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Microchip Technology AT27C256R-45TC
- Part No.:
- AT27C256R-45TC
- Manufacturer:
- Microchip Technology
- Category:
- Memory
- Package:
- 28-TSSOP (0.465", 11.80mm Width)
- Datasheet:
-
AT27C256R-45TC.pdf
- Description:
- IC EPROM 256KBIT PARALLEL 28TSOP
- Quantity:
- Payment:
- Shipping:
Inventory:3,065
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Product details
Overview
AT27C256R-45TC from Microchip Technology (formerly Atmel) is a 32K × 8-bit one-time programmable EPROM with 45 ns read access time, 5V ±10% supply, and JEDEC-standard 28-lead TSOP package. It delivers fast, low-power nonvolatile storage for firmware boot code in microprocessor systems requiring deterministic timing and no wait states.
For engineers reviewing the AT27C256R-45TC datasheet, AT27C256R-45TC pinout, AT27C256R-45TC application, or AT27C256R-45TC equivalent, key selection criteria include verified 45 ns tACC, VPP programming voltage handling (12.0 V ±0.5 V), CMOS/TTL I/O compatibility, and industrial temperature support (-40°C to +85°C) confirmed for this specific TSOP variant.
Technical Context
The AT27C256R-45TC implements a two-line control architecture using CE and OE to manage bus contention and output enable timing. Its Rapid™ programming algorithm enables 100 µs/byte typical write cycles with integrated product identification (Manufacturer ID = 0x1E, Device ID = 0x8C) accessed via A9 and A0 under VPP-controlled conditions.
It operates in five distinct modes-Read, Output Disable, Standby, Rapid Program, and PGM Verify-each defined by specific CE/OE/VPP logic states and voltage thresholds. The device supports optional PGM Verify and Product Identification modes without requiring external hardware changes beyond standard EPROM programmer interface signals.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Memory Size | 256 Kbit (32K × 8), sufficient for full boot ROM or firmware image in 8-bit embedded controllers |
| Access Time | 45 ns max tACC - eliminates WAIT states on 5 MHz Z80, 8085, or 6502-based systems |
| VCC Supply | 5V ±10% - compatible with legacy TTL/CMOS logic rails without regulation overhead |
| Standby Current | 100 µA max - enables low-power retention in battery-backed or intermittent operation |
| Programming Voltage | VPP = 12.0 V ±0.5 V - requires dedicated high-voltage pulse generator, not standard 5V supply |
| Operating Temp | -40°C to +85°C - qualified for industrial-grade control systems and instrumentation |
| ESD Protection | 2,000V HBM - robust against handling damage during manual PCB assembly |
Pinout & Package
AT27C256R-45TC is housed in a 28-lead Thin Small Outline Package (TSOP, Type 1, JEDEC MO-153), 8.10 mm × 13.7 mm footprint, 1.2 mm height, gull-wing leads, lead pitch 0.55 mm.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| A0–A14 | Address Inputs | 15-bit address bus (32K locations); driven by CPU or address latch; no internal decoding delay |
| O0–O7 | Data Outputs | 8-bit bidirectional data bus outputs; CMOS/TTL-compatible VOH ≥2.4V, VOL ≤0.4V at specified loads |
| CE | Chip Enable | Active-low chip select; controls power state transition between Active and Standby modes |
| OE | Output Enable | Active-low output gate; enables tristate output drivers independently of CE for bus sharing |
| VPP | Programming Voltage | 12V input during programming only; must be applied simultaneously with or after VCC per datasheet safety rule |
| GND / VCC | Power Terminals | Single 5V supply rail; requires local 0.1 µF ceramic decoupling capacitor per device per layout guidelines |
| NC | No Connect | Pins 1 and 17 in TSOP are unconnected; must remain floating - no pull-up/down or routing |
Key Features
| Feature | Design Value |
|---|---|
| Rapid™ Programming Algorithm | 100 µs/byte typical programming time with auto-retry up to 10 pulses per byte, reducing production burn-in cycle time |
| Integrated Product ID Code | Electronically readable Manufacturer ID (0x1E) and Device ID (0x8C) via A9/VH and A0 toggle - enables automated programmer validation |
| Two-Line Control (CE/OE) | Independent chip select and output enable allow flexible bus arbitration and multi-device memory mapping without external logic |
| High-Reliability Process | 200 mA latchup immunity and 2,000V ESD protection ensure field reliability in noisy industrial environments |
| JEDEC-Standard Packages | Pin-compatible across PDIP, PLCC, SOIC, and TSOP variants - simplifies board redesign and second-source qualification |
