Microchip Technology 25AA640-I/SN

Overview

25AA640-I/SN from Microchip Technology Inc. is a 64 Kbit SPI Serial EEPROM with 8192 × 8-bit organization, 1.8–5.5 V supply range, and industrial temperature rating (–40°C to +85°C). It features 32-byte page write capability, 5 ms max internal write cycle time, and hardware write protection via WP pin and STATUS register. Used for nonvolatile parameter storage in embedded control systems requiring low-power, reliable data retention.

For engineers reviewing the 25AA640-I/SN datasheet, 25AA640-I/SN pinout, 25AA640-I/SN application, or 25AA640-I/SN equivalent, this page delivers verified electrical specs, SPI timing constraints, HOLD/CS/WP functional behavior, package-confirmed pin mapping, and real-world use cases in industrial sensing and firmware configuration storage.

Technical Context

The 25AA640-I/SN implements a standard SPI Mode 0,0 interface with separate SI (data-in) and SO (data-out) lines, requiring CS assertion and SCK synchronization for all operations. Its internal architecture includes an 8-bit instruction register, auto-incrementing address pointer for sequential reads, and a STATUS register with WIP, WEL, BP0/BP1, and WPEN bits.

Write operations require explicit WREN instruction before WRITE or WRSR commands; CS must go high after final data bit to initiate self-timed 5 ms internal write cycle. HOLD pin enables mid-sequence suspension without bus reinitialization, and WP pin-when enabled via WPEN-blocks writes to nonvolatile STATUS bits while permitting array access.

Key Specifications

Pinout & Package

25AA640-I/SN is packaged in an 8-pin Plastic Small Outline Integrated Circuit (SOIC) with 150 mil body width, JEDEC MS-012AC compliant, lead-free matte tin finish.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 25AA640A-I/SN, the 25AA640-I/SN offers identical functionality but lower ESD rating and looser timing tolerances-acceptable for cost-sensitive industrial controls where layout-level filtering is applied. Versus AT25DF041A-SSHN-B, it provides superior endurance, true byte-write capability, and broader VCC range for mixed-voltage systems.

Availability

25AA640-I/SN is available at Aetrix Electronics and suitable for industrial sensor calibration, embedded firmware configuration, medical device settings backup, and automotive ECU parameter storage requiring stable component supply across multi-year production cycles.

Supply support for 25AA640-I/SN 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, and memory solutions, headquartered in Chandler, Arizona, with global design and manufacturing operations.

The 25AA640-I/SN belongs to Microchip's 25XX640 family of SPI Serial EEPROMs, designed specifically for low-voltage, low-power embedded systems requiring robust, byte-addressable nonvolatile storage with hardware write protection.

FAQ

What is the maximum clock frequency supported by the 25AA640-I/SN?

The 25AA640-I/SN supports up to 1 MHz maximum clock frequency across its full 1.8–5.5 V supply range and –40°C to +85°C operating temperature. This limit ensures reliable setup/hold timing for SI and SO signals under worst-case voltage and temperature conditions, as specified in Table 1-2 of DS21223H.

Does the 25AA640-I/SN support page write operations?

Yes, the 25AA640-I/SN supports page write operations with a 32-byte page size. Up to 32 bytes can be loaded into the internal buffer before initiating the 5 ms internal write cycle, provided all addresses reside within the same page boundary (e.g., 0x0000–0x001F). Exceeding the page boundary causes wraparound and data corruption.

How does the HOLD pin function during SPI communication?

The HOLD pin on the 25AA640-I/SN suspends ongoing SPI transactions when pulled low while SCK is low. During HOLD, SI, SCK, and SO enter high-impedance states and ignore input transitions except CS. Communication resumes when HOLD is raised while SCK remains low, preserving the exact byte and bit position in the sequence.

What write protection mechanisms are implemented in the 25AA640-I/SN?

The 25AA640-I/SN implements three-tiered write protection: (1) software-controlled via WREN/WRDI instructions and WEL bit, (2) block-level via BP0/BP1 bits in the STATUS register, and (3) hardware-enforced via the WP pin when WPEN = 1. These operate independently and can be combined for layered security in critical configuration storage.

Is the 25AA640-I/SN pin-compatible with the 25LC640-I/SN?

No, the 25AA640-I/SN and 25LC640-I/SN share identical SOIC-8 packaging and pinout but differ in VCC range and max clock speed: 25AA640-I/SN operates from 1.8–5.5 V at ≤1 MHz, while 25LC640-I/SN requires ≥2.5 V and supports up to 2 MHz. Interchangeability requires verification of system voltage and timing margins.