Microchip Technology 23K640-I/ST

Overview

23K640-I/ST from Microchip Technology is a 64 Kbit (8192 × 8) SPI Serial SRAM with 32-byte page write capability, 20 MHz max clock frequency, and industrial temperature range (–40°C to +85°C). It operates from 2.7V to 3.6V, draws only 3 mA read current at 1 MHz, and features HOLD pin for interrupt-safe bus suspension - used in microcontroller-based data logging, real-time buffering, and firmware parameter storage.

For engineers reviewing the 23K640-I/ST datasheet, 23K640-I/ST pinout, 23K640-I/ST application, or 23K640-I/ST equivalent, key selection criteria include SPI-compatible serial interface timing, low-standby-current operation (≤4 µA at +85°C), 8-pin TSSOP package compatibility, and support for byte/page/sequential access modes without external address latches.

Technical Context

The 23K640-I/ST implements a true SPI-compatible serial interface with separate SI/SO lines, CS-controlled chip select, and SCK-synchronized data transfer (MSB-first). Its internal 8-bit instruction register accepts READ (0x03), WRITE (0x02), RDSR (0x05), and WRSR (0x01) commands, enabling flexible memory access without parallel bus overhead.

It supports three configurable operating modes via STATUS register bits 7–6: Byte mode (default), Page mode (32-byte auto-increment within page), and Sequential mode (full 8192-byte wraparound). The HOLD pin suspends active transfers while preserving internal state, allowing host MCU to service higher-priority interrupts without reinitializing the transaction.

Key Specifications

Pinout & Package

23K640-I/ST is housed in an 8-lead TSSOP (Thin Shrink Small Outline Package) with 0.65 mm lead pitch, optimized for high-density PCB layouts and automated assembly. Pin 1 is marked by a dot or beveled corner per JEDEC MO-153.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 23LC640-I/ST and FM25V05-G, the 23K640-I/ST delivers optimal balance of industrial temperature support, ultra-low standby current, and deterministic HOLD-based interrupt handling - making it preferred for resource-constrained embedded systems where predictable timing and power efficiency are prioritized over maximum density or write speed.

Availability

23K640-I/ST is available at Aetrix Electronics and suitable for industrial automation, medical device data buffering, and battery-powered sensor node applications requiring stable component supply across extended product lifecycles.

Supply support for 23K640-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 components, and memory solutions, headquartered in Chandler, Arizona, with global design and manufacturing operations.

The 23K640 belongs to Microchip's legacy SPI Serial SRAM product line, engineered specifically for low-power, space-constrained embedded systems needing simple, reliable, and fast serial memory expansion without parallel bus complexity.

FAQ

What is the maximum clock frequency supported by the 23K640-I/ST?

The 23K640-I/ST supports a maximum clock frequency of 20 MHz under industrial temperature conditions (–40°C to +85°C) at VCC = 3.0V. This allows sustained serial data transfer rates up to 2.5 MB/s in sequential read/write mode, verified per DS22126E AC Characteristics Table 1-2.

Does the 23K640-I/ST require external pull-up resistors on its SO pin?

Yes, the 23K640-I/ST SO pin is tri-state and requires an external pull-up resistor (typically 4.7 kΩ to VCC) when shared with other SPI devices on the same bus. This ensures defined logic-high states during CS deassertion and prevents floating inputs that could cause spurious communication errors.

How does the HOLD function operate in the 23K640-I/ST?

The HOLD function in the 23K640-I/ST pauses active SPI communication when the HOLD pin is driven low while SCK is low. During HOLD, SI, SCK, and SO enter high-impedance states and all inputs except CS are ignored. Resuming requires bringing HOLD high while SCK remains low - the 23K640-I/ST continues exactly where it left off.

What is the page size and how many pages does the 23K640-I/ST contain?

The 23K640-I/ST has a fixed page size of 32 bytes and contains 1024 pages (8192 total bytes ÷ 32 bytes/page). Page mode enables writing up to 32 consecutive bytes starting from any address within the same page, with automatic internal address increment - wrapping to page start upon boundary crossing.

Is the 23K640-I/ST compatible with standard SPI protocol masters?

Yes, the 23K640-I/ST is fully compatible with standard SPI protocol masters. It uses standard SPI signals (CS, SCK, SI, SO), supports MSB-first transmission, and implements common instructions (READ 0x03, WRITE 0x02) - requiring no special driver modifications beyond standard SPI peripheral configuration.