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Microchip Technology AT28HC256-90JU-T
- Part No.:
- AT28HC256-90JU-T
- Manufacturer:
- Microchip Technology
- Category:
- Memory
- Package:
- 32-LCC (J-Lead)
- Datasheet:
-
AT28HC256-90JU-T.pdf
- Description:
- IC EEPROM 256KBIT PAR 32PLCC
- Quantity:
- Payment:
- Shipping:
Inventory:1,742
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Product details
Overview
AT28HC256-90JU-T from Microchip Technology is a 256-Kbit (32,768 × 8) parallel EEPROM with 90 ns read access time, single 5V ±10% supply operation, and industrial temperature range (–40°C to +85°C). It supports 1–64-byte page writes with ≤10 ms internal write cycle time and features hardware/software data protection for embedded control and firmware storage applications.
For engineers reviewing the AT28HC256-90JU-T datasheet, AT28HC256-90JU-T pinout, AT28HC256-90JU-T application, or AT28HC256-90JU-T equivalent, key selection considerations include JEDEC byte-wide pin compatibility, DATA Polling/Toggle Bit write completion detection, 3 mA standby current, and PLCC-32 packaging for legacy board designs requiring nonvolatile memory with SRAM-like interface simplicity.
Technical Context
The AT28HC256-90JU-T implements a CMOS-based parallel EEPROM architecture with internal 64-byte page latches and autonomous write timing. Its dual-line chip enable (CE) and output enable (OE) logic enables bus contention avoidance in multi-device systems, while VCC sense and 5 ms power-on delay prevent inadvertent writes during power transitions.
It supports three write modes: byte write, page write (with 150 µs inter-byte load window), and optional software chip erase. Write completion is confirmed via I/O7 DATA Polling or I/O6 Toggle Bit, both operable without external timing components - eliminating need for wait-state logic in microcontroller interfaces.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Memory size | 256 Kbit (32,768 × 8) - provides sufficient space for boot code, calibration tables, or configuration data in resource-constrained embedded systems |
| Read access time | 90 ns - enables direct interfacing with 8-bit/16-bit microcontrollers operating at ≤10 MHz without wait states |
| Page write time | ≤10 ms - reduces firmware update latency compared to byte-by-byte programming; supports efficient field reprogramming |
| Supply voltage | 5V ±10% - compatible with legacy 5V logic families and eliminates need for level-shifting circuitry |
| Standby current | 3 mA - minimizes power consumption in always-on industrial controllers during idle periods |
| Endurance | 10,000 write cycles - suitable for infrequent parameter logging or configuration storage, not high-frequency data logging |
| Data retention | 10 years - ensures long-term reliability in unattended equipment such as metering or remote sensors |
Pinout & Package
AT28HC256-90JU-T is packaged in a 32-lead Plastic Leaded Chip Carrier (PLCC) with JEDEC-standard byte-wide pinout. Pins 1 and 17 are designated "Don't Connect" and must remain unconnected on PCB layout.
| 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 interface; I/O7 used for DATA Polling, I/O6 for Toggle Bit status indication during writes |
| CE | Chip Enable | Active-low device select; when high, places outputs in high-impedance state regardless of OE/WE state |
| OE | Output Enable | Active-low read control; enables data output only when CE is also low - prevents bus contention |
| WE | Write Enable | Active-low write strobe; falling edge latches address/data; rising edge initiates internal write timer |
| VCC / GND | Power supply | Single 5V supply with 3 mA standby draw; ground pin (16) must be low-inductance connection for noise immunity |
Key Features
| Feature | Design Value |
|---|---|
| JEDEC byte-wide pinout | Ensures drop-in compatibility with legacy SRAM and EPROM sockets in industrial control boards and instrumentation |
| Hardware write protection | VCC sense (inhibits write below 3.8V) and 5 ms power-on delay eliminate need for external reset supervisors |
| Software data protection | Three-step command sequence (AAh/55h/A0h) enables user-configurable lock/unlock of entire memory array |
| DATA Polling & Toggle Bit | Dual asynchronous write completion detection methods reduce CPU polling overhead and simplify firmware integration |
| 64-byte page register | Allows burst loading of up to 64 bytes before internal write begins - improves throughput vs. sequential byte writes |
Applications
| Industrial PLC Configuration Storage | Medical Device Calibration Data |
|---|---|
Use Scenario: Storing I/O mapping, PID tuning parameters, and alarm thresholds in programmable logic controllers that operate continuously in factory environments. IC Role / Device Role / Timing Role: Nonvolatile configuration memory accessed during boot and runtime; requires 90 ns read speed to keep pace with scan-cycle execution. Use Value: 10-year data retention and 10,000-cycle endurance ensure parameter integrity across extended maintenance intervals without battery backup. | Use Scenario: Holding sensor calibration coefficients and safety-critical operational limits in portable diagnostic equipment subject to frequent power cycling. IC Role / Device Role / Timing Role: Firmware-adjacent data store; accessed via 8-bit parallel bus during initialization and recalibration routines. Use Value: Hardware write protection prevents corruption during brown-out conditions, meeting IEC 62304 Class B software safety requirements. |
| Legacy Automotive ECU Bootloader Storage | Test Equipment Firmware Patch Area |
Use Scenario: Hosting bootloader code and secure update metadata in engine control units where CAN-based reprogramming occurs infrequently. IC Role / Device Role / Timing Role: Read-only execution memory during startup; write-enabled only during authenticated firmware updates. Use Value: Software data protection (SDP) allows selective locking of bootloader region while permitting patch writes to application sectors. | Use Scenario: Providing field-upgradable firmware patches in automated test systems where downtime must be minimized during calibration updates. IC Role / Device Role / Timing Role: Secondary code storage accessed over ISA or custom parallel bus; updated via page-write mode to reduce reprogramming time. Use Value: 10 ms max page write time cuts patch deployment duration by >95% versus byte-by-byte programming, accelerating production line changeovers. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar parallel EEPROM applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| AT28C256-90PU | Same 256-Kbit organization and 90 ns access, but in 28-pin PDIP package; no PLCC footprint compatibility | Suitable for through-hole prototyping or legacy DIP-based systems; lacks PLCC thermal/mechanical robustness for vibration-prone environments | Select when board layout uses DIP sockets or manual assembly is required; verify pinout alignment with A0–A14/I/O0–I/O7 mapping |
| FM24CL256-G | F-RAM with 10¹⁴ write endurance and 150 ns access; operates at 2.7–3.6V only; serial I²C interface instead of parallel | Replaces parallel EEPROM in low-power, high-write-cycle applications but requires bus interface redesign and voltage translation | Choose only if system already uses I²C infrastructure and demands >1 million write cycles; not a drop-in replacement due to interface and voltage mismatch |
Compared with AT28HC256-90JU-T, AT28C256-90PU offers identical electrical behavior but incompatible packaging, while FM24CL256-G delivers superior endurance and speed at the cost of interface redesign and supply voltage constraints - making AT28HC256-90JU-T optimal for maintaining legacy 5V parallel bus designs with industrial reliability requirements.
