Microchip Technology 25LC640AT-H/ST16KVAO

Overview

25LC640AT-H/ST16KVAO from Microchip Technology is a 64 Kbit (8,192 × 8) high-temperature SPI serial EEPROM with 5 MHz max clock speed, 32-byte page size, and extended temperature range of –40°C to +150°C. It supports byte/page write, sequential read, hardware write protection via WP pin, and is AEC-Q100 qualified for automotive under-hood applications.

For engineers reviewing the 25LC640AT-H/ST16KVAO datasheet, 25LC640AT-H/ST16KVAO pinout, 25LC640AT-H/ST16KVAO application, or 25LC640AT-H/ST16KVAO equivalent, this device delivers deterministic 6 ms max internal write cycle time, >1,000,000 erase/write endurance, and robust hold/pause functionality for interrupt-safe SPI communication in harsh environments.

Technical Context

The 25LC640AT-H/ST16KVAO implements a standard SPI Mode 0,0 interface with separate SI (data in) and SO (data out) lines, requiring CS, SCK, and HOLD control. Its internal architecture includes an 8-bit instruction register, status register with WIP/WEL/BP bits, and page latches enabling atomic 32-byte writes without external buffering.

It features dual-level write protection: nonvolatile BP0/BP1 bits configure block protection (none/¼/½/all array), while the WP pin-enabled only when WPEN=1-provides hardware lockout of STATUS register writes. Power-on reset clears the write enable latch, and all write cycles initiate on CS rising edge after valid command sequence.

Key Specifications

Pinout & Package

8-Lead SOIC (SN) package, 3.90 mm body width, RoHS-compliant matte tin finish, JEDEC MS-012AC variant.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 25AA640A-I/SN, the 25LC640AT-H/ST16KVAO provides guaranteed operation up to +150°C and AEC-Q100 qualification, while AT25DF641-AU offers vastly greater capacity but demands full interface redesign and loses deterministic write timing.

Availability

25LC640AT-H/ST16KVAO is available at Aetrix Electronics and suitable for automotive powertrain control, industrial motor drives, and aerospace sensor conditioning requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for 25LC640AT-H/ST16KVAO 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, and Flash-IP solutions, serving automotive, industrial, and consumer markets with high-reliability silicon and development tools.

The 25LCxxx family delivers mid-density serial EEPROMs optimized for SPI-based embedded systems needing robust nonvolatile storage in extreme thermal environments, especially automotive under-hood and industrial process control applications.

FAQ

What is the maximum clock frequency supported by the 25LC640AT-H/ST16KVAO across its full voltage range?

The 25LC640AT-H/ST16KVAO supports up to 5 MHz clock frequency when VCC is 4.5V–5.5V, and 3 MHz when VCC is 2.5V–4.5V. These limits are defined in Table 1-2 AC Characteristics and apply across the full –40°C to +150°C operating range. Exceeding these frequencies risks setup/hold violations and data corruption, particularly at temperature extremes or low VCC.

Does the 25LC640AT-H/ST16KVAO require external pull-up resistors on its SO or SI lines?

No, the 25LC640AT-H/ST16KVAO does not require external pull-ups on SO or SI. Its SO pin is actively driven and tri-stated when CS is high or HOLD is low; SI is CMOS input with leakage <±2 μA (D007). Pull-ups may interfere with SPI timing margins and are omitted in Microchip's recommended layouts. Only CS, WP, and HOLD may need weak pull-ups depending on host controller drive strength.

How does the HOLD function interact with an ongoing write cycle in the 25LC640AT-H/ST16KVAO?

The HOLD function has no effect on an active internal write cycle in the 25LC640AT-H/ST16KVAO. Once initiated by CS rising edge after a valid write sequence, the 6 ms internal write proceeds autonomously. HOLD only pauses serial instruction/address/data transfers-not the write execution itself. The STATUS register's WIP bit remains '1' until completion, and SO stays high-Z during HOLD assertion.

Can the 25LC640AT-H/ST16KVAO be used in a daisy-chained SPI configuration with multiple devices?

No, the 25LC640AT-H/ST16KVAO does not support daisy-chaining. It uses standard SPI with separate SI and SO lines (not shared MISO/MOSI), requiring individual CS lines for each device. Multiple units share SCK, WP, HOLD, and VCC/VSS, but each needs dedicated CS and SO routing. Daisy-chain capability would require a single data line with shift-register chaining, which this device lacks.

What happens to the write enable latch after issuing a WRITE instruction to the 25LC640AT-H/ST16KVAO?

After a WRITE instruction completes successfully-including CS going high after the last data bit-the write enable latch in the 25LC640AT-H/ST16KVAO is automatically reset to '0'. This means the next write attempt will fail unless WREN is reissued. The latch also resets on power-up, WRDI execution, WRSR completion, or any successful WRITE, enforcing explicit enable-before-write discipline for data integrity.