Microchip Technology 25LC040A-E/ST

Overview

25LC040A-E/ST from Microchip Technology is a 4 Kbit (512 × 8) SPI Serial EEPROM with 2.5–5.5 V supply range, 16-byte page write capability, 10 MHz max clock frequency, and automotive-grade temperature support (–40°C to +125°C). It features hardware write protection (WP pin), HOLD functionality for interrupt-safe serial pauses, and block-level array protection (none/1/4/1/2/all). Used in engine control units, ADAS sensor modules, and automotive infotainment firmware storage.

For engineers reviewing the 25LC040A-E/ST datasheet, 25LC040A-E/ST pinout, 25LC040A-E/ST application, or 25LC040A-E/ST equivalent, key selection criteria include automotive temperature qualification, SPI timing compliance at 2.5 V, WP/HOLD pin behavior under voltage ramp conditions, and page-boundary-aware firmware write logic.

Technical Context

The 25LC040A-E/ST implements a standard SPI Mode 0,0/Master-Slave interface with separate SI (MOSI) and SO (MISO) lines, requiring CS assertion for device selection and SCK synchronization. Its internal architecture includes a nonvolatile STATUS register controlling BP0/BP1 block protection bits and WEL/WIP flags, with write enable latching required before all write operations.

It supports byte and page writes (up to 16 bytes within same physical page), self-timed internal write cycles (≤5 ms), and automatic address rollover during sequential reads. The HOLD pin suspends ongoing SPI transfers without resetting state, enabling host CPU servicing of higher-priority interrupts while preserving transaction context.

Key Specifications

Pinout & Package

25LC040A-E/ST is packaged in an 8-lead TSSOP (ST suffix), with lead pitch 0.65 mm, body size 4.4 mm × 3.0 mm × 1.2 mm, and Pb-free/RoHS-compliant finish.

Key Features

Applications

Equivalent & Alternatives

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

Compared with AT25040B-MAHL-T and BR25L040FJ-WE2, the 25LC040A-E/ST uniquely combines AEC-Q100 Grade 1 qualification, integrated HOLD pin for interrupt-safe operation, and ST-packaged TSSOP for high-density automotive PCBs - making it the only option supporting both thermal robustness and deterministic SPI pausing in safety-critical systems.

Availability

25LC040A-E/ST is available at Aetrix Electronics and suitable for automotive powertrain control, ADAS sensor fusion, and infotainment firmware storage requiring stable component supply across extended product lifecycles.

Supply support for 25LC040A-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 microcontroller, mixed-signal, analog, and Flash-IP solutions, serving automotive, industrial, consumer, and communications markets with high-reliability silicon and development tools.

The 25LC040A product line delivers automotive-qualified SPI EEPROMs optimized for firmware storage, calibration data retention, and secure configuration management in harsh-temperature electronic control units.

FAQ

What is the maximum clock frequency supported by the 25LC040A-E/ST across its full voltage range?

The 25LC040A-E/ST supports up to 10 MHz at VCC ≥ 4.5 V, 5 MHz at 2.5 V ≤ VCC < 4.5 V, and 3 MHz at 1.8 V ≤ VCC < 2.5 V. Since the 25LC040A-E/ST is specified for 2.5–5.5 V operation, its maximum usable clock is 10 MHz (at ≥4.5 V) or 5 MHz (at 2.5 V). These values are confirmed in Table 1-2 AC Characteristics of DS21827H.

Does the 25LC040A-E/ST require external pull-up resistors on its SO or SI lines?

No, the 25LC040A-E/ST does not require external pull-ups on SO or SI. Its SO output is actively driven (not open-drain), and SI is a standard CMOS input with leakage current ≤±1 µA (D007/D008). Pull-ups may cause bus contention or violate VIH/VIL thresholds; proper SPI bus termination follows standard point-to-point or multi-drop SPI layout rules without added resistors.

How does the HOLD pin behave during power-up or brown-out conditions on the 25LC040A-E/ST?

During power-up, the 25LC040A-E/ST initializes HOLD as a high-impedance input; it must be externally pulled high (typically via 10 kΩ to VCC) to ensure functional readiness. If HOLD is low during power-on reset, the device enters HOLD mode immediately upon VCC crossing the minimum threshold, freezing any pending SPI state - a condition that persists until HOLD is raised while SCK is low. This behavior is documented in Section 3.6 and Figure 2-1.

Can the 25LC040A-E/ST be used interchangeably with the 25AA040A in a design?

No, the 25LC040A-E/ST and 25AA040A are not interchangeable without validation. While functionally similar, the 25LC040A-E/ST operates from 2.5–5.5 V and is automotive-qualified (–40°C to +125°C), whereas the 25AA040A supports 1.8–5.5 V and is rated for industrial temperature only (–40°C to +85°C). Substituting them risks timing violations at 1.8 V or thermal failure in automotive environments. The 25LC040A-E/ST datasheet explicitly lists separate VCC and temperature ranges.

What happens if a page write crosses a 16-byte boundary on the 25LC040A-E/ST?

If a page write command attempts to cross a 16-byte physical page boundary (e.g., writing bytes at addresses 0x0F through 0x12), the 25LC040A-E/ST wraps the address back to the start of the current page (0x00 in this example) and overwrites prior data - it does not advance to the next page. This wrap-around behavior is explicitly stated in Section 2.3 and Note on DS21827H-page 6. Firmware must enforce page-aligned writes or split multi-page operations manually.