Microchip Technology 25LC040A-I/ST

Overview

25LC040A-I/ST from Microchip Technology Inc. is a 4 Kbit SPI Serial EEPROM with 512 × 8-bit organization, 16-byte page write capability, and industrial temperature range (–40°C to +85°C). It operates from 2.5V to 5.5V, supports up to 10 MHz clock frequency, and features hardware write protection via WP pin and HOLD functionality for interrupt-safe bus suspension. It is commonly used in microcontroller-based systems for storing calibration data, configuration settings, and firmware parameters.

For engineers reviewing the 25LC040A-I/ST datasheet, 25LC040A-I/ST pinout, 25LC040A-I/ST application, or 25LC040A-I/ST equivalent, key selection criteria include SPI interface compatibility, 16-byte page write boundary handling, VCC voltage range (2.5–5.5V), industrial-grade temperature operation, and hardware-level write protection using both WP pin and STATUS register BP bits.

Technical Context

The 25LC040A-I/ST implements a standard SPI Mode 0,0 (CPOL=0, CPHA=0) interface with separate SI (MOSI) and SO (MISO) lines, requiring CS, SCK, SI, SO, WP, HOLD, VCC, and VSS. Its internal architecture includes a 512-byte EEPROM array, page latches, status register (WIP/WEL/BP0/BP1), and HV generator for write/erase cycles.

Write operations require explicit WREN instruction followed by CS high to latch enable state; writes are self-timed (≤5 ms), and page boundaries are fixed at 16-byte intervals (addresses ending in 0x0F). The HOLD pin suspends serial communication while preserving internal state, enabling host CPU to service higher-priority interrupts without reinitializing the transaction.

Key Specifications

Pinout & Package

25LC040A-I/ST is packaged in an 8-lead TSSOP (ST package code), 3.0 mm × 4.4 mm body, 0.65 mm pitch, with exposed pad optional for thermal relief. Pin 1 is marked by laser dot; pin 1 location matches JEDEC MO-153 standard.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 25AA040A-I/ST and AT25040B-SSHL-T, the 25LC040A-I/ST offers optimal balance of industrial temperature support, hardware HOLD capability, and 2.5V minimum VCC-making it ideal for robust embedded control where deterministic bus arbitration and wide supply tolerance are critical.

Availability

25LC040A-I/ST is available at Aetrix Electronics and suitable for industrial sensor calibration, medical device configuration, automotive body control modules, and smart energy metering requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for 25LC040A-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, manufacturing, and sales operations.

The 25LC040A belongs to Microchip's serial EEPROM product line, designed specifically for reliable, low-power, SPI-based nonvolatile storage in cost-sensitive, space-constrained embedded systems across industrial, automotive, and medical markets.

FAQ

What is the maximum clock frequency supported by the 25LC040A-I/ST?

The 25LC040A-I/ST supports a maximum clock frequency of 10 MHz 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 (not applicable to 25LC040A), it would be 3 MHz. These limits ensure setup/hold timing margins are met across voltage and temperature ranges per DS21827H Table 1-2.

Does the 25LC040A-I/ST support page write operations, and what is the page size?

Yes, the 25LC040A-I/ST supports page write mode with a fixed page size of 16 bytes. Page writes allow up to 16 consecutive bytes to be loaded into the page buffer before initiating the internal write cycle. Addresses must reside within the same physical page (e.g., 0x00–0x0F, 0x10–0x1F); crossing boundaries wraps to the start of the current page - firmware must validate address alignment prior to issuing WRITE commands.

How does the HOLD pin function in the 25LC040A-I/ST, and what are its timing requirements?

The HOLD pin in the 25LC040A-I/ST pauses ongoing SPI communication while preserving internal state (address pointer, instruction phase). To activate HOLD, the pin must be driven low while SCK is low; deactivation requires HOLD high while SCK is low. Minimum HOLD setup/hold times are 20–80 ns depending on VCC, per DS21827H Table 1-2 Param 16–17. During HOLD, SI/SO/SCK are tri-stated and ignored except CS.

What write protection mechanisms are available on the 25LC040A-I/ST?

The 25LC040A-I/ST provides dual-layer write protection: (1) hardware via the WP pin (low = full array + STATUS register write disable), and (2) software-configurable block protection via BP0/BP1 bits in the STATUS register (00 = none, 01 = upper 1/4, 10 = upper 1/2, 11 = full array). Both mechanisms operate independently; WP takes precedence and resets WEL regardless of STATUS register state.

Is the 25LC040A-I/ST pin-compatible with other members of the 25XX040A family?

Yes, the 25LC040A-I/ST is pin-compatible with all 25XX040A variants (e.g., 25AA040A-I/ST, 25LC040A-E/ST) in the same package (TSSOP-8, ST code). All share identical pinout, electrical characteristics, and SPI protocol. However, VCC range differs: 25LC040A requires 2.5–5.5V, whereas 25AA040A supports 1.8–5.5V - direct substitution is valid only if system VCC meets the stricter 25LC040A lower limit.