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Microchip Technology AT29C257-20JC
- Part No.:
- AT29C257-20JC
- Manufacturer:
- Microchip Technology
- Category:
- Memory
- Package:
- 32-LCC (J-Lead)
- Datasheet:
-
AT29C257-20JC.pdf
- Description:
- IC FLASH 256KBIT PARALLEL 32PLCC
- Quantity:
- Payment:
- Shipping:
Inventory:3,824
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Product details
Overview
AT29C257-20JC from Atmel (now Microchip) is a 256 Kbit (32K × 8) CMOS parallel EEPROM with 200 ns maximum access time, single 5V supply operation, and hardware write protection via the WP pin. It serves as nonvolatile program/data storage in microcontroller-based systems requiring byte-level erasure and reprogramming.
For engineers reviewing the AT29C257-20JC datasheet, AT29C257-20JC pinout, AT29C257-20JC application, or AT29C257-20JC equivalent, key selection factors include 5V-only operation, 200 ns access timing, hardware write protect, byte-erasable architecture, and JEDEC-standard 32-pin PLCC package compatibility.
Technical Context
The AT29C257-20JC implements a standard parallel interface with address latching via CE and OE controls, supports full array erase or byte-by-byte programming, and uses internal charge pump circuitry for write/erase operations without external high-voltage supply. Its write cycle includes automatic internal timing and status polling capability.
It features a 100,000 write/erase endurance rating and data retention exceeding 10 years at 25°C. The device complies with JEDEC standard pinout for 32-pin PLCC and supports TTL/CMOS level compatibility on all control and data lines.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Memory Size | 256 Kbit (32K × 8), providing sufficient nonvolatile storage for firmware boot code or configuration tables in 8-bit embedded systems. |
| Access Time | 200 ns max at VCC = 5V ±10%, enabling direct interfacing with legacy 8-bit microcontrollers running at ≤5 MHz without wait states. |
| Supply Voltage | 5.0V ±10%, eliminating need for dual-supply design or voltage translation in 5V system architectures. |
| Write Protection | Hardware-enabled via dedicated WP pin, preventing accidental writes during power-up/down or noise events without software overhead. |
| Endurance | 100,000 write/erase cycles per byte, supporting field-updatable calibration data or logging applications with moderate update frequency. |
| Data Retention | 10 years minimum at 25°C, ensuring long-term reliability in industrial control panels or medical device configuration storage. |
Pinout & Package
AT29C257-20JC is housed in a 32-pin Plastic Leaded Chip Carrier (PLCC) package with J-lead configuration, compliant with JEDEC MO-047AB standard and rated for operation from 0°C to 70°C.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| A0–A14 | Address Inputs | 15-bit address bus accepting 00000h–7FFFh range to select one of 32,768 bytes. |
| Q0–Q7 | Data Outputs / Inputs | Bi-directional 8-bit data bus compatible with TTL/CMOS logic levels for read/write transfers. |
| CE | Chip Enable | Active-low signal enabling memory access only when asserted; used for device selection in multi-chip systems. |
| OE | Output Enable | Active-low control for output buffer; allows data read without initiating internal read cycle if CE inactive. |
| WE | Write Enable | Active-low strobe initiating byte-program or erase command sequence when CE and OE are properly controlled. |
| WP | Write Protect | Active-low hardware lock disabling all write/erase operations regardless of WE state, critical for power-fail safety. |
| VCC | Power Supply | +5V supply pin; internal charge pump draws current only during write/erase cycles. |
| GND | Ground | Reference return path for all digital and internal pump circuits. |
Key Features
| Feature | Design Value |
|---|---|
| Single 5V Supply Operation | Eliminates need for +12V or -5V programming voltages, simplifying power design and reducing BOM count in legacy 5V systems. |
| Byte-Level Erase and Program | Enables selective updates of individual configuration parameters without erasing entire memory array, preserving valid data during field maintenance. |
| Hardware Write Protection (WP) | Provides deterministic, glitch-immune write blocking independent of firmware state-essential for fail-safe boot loader environments. |
| JEDEC-Standard PLCC-32 Pinout | Ensures drop-in replacement compatibility with other 32K×8 parallel EEPROMs in existing PCB layouts using PLCC sockets or soldered footprints. |
| Status Polling Support | Allows host controller to monitor write completion via Q7 data line toggling, removing need for fixed delay timers in real-time systems. |
Applications
| Industrial PLC Configuration Storage | Legacy PC BIOS Firmware Backup |
|---|---|
Use Scenario: Storing I/O mapping, PID tuning parameters, and alarm thresholds in programmable logic controllers deployed in factory automation. IC Role / Device Role / Timing Role: Nonvolatile configuration register bank accessed during startup and runtime via 8-bit parallel bus. Use Value: Enables field reconfiguration without firmware reload; WP pin prevents corruption during electrical transients common in industrial EMI environments. | Use Scenario: Holding backup copy of system BIOS code in early x86-based industrial PCs where main flash may be write-locked during operation. IC Role / Device Role / Timing Role: Secondary boot memory mapped into CPU address space for recovery boot path. Use Value: 200 ns access time ensures zero-wait-state execution from backup image; 5V-only operation matches legacy motherboard power rails. |
| Point-of-Sale Terminal Settings | Medical Device Calibration Data |
Use Scenario: Retaining tax rate tables, language packs, and printer settings across power cycles in retail POS terminals with frequent software updates. IC Role / Device Role / Timing Role: Parameter store accessed by 8051 or Z80 derivative MCU during initialization and menu navigation. Use Value: Byte-erasable architecture allows updating single tax table entries without invalidating stored receipt formats or user preferences. | Use Scenario: Storing sensor offset/gain coefficients and regulatory compliance flags in portable diagnostic equipment requiring recalibration every 6–12 months. IC Role / Device Role / Timing Role: Calibration vault accessed during self-test sequence prior to clinical use. Use Value: 100,000-cycle endurance supports repeated recalibration over product lifetime; 10-year data retention meets FDA Class II device archival requirements. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar parallel EEPROM applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| AT29C256-20JC | 256 Kbit capacity same, but lacks hardware WP pin; relies on software write inhibit. | No hardware-level write blocking during power transitions; unsuitable for safety-critical boot storage. | Select only when WP functionality is not required and firmware-controlled protection suffices. |
| MX29LV256DTTC-90G | 32Mbit capacity, 3.3V core, requires VPP = 12V for programming; different pinout and voltage domains. | Not pin-compatible; demands level-shifting and additional power rail-unsuitable for direct replacement. | Consider only for new designs targeting higher density and lower voltage, not retrofit. |
Compared with AT29C257-20JC, AT29C256-20JC omits hardware write protection-reducing robustness in uncontrolled power environments-while MX29LV256DTTC-90G offers greater density but introduces voltage translation complexity and layout incompatibility.
