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Microchip Technology 24CS256T-E/ST66KVAO

Name: 24CS256T-E/ST66KVAO
Brand: Microchip Technology
SKU: 24CS256T-E/ST66KVAO
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: 24CS256T-E/ST66KVAO

Manufacturer:: Microchip Technology

Category:: Memory

Package:: 8-TSSOP (0.173", 4.40mm Width)

Datasheet:: 24CS256T-E/ST66KVAO.pdf

Description:: IC EEPROM 256KBIT I2C 8TSSOP

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Product details

Overview

24CS256T-E/ST66KVAO from Microchip Technology is a 256-Kbit I²C serial EEPROM organized as 32,768 × 8-bit, supporting byte/page writes (up to 64 bytes), self-timed write cycles ≤5 ms, and high-speed I²C up to 3.4 MHz. It features a factory-programmed 128-bit unique serial number, user-lockable 64-byte ID page, built-in ECC for single-bit correction, and hardware/software write protection - deployed in automotive infotainment control modules for configuration storage.

For engineers reviewing the 24CS256T-E/ST66KVAO datasheet, 24CS256T-E/ST66KVAO pinout, 24CS256T-E/ST66KVAO application, or 24CS256T-E/ST66KVAO equivalent, key selection considerations include its AEC-Q100 qualification, extended temperature range (–40°C to +125°C), dual write-protection modes (WP pin + configurable zone locking), and I²C manufacturer ID support for system-level device identification.

Technical Context

The 24CS256T-E/ST66KVAO implements a two-wire I²C interface with Schmitt-trigger inputs, slope-controlled outputs, and programmable high-speed mode (3.4 MHz at VCC ≥2.5V). Its memory architecture separates the main 256-Kbit array (0000h–7FFFh) from a dedicated 1-Kbit security register containing read-only serial number (0800h–080Fh) and lockable user ID page (0840h–087Fh).

Device operation is governed by three registers: Configuration register (enables enhanced software write protection per 32-Kbit zone), Security register (factory-serialized + user-programmable), and Manufacturer ID register (24-bit read-only I²C-compliant ID). Write endurance exceeds 1 million cycles; data retention exceeds 200 years at 55°C.

Key Specifications

Parameter	Value and Actual Design Meaning
Memory Size	256 Kbit (32,768 × 8-bit), organized in 512 pages of 64 bytes each - enables efficient firmware parameter storage with page-aligned updates.
I²C Speed Support	Up to 3.4 MHz (High-Speed mode), plus 1 MHz / 400 kHz / 100 kHz - compatible with modern microcontrollers requiring fast nonvolatile config reads/writes.
Write Cycle Time	≤5 ms max (self-timed), supports byte or 64-byte page writes - reduces host MCU wait time and improves system responsiveness during configuration saves.
Operating Voltage	1.7V to 5.5V - interoperable across 1.8V logic systems and legacy 3.3V/5V designs without level-shifting.
Temperature Range	–40°C to +125°C (Extended grade, E-temp) - qualified for under-hood automotive and industrial edge nodes.
Reliability	1,000,000 write cycles; >200-year data retention at 55°C; built-in ECC corrects single-bit errors per 4-byte read - ensures long-term integrity of calibration and security-critical data.
Security Features	Factory-programmed 128-bit globally unique serial number + 64-byte user-lockable ID page - eliminates manufacturing serialization overhead and enables secure device binding.

Pinout & Package

24CS256T-E/ST66KVAO is packaged in an 8-lead UDFN (2 mm × 3 mm, wettable flank) with exposed pad. Pin functions are electrically identical across all 8-pin variants (SOIC, TSSOP, MSOP, VDFN); this UDFN variant supports automated optical inspection (AOI) and improved thermal performance.