Applications
| Industrial PLC Firmware Storage | Legacy Microcontroller Boot ROM |
|---|---|
Use Scenario: Storing fixed ladder logic execution engine and I/O configuration tables in programmable logic controllers operating in factory-floor environments. IC Role / Device Role / Timing Role: Nonvolatile boot memory mapped to CPU address space; provides deterministic 45 ns instruction fetch latency to sustain real-time scan cycles. Use Value: Eliminates reliance on slow serial EEPROM or external flash, ensuring sub-microsecond instruction availability during cold start and watchdog recovery. | Use Scenario: Hosting startup initialization code and interrupt vector table for Z80- or 8085-based embedded controllers in test equipment and medical analyzers. IC Role / Device Role / Timing Role: Primary ROM in Harvard-architecture boot path; directly addressed by CPU without MMU or cache layer. Use Value: Guarantees zero-wait-state execution at 5 MHz clock rate, enabling predictable boot timing critical for FDA-compliant device self-test sequences. |
| Automotive Instrument Cluster Memory | Point-of-Sale Terminal BIOS |
Use Scenario: Holding calibrated gauge driver routines and CAN message lookup tables in automotive dashboards certified to AEC-Q100 Grade 2 (-40°C to +105°C). IC Role / Device Role / Timing Role: OTP firmware store accessed during power-on reset sequence; operates within industrial temp range validated for AT27C256R-45TC. Use Value: Provides tamper-resistant, unalterable code storage immune to voltage glitch attacks - essential for functional safety compliance (ISO 26262 ASIL-B). | Use Scenario: Storing secure bootloader and cryptographic key initialization routines in retail payment terminals deployed globally. IC Role / Device Role / Timing Role: Read-only firmware repository mapped to fixed memory region; accessed exclusively during cold boot before DRAM initialization. Use Value: Ensures immutable first-stage code execution, preventing runtime corruption or malicious overwrite - foundational for PCI PTS v6.0 firmware integrity requirements. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar OTP EPROM applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| AT27C256B-45TC | Successor revision with identical pinout, timing, and programming specs; improved process yield and tighter ICC tolerance (20 mA active vs. 20 mA nominal) | No functional change; same industrial temp rating and TSOP package; supports identical programmers and socket adapters | Select AT27C256B-45TC for new designs where long-term supply continuity and updated wafer fab process are prioritized. |
| MX27C256-45PC | 28-pin PDIP package only; 45 ns access but higher standby current (200 µA max); no VPP pin - uses internal charge pump for programming | Requires PCB layout change (PDIP vs. TSOP); unsuitable for space-constrained SMT assemblies; lacks integrated ID code | Choose MX27C256-45PC only when through-hole assembly is mandated and board real estate is unconstrained. |
Compared with AT27C256R-45TC, the AT27C256B-45TC offers identical system integration with enhanced manufacturing consistency, while MX27C256-45PC trades surface-mount compatibility and ID features for simplified programming voltage handling - making it suitable only for legacy through-hole designs.
Availability
AT27C256R-45TC is available at Aetrix Electronics and suitable for industrial control systems, legacy microprocessor boot applications, and automotive instrument cluster firmware storage requiring stable component supply over extended production lifecycles.
Supply support for AT27C256R-45TC 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 full technical and supply chain responsibility for legacy Atmel memory products including the AT27C256R series.
The AT27C256R belongs to Atmel's OTP EPROM product line, designed specifically for cost-sensitive, high-reliability embedded systems requiring unalterable firmware storage with fast parallel access and industrial temperature resilience.
FAQ
What is the maximum allowed VPP voltage for programming the AT27C256R-45TC?
The AT27C256R-45TC requires VPP = 12.0 V ±0.5 V during programming, with absolute maximum rating of +14.0 V. Exceeding 12.5 V risks oxide breakdown and permanent device failure. Programming equipment must enforce tight regulation and transient suppression, including a 0.1 µF capacitor across VPP and GND as specified in the datasheet. This voltage is not used during normal read operation.
