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Microchip Technology AT28HC256-70TU-T
- Part No.:
- AT28HC256-70TU-T
- Manufacturer:
- Microchip Technology
- Category:
- Memory
- Package:
- 28-TSSOP (0.465", 11.80mm Width)
- Datasheet:
-
AT28HC256-70TU-T.pdf
- Description:
- IC EEPROM 256KBIT PAR 28TSOP
- Quantity:
- Payment:
- Shipping:
Inventory:3,760
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Product details
Overview
AT28HC256-70TU-T from Microchip Technology is a military-grade 256-Kbit (32,768 × 8) paged parallel EEPROM with 90 ns read access time, 3 ms or 10 ms page write cycle time, and full operation across –55°C to +125°C. It features hardware/software data protection, DATA polling for write completion detection, and JEDEC-approved byte-wide pinout-used in avionics control memory, secure boot storage, and radiation-tolerant instrumentation.
For engineers reviewing the AT28HC256-70TU-T datasheet, AT28HC256-70TU-T pinout, AT28HC256-70TU-T application, or AT28HC256-70TU-T equivalent, key selection criteria include military temperature compliance, 64-byte page write capability, VCC sense-based write inhibit, toggle-bit or polling-based write status monitoring, and compatibility with legacy 5V parallel bus architectures requiring high-reliability nonvolatile storage.
Technical Context
The AT28HC256-70TU-T implements a static RAM-compatible interface with dual-line chip enable (CE) and output enable (OE) control, enabling bus contention avoidance in multi-master systems. Its internal 64-byte page register latches address and data during write cycles, freeing the bus while an internal timer executes programming.
Write operations support three modes: byte write, page write (1–64 bytes within same A6–A14 page), and optional software chip erase. End-of-write detection uses either I/O7 DATA polling (complement-to-data then true data) or I/O6 toggle-bit behavior-both usable at any point during tWC without external timing constraints.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Memory size | 256 Kbit (32,768 × 8), organized as 64-byte pages for efficient bulk writes |
| Read access time | 90 ns maximum-enables direct replacement of SRAM in legacy 5V bus systems |
| Page write time | 3 ms or 10 ms max-determines minimum interval between successive page writes |
| Operating temperature | –55°C to +125°C-fully qualified for MIL-STD-883 Class B military applications |
| Supply voltage | 5 V ±10%-compatible with standard TTL/CMOS logic rails without regulation |
| Endurance | 10,000 or 100,000 write/erase cycles-depends on specific variant marking; supports long-life field deployment |
| Data retention | 10 years at +125°C-guaranteed nonvolatile storage under worst-case thermal stress |
| Power dissipation | 440 mW active (80 mA @ 5.5 V), <3 mA CMOS standby-reduces thermal load in sealed enclosures |
Pinout & Package
AT28HC256-70TU-T is supplied in a 32-lead CLCC (Ceramic Leadless Chip Carrier) package with "Don't Connect" pins at positions 1 and 17. The package meets MIL-STD-1835 C-12 and is hermetically sealed for high-reliability environments.
