Microchip Technology 25AA040A-I/SN

Overview

25AA040A-I/SN 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 parameter storage in microcontroller-based embedded systems requiring low-power, high-reliability data retention.

For engineers reviewing the 25AA040A-I/SN datasheet, 25AA040A-I/SN pinout, 25AA040A-I/SN application, or 25AA040A-I/SN equivalent, key selection criteria include SPI interface compatibility, 1.8 V minimum VCC operation, page-write timing constraints, and hardware write-protect functionality across SOIC-8 packaging.

Technical Context

The 25AA040A-I/SN implements a standard SPI Mode 0,0/Master-Slave interface with separate SI (data in), SO (data out), SCK (clock), CS (chip select), WP (write-protect), and HOLD (suspend) signals. Its internal architecture includes an 8-bit instruction register, page latches, and high-voltage generator for EEPROM programming.

It uses self-timed internal write cycles (≤5 ms), supports sequential read with automatic address roll-over, and provides nonvolatile block protection (BP1/BP0 bits) for 0%, 25%, 50%, or 100% of the 512-byte array. The HOLD function pauses ongoing serial transfers without resetting the sequence, enabling interrupt servicing in real-time systems.

Key Specifications

Pinout & Package

25AA040A-I/SN is packaged in 8-lead SOIC (SN), with lead pitch 1.27 mm and body dimensions 3.9 mm × 4.9 mm. Pin 1 is marked by laser indentation; package is Pb-free and RoHS compliant.

Key Features

Applications

Equivalent & Alternatives

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

Compared with AT25040B-SSHL-T and M95040-DRMN6TP/K, the 25AA040A-I/SN offers optimal cost-performance balance for industrial-grade 1.8 V–5.5 V systems where 10 MHz bandwidth and 85°C operation suffice - avoiding over-specification while ensuring full functional equivalence in SOIC-8 footprint.

Availability

25AA040A-I/SN is available at Aetrix Electronics and suitable for industrial control panels, medical diagnostics equipment, and smart utility metering requiring stable component supply, long-term lifecycle support, and RoHS-compliant sourcing.

Supply support for 25AA040A-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 leading provider of microcontrollers, analog devices, and memory solutions, headquartered in Chandler, Arizona, with global design and manufacturing operations.

The 25AA040A-I/SN belongs to Microchip's legacy SPI Serial EEPROM product line, designed specifically for reliable, low-power nonvolatile data storage in resource-constrained embedded systems across industrial, medical, and consumer applications.

FAQ

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

The 25AA040A-I/SN 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 limits are defined in Table 1-2 of the DS21827H datasheet and directly impact achievable read/write throughput in the target system using the 25AA040A-I/SN.

Does the 25AA040A-I/SN require external pull-up resistors on its SO or SI lines?

No, the 25AA040A-I/SN does not require external pull-ups on SI or SO. SI is a CMOS input with no pull-up; SO is an active-push/pull output (not open-drain), so it drives both logic levels actively. External pull-ups may cause contention or excessive current draw and are unnecessary for proper 25AA040A-I/SN operation.

How does the HOLD pin function during an ongoing SPI transaction with the 25AA040A-I/SN?

The HOLD pin suspends SPI communication mid-sequence when asserted low while SCK is low. During HOLD, SI, SCK, and SO enter high-impedance states and are ignored; CS must remain low. Resuming requires bringing HOLD high while SCK is low. This preserves internal state for the 25AA040A-I/SN, allowing the host MCU to service interrupts without reinitializing the transaction.

Can the 25AA040A-I/SN be used with a 1.8 V microcontroller without level shifters?

Yes, the 25AA040A-I/SN operates natively from 1.8 V to 5.5 V and specifies VIH1 = 0.7×VCC and VIL1 = 0.3×VCC, making it fully compatible with 1.8 V logic thresholds. Its 1.8 V min VCC and guaranteed DC/AC characteristics down to that voltage confirm direct interfacing with 1.8 V MCUs - no level shifting needed for the 25AA040A-I/SN.

What happens if a page write crosses a 16-byte boundary on the 25AA040A-I/SN?

If a page write command attempts to cross a 16-byte boundary (e.g., writing 16 bytes starting at address 0x0F), the 25AA040A-I/SN wraps the data back to the start of the current page (0x00) and overwrites prior bytes. This behavior is documented in Section 2.3 and requires application firmware to enforce page-aligned writes - failure to do so corrupts data within the 25AA040A-I/SN's memory array.