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Microchip Technology 25AA640A-I/ST

Name: 25AA640A-I/ST
Brand: Microchip Technology
SKU: 25AA640A-I/ST
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: 25AA640A-I/ST

Manufacturer:: Microchip Technology

Category:: Memory

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

Datasheet:: 25AA640A-I/ST.pdf

Description:: IC EEPROM 64KBIT SPI 8TSSOP

Quantity:: RFQ Add To RFQ list

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Product details

Overview

25AA640A-I/ST from Microchip Technology Inc. is a 64-Kbit SPI Serial EEPROM with 8192 × 8-bit organization, 32-byte page size, and 1.8V–5.5V supply range. It supports up to 10 MHz clock frequency at 4.5–5.5V, features hardware write protection via WP pin and STATUS register, and delivers 1 million erase/write cycles with >200-year data retention - used for firmware parameter storage in industrial controllers.

For engineers reviewing the 25AA640A-I/ST datasheet, 25AA640A-I/ST pinout, 25AA640A-I/ST application, or 25AA640A-I/ST equivalent, key selection criteria include V_CC compatibility (1.8–5.5V), SPI timing compliance across voltage ranges, HOLD functionality for interrupt-safe bus arbitration, and block-level write protection granularity (none/¼/½/all array).

Technical Context

The 25AA640A-I/ST implements a standard SPI Mode 0,0/Master-Slave interface with separate SI (data-in) and SO (data-out) lines, requiring CS, SCK, and optional HOLD/WP control. Its internal architecture includes a 32-byte page latch, HV generator for EEPROM programming, and status register with WIP, WEL, BP0/BP1, and WPEN bits.

Write operations require explicit WREN instruction before WRITE or WRSR; CS rising edge initiates self-timed internal write cycle (≤5 ms). HOLD suspends ongoing serial transfers without resetting address pointer, enabling host CPU to service higher-priority interrupts while preserving transaction state.

Key Specifications

Parameter	Value and Actual Design Meaning
Memory Size	64 Kbit (8192 × 8-bit array) - supports persistent storage of configuration data, calibration tables, or boot parameters in resource-constrained systems.
Interface	SPI-compatible serial bus (Mode 0,0) - interoperable with PIC® and other microcontrollers' hardware SPI peripherals without bit-banging overhead.
Page Size	32 bytes - limits maximum atomic write burst; crossing page boundaries wraps data within same page, requiring software boundary checks.
Max Clock Frequency	10 MHz at V_CC ≥ 4.5V - enables fast read/write throughput (up to ~1.2 MB/s theoretical read rate) while maintaining timing margins per AC specs.
Write Endurance	1,000,000 erase/write cycles - suitable for applications with frequent field-updatable settings, such as energy meter tariff schedules or sensor offset calibration.
Data Retention	>200 years at +25°C - ensures long-term reliability for infrequently updated system identifiers or cryptographic keys stored in nonvolatile memory.
Operating Temp	−40°C to +85°C (Industrial grade) - validated for deployment in factory automation PLCs, motor drives, and outdoor IoT gateways.

Pinout & Package

25AA640A-I/ST is packaged in an 8-lead SOIC (SN) with 150-mil body width and standard JEDEC MS-012AC footprint. Pin 1 is marked by notch or beveled corner; package is RoHS-compliant and Pb-free.