Pin/Terminal	Circuit Role	Design Meaning
A0	Hardware Address Input	LSB of 3-bit client address; sets device I²C address (1010xxx) - allows up to eight 24CS256T-E/ST66KVAO devices on one bus.
A1	Hardware Address Input	Middle bit of 3-bit client address - used with A0/A2 to configure unique I²C slave address in multi-device systems.
A2	Hardware Address Input	MSB of 3-bit client address - hardwired to VSS or VCC to select among eight possible addresses (1010000b to 1010111b).
VSS	Ground Reference	Primary return path for all internal circuits and I/O - must be low-impedance connection to minimize noise coupling into SDA/SCL lines.
SDA	Serial Data Bidirectional Line	Open-drain I²C data line requiring external pull-up - transmits/receives device address, word address, and data; supports ACK/NACK signaling.
SCL	Serial Clock Input	Master-generated clock synchronizing all I²C transfers - rise/fall times constrained to meet timing specs (e.g., ≤1000 ns at 100 kHz).
WP	Hardware Write-Protect Input	Active-high pin disabling all writes to main array and security register when tied to VCC - provides fail-safe protection against accidental overwrites.
VCC	Power Supply	1.7V–5.5V supply input powering EEPROM core and I/O buffers - decoupling capacitor (0.1 µF) required near pin for stable operation.

Key Features

Feature	Design Value
128-bit Factory-Serialized ID	Globally unique identifier preprogrammed at wafer level - eliminates post-manufacturing serialization cost and enables traceability in Tier-1 automotive supply chains.
Configurable Zone Write Protection	Eight independent 32-Kbit zones can be individually locked via Configuration register - supports hierarchical access control (e.g., lock bootloader params while allowing runtime config updates).
Built-in ECC Logic	Corrects single-bit errors within any 4-byte read window and latches error state in ECS bit - prevents silent data corruption in safety-critical logging applications.
I²C Manufacturer ID Support	Returns unique 24-bit value upon I²C host command - enables automatic firmware detection of 24CS256T-E/ST66KVAO vs. legacy 24AA256/AT24C256 in mixed-bill-of-materials systems.
AEC-Q100 Qualified	Qualified to Grade 1 (–40°C to +125°C) per AEC-Q100 Rev G - meets automotive reliability requirements for powertrain, ADAS, and body electronics.

Applications

Automotive Infotainment Calibration Storage	Industrial PLC Configuration Backup
Use Scenario: Storing display gamma tables, audio EQ presets, and user profile settings in head-unit ECUs where power loss must not corrupt calibration data. IC Role / Device Role / Timing Role: Nonvolatile configuration storage with guaranteed write completion and ECC-protected reads - acts as persistent parameter repository accessed via I²C during boot and runtime. Use Value: Factory-programmed 128-bit serial number enables anti-counterfeit verification; extended temperature rating ensures reliability in dashboard environments reaching +105°C ambient.	Use Scenario: Retaining ladder logic parameters, I/O mapping, and alarm thresholds in programmable logic controllers subjected to frequent brownouts and vibration. IC Role / Device Role / Timing Role: High-reliability backup memory interfaced to ARM Cortex-M7 host MCU - leverages 3.4 MHz I²C for rapid config reload after reset. Use Value: Hardware WP pin provides immediate, zero-software-overhead protection during firmware updates; >200-year data retention eliminates field replacement concerns.
Medical Device Serial Number Binding	Smart Meter Firmware Parameter Vault
Use Scenario: Securely storing device-specific cryptographic keys and regulatory compliance IDs in Class II medical instruments requiring FDA audit trails. IC Role / Device Role / Timing Role: Tamper-resistant identity anchor - user-programmable 64-byte ID page is permanently lockable via software sequence to prevent post-deployment modification. Use Value: Dual protection (hardware WP + software-configurable zone locks) satisfies IEC 62304 security requirements; AEC-Q100 qualification validates robustness for portable battery-powered use.	Use Scenario: Archiving tariff schedules, metering constants, and utility authentication tokens in ANSI C12.22-compliant smart electricity meters operating in outdoor enclosures. IC Role / Device Role / Timing Role: Long-life data vault interfaced to TI MSP430 metrology MCU - uses low-power standby current (1 µA) to extend battery life during grid outages. Use Value: Built-in ECC prevents undetected corruption of billing-critical parameters; 1.7V minimum VCC supports operation during brownout conditions down to 1.8V rail.

Automotive Infotainment Calibration Storage

Industrial PLC Configuration Backup

Use Scenario: Storing display gamma tables, audio EQ presets, and user profile settings in head-unit ECUs where power loss must not corrupt calibration data.

