Microchip Technology 25LC128X-I/ST

Overview

25LC128X-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 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 25LC128X-I/ST datasheet, 25LC128X-I/ST pinout, 25LC128X-I/ST application, or 25LC128X-I/ST equivalent, key selection criteria include SPI interface compatibility, 2.5V–5.5V supply range, TSSOP-8 package footprint, block-level write protection (BP0/BP1), and endurance of 1,000,000 erase/write cycles.

Technical Context

The 25LC128X-I/ST implements a standard SPI Mode 0,0/Master-Slave interface with separate SI (data-in) and SO (data-out) lines, CS-controlled selection, and HOLD pin for transaction suspension. Its internal architecture includes a 64-byte page latch, status register with WIP/WEL/BP0/BP1 bits, and high-voltage generator for EEPROM programming.

It supports byte and page write operations (max 64 bytes/page), self-timed internal write cycles (≤5 ms), and sequential read with automatic address increment. Write enable requires explicit WREN instruction, and hardware write protection engages only when WPEN=1 and WP=low - enabling selective array locking without software overhead.

Key Specifications

Pinout & Package

25LC128X-I/ST is packaged in an 8-lead TSSOP (Thin Shrink Small Outline Package) with 0.65 mm pitch, JEDEC MO-153 compliant, and marked "25LC128I/ST" on top surface. The exposed pad is not electrically connected and may be left floating or tied to VSS for thermal enhancement.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 25AA128-I/ST and AT25128B-SSHL-T, the 25LC128X-I/ST delivers optimal trade-off between voltage flexibility, feature completeness (HOLD, BP granularity), and industrial temperature assurance - making it the default choice for new 2.5–5.5 V designs requiring robust configuration storage.

Availability

25LC128X-I/ST is available at Aetrix Electronics and suitable for industrial PLCs, automotive ECUs, medical diagnostics, smart meters, and IoT edge nodes requiring stable component supply with guaranteed long-term availability.

Supply support for 25LC128X-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 25LC128X-I/ST belongs to Microchip's serial EEPROM product line, engineered specifically for reliable, low-pin-count nonvolatile storage in resource-constrained embedded systems requiring SPI simplicity and industrial-grade reliability.

FAQ

What is the maximum operating clock frequency for the 25LC128X-I/ST?

The 25LC128X-I/ST supports up to 10 MHz SPI clock frequency when VCC is 4.5 V to 5.5 V. At 2.5 V ≤ VCC < 4.5 V, the maximum clock drops to 5 MHz. This voltage-dependent speed scaling ensures timing margin and signal integrity across its full 2.5–5.5 V supply range - a key design consideration for mixed-voltage systems using the 25LC128X-I/ST.

Does the 25LC128X-I/ST require external pull-up resistors on its SPI lines?

No, the 25LC128X-I/ST does not require external pull-ups on SI, SO, or SCK. Its inputs (CS, WP, HOLD) have internal weak pull-ups only when enabled via STATUS register configuration - but these are not active by default. External pull-ups are recommended only on CS for noise immunity in noisy environments, and on WP if hardware write protection is desired in default-low state. The 25LC128X-I/ST itself drives SO actively and samples SI/SCK without external biasing.

How does the HOLD function work on the 25LC128X-I/ST during an active SPI transfer?

The HOLD pin on the 25LC128X-I/ST suspends an ongoing SPI transaction when pulled low while SCK is low; SI, SCK, and SO enter high-impedance states, and all input transitions (except CS) are ignored. To resume, HOLD must be raised while SCK remains low - then communication continues from the exact bit position where it paused. This allows the host MCU to service higher-priority interrupts without losing sync, a capability confirmed in the 25LC128X-I/ST's functional description and timing diagrams.

Can the 25LC128X-I/ST be used in place of the 25LC128-I/ST?

Yes, the 25LC128X-I/ST is a direct replacement for the 25LC128-I/ST. Both share identical electrical specifications, pinout, package (TSSOP-8), and functional behavior. The "X" suffix denotes updated wafer fabrication or test flow per Microchip's part numbering convention - not a functional revision. All documentation, firmware drivers, and PCB footprints for 25LC128-I/ST apply unchanged to the 25LC128X-I/ST.

What happens to the write enable latch after a successful write operation on the 25LC128X-I/ST?

After a successful WRITE, WRSR, or WRDI instruction, the write enable latch (WEL bit) in the 25LC128X-I/ST is automatically reset to '0'. This means each write operation requires an explicit prior WREN instruction - preventing accidental writes due to noise or incomplete commands. Power-up also resets the latch, ensuring the 25LC128X-I/ST starts in write-disabled state, a safety feature documented in Section 3.4 of the datasheet.