Microchip Technology 25LC640AT-I/SN

Overview

25LC640AT-I/SN from Microchip Technology Inc. is a 64-Kbit SPI Serial EEPROM with 8192 × 8-bit organization, 32-byte page size, and industrial temperature range (–40°C to +85°C). It operates at up to 10 MHz clock frequency with 1 µA standby current and supports hardware write protection via WP pin and STATUS register control. It is used in microcontroller-based systems for nonvolatile parameter storage, calibration data retention, and firmware configuration.

For engineers reviewing the 25LC640AT-I/SN datasheet, 25LC640AT-I/SN pinout, 25LC640AT-I/SN application, or 25LC640AT-I/SN equivalent, key selection criteria include VCC range (2.5V–5.5V), SPI interface timing compliance, block write protection granularity, endurance (1M cycles), and SOIC-8 (SN) package compatibility with legacy PCB layouts.

Technical Context

The 25LC640AT-I/SN implements a standard SPI Mode 0,0/Motorola-compatible serial interface with separate SI (data in) and SO (data out) lines, controlled by CS, SCK, and HOLD. It uses an internal high-voltage generator for EEPROM programming and features automatic address rollover during sequential reads.

Its write-enable mechanism requires explicit WREN instruction before WRITE or WRSR operations, and internal write cycles complete in ≤5 ms. Block protection is configurable via BP0/BP1 bits to lock none, upper 1/4, upper 1/2, or entire memory array - independent of WP pin state when WPEN = 0.

Key Specifications

Pinout & Package

8-Lead Plastic Small Outline (SOIC-Narrow), package code SN, 3.90 mm body width, standard JEDEC MS-012AC footprint. Pin 1 marked with notch or dot; lead finish is matte tin (Pb-free).

Key Features

Applications

Equivalent & Alternatives

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

Compared with 25AA640AT-I/SN, the 25LC640AT-I/SN offers tighter VCC min specification (2.5V vs. 1.8V) but identical timing, endurance, and package - making it optimal for stable 3.3V/5V systems. Versus AT25DF041A-SHN-T, it provides proven interoperability with legacy PIC SPI stacks but lacks quad-mode speed and density scalability.

Availability

25LC640AT-I/SN is available at Aetrix Electronics and suitable for smart metering, automotive body control units, and industrial PLC I/O modules requiring stable component supply, long-lifecycle support, and AEC-Q100-compliant nonvolatile memory.

Supply support for 25LC640AT-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 U.S.-based semiconductor company specializing in microcontrollers, analog devices, and memory products, with global manufacturing and quality certifications including ISO 9001 and IATF 16949.

The 25LC640A family was designed for cost-sensitive, high-reliability embedded systems needing SPI EEPROM with industrial temperature range, hardware write protection, and minimal external components - targeting metering, automotive, and industrial control markets.

FAQ

What is the maximum clock frequency supported by the 25LC640AT-I/SN?

The 25LC640AT-I/SN supports up to 10 MHz clock frequency when VCC is between 4.5V and 5.5V. At 2.5V ≤ VCC < 4.5V, the maximum clock drops to 5 MHz, and at 1.8V ≤ VCC < 2.5V, it is limited to 3 MHz. These derating steps ensure reliable setup/hold timing across voltage ranges. The 25LC640AT-I/SN datasheet specifies these limits in Table 1-2 under FCLK parameter.

Does the 25LC640AT-I/SN require external pull-up resistors on its SPI lines?

The 25LC640AT-I/SN does not require external pull-ups on SI, SCK, or CS - these inputs have internal weak pull-downs. However, SO is open-drain and requires an external pull-up resistor (typically 4.7 kΩ to VCC) to ensure valid logic-high levels. WP and HOLD also benefit from pull-up resistors if left unconnected in system design, though they default to inactive (high) states internally.

How does the HOLD function operate on the 25LC640AT-I/SN during an active SPI transaction?

The HOLD pin on the 25LC640AT-I/SN suspends SPI communication mid-sequence when pulled low while SCK is low. During HOLD, SI, SCK, and SO enter high-impedance states and ignore transitions; the internal address pointer and command state are preserved. To resume, HOLD must be raised while SCK remains low - then normal SPI operation continues from the exact bit position where it paused. This behavior is defined in Section 2.6 and Figure 1-1 of the 25LC640AT-I/SN datasheet.

Can the 25LC640AT-I/SN be used in automotive applications?

Yes - the 25LC640AT-I/SN is AEC-Q100 qualified for automotive use and rated for Industrial temperature range (–40°C to +85°C), matching Grade 2 requirements. Its 1 µA standby current, 4 kV ESD rating, and hardware write protection via WP pin make it suitable for body control modules, infotainment configuration storage, and ADAS sensor calibration memory. The "T" suffix denotes tape-and-reel packaging appropriate for automated SMT assembly.

What is the page size and write-cycle time for the 25LC640AT-I/SN?

The 25LC640AT-I/SN has a fixed 32-byte page size, meaning up to 32 bytes can be written in a single page-write command - provided all addresses fall within the same physical page boundary (e.g., 0x0000–0x001F). Each internal write cycle completes in ≤5 ms, as specified in parameter TWC (Table 1-2). Attempting to cross a page boundary wraps data to the start of the current page rather than advancing to the next, requiring firmware to manage page alignment.