Pin/Terminal	Circuit Role	Design Meaning
CS (Pin 1)	Chip Select Input	Active-low enable: pulls device out of standby; rising edge after valid write sequence triggers internal write cycle; high-Z SO when deasserted enables multi-device SPI bus sharing.
SO (Pin 2)	Serial Data Output	Tri-state output driven on falling SCK edge; high-impedance during HOLD or CS high; supports daisy-chaining only if externally managed.
WP (Pin 3)	Hardware Write-Protect Input	Low-active pin that - when WPEN=1 in STATUS register - blocks writes to nonvolatile STATUS bits; does not affect array writes unless BP bits are set.
VSS (Pin 4)	Ground Reference	Primary return path for all I/O and core logic; must be low-impedance connection to minimize noise coupling into sensitive EEPROM cell programming.
SI (Pin 5)	Serial Data Input	Latches instruction/address/data on rising SCK edge; accepts 8-bit opcodes (e.g., 0x03 for READ, 0x02 for WRITE) and 16-bit addresses with 3 MSBs "don't care".
SCK (Pin 6)	Serial Clock Input	Synchronizes all data transfers; rising edge clocks SI, falling edge updates SO; max 10 MHz at 5.5V; rise/fall times ≤100 ns required for timing compliance.
HOLD (Pin 7)	Serial Transfer Pause Input	Active-low suspend signal: must be asserted while SCK is low; places SI/SO/SCK in high-Z state and freezes internal address pointer for seamless resume post-interrupt.
VCC (Pin 8)	Supply Voltage	1.8V–5.5V operation range; internal regulation enables stable EEPROM programming across wide input; standby current ≤1 µA at 5.5V/85°C.

Key Features

Feature	Design Value
Block Write Protection	Configurable via BP0/BP1 bits to protect none, upper 1/4 (1800h–1FFFh), upper 1/2 (1000h–1FFFh), or entire array (0000h–1FFFh) - enables secure partitioning of firmware vs. user data regions.
Self-Timed Write Cycle	Internal 5 ms max write completion (TWC) eliminates need for external delay loops; WIP bit in STATUS register allows polling-based synchronization without fixed timeouts.
Power-On Data Protection	Write enable latch resets at power-up, and WRDI executes automatically on POR - prevents spurious writes during brown-out or supply ramp conditions.
HOLD Functionality	Pauses active SPI transactions without losing byte alignment or address state - critical for real-time systems where host MCU must service urgent interrupts mid-EEPROM access.
Wide Voltage Operation	1.8V–5.5V V_CC range supports direct interfacing with both 3.3V and 5V microcontrollers, eliminating level-shifter requirements in mixed-voltage designs.

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 deployed in harsh factory environments. IC Role / Device Role / Timing Role: Nonvolatile parameter repository accessed via SPI during boot and runtime; HOLD pin used to pause reads during motion-control interrupt servicing. Use Value: Ensures deterministic startup behavior and field-upgradable settings without battery backup; 1M endurance supports daily recalibration logs over 10+ years.	Use Scenario: Retaining sensor offset/gain coefficients and patient-specific therapy profiles in portable infusion pumps and diagnostic monitors. IC Role / Device Role / Timing Role: Secure, tamper-resistant storage for FDA-regulated calibration data; WP pin hardwired low with WPEN=1 to prevent accidental overwrite during firmware updates. Use Value: Meets IEC 62304 Class B software safety requirements via hardware-enforced write protection and >200-year data retention.
Automotive Body Control Module	Smart Energy Meter Firmware Parameters
Use Scenario: Holding door lock logic states, mirror position presets, and lighting configuration in AEC-Q100 qualified body control units. IC Role / Device Role / Timing Role: SPI-connected EEPROM interfaced to 8-bit automotive MCU; operates across −40°C to +125°C extended temp range (E-grade variant), though this part is I-grade. Use Value: Industrial-grade 25AA640A-I/ST provides cost-optimized solution for non-safety-critical modules where E-grade qualification is not mandated.	Use Scenario: Storing tariff schedules, demand-response thresholds, and meter serial number in ANSI C12.20-certified smart meters with 15+ year field life. IC Role / Device Role / Timing Role: Primary nonvolatile memory for time-of-use billing logic; sequential read capability enables fast retrieval of multi-day rate tables during billing cycles. Use Value: 8192-byte capacity accommodates 365 days × 24 hours × 4-byte tariff entries; 1 µA standby current extends battery backup life in mains-fail scenarios.

Industrial PLC Configuration Storage

Medical Device Calibration Data

Use Scenario: Storing I/O mapping, PID tuning parameters, and alarm thresholds in programmable logic controllers deployed in harsh factory environments.