Availability
AT28HC256-90JU-T is available at Aetrix Electronics and suitable for industrial PLCs, medical calibration systems, automotive ECUs, and test equipment requiring stable component supply with long lifecycle support.
Supply support for AT28HC256-90JU-T 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 semiconductor company specializing in microcontrollers, analog devices, and nonvolatile memory solutions for industrial, automotive, and consumer applications.
The AT28HC256 product line delivers high-reliability parallel EEPROMs optimized for legacy system upgrades and applications demanding SRAM-compatible timing with nonvolatile storage - targeting industrial control, instrumentation, and embedded firmware storage.
FAQ
What is the maximum write cycle time for AT28HC256-90JU-T during page write operations?
The AT28HC256-90JU-T has a maximum page write cycle time of 10 ms, as specified in its datasheet for standard endurance grade devices. This applies to all 1–64-byte page writes and reflects the internal timer duration after the final byte is latched. The AT28HC256-90JU-T does not support the 3 ms fast-write variant (marked with 'F' suffix); users requiring faster writes must select AT28HC256F-90JU-T instead.
Does AT28HC256-90JU-T support software data protection, and how is it enabled?
Yes, AT28HC256-90JU-T supports software data protection (SDP) via a three-step command sequence: write AAh to address 5555h, then 55h to 2AAAh, then A0h to 5555h. After this sequence completes, the entire memory array is locked against unintended writes. The AT28HC256-90JU-T ships with SDP disabled by default, and the feature remains active across power cycles until explicitly disabled using the corresponding unlock sequence.
Can AT28HC256-90JU-T be used as a direct replacement for older 27C256 EPROMs in existing designs?
No, AT28HC256-90JU-T is not a direct replacement for 27C256 EPROMs despite identical pin count and memory size. Unlike EPROMs, the AT28HC256-90JU-T requires no UV erasure, uses different write control signals (WE instead of PGM), and has distinct timing for write cycles and output enable behavior. Board-level changes to write strobe logic and removal of UV window provisions are necessary when migrating from 27C256 to AT28HC256-90JU-T.
What is the function of pins 1 and 17 on the AT28HC256-90JU-T PLCC package?
Pins 1 and 17 of the AT28HC256-90JU-T PLCC package are designated "Don't Connect" (DC) per the official Microchip datasheet. These pins must remain unconnected on the PCB - neither tied to VCC, GND, nor any signal net. Connecting them may cause undefined behavior or damage. The AT28HC256-90JU-T's functional pin count is 30, with DC pins serving only mechanical alignment and thermal relief roles in the PLCC package.
How does DATA Polling work on AT28HC256-90JU-T, and which pin is monitored?
DATA Polling on AT28HC256-90JU-T monitors I/O7: during an active write cycle, reading the last written byte returns the complement of the data on I/O7; once the write completes, true data appears. This allows the host microcontroller to poll I/O7 without halting execution or relying on fixed delays. The AT28HC256-90JU-T supports continuous polling from any time after write initiation, and the method is electrically identical across all variants in the AT28HC256 family.
AT28HC256-90JU-T Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Microchip Technology
- Series:
- -
- Package/Case:
- 32-LCC (J-Lead)
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- 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:
- 90 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 (11.43x13.97)
AT28HC256-90JU-T FAQ
1.How can I place an order for AT28HC256-90JU-T through Aetrix?
Please submit a Request for Quotation (RFQ) for AT28HC256-90JU-T 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 AT28HC256-90JU-T reliable?
The price and inventory of AT28HC256-90JU-T are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for AT28HC256-90JU-T is usually 5 days.
3.What payment methods are accepted for AT28HC256-90JU-T?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for AT28HC256-90JU-T transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for AT28HC256-90JU-T?
AT28HC256-90JU-T orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your AT28HC256-90JU-T 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 AT28HC256-90JU-T?
For technical support, including AT28HC256-90JU-T datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your AT28HC256-90JU-T requirements.
6.How does Aetrix verify that AT28HC256-90JU-T is sourced from the original manufacturer or authorized distributors?
All AT28HC256-90JU-T 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 AT28HC256-90JU-T meets industry standards.
7.What is the process for return or replacement of AT28HC256-90JU-T?
All AT28HC256-90JU-T units undergo pre-shipment inspection (PSI). If there is an issue with AT28HC256-90JU-T, 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 AT28HC256-90JU-T part is unused and in its original packaging.
Return procedure for AT28HC256-90JU-T:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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