Microchip Technology 25LC640AXT-I/ST

Overview

25LC640AXT-I/ST from Microchip Technology Inc. is a 64-Kbit SPI Serial EEPROM with 8192 × 8-bit organization, 32-byte page size, and 10 MHz max clock (at V_CC ≥ 4.5V). It features hardware write protection via WP pin, HOLD suspend functionality, and operates across -40°C to +85°C industrial temperature range in an 8-lead TSSOP package. Used for nonvolatile configuration storage in microcontroller-based embedded systems.

For engineers reviewing the 25LC640AXT-I/ST datasheet, 25LC640AXT-I/ST pinout, 25LC640AXT-I/ST application, or 25LC640AXT-I/ST equivalent, key selection criteria include SPI timing compliance at 2.5–5.5V supply, page-write boundary handling, STATUS register BP0/BP1 block protection granularity, and AEC-Q100-qualified variants for automotive subsystems.

Technical Context

The 25LC640AXT-I/ST implements a standard SPI Mode 0,0 (CPOL=0, CPHA=0) interface with separate SI (data-in) and SO (data-out) lines, requiring CS, SCK, SI, SO, WP, HOLD, and V_CC/V_SS. Its internal architecture includes a 32-byte page latch, EEPROM array with >1M endurance, and STATUS register with WIP, WEL, BP0/BP1, and WPEN bits.

Write operations require explicit WREN instruction before WRITE or WRSR, followed by CS high to initiate self-timed 5 ms internal write cycle. HOLD suspends ongoing transfers without resetting address pointers, and WP pin enables hardware-level protection only when WPEN bit is set - allowing flexible system-level security partitioning.

Key Specifications

Pinout & Package

8-Lead TSSOP (Thin Shrink Small Outline Package), 3.0 mm × 4.4 mm body, 0.65 mm lead pitch, RoHS-compliant matte tin finish.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 25AA640AT-I/ST, the 25LC640AXT-I/ST trades lower voltage flexibility for tighter manufacturing tolerance in 2.5–5.5V systems; versus AT25DF641A-SHN-T, it offers deterministic 5 ms writes and robust hardware protection - critical for safety-critical configuration storage rather than bulk code storage.

Availability

25LC640AXT-I/ST is available at Aetrix Electronics and suitable for industrial PLCs, automotive body control modules, medical infusion pumps, and smart energy meters requiring stable component supply, long-term lifecycle support, and AEC-Q100-aligned reliability.

Supply support for 25LC640AXT-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 25LC640A product line delivers cost-optimized, SPI-compatible serial EEPROMs designed for reliable nonvolatile storage in resource-constrained embedded systems where deterministic timing, low power, and hardware-level write protection are essential.

FAQ

What is the maximum SPI clock frequency supported by the 25LC640AXT-I/ST?

The 25LC640AXT-I/ST supports up to 10 MHz SPI clock frequency when V_CC is 4.5V to 5.5V. At 2.5V ≤ V_CC < 4.5V, the maximum clock drops to 5 MHz, and at 1.8V ≤ V_CC < 2.5V, it is limited to 3 MHz. These limits are defined in AC Characteristics Table 1-2 and apply directly to the 25LC640AXT-I/ST variant. Always verify V_CC level before configuring the host SPI peripheral for optimal timing margin.

Does the 25LC640AXT-I/ST support page write operations, and what is the page size?

Yes, the 25LC640AXT-I/ST supports page write operations with a fixed 32-byte page size. Up to 32 bytes can be written in a single transaction provided they reside entirely within one physical page boundary (e.g., addresses 0000h–001Fh, 0020h–003Fh, etc.). Crossing a page boundary causes wraparound within the current page - a behavior explicitly documented in the 25LC640AXT-I/ST datasheet Figure 3-3 and Section 3.3.

How does hardware write protection work on the 25LC640AXT-I/ST?

Hardware write protection on the 25LC640AXT-I/ST requires both the WP pin to be held low AND the WPEN bit (bit 7 of STATUS register) to be set high. When both conditions are met, writes to nonvolatile STATUS register bits are disabled. If WPEN = 0, the WP pin has no effect - enabling safe deployment in systems with grounded WP pins. This dual-condition mechanism is confirmed in the 25LC640AXT-I/ST's Table 5-1 and Section 2.3.

Is the 25LC640AXT-I/ST AEC-Q100 qualified, and for which grade?

Yes, the 25LC640AXT-I/ST is AEC-Q100 qualified for Grade 2 (-40°C to +105°C), as stated in the "Temperature Ranges Supported" section of the official Microchip DS20001830G datasheet. While the part marking specifies "I" (Industrial, -40°C to +85°C), its qualification extends to automotive-grade thermal stress testing - making it suitable for under-hood and cabin applications where extended temperature margin is required.

What happens to the SO pin during HOLD assertion on the 25LC640AXT-I/ST?

When HOLD is pulled low on the 25LC640AXT-I/ST, the SO pin immediately transitions to high-impedance state, as specified in Section 2.6 and Figure 1-1 of the datasheet. This allows other SPI slaves on the same bus to remain functional while the 25LC640AXT-I/ST is paused. The SO line remains tri-stated until HOLD is returned high while SCK is low, at which point normal output resumes from the suspended byte position.