Microchip Technology 25AA040A-I/MS

Overview

25AA040A-I/MS from Microchip Technology Inc. is a 4 Kbit SPI Serial EEPROM with 512 × 8-bit organization, 1.8–5.5 V supply range, and industrial temperature rating (–40°C to +85°C). It supports up to 10 MHz clock frequency, 16-byte page write, and hardware write protection via WP pin - used for nonvolatile configuration storage in microcontroller-based embedded systems.

For engineers reviewing the 25AA040A-I/MS datasheet, 25AA040A-I/MS pinout, 25AA040A-I/MS application, or 25AA040A-I/MS equivalent, key selection criteria include SPI interface compatibility, low-voltage operation down to 1.8 V, page-write timing (≤5 ms), block protection granularity (none/¼/½/all), and MSOP-8 package footprint for space-constrained PCBs.

Technical Context

The 25AA040A-I/MS implements a standard SPI Mode 0,0 or Mode 1,1 interface with separate SI (data in) and SO (data out) lines, CS-controlled selection, and HOLD input for transaction suspension. Its internal architecture includes an 8-bit instruction register, page latches, and EEPROM array with high-voltage programming circuitry.

Write operations require explicit WREN instruction followed by CS high to latch enable state; writes are self-timed (max 5 ms), and status polling via RDSR (WIP bit) is supported. Block protection is controlled nonvolatively via BP0/BP1 bits in the STATUS register, enabling selective write-lock of memory segments.

Key Specifications

Pinout & Package

25AA040A-I/MS is housed in an 8-lead MSOP (Mini Small Outline Package) with 0.65 mm lead pitch and exposed pad option (not connected by default). The package measures 3.0 mm × 3.0 mm × 1.0 mm and is RoHS-compliant and Pb-free.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 25LC040A-I/MS and AT25040B-MAU-2.7, the 25AA040A-I/MS uniquely supports 1.8 V operation while retaining HOLD and identical block protection - making it optimal for ultra-low-voltage, interrupt-sensitive embedded designs.

Availability

25AA040A-I/MS is available at Aetrix Electronics and suitable for industrial sensor nodes, medical device configuration storage, and automotive body control modules requiring stable component supply with long-term lifecycle assurance.

Supply support for 25AA040A-I/MS 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 25AA040A belongs to Microchip's serial EEPROM product line, engineered for reliable, low-power nonvolatile storage in cost-sensitive, space-constrained embedded systems across industrial, medical, and automotive markets.

FAQ

What is the maximum clock frequency supported by the 25AA040A-I/MS?

The 25AA040A-I/MS supports up to 10 MHz clock frequency when VCC is 4.5 V to 5.5 V. At lower voltages (2.5–4.5 V), max clock drops to 5 MHz, and at 1.8–2.5 V, it is limited to 3 MHz. These AC timing limits are defined in Table 1-2 of the DS21827H datasheet and must be observed to ensure reliable read/write operation of the 25AA040A-I/MS.

Does the 25AA040A-I/MS support page write, and what is the page size?

Yes, the 25AA040A-I/MS supports page write mode with a fixed page size of 16 bytes. Writes crossing a 16-byte boundary will wrap within the current page instead of advancing to the next, so firmware must enforce alignment. This behavior is documented in Section 2.3 and Figure 2-3 of the 25AA040A-I/MS datasheet.

How does the WP pin function on the 25AA040A-I/MS?

The WP (Write-Protect) pin on the 25AA040A-I/MS is a hardware-level disable: when held low, it blocks all writes to memory and the STATUS register regardless of WEL or BP bit states. It does not affect reads or status polling. This behavior is confirmed in Table 2-4 and Section 3.3 of the 25AA040A-I/MS datasheet.

What package type is used for the 25AA040A-I/MS?

The 25AA040A-I/MS uses an 8-lead MSOP (Mini Small Outline Package) with 3.0 mm × 3.0 mm body, 0.65 mm lead pitch, and optional exposed thermal pad (unconnected by default). This is explicitly listed in the Device Selection Table and Package Types section of the DS21827H datasheet for the 25AA040A variant.

Can the 25AA040A-I/MS operate from a 1.8 V supply?

Yes, the 25AA040A-I/MS is fully specified for operation from 1.8 V to 5.5 V, unlike the 25LC040A which requires minimum 2.5 V. At 1.8 V, its maximum clock frequency is 3 MHz, and standby current remains ≤1 µA - enabling use in ultra-low-power battery-operated systems relying on the 25AA040A-I/MS.