Microchip Technology 25LC128T-I/SM

Overview

25LC128T-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 at up to 10 MHz clock frequency with 5 mA read/write current at 5.5 V and features hardware write protection via WP pin and STATUS register control. It is used in microcontroller-based systems for nonvolatile parameter storage, calibration data retention, and firmware configuration.

For engineers reviewing the 25LC128T-I/SM datasheet, 25LC128T-I/SM pinout, 25LC128T-I/SM application, or 25LC128T-I/SM equivalent, key selection considerations include V_CC range (2.5–5.5 V), TSSOP-8 packaging, block-level write protection (BP0/BP1), HOLD functionality for interrupt-safe SPI pauses, and AEC-Q100 qualification for automotive-grade reliability.

Technical Context

The 25LC128T-I/SM implements a standard SPI Mode 0,0/Master-Slave interface with separate SI (data-in) and SO (data-out) lines, CS-controlled selection, and SCK-synchronized transfers. All instructions (READ, WRITE, WREN, RDSR, WRSR) are 8-bit MSB-first, with address and data transferred sequentially after instruction latching on rising SCK edges.

It integrates an internal high-voltage generator for EEPROM programming, self-timed 5 ms max write cycles, and a status register with WIP, WEL, BP0/BP1, and WPEN bits. Write protection is configurable at four levels (none, 1/4, 1/2, or full array), and hardware protection requires both WP pin low and WPEN bit set - enabling robust field-programmable security without firmware dependency.

Key Specifications

Pinout & Package

25LC128T-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 for thermal relief or grounding. Pin 1 is marked by a beveled corner or dot; pin numbering follows standard counter-clockwise orientation when viewed from top.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 25AA128T-I/SM and AT25DF041A-SSH-T, the 25LC128T-I/SM delivers optimal balance of industrial temperature rating, proven SPI EEPROM simplicity, and cost-effective 128 Kbit capacity - making it ideal for parameter storage where reliability and firmware compatibility outweigh raw density or speed needs.

Availability

25LC128T-I/SM is available at Aetrix Electronics and suitable for automotive ECU design, industrial PLC commissioning, and medical device calibration requiring stable component supply across extended product lifecycles.

Supply support for 25LC128T-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 microcontrollers, analog devices, and memory solutions, headquartered in Chandler, Arizona, with global design and manufacturing operations.

The 25LC128T-I/SM belongs to Microchip's 25XX128 family of SPI Serial EEPROMs, engineered for robust, low-power nonvolatile storage in automotive, industrial, and medical systems where data integrity and long-term reliability are mission-critical.

FAQ

What is the maximum clock frequency supported by the 25LC128T-I/SM?

The 25LC128T-I/SM supports up to 10 MHz clock frequency when V_CC is between 4.5 V and 5.5 V. At 2.5 V ≤ V_CC < 4.5 V, the maximum is 5 MHz, and at 1.8 V ≤ V_CC < 2.5 V, it drops to 3 MHz. These limits ensure timing margins for setup/hold and output validity across voltage and temperature ranges - all verified per DS20001831F AC characteristics Table 1-2.

Does the 25LC128T-I/SM require external pull-up resistors on its SPI lines?

No, the 25LC128T-I/SM does not require external pull-up resistors on SI, SO, SCK, or CS. Its inputs meet standard CMOS voltage thresholds (VIH ≥ 0.7 V_CC, VIL ≤ 0.3 V_CC), and SO is actively driven or tri-stated - eliminating pull-up dependencies. However, proper PCB routing and local V_CC/V_SS decoupling remain essential for noise immunity at 10 MHz operation.

How does the HOLD function behave during an active write cycle in the 25LC128T-I/SM?

The HOLD function is disabled during an internal write cycle (TWC) in the 25LC128T-I/SM. While CS remains low and the write is in progress, pulling HOLD low has no effect - the device continues the write and ignores HOLD transitions. HOLD only operates during active read or instruction phases, ensuring write atomicity and preventing partial writes due to premature hold assertion.

Can the 25LC128T-I/SM be used in automotive applications requiring AEC-Q100 compliance?

Yes, the 25LC128T-I/SM is explicitly AEC-Q100 qualified for Automotive Grade 3 (−40°C to +85°C) per the device selection table and package marking "I/SM" (Industrial temp, TSSOP package). Its qualification includes HTOL, ESD (>4 kV HBM), and temperature cycling - meeting baseline requirements for engine control, body electronics, and infotainment subsystems.

What happens if a page write crosses a 64-byte boundary in the 25LC128T-I/SM?

If a page write command attempts to cross a 64-byte boundary in the 25LC128T-I/SM, data wraps around to the start of the same page instead of advancing to the next page. For example, writing 10 bytes starting at address 0x003E overwrites bytes 0x003E–0x003F and then 0x0000–0x0007. This behavior is documented in Section 3.3 and requires firmware to enforce page-aligned writes or split multi-page transfers manually.