| 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 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 device select; must be low with OE low and WE high for read access |
| OE | Output Enable | Active-low output gate; enables high-impedance state when high to prevent bus contention |
| WE | Write Enable | Active-low write strobe; falling edge latches address/data; initiates byte or page programming |
| VCC | Power supply | +5 V ±10% input; includes internal VCC sense circuitry that inhibits writes below ~3.8 V |
| GND | Ground reference | Signal and power return path; required for stable DC bias and noise immunity |
| DC (pins 1, 17) | Don't Connect | No internal connection; must remain unconnected per datasheet to avoid functional disruption |
Key Features
| Feature | Design Value |
|---|---|
| JEDEC byte-wide pinout | Ensures drop-in compatibility with legacy 27C256/27C512 sockets and PCB layouts |
| Hardware write protection | VCC sense + 5 ms power-on delay + noise filtering (<15 ns pulses rejected) prevents spurious writes during power transients |
| Software data protection (SDP) | User-enabled 3-byte unlock sequence (AAh/55h/A0h) blocks all writes until re-issued-supports secure firmware update workflows |
| 64-byte page register | Enables burst loading of up to 64 bytes before internal programming begins-reduces host CPU overhead by >90% vs. byte-by-byte writes |
| Device identification area | 64-byte reserved sector (7FC0h–7FFFh) accessible via 12 V on A9-used for traceability, calibration data, or unique device ID storage |
Applications
| Avionics Flight Control Memory | Secure Boot Configuration Storage |
|---|---|
Use Scenario: Storing flight-critical configuration parameters and trim tables in airborne guidance computers operating under extreme thermal cycling and vibration. IC Role / Device Role / Timing Role: Nonvolatile memory holding immutable system initialization data accessed during cold start and runtime recalibration. Use Value: Guaranteed 10-year data retention at +125°C and 10,000+ endurance cycles ensure parameter integrity over aircraft service life without refresh. | Use Scenario: Holding cryptographic keys, bootloader signatures, and secure boot policy flags in defense-grade embedded systems with anti-tamper requirements. IC Role / Device Role / Timing Role: Trusted storage element interfacing directly with microcontroller's parallel bus during pre-boot validation phase. Use Value: Hardware VCC-sense and software data protection prevent unauthorized modification-even during brown-out or glitch attacks. |
| Radiation-Hardened Instrumentation | Military Communications Radio Firmware |
Use Scenario: Logging sensor calibration coefficients and fault history in space-qualified telemetry modules exposed to total ionizing dose (TID) >100 krad(Si). IC Role / Device Role / Timing Role: Radiation-tolerant EEPROM providing persistent storage independent of upstream FPGA or processor uptime. Use Value: Hermetic 32-lead CLCC packaging and CMOS process technology deliver proven TID resilience in orbital and high-altitude platforms. | Use Scenario: Storing frequency-hopping tables, encryption keys, and channel mapping data in manpack and vehicular radios operating in contested EM environments. IC Role / Device Role / Timing Role: Parallel-interface nonvolatile memory supporting deterministic read latency (<90 ns) for real-time waveform generation. Use Value: JEDEC pinout and 5V TTL/CMOS compatibility allow integration into legacy radio baseband ASIC designs without interface translation. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar parallel EEPROM applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| AT28HC256-12TU-T | 120 ns read access time; otherwise identical architecture, pinout, and military temp rating | Suitable where timing margin allows slower access; lower cost in volume | Select when system clock budget permits 120 ns latency and cost optimization is prioritized over peak performance |
| AT28C256-15PU | Commercial grade (0°C to +70°C); 150 ns access; PDIP-28 package; no military qualification or VCC sense | Limited to benign-environment industrial controls or lab equipment | Use only in non-military, non-extended-temperature applications where hermetic sealing and radiation tolerance are unnecessary |
Compared with AT28HC256-12TU-T, the -70TU-T delivers tighter read timing critical for high-speed bus arbitration; versus AT28C256-15PU, it provides full MIL-STD-883 qualification, extended temperature range, and robust hardware write protection essential for deployed defense systems.
Availability
AT28HC256-70TU-T is available at Aetrix Electronics and suitable for avionics control memory, secure boot storage, and radiation-hardened instrumentation requiring stable component supply across extended product lifecycles.
Supply support for AT28HC256-70TU-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 memory solutions with emphasis on reliability and long-term support.
The AT28HC256 belongs to Microchip's military-grade parallel EEPROM product line, designed specifically for high-integrity, mission-critical applications in aerospace, defense, and industrial systems demanding extended temperature operation and data security.
FAQ
What is the guaranteed data retention period for AT28HC256-70TU-T at maximum operating temperature?
