Microchip Technology 25AA640A-E/ST

Overview

25AA640A-E/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 (at VCC ≥ 4.5V), features hardware write protection via WP pin and STATUS register, and delivers 1 million erase/write cycles with >200-year data retention. It is used in industrial control systems for storing calibration data, firmware configuration, and device identity.

For engineers reviewing the 25AA640A-E/ST datasheet, 25AA640A-E/ST pinout, 25AA640A-E/ST application, or 25AA640A-E/ST equivalent, key selection criteria include voltage compatibility (1.8V min), SPI timing margins at low VCC, HOLD functionality for interrupt-safe operation, and block-level write protection granularity (none/¼/½/all array).

Technical Context

The 25AA640A-E/ST implements a standard SPI Mode 0,0/Motorola-compatible interface with separate SI (data-in) and SO (data-out) lines, requiring CS, SCK, SI, SO, WP, HOLD, and VCC/VSS. 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.

It supports sequential read across address boundaries with automatic rollover, byte/page write with CS-driven internal write cycle initiation (TWC ≤ 5 ms), and HOLD pin suspension of ongoing SPI transfers without sequence reset - critical for real-time host interrupt handling.

Key Specifications

Pinout & Package

25AA640A-E/ST is packaged in an 8-lead TSSOP (Thin Shrink Small Outline Package) with 0.65 mm pitch, body size 4.4 mm × 3.0 mm × 1.2 mm, and exposed pad optional for thermal relief.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 25LC640A-E/ST, the 25AA640A-E/ST enables true 1.8V operation in battery-backed systems, while AT25DF641A-SHN-T trades hardware safety features for density and speed - making it unsuitable as a drop-in replacement for configuration-critical roles.

Availability

25AA640A-E/ST is available at Aetrix Electronics and suitable for industrial automation, automotive electronics, and medical device manufacturing requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for 25AA640A-E/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 microcontrollers, analog, FPGA, and memory solutions, serving industrial, automotive, and consumer markets with vertically integrated silicon and development tools.

The 25AA640A belongs to Microchip's serial EEPROM product line, designed specifically for reliable, low-power, SPI-based nonvolatile storage in resource-constrained embedded systems with stringent environmental and longevity requirements.

FAQ

What is the minimum operating voltage for the 25AA640A-E/ST?

The 25AA640A-E/ST operates down to 1.8V, enabling compatibility with modern low-power MCUs and battery-supplied systems. At 1.8V–2.4V, its maximum SPI clock frequency is 3 MHz, and standby current remains ≤5 µA at +125°C. This specification is confirmed in Table 1-1 (DC Characteristics) and Table 1-2 (AC Characteristics) of DS20001830G.

Does the 25AA640A-E/ST support hardware write protection?

Yes, the 25AA640A-E/ST supports dual-layer hardware write protection: the WP pin disables nonvolatile STATUS register writes when WPEN = 1, and the BP0/BP1 bits configure block-level array protection (none/¼/½/all). These features are fully documented in Sections 2.3 and 3.6 of DS20001830G, and the WP pin function is validated for the 25AA640A-E/ST package variant.

How does the HOLD pin function during an active SPI transaction on the 25AA640A-E/ST?

The HOLD pin on the 25AA640A-E/ST suspends ongoing SPI communication without resetting the sequence: when pulled low while SCK is low, SI/SO/SCK enter high-impedance state and input transitions are ignored except CS. Resuming requires HOLD high while SCK is low. This behavior is defined in Section 2.6 and Figure 1-1 of DS20001830G and applies identically to the 25AA640A-E/ST TSSOP package.

What is the page size and maximum write length for the 25AA640A-E/ST?

The 25AA640A-E/ST has a fixed 32-byte page size. Up to 32 bytes may be written in a single page-write command, but all bytes must reside within the same physical page boundary (e.g., addresses 0000h–001Fh). Crossing a boundary causes wraparound within the page, not continuation - a constraint explicitly stated in Figure 3-3 and Section 3.3 of DS20001830G.

Is the 25AA640A-E/ST AEC-Q100 qualified and for which grade?

Yes, the 25AA640A-E/ST is AEC-Q100 qualified for Grade 1 (−40°C to +125°C), as confirmed in the "Temperature Ranges Supported" section and Device Selection Table of DS20001830G. The "E" suffix denotes Extended temperature range, and "ST" indicates TSSOP packaging - both consistent with AEC-Q100 test scope for this part number.