IC Role / Device Role / Timing Role: Nonvolatile configuration storage with guaranteed write completion and ECC-protected reads - acts as persistent parameter repository accessed via I²C during boot and runtime.

Use Value: Factory-programmed 128-bit serial number enables anti-counterfeit verification; extended temperature rating ensures reliability in dashboard environments reaching +105°C ambient.

Use Scenario: Retaining ladder logic parameters, I/O mapping, and alarm thresholds in programmable logic controllers subjected to frequent brownouts and vibration.

IC Role / Device Role / Timing Role: High-reliability backup memory interfaced to ARM Cortex-M7 host MCU - leverages 3.4 MHz I²C for rapid config reload after reset.

Use Value: Hardware WP pin provides immediate, zero-software-overhead protection during firmware updates; >200-year data retention eliminates field replacement concerns.

Medical Device Serial Number Binding

Smart Meter Firmware Parameter Vault

Use Scenario: Securely storing device-specific cryptographic keys and regulatory compliance IDs in Class II medical instruments requiring FDA audit trails.

IC Role / Device Role / Timing Role: Tamper-resistant identity anchor - user-programmable 64-byte ID page is permanently lockable via software sequence to prevent post-deployment modification.

Use Value: Dual protection (hardware WP + software-configurable zone locks) satisfies IEC 62304 security requirements; AEC-Q100 qualification validates robustness for portable battery-powered use.

Use Scenario: Archiving tariff schedules, metering constants, and utility authentication tokens in ANSI C12.22-compliant smart electricity meters operating in outdoor enclosures.

IC Role / Device Role / Timing Role: Long-life data vault interfaced to TI MSP430 metrology MCU - uses low-power standby current (1 µA) to extend battery life during grid outages.

Use Value: Built-in ECC prevents undetected corruption of billing-critical parameters; 1.7V minimum VCC supports operation during brownout conditions down to 1.8V rail.

Equivalent & Alternatives

The following parts are listed as comparable options for similar serial EEPROM applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
AT24C256C-SSHL-T	No built-in ECC; no security register; only hardware WP; max I²C speed = 1 MHz; not AEC-Q100 qualified.	Lacks factory serial number and zone-level write protection - unsuitable for automotive or security-sensitive deployments.	Select only for cost-sensitive consumer applications where ECC and serialization are unnecessary.
24AA256-I/P	No high-speed mode (max 400 kHz); no security register; no ECC; industrial temp only (–40°C to +85°C); no manufacturer ID support.	Cannot replace 24CS256T-E/ST66KVAO in extended-temp or high-bandwidth systems - requires PCB redesign for slower timing margins.	Use only in legacy industrial designs already committed to Microchip's AA family and not requiring ECC or extended temperature operation.

Compared with AT24C256C-SSHL-T and 24AA256-I/P, the 24CS256T-E/ST66KVAO delivers differentiated value through AEC-Q100 qualification, ECC-enabled data integrity, factory-serialized identity, and 3.4 MHz I²C - making it the sole choice for next-generation automotive, medical, and smart infrastructure applications demanding verified reliability and security.

Availability

24CS256T-E/ST66KVAO is available at Aetrix Electronics and suitable for automotive infotainment systems, industrial PLCs, medical diagnostic equipment, and smart metering platforms requiring stable component supply across extended temperature and long product lifecycles.

Supply support for 24CS256T-E/ST66KVAO 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 Inc. is a leading provider of microcontroller, analog, FPGA, and memory solutions, serving automotive, industrial, communications, and consumer markets with vertically integrated silicon and software.

The 24CS256T-E/ST66KVAO belongs to Microchip's CS-series serial EEPROM family, designed specifically for automotive-grade, high-reliability nonvolatile storage with integrated security and error resilience - addressing the need for trusted configuration and identity management in safety-critical systems.

FAQ

What is the maximum I²C clock frequency supported by the 24CS256T-E/ST66KVAO?

The 24CS256T-E/ST66KVAO supports I²C High-Speed mode up to 3.4 MHz when VCC is ≥2.5V and operating in Industrial temperature range. At lower voltages (1.7V–2.5V) or Extended temperature range, maximum clock frequency is 1 MHz. This enables faster configuration loading in real-time systems compared to legacy 400 kHz EEPROMs.