IC Role / Device Role / Timing Role: Nonvolatile parameter repository accessed via SPI during boot and runtime; HOLD pin used to pause reads during motion-control interrupt servicing.

Use Value: Ensures deterministic startup behavior and field-upgradable settings without battery backup; 1M endurance supports daily recalibration logs over 10+ years.

Use Scenario: Retaining sensor offset/gain coefficients and patient-specific therapy profiles in portable infusion pumps and diagnostic monitors.

IC Role / Device Role / Timing Role: Secure, tamper-resistant storage for FDA-regulated calibration data; WP pin hardwired low with WPEN=1 to prevent accidental overwrite during firmware updates.

Use Value: Meets IEC 62304 Class B software safety requirements via hardware-enforced write protection and >200-year data retention.

Automotive Body Control Module

Smart Energy Meter Firmware Parameters

Use Scenario: Holding door lock logic states, mirror position presets, and lighting configuration in AEC-Q100 qualified body control units.

IC Role / Device Role / Timing Role: SPI-connected EEPROM interfaced to 8-bit automotive MCU; operates across −40°C to +125°C extended temp range (E-grade variant), though this part is I-grade.

Use Value: Industrial-grade 25AA640A-I/ST provides cost-optimized solution for non-safety-critical modules where E-grade qualification is not mandated.

Use Scenario: Storing tariff schedules, demand-response thresholds, and meter serial number in ANSI C12.20-certified smart meters with 15+ year field life.

IC Role / Device Role / Timing Role: Primary nonvolatile memory for time-of-use billing logic; sequential read capability enables fast retrieval of multi-day rate tables during billing cycles.

Use Value: 8192-byte capacity accommodates 365 days × 24 hours × 4-byte tariff entries; 1 µA standby current extends battery backup life in mains-fail scenarios.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
25LC640A-I/ST	V_CC range 2.5–5.5V only; identical pinout, timing, and feature set otherwise.	Not suitable for 1.8V systems; otherwise drop-in replacement where supply rails are ≥2.5V.	Select 25LC640A-I/ST only if system V_CC never drops below 2.5V - avoids unnecessary margin in 3.3V/5V-only designs.
AT25DF041A-SSH-T	4-Mbit density, quad SPI interface, 8-pin SOIC package; no HOLD pin; different command set and status register layout.	Higher density and faster random read (via fast-read commands), but requires firmware porting and lacks HOLD functionality.	Choose AT25DF041A-SSH-T only when migrating to larger memory footprint and accepting SPI protocol changes; not a functional substitute for HOLD-dependent use cases.

Compared with 25LC640A-I/ST, the 25AA640A-I/ST enables 1.8V operation critical for ultra-low-power systems, while the AT25DF041A-SSH-T trades HOLD support and command compatibility for higher density and quad-speed read performance - making each alternative optimal only under distinct voltage, interface, or capacity constraints.

Availability

25AA640A-I/ST is available at Aetrix Electronics and suitable for industrial control systems, medical instrumentation, and smart metering applications requiring stable component supply, long-term lifecycle support, and AEC-Q100-aligned reliability.

Supply support for 25AA640A-I/ST 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, headquartered in Chandler, Arizona, with global design and manufacturing operations.

The 25AA640A belongs to Microchip's serial EEPROM product line, engineered for robust, low-power nonvolatile data storage in industrial, automotive, and consumer systems where SPI interface simplicity and proven reliability are essential.

FAQ

What is the minimum V_CC required for reliable operation of the 25AA640A-I/ST?

The 25AA640A-I/ST operates reliably down to 1.8V across its full industrial temperature range (−40°C to +85°C). At V_CC = 1.8V, maximum clock frequency is reduced to 3 MHz per AC specifications, and write current drops to 3 mA. This 1.8V capability distinguishes the 25AA640A-I/ST from the 25LC640A-I/ST, which requires ≥2.5V.