The AT28HC256-70TU-T guarantees 10 years of data retention at +125°C. This specification is validated per MIL-STD-883 test method 1008 and applies to both standard (10K-cycle) and extended (100K-cycle) endurance variants. The retention period is measured under continuous bias at rated VCC and temperature, with no refresh required during service life. AT28HC256-70TU-T achieves this through advanced oxide processing and hermetic CLCC packaging that minimizes moisture ingress and charge leakage.
Does AT28HC256-70TU-T support true page write operations, and what is the maximum page size?
Yes, AT28HC256-70TU-T supports true page write operations with a fixed 64-byte page size. The device uses an internal page register to latch up to 64 bytes of data before initiating internal programming-enabling burst writes without intermediate bus release. All bytes in a page write must reside within the same page boundary defined by address bits A6–A14; A0–A5 select individual bytes within that page. AT28HC256-70TU-T enforces a 150 µs inter-byte load window (tBLC) to maintain page integrity.
How does hardware write protection function in AT28HC256-70TU-T during power-up sequences?
AT28HC256-70TU-T implements three-tier hardware write protection during power-up: (1) VCC sense circuitry disables writes until VCC exceeds ~3.8 V; (2) a built-in 5 ms power-on delay timer prevents writes for 5 ms after VCC stabilization; and (3) noise filters reject CE/WE pulses shorter than 15 ns. These features collectively eliminate inadvertent writes caused by power rail overshoot, undershoot, or switching transients. AT28HC256-70TU-T maintains this protection across its full –55°C to +125°C range without external components.
Can AT28HC256-70TU-T be used as a direct replacement for older 27C256 EPROMs in existing designs?
No, AT28HC256-70TU-T is not a direct replacement for 27C256 EPROMs due to fundamental differences: it requires no UV erasure, supports electrical byte/page writes, and uses different control timing (CE/OE/WE vs. OE/CE/G). However, its JEDEC-approved byte-wide pinout and 5V operation allow PCB reuse if the host system implements proper write sequencing and status polling. AT28HC256-70TU-T replaces 27C256 in applications needing field-upgradable firmware-not mask-programmed ROM.
What is the purpose and access method for the 64-byte device identification area in AT28HC256-70TU-T?
AT28HC256-70TU-T includes a dedicated 64-byte device identification area (addresses 7FC0h–7FFFh) for storing calibration data, serial numbers, or manufacturing trace codes. Access requires raising A9 to 12.0 V ± 0.5 V while applying standard VCC and address/data signals-activating a high-voltage decode path. Reads/writes to this region use identical timing as main array operations. AT28HC256-70TU-T isolates this sector from normal operation to prevent accidental overwrite during routine firmware updates.
AT28HC256-70TU-T Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Microchip Technology
- Series:
- -
- Package/Case:
- 28-TSSOP (0.465", 11.80mm Width)
- Packaging:
- Tape & Reel (TR)
- 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:
- 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-TSOP
AT28HC256-70TU-T FAQ
1.How can I place an order for AT28HC256-70TU-T through Aetrix?
Please submit a Request for Quotation (RFQ) for AT28HC256-70TU-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 AT28HC256-70TU-T reliable?
The price and inventory of AT28HC256-70TU-T are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for AT28HC256-70TU-T is usually 5 days.
3.What payment methods are accepted for AT28HC256-70TU-T?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for AT28HC256-70TU-T transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for AT28HC256-70TU-T?
AT28HC256-70TU-T orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your AT28HC256-70TU-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 AT28HC256-70TU-T?
For technical support, including AT28HC256-70TU-T datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your AT28HC256-70TU-T requirements.
6.How does Aetrix verify that AT28HC256-70TU-T is sourced from the original manufacturer or authorized distributors?
All AT28HC256-70TU-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 AT28HC256-70TU-T meets industry standards.
7.What is the process for return or replacement of AT28HC256-70TU-T?
All AT28HC256-70TU-T units undergo pre-shipment inspection (PSI). If there is an issue with AT28HC256-70TU-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 AT28HC256-70TU-T part is unused and in its original packaging.
Return procedure for AT28HC256-70TU-T:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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