Availability
AT29C257-20JC is available at Aetrix Electronics and suitable for industrial PLCs, legacy BIOS backup systems, and medical calibration storage requiring stable component supply and long-lifecycle support.
Supply support for AT29C257-20JC 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 acquired Atmel in 2016 and maintains legacy Atmel memory products including the AT29C series for backward compatibility and long-term industrial support.
The AT29C family was designed specifically for 5V parallel EEPROM replacement in mature 8-bit embedded systems where reliability, simplicity, and JEDEC-standard footprint are prioritized over density or low-voltage operation.
FAQ
What is the maximum access time specification for AT29C257-20JC?
The AT29C257-20JC has a maximum access time of 200 ns at VCC = 5V ±10% and TA = 25°C. This timing allows direct connection to 8-bit microcontrollers such as the 8051 or Z80 operating at up to 5 MHz without requiring wait-state insertion. The "-20" suffix in AT29C257-20JC explicitly denotes this 200 ns speed grade.
Does AT29C257-20JC require an external high-voltage supply for programming?
No, AT29C257-20JC does not require an external high-voltage supply. It uses an internal charge pump to generate the necessary programming voltage from the standard 5V VCC rail. This eliminates the need for +12V or VPP pins, simplifying board design and reducing external component count compared to older EPROM or early EEPROM technologies.
How is hardware write protection implemented on AT29C257-20JC?
Hardware write protection on AT29C257-20JC is implemented via the dedicated WP (Write Protect) pin, which is active-low. When WP is held low, all write and erase operations are inhibited regardless of WE, CE, or OE states. This provides deterministic, power-fail-safe protection that cannot be overridden by firmware errors or bus glitches-critical for boot code integrity.
Is AT29C257-20JC compatible with standard PLCC-32 sockets?
Yes, AT29C257-20JC uses a JEDEC-standard 32-pin Plastic Leaded Chip Carrier (PLCC) package conforming to MO-047AB dimensions and lead pitch. It is mechanically and electrically compatible with industry-standard PLCC-32 sockets and PCB footprints, enabling straightforward integration into legacy systems designed for similar parallel memory devices.
What is the data retention period for AT29C257-20JC under normal operating conditions?
AT29C257-20JC guarantees a minimum data retention period of 10 years at 25°C ambient temperature. Retention is specified under typical operating conditions (VCC = 5V, no cycling stress), and actual retention may extend beyond 10 years depending on storage temperature and usage history. This meets long-term archival requirements for industrial and medical applications.
AT29C257-20JC Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Microchip Technology
- Series:
- -
- Package/Case:
- 32-LCC (J-Lead)
- Packaging:
- Tube
- Product Status:
- Obsolete
- Programmable:
- Not Verified
- Memory Type:
- Non-Volatile
- Memory Format:
- FLASH
- Technology:
- FLASH
- 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:
- 4.5V ~ 5.5V
- Operating Temperature:
- 0°C ~ 70°C (TC)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 32-PLCC (13.97x11.43)
AT29C257-20JC FAQ
1.How can I place an order for AT29C257-20JC through Aetrix?
Please submit a Request for Quotation (RFQ) for AT29C257-20JC 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 AT29C257-20JC reliable?
The price and inventory of AT29C257-20JC are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for AT29C257-20JC is usually 5 days.
3.What payment methods are accepted for AT29C257-20JC?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for AT29C257-20JC transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for AT29C257-20JC?
AT29C257-20JC orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your AT29C257-20JC 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 AT29C257-20JC?
For technical support, including AT29C257-20JC datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your AT29C257-20JC requirements.
6.How does Aetrix verify that AT29C257-20JC is sourced from the original manufacturer or authorized distributors?
All AT29C257-20JC 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 AT29C257-20JC meets industry standards.
7.What is the process for return or replacement of AT29C257-20JC?
All AT29C257-20JC units undergo pre-shipment inspection (PSI). If there is an issue with AT29C257-20JC, 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 AT29C257-20JC part is unused and in its original packaging.
Return procedure for AT29C257-20JC:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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