Does the 24CS256T-E/ST66KVAO include error correction capability?

Yes, the 24CS256T-E/ST66KVAO integrates built-in Error Correction Code (ECC) logic that corrects up to one incorrectly read bit within any four-byte read window. The Configuration register includes a read-only Error Correction State (ECS) latch that indicates when ECC correction has been applied - ensuring data integrity without host intervention.

How is the 128-bit serial number implemented in the 24CS256T-E/ST66KVAO?

The 24CS256T-E/ST66KVAO contains a factory-programmed, globally unique 128-bit serial number stored in the read-only portion of its Security register (address range 0800h–080Fh). This identifier is programmed at wafer level and is unique across the entire CS-series EEPROM family - eliminating the need for post-production serialization in high-volume manufacturing.

Can the 24CS256T-E/ST66KVAO be used in automotive applications?

Yes, the 24CS256T-E/ST66KVAO is AEC-Q100 qualified for Grade 1 (–40°C to +125°C) and rated for extended temperature operation. Its built-in ECC, 128-bit serial number, and dual write-protection modes (hardware WP pin + software-configurable zone locks) meet functional safety requirements for automotive infotainment, ADAS, and body control modules.

What package type does the 24CS256T-E/ST66KVAO use?

The 24CS256T-E/ST66KVAO uses an 8-lead UDFN package (2 mm × 3 mm) with wettable flank terminations. This compact, leadless package supports automated optical inspection (AOI), offers improved thermal dissipation over SOIC, and is compatible with standard reflow profiles - ideal for space-constrained automotive and industrial PCBs.

24CS256T-E/ST66KVAO Specifications

Product attributes: Attribute value

Manufacturer:: Microchip Technology

Series:: -

Package/Case:: 8-TSSOP (0.173", 4.40mm Width)

Packaging:: Tape & Reel (TR)

Product Status:: Active

Programmable:: -

Memory Type:: Non-Volatile

Memory Format:: EEPROM

Technology:: EEPROM

Memory Size:: 256Kbit

Memory Organization:: 32K x 8

Memory Interface:: I2C

Clock Frequency:: 1 MHz

Write Cycle Time - Word, Page:: 5ms

Access Time:: 400 ns

Voltage - Supply:: 1.7V ~ 5.5V

Operating Temperature:: -40°C ~ 125°C (TA)

Grade:: -

Qualification:: -

Mounting Type:: Surface Mount

Supplier Device Package:: 8-TSSOP

24CS256T-E/ST66KVAO FAQ

1.How can I place an order for 24CS256T-E/ST66KVAO through Aetrix?

Please submit a Request for Quotation (RFQ) for 24CS256T-E/ST66KVAO 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 24CS256T-E/ST66KVAO reliable?

The price and inventory of 24CS256T-E/ST66KVAO are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for 24CS256T-E/ST66KVAO is usually 5 days.

3.What payment methods are accepted for 24CS256T-E/ST66KVAO?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for 24CS256T-E/ST66KVAO transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for 24CS256T-E/ST66KVAO?

24CS256T-E/ST66KVAO orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your 24CS256T-E/ST66KVAO 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 24CS256T-E/ST66KVAO?

For technical support, including 24CS256T-E/ST66KVAO datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your 24CS256T-E/ST66KVAO requirements.

6.How does Aetrix verify that 24CS256T-E/ST66KVAO is sourced from the original manufacturer or authorized distributors?

All 24CS256T-E/ST66KVAO 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 24CS256T-E/ST66KVAO meets industry standards.

7.What is the process for return or replacement of 24CS256T-E/ST66KVAO?

All 24CS256T-E/ST66KVAO units undergo pre-shipment inspection (PSI). If there is an issue with 24CS256T-E/ST66KVAO, 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 24CS256T-E/ST66KVAO part is unused and in its original packaging.

Return procedure for 24CS256T-E/ST66KVAO:

1.Submit a request within 90 days.

2.Obtain a Return Material Authorization (RMA) from Aetrix.

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