Microchip Technology 25LC040A-I/P

Overview

25LC040A-I/P from Microchip Technology is a 4 Kbit (512 × 8) SPI bus serial EEPROM with 2.5–5.5 V supply range, 10 MHz max clock, 16-byte page write capability, and industrial temperature rating (−40°C to +85°C). It features hardware write protection (WP pin), HOLD functionality for interrupt-safe pausing, and block-level array protection (none/¼/½/all). Used in microcontroller-based systems for configuration storage, calibration data, and firmware parameter retention.

For engineers reviewing the 25LC040A-I/P datasheet, 25LC040A-I/P pinout, 25LC040A-I/P application, or 25LC040A-I/P equivalent, key selection criteria include SPI timing compliance at 2.5 V, WP/HOLD pin behavior under voltage transitions, endurance (1M cycles), data retention (>200 years), and package-specific thermal performance in PDIP-8.

Technical Context

The 25LC040A-I/P implements a standard SPI Mode 0,0/Master-Slave interface with separate SI/SO lines and CS-controlled device selection. Its internal architecture includes a 9-bit address space, page latches enabling up to 16-byte writes within aligned 16-byte boundaries, and a nonvolatile STATUS register controlling BP0/BP1 block protection bits.

Write operations require explicit WREN instruction followed by CS high-to-low transition to initiate self-timed internal write cycle (≤5 ms); read operations support sequential addressing with automatic rollover. HOLD pin suspends communication while preserving internal state, and WP pin disables all writes regardless of WEL status when asserted low.

Key Specifications

Pinout & Package

25LC040A-I/P is packaged in 8-lead PDIP (Plastic Dual In-line Package), with lead pitch 0.1 inch (2.54 mm) and body width 0.3 inch (7.62 mm). Pin 1 is marked by notch or dot; pin numbering follows standard counter-clockwise layout.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 25AA040A-I/P and AT25040B-SSHL-T, the 25LC040A-I/P offers optimal balance of industrial temperature support, hardware write protection, HOLD functionality, and proven interoperability with Microchip PIC® MCUs - making it preferred for safety-critical and interrupt-driven embedded designs.

Availability

25LC040A-I/P is available at Aetrix Electronics and suitable for industrial automation, automotive subsystems, and medical device manufacturing requiring stable component supply, full traceability, and long-term lifecycle assurance.

Supply support for 25LC040A-I/P 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 components, and memory solutions, headquartered in Chandler, Arizona, with global design and manufacturing operations.

The 25LC040A belongs to Microchip's serial EEPROM product line, engineered for robust, low-power nonvolatile storage in resource-constrained embedded systems where SPI interface simplicity and data integrity are critical.

FAQ

What is the maximum clock frequency supported by the 25LC040A-I/P at 3.3 V operation?

The 25LC040A-I/P supports up to 5 MHz maximum clock frequency when VCC is between 2.5 V and 4.5 V, as specified in Table 1-2 AC Characteristics. At 3.3 V, this limit applies directly - exceeding it risks setup/hold violations and unreliable communication. The 10 MHz rating requires VCC ≥ 4.5 V. Always verify timing margins using TCSS, TCSH, and Tsu values from the datasheet for your specific MCU SPI peripheral configuration.

Does the 25LC040A-I/P support SPI Mode 1,1 or only Mode 0,0?

The 25LC040A-I/P supports only SPI Mode 0,0 (CPOL = 0, CPHA = 0), as confirmed by Figure 1-2 and Section 2.1. Data is sampled on the rising edge of SCK and output changes on the falling edge. Attempting Mode 1,1 will result in misaligned sampling and corrupted reads/writes. The device does not auto-detect or adapt to alternate SPI modes.

How does the HOLD pin behave when pulled low during an active write cycle?

The HOLD pin has no effect on an ongoing internal write cycle (TWC); once initiated by CS high-to-low transition, the 5 ms write completes regardless of HOLD state. However, HOLD can pause read or command sequences mid-transfer. During HOLD assertion, SO goes high-impedance and SI/SCK inputs are ignored - but the internal address pointer and command state remain preserved for seamless resumption.

Can the 25LC040A-I/P be used with 1.8 V microcontrollers?

No - the 25LC040A-I/P requires a minimum VCC of 2.5 V and is not rated for 1.8 V operation. For 1.8 V systems, use the pin-compatible 25AA040A-I/P, which shares identical functionality and package but supports 1.8–5.5 V. Using 25LC040A-I/P below 2.5 V may cause unpredictable read/write failures and violates Absolute Maximum Ratings.

What happens to the write enable latch after issuing a WRITE instruction?

After a successful WRITE instruction (with CS brought high after the final data bit), the write enable latch (WEL) is automatically reset to '0', disabling further writes until WREN is reissued. This behavior is documented in Section 2.3 and Table 2-2. It prevents accidental multi-byte writes and enforces explicit re-enablement - a critical safety feature for configuration-critical applications using the 25LC040A-I/P.