Does the 25AA640A-I/ST support SPI Mode 1,1 or only Mode 0,0?

The 25AA640A-I/ST supports SPI Mode 0,0 exclusively - sample on rising SCK edge, output on falling SCK edge, with CPOL = 0 and CPHA = 0. It does not support Mode 1,1 or other SPI variants. The device's timing diagrams and functional description confirm strict adherence to Mode 0,0, and attempting Mode 1,1 will result in incorrect data sampling or communication failure.

How does the HOLD function behave if asserted while SCK is high?

If HOLD is pulled low while SCK is high, the 25AA640A-I/ST ignores the request until the next SCK high-to-low transition, per Section 2.6 of the datasheet. To ensure immediate suspension, HOLD must be asserted only when SCK is low. Violating this timing causes undefined behavior - potentially incomplete byte transfers or corrupted address pointers - so firmware must synchronize HOLD assertion with SCK state.

Can the 25AA640A-I/ST be used in AEC-Q100 qualified automotive applications?

The 25AA640A-I/ST is rated for Industrial temperature range (−40°C to +85°C) and is not AEC-Q100 qualified. While the datasheet notes "Automotive AEC-Q100 Qualified" applies to the 25XX640A family generically, the specific 25AA640A-I/ST variant carries the 'I' suffix denoting Industrial grade. For AEC-Q100 compliance, Microchip offers the 25AA640AT-I/ST (with 'T' suffix) or 25LC640A variants explicitly qualified to Grade 2 or Grade 3.

What happens to the write enable latch after a successful WRITE instruction completes on the 25AA640A-I/ST?

After a successful WRITE instruction completes - signaled by CS rising edge following the last data bit - the write enable latch (WEL bit) is automatically reset to '0', disabling further writes until WREN is reissued. This behavior is documented in Section 3.4 and Table 5-1, ensuring that transient noise or software errors cannot cause unintended subsequent writes. The 25AA640A-I/ST enforces this reset regardless of WP pin state or STATUS register configuration.

25AA640A-I/ST Specifications

Product attributes: Attribute value

Manufacturer:: Microchip Technology

Series:: -

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

Packaging:: Tube

Product Status:: Active

Programmable:: Not Verified

Memory Type:: Non-Volatile

Memory Format:: EEPROM

Technology:: EEPROM

Memory Size:: 64Kbit

Memory Organization:: 8K x 8

Memory Interface:: SPI

Clock Frequency:: 10 MHz

Write Cycle Time - Word, Page:: 5ms

Access Time:: -

Voltage - Supply:: 1.8V ~ 5.5V

Operating Temperature:: -40°C ~ 85°C (TA)

Grade:: -

Qualification:: -

Mounting Type:: Surface Mount

Supplier Device Package:: 8-TSSOP

25AA640A-I/ST FAQ

1.How can I place an order for 25AA640A-I/ST through Aetrix?

Please submit a Request for Quotation (RFQ) for 25AA640A-I/ST 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 25AA640A-I/ST reliable?

The price and inventory of 25AA640A-I/ST are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for 25AA640A-I/ST is usually 5 days.

3.What payment methods are accepted for 25AA640A-I/ST?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for 25AA640A-I/ST transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for 25AA640A-I/ST?

25AA640A-I/ST orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your 25AA640A-I/ST 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 25AA640A-I/ST?

For technical support, including 25AA640A-I/ST datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your 25AA640A-I/ST requirements.

6.How does Aetrix verify that 25AA640A-I/ST is sourced from the original manufacturer or authorized distributors?

All 25AA640A-I/ST 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 25AA640A-I/ST meets industry standards.

7.What is the process for return or replacement of 25AA640A-I/ST?

All 25AA640A-I/ST units undergo pre-shipment inspection (PSI). If there is an issue with 25AA640A-I/ST, 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 25AA640A-I/ST part is unused and in its original packaging.

Return procedure for 25AA640A-I/ST:

1.Submit a request within 90 days.

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

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