ns read timing aligns with 8/16-bit microcontroller bus cycles. Use Value: 100,000 write cycles and 10-year data retention ensure decades of unattended operation without recalibration or manual backup. | Use Scenario: Preserving boot firmware, hardware initialization code, and system settings in legacy medical instruments and test equipment using Z80 or 8051-based controllers. IC Role / Device Role / Timing Role: Drop-in SRAM replacement with identical JEDEC pinout; CE/OE dual-control prevents bus conflicts during reset or interrupt handling. Use Value: Software data protection prevents accidental corruption during power cycling, while page write reduces update time versus byte-by-byte programming. |
| Motor Drive Parameter Calibration | Smart Sensor Node Configuration |
Use Scenario: Holding torque curves, PID coefficients, and thermal derating tables in AC servo drives requiring field-adjustable tuning without firmware reflash. IC Role / Device Role / Timing Role: Field-programmable parameter store accessed during startup or runtime via dedicated MCU GPIOs; 3 ms page write enables rapid calibration uploads. Use Value: Industrial temperature rating (–40°C to +85°C) and hardware VCC-sense protection ensure integrity across wide ambient and load-induced thermal swings. | Use Scenario: Storing sensor calibration offsets, communication addresses, and sampling rate presets in battery-powered environmental monitors with infrequent configuration changes. IC Role / Device Role / Timing Role: Low-power nonvolatile memory; 3 mA standby current extends battery life; DATA Polling avoids fixed-delay polling loops that waste energy. Use Value: Green RoHS-compliant packaging meets regulatory requirements for consumer-facing IoT deployments, while 5 V compatibility simplifies power architecture. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar parallel EEPROM applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| AT28C256-70PU | Same 256-Kbit organization and 70 ns speed, but rated for 10,000 write cycles and uses plastic DIP package. | Limited to lab/test fixtures or low-cycle-count applications; lacks extended endurance and SOIC footprint. | Select only for prototyping or non-industrial use where 10k-cycle endurance suffices and through-hole assembly is preferred. |
| M95256-DW DW | 256-Kbit SPI EEPROM with 5 MHz clock, 5 ms write time, and 400 kHz I²C-compatible mode; no parallel interface. | Requires serial interface redesign; eliminates address/data bus but adds protocol overhead and reduces peak throughput. | Choose for space-constrained designs where PCB real estate is premium and host MCU supports SPI/I²C - not a pin-compatible substitute. |
Compared with AT28HC256E-70SU, AT28C256-70PU offers identical speed and density but lower endurance and through-hole packaging, while M95256-DW DW trades parallel simplicity for serial interface flexibility and smaller footprint - neither matches the AT28HC256E-70SU's combination of industrial-grade endurance, JEDEC SOIC compatibility, and 70 ns timing in legacy parallel systems.
Availability
AT28HC256E-70SU is available at Aetrix Electronics and suitable for industrial PLC configuration storage, legacy embedded system BIOS backup, and motor drive parameter calibration requiring stable component supply across extended production lifecycles.
Supply support for AT28HC256E-70SU 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 is a global provider of microcontrollers, analog components, and memory solutions, serving industrial, automotive, and consumer markets with vertically integrated silicon and software platforms.
The AT28HC256 product line delivers high-reliability parallel EEPROMs optimized for legacy system upgrades, industrial control firmware storage, and applications demanding proven JEDEC-compliant timing and robust write-protection schemes.
FAQ
What is the maximum page write cycle time for AT28HC256E-70SU?
The AT28HC256E-70SU supports two page write cycle options: 3 ms (for extended endurance variants like the "F" suffix) or 10 ms (standard). The "E" in AT28HC256E-70SU denotes 100,000 write cycles and corresponds to the 10 ms option. This timing is guaranteed under industrial temperature and 5 V ±10% supply conditions per DS20006428B.
How does DATA Polling work on AT28HC256E-70SU?
During a write cycle, reading the last written byte from AT28HC256E-70SU returns the complement of the data on I/O7. Once the internal programming completes, true data appears on all I/O lines. This allows the host MCU to poll I/O7 without fixed delays - a critical feature for deterministic real-time systems relying on AT28HC256E-70SU for configuration storage.
Is AT28HC256E-70SU pin-compatible with standard 28-pin SOIC SRAMs?
Yes - AT28HC256E-70SU uses a JEDEC-approved byte-wide pinout identical to industry-standard 28-pin SOIC SRAMs (e.g., 62256). Address (A0–A14), data (I/O0–I/O7), CE, OE, WE, VCC, and GND map directly, enabling drop-in replacement in existing PCB layouts without trace modifications.
What voltage is required to access the device identification area in AT28HC256E-70SU?
The 64-byte device identification area (7FC0h–7FFFh) in AT28HC256E-70SU requires A9 to be raised to 12.0 V ± 0.5 V. This elevated voltage enables secure, factory-only programming of serial numbers or calibration data without affecting normal 5 V operation of the main memory array.
Does AT28HC256E-70SU support both hardware and software write protection?
Yes - AT28HC256E-70SU integrates dual-layer protection: hardware features (VCC sense <3.8 V, 5 ms power-on delay, noise filtering) and software data protection (SDP) enabled via AAh/55h/A0h command sequence. SDP remains active across power cycles and must be explicitly disabled using the 55h/2AAA/80h/55h/2AAA/20h sequence - a key safeguard for AT28HC256E-70SU in mission-critical firmware storage.
AT28HC256E-70SU Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Microchip Technology
- Series:
- -
- Package/Case:
- 28-SOIC (0.295", 7.50mm Width)
- Packaging:
- Tube
- Product Status:
- Discontinued at Digi-Key
- 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:
- 70 ns
- Voltage - Supply:
- 4.5V ~ 5.5V
- Operating Temperature:
- -40°C ~ 85°C (TC)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 28-SOIC
AT28HC256E-70SU FAQ
1.How can I place an order for AT28HC256E-70SU through Aetrix?
Please submit a Request for Quotation (RFQ) for AT28HC256E-70SU 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 AT28HC256E-70SU reliable?
The price and inventory of AT28HC256E-70SU are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for AT28HC256E-70SU is usually 5 days.
3.What payment methods are accepted for AT28HC256E-70SU?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for AT28HC256E-70SU transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for AT28HC256E-70SU?
AT28HC256E-70SU orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your AT28HC256E-70SU 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 AT28HC256E-70SU?
For technical support, including AT28HC256E-70SU datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your AT28HC256E-70SU requirements.
6.How does Aetrix verify that AT28HC256E-70SU is sourced from the original manufacturer or authorized distributors?
All AT28HC256E-70SU 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 AT28HC256E-70SU meets industry standards.
7.What is the process for return or replacement of AT28HC256E-70SU?
All AT28HC256E-70SU units undergo pre-shipment inspection (PSI). If there is an issue with AT28HC256E-70SU, 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 AT28HC256E-70SU part is unused and in its original packaging.
Return procedure for AT28HC256E-70SU:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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