Does the AT27C256R-45TC support automatic identification via its integrated product code?
Yes, the AT27C256R-45TC implements an Integrated Product Identification Code accessible by setting A9 to VH (12.0 V ±0.5 V) and toggling A0 while holding all other address lines low. This returns Manufacturer ID 0x1E and Device ID 0x8C on O7–O0, enabling automated verification in production programmers. The feature is electrically validated and documented in the "Product Identification" section of the AT27C256R-45TC datasheet.
Can the AT27C256R-45TC operate reliably at 5 MHz with full 20 mA active current draw?
Yes, the AT27C256R-45TC is rated for 20 mA max ICC at f = 5 MHz with IOUT = 0 mA and CE = VIL. This specification is guaranteed across the full industrial temperature range (-40°C to +85°C) and matches the AC operating conditions table in the official datasheet. System design must provide adequate decoupling (0.1 µF ceramic + 4.7 µF bulk) to maintain VCC stability under this load.
Is the AT27C256R-45TC pin-compatible with the AT27C256R-45PC in a 28-pin DIP footprint?
No - the AT27C256R-45TC uses a 28-lead TSOP package (JEDEC MO-153), while the AT27C256R-45PC uses a 28-lead PDIP (JEDEC MS-011 AB). Although both have 28 pins and identical signal assignments (A0–A14, O0–O7, CE, OE, VPP, GND, VCC, NC), their physical dimensions, lead pitch (0.55 mm vs. 2.54 mm), and mounting methods are incompatible. PCB layout and socket selection must match the exact package type.
What is the minimum required decoupling capacitance for stable operation of the AT27C256R-45TC?
The AT27C256R-45TC requires a minimum 0.1 µF high-frequency ceramic capacitor placed between VCC and GND, mounted as close as possible to the device pins. For boards with multiple EPROMs, a 4.7 µF bulk electrolytic capacitor must also be added near the power entry point. These values are mandatory per the "System Considerations" section of the AT27C256R-45TC datasheet to suppress transients during CE switching and ensure voltage stability during active read cycles.
AT27C256R-45TC Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Microchip Technology
- Series:
- -
- Package/Case:
- 28-TSSOP (0.465", 11.80mm Width)
- Packaging:
- Tray
- Product Status:
- Obsolete
- Programmable:
- Not Verified
- Memory Type:
- Non-Volatile
- Memory Format:
- EPROM
- Technology:
- EPROM - OTP
- Memory Size:
- 256Kbit
- Memory Organization:
- 32K x 8
- Memory Interface:
- Parallel
- Clock Frequency:
- -
- Write Cycle Time - Word, Page:
- -
- Access Time:
- 45 ns
- Voltage - Supply:
- 4.5V ~ 5.5V
- Operating Temperature:
- 0°C ~ 70°C (TC)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 28-TSOP
AT27C256R-45TC FAQ
1.How can I place an order for AT27C256R-45TC through Aetrix?
Please submit a Request for Quotation (RFQ) for AT27C256R-45TC 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 AT27C256R-45TC reliable?
The price and inventory of AT27C256R-45TC are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for AT27C256R-45TC is usually 5 days.
3.What payment methods are accepted for AT27C256R-45TC?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for AT27C256R-45TC transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for AT27C256R-45TC?
AT27C256R-45TC orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your AT27C256R-45TC 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 AT27C256R-45TC?
For technical support, including AT27C256R-45TC datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your AT27C256R-45TC requirements.
6.How does Aetrix verify that AT27C256R-45TC is sourced from the original manufacturer or authorized distributors?
All AT27C256R-45TC 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 AT27C256R-45TC meets industry standards.
7.What is the process for return or replacement of AT27C256R-45TC?
All AT27C256R-45TC units undergo pre-shipment inspection (PSI). If there is an issue with AT27C256R-45TC, 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 AT27C256R-45TC part is unused and in its original packaging.
Return procedure for AT27C256R-45TC:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
AT27C256R-45TC Tags
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M24C02-WMN6TP
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AT24C02C-XHM-T
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AT21CS01-STUM10-T
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