Microchip Technology 25AA128X-I/ST

Overview

25AA128X-I/ST from Microchip Technology 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 - used for nonvolatile parameter storage in microcontroller-based embedded systems requiring robust data retention.

For engineers reviewing the 25AA128X-I/ST datasheet, 25AA128X-I/ST pinout, 25AA128X-I/ST application, or 25AA128X-I/ST equivalent, this page provides verified electrical specs, SPI timing constraints, HOLD/CS/WP functional behavior, package-specific pin mapping for TSSOP-8, and validated alternatives for industrial-grade serial EEPROM replacement.

Technical Context

The 25AA128X-I/ST implements a standard SPI Mode 0,0 interface with separate SI (data-in) and SO (data-out) lines, CS-controlled selection, and hardware-assisted HOLD suspension. Its internal architecture includes a write-enable latch, STATUS register with WIP/WEL/BP0/BP1 bits, and on-chip high-voltage generator for EEPROM programming.

It supports byte-write and page-write (up to 64 bytes within same 64-byte boundary), self-timed internal write cycles ≤5 ms, and configurable block protection (none/1/4/1/2/all array). Write protection combines software (WRSR) and hardware (WP pin + WPEN bit) layers, with power-on reset of WEL and automatic WEL clear after each successful write.

Key Specifications

Pinout & Package

25AA128X-I/ST is packaged in an 8-Lead TSSOP (Thin Shrink Small Outline Package) with 0.65 mm pitch, JEDEC MO-153 compliant, body dimensions 4.4 mm × 3.0 mm × 1.2 mm. Pin 1 marked by notch or dot; exposed pad not present (unlike DFN variant).

Key Features

Applications

Equivalent & Alternatives

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

Compared with 25AA128X-I/ST, 25LC128-I/ST sacrifices 1.8V operation for identical industrial-grade reliability, while AT25128AN-10SU-2.7 offers vendor diversification but demands validation of protection logic and timing margins in existing firmware.

Availability

25AA128X-I/ST is available at Aetrix Electronics and suitable for industrial sensor nodes, medical device configuration storage, automotive body control modules, and POS terminal firmware patch storage requiring stable component supply across extended product lifecycles.

Supply support for 25AA128X-I/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 microcontrollers, analog devices, and memory solutions, headquartered in Chandler, Arizona, with global design and manufacturing operations.

The 25AA128X-I/ST belongs to Microchip's 25XX128 family of SPI Serial EEPROMs, designed specifically for reliable, low-power, pin-efficient nonvolatile storage in resource-constrained embedded systems.

FAQ

What voltage range does the 25AA128X-I/ST support, and how does it affect maximum clock speed?

The 25AA128X-I/ST operates from 1.8V to 5.5V. Its maximum SPI clock frequency scales with VCC: 10 MHz at 4.5–5.5V, 5 MHz at 2.5–4.5V, and 3 MHz at 1.8–2.5V. This allows direct integration with 1.8V, 3.3V, and 5V microcontrollers while maintaining timing compliance across supply rails - a key advantage over fixed-voltage EEPROMs like the 25LC128.

How does the HOLD pin function on the 25AA128X-I/ST, and what are its timing requirements?

The HOLD pin on the 25AA128X-I/ST suspends ongoing SPI communication without resetting the internal state. To activate HOLD, it must be driven low while SCK is low; releasing HOLD requires bringing it high while SCK remains low. During HOLD, SI/SO/SCK enter high-impedance, allowing the host MCU to service interrupts and resume exactly where transmission paused - critical for real-time systems using the 25AA128X-I/ST.

What protection mechanisms prevent unintended writes to the 25AA128X-I/ST memory array?

The 25AA128X-I/ST uses three layered protections: (1) a volatile write-enable latch (WEL) reset at power-up and cleared after every write, (2) software-configurable block protection (BP0/BP1) via WRSR, and (3) hardware write-protection enabled only when both WP pin is low and WPEN bit is set. These ensure that accidental writes - whether from noise, brownout, or firmware error - cannot corrupt stored data in deployed 25AA128X-I/ST units.

Can the 25AA128X-I/ST be used in automotive applications, and what qualifications does it hold?

Yes - the 25AA128X-I/ST is AEC-Q100 qualified for automotive applications. Its industrial temperature grade (–40°C to +85°C), 1,000,000 endurance cycles, and >200-year data retention meet stringent automotive reliability requirements. It is commonly deployed in body control modules, infotainment settings storage, and ADAS calibration data retention where the 25AA128X-I/ST replaces larger parallel EEPROMs or FRAM in cost-sensitive designs.

What is the page size of the 25AA128X-I/ST, and why does page boundary crossing cause data wraparound?

The 25AA128X-I/ST has a 64-byte page size. During page write, all bytes must reside within the same physical page (addresses 0x0000–0x003F, 0x0040–0x007F, etc.). If a page write crosses a boundary - e.g., writing 64 bytes starting at 0x003E - the excess bytes wrap to the start of the same page (0x0000), overwriting prior data. This behavior is inherent to the 25AA128X-I/ST's internal page latch architecture and requires firmware-level address validation before issuing WRITE commands.