Microchip Technology 25AA128T-I/SM

Overview

25AA128T-I/SM from Microchip Technology Inc. is a 128 Kbit SPI Serial EEPROM with 16,384 × 8-bit organization, 64-byte page size, and industrial temperature range (–40°C to +85°C). It operates from 1.8V to 5.5V, supports up to 10 MHz clock at 4.5–5.5V, and delivers 5 µA standby current - ideal for battery-backed data logging in embedded control systems.

For engineers reviewing the 25AA128T-I/SM datasheet, 25AA128T-I/SM pinout, 25AA128T-I/SM application, or 25AA128T-I/SM equivalent, key selection criteria include VCC range compatibility (1.8–5.5V), SPI timing compliance (TWC ≤ 5 ms), hardware write protection via WP pin, HOLD functionality for interrupt-safe bus sharing, and AEC-Q100 qualification for automotive-adjacent designs.

Technical Context

The 25AA128T-I/SM implements a standard SPI Mode 0,0/Master-Slave interface with separate SI (data-in) and SO (data-out) lines, requiring CS, SCK, SI, SO, WP, HOLD, VCC, and VSS. Its internal architecture includes a status register with WIP/WEL/BP0/BP1 bits, programmable block protection (none/¼/½/all), and a write-enable latch that resets on power-up or after each successful WRITE/WRSR/WRDI operation.

It features self-timed internal write cycles (max 5 ms), sequential read capability with automatic address rollover, and robust data retention (>200 years) backed by 1,000,000 erase/write endurance. The HOLD pin suspends ongoing SPI transfers without resetting state, enabling deterministic host interrupt handling while preserving transaction context.

Key Specifications

Pinout & Package

25AA128T-I/SM is packaged in an 8-lead TSSOP (Thin Shrink Small Outline Package) with 0.65 mm pitch, body dimensions 4.4 mm × 3.0 mm × 1.2 mm, and exposed pad (optional VSS connection). Pin 1 is marked with a dot; orientation follows standard TSSOP top-view labeling.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 25LC128T-I/SM, the original part offers broader voltage range and lower minimum VCC, while AT25DF041A-SSH-T trades pin compatibility and HOLD support for higher density and speed - making 25AA128T-I/SM optimal for low-power, interrupt-resilient, mixed-voltage embedded systems.

Availability

25AA128T-I/SM is available at Aetrix Electronics and suitable for industrial sensor nodes, automotive body control modules, medical infusion pumps, and smart energy meters requiring stable component supply, long-term data retention, and AEC-Q100-compliant reliability.

Supply support for 25AA128T-I/SM 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 and manufacturing operations.

The 25AA128T-I/SM belongs to Microchip's serial EEPROM product line, engineered for robust, low-power nonvolatile data storage in resource-constrained embedded systems where SPI simplicity, voltage flexibility, and long-term reliability are essential.

FAQ

What is the minimum supply voltage required for reliable operation of the 25AA128T-I/SM?

The 25AA128T-I/SM operates reliably from 1.8V to 5.5V. At 1.8V, maximum clock frequency is reduced to 3 MHz, and certain AC parameters (e.g., TCSS, THD) have relaxed timing limits. All functionality-including READ, WRITE, RDSR, and HOLD-remains fully supported across this range, making 25AA128T-I/SM suitable for battery-powered applications where voltage droop occurs.

Does the 25AA128T-I/SM support page write operations, and what is the maximum page size?

Yes, the 25AA128T-I/SM supports page write operations with a fixed 64-byte page size. Up to 64 bytes can be written in a single WRITE instruction, provided all addresses fall within the same physical page boundary (e.g., 0x0000–0x003F). Crossing a page boundary causes wraparound within the current page, so firmware must validate address alignment before initiating page writes.

How does the HOLD pin function during an active SPI transaction on the 25AA128T-I/SM?

The HOLD pin on the 25AA128T-I/SM pauses an ongoing SPI sequence without resetting internal state. When pulled low while SCK is low, it tri-states SO, SI, and SCK, ignores further input transitions (except CS), and preserves the current address pointer and instruction context. Resuming requires bringing HOLD high while SCK remains low - enabling deterministic interrupt handling in time-critical MCU firmware.

What write protection mechanisms are implemented in the 25AA128T-I/SM?

The 25AA128T-I/SM implements three-tiered write protection: (1) Software-controlled BP0/BP1 bits for block-level array protection (none/¼/½/all), (2) WPEN bit + WP pin for hardware lock of STATUS register nonvolatile bits, and (3) write-enable latch (WEL) that must be set via WREN prior to any array or STATUS register write. All protections persist through power cycles.

Is the 25AA128T-I/SM compatible with standard SPI Mode 0,0, and what are its timing constraints at 5.5V?

Yes, the 25AA128T-I/SM is fully compliant with SPI Mode 0,0 (CPOL=0, CPHA=0). At VCC = 5.5V, it supports up to 10 MHz clock frequency with verified timing margins: TCSS ≥ 50 ns, THD ≥ 20 ns, TSU ≥ 10 ns, and TWC ≤ 5 ms. These values ensure interoperability with standard SPI peripherals in PIC®, ARM Cortex-M, and other microcontrollers without custom timing adjustments.