Microchip Technology SST25WF040B-40E/SN

Overview

SST25WF040B-40E/SN from Microchip Technology is a 4 Mbit (512 KByte), 1.8V SPI serial flash memory IC with SuperFlash technology, supporting 40 MHz high-speed read, dual-output and dual I/O modes, and uniform 4 KByte sector/64 KByte block erase architecture. It operates from 1.65–1.95 V, delivers 4 mA typical active read current, and targets firmware storage in space-constrained industrial microcontroller systems.

For engineers reviewing the SST25WF040B-40E/SN datasheet, SST25WF040B-40E/SN pinout, SST25WF040B-40E/SN application, or SST25WF040B-40E/SN equivalent, key selection criteria include single-supply 1.8V operation, SPI Mode 0/3 compatibility, 2 µA power-down standby current, software/hardware write protection, and SOIC-8/USON-8 package options for PCB layout flexibility.

Technical Context

This SPI flash uses Microchip's proprietary SuperFlash split-gate cell technology, enabling lower program/erase energy versus conventional NOR flash via reduced current draw and shorter erase times. Its functional block diagram integrates dedicated I/O buffers, X/Y decoders, and control logic to manage command decoding, address latching, and status register access.

The device implements full SPI protocol compliance-including Mode 0 (CPOL=0, CPHA=0) and Mode 3 (CPOL=1, CPHA=1)-with rising-edge sampling on SI/SIO0 and falling-edge output on SO/SIO1. Dual I/O mode supports two-bit-per-clock address input and simultaneous odd/even bit data output, accelerating effective throughput without increasing clock frequency.

Key Specifications

Pinout & Package

Available in 8-lead SOIC (150 mil) and 8-contact USON (2 mm × 3 mm) packages. Both share identical pin functions and electrical behavior.

Key Features

Applications

Equivalent & Alternatives

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

Compared with Winbond W25Q40EW and Cypress S25FL004A, SST25WF040B-40E/SN uniquely combines 1.8V operation, hardware HOLD#, Dual I/O acceleration, and 2 µA power-down current-making it optimal for compact, low-power, interrupt-resilient embedded systems where voltage headroom and real-time suspend capability are critical.

Availability

SST25WF040B-40E/SN is available at Aetrix Electronics and suitable for industrial PLCs, medical diagnostics, automotive body control modules, and smart energy metering requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for SST25WF040B-40E/SN 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 is a U.S.-based semiconductor company specializing in microcontrollers, analog devices, and memory solutions, with emphasis on reliability, longevity, and industrial-grade qualification.

The SST25WF serial flash product line is designed for cost-sensitive, space-constrained embedded systems requiring robust nonvolatile storage with low-voltage operation, high endurance, and flexible erase granularity.

FAQ

What is the maximum clock frequency supported by SST25WF040B-40E/SN for high-speed read operations?

The SST25WF040B-40E/SN supports up to 40 MHz for high-speed read operations using the High-Speed Read (0BH), Fast-Read Dual-Output (3BH), and Fast-Read Dual I/O (BBH) instructions. This is confirmed in the official Microchip datasheet DS20005193E, where timing specifications list tCH and tCL min/max values consistent with 40 MHz operation under 1.65–1.95 V supply conditions. The SST25WF040B-40E/SN achieves this while maintaining full SPI Mode 0/3 compatibility and signal integrity across both SOIC and USON packages.

Does SST25WF040B-40E/SN support both SPI Mode 0 and Mode 3, and how is this implemented?

Yes, SST25WF040B-40E/SN supports both SPI Mode 0 (CPOL=0, CPHA=0) and Mode 3 (CPOL=1, CPHA=1), as explicitly stated in the "Features" section of DS20005193E. In Mode 0, SCK idles low and data is sampled on the rising edge; in Mode 3, SCK idles high and sampling remains on the rising edge. The SST25WF040B-40E/SN internally detects the idle state of SCK at CE# activation and adapts timing accordingly-no configuration register setting is required. This dual-mode support ensures interoperability with diverse host controllers without firmware modification.

How does the HOLD# functionality work in SST25WF040B-40E/SN, and what are its timing constraints?

The HOLD# pin in SST25WF040B-40E/SN suspends an active SPI transaction without deselecting the device, preserving internal address and command state. Activation requires CE# low and a falling edge on HOLD# synchronized with SCK low; release requires a rising edge on HOLD# also synchronized with SCK low. During hold, SO enters high-impedance while SI and SCK may be driven arbitrarily. This behavior is fully documented in Figure 4-2 and Section 4.0.1 of DS20005193E. The SST25WF040B-40E/SN uses this to enable deterministic interrupt handling in real-time systems without aborting ongoing flash operations.

What write protection mechanisms are available on SST25WF040B-40E/SN, and how do they interact?

SST25WF040B-40E/SN provides three layered write protection mechanisms: (1) Hardware WP# pin enabling BPL bit lock-down, (2) Software Block-Protection bits (BP0–BP2, TB) defining protected memory regions, and (3) Write-Enable-Latch (WEL) bit requiring explicit WREN instruction before any write. When WP# is low and BPL=1, BP0–BP2, TB, and BPL become read-only; otherwise, they are modifiable via WRSR. All protections are nonvolatile and persist across power cycles. This hierarchy is defined in Tables 4-1 through 4-3 of DS20005193E and ensures SST25WF040B-40E/SN meets secure boot requirements in certified medical and industrial systems.

What is the page size and programming behavior of SST25WF040B-40E/SN, and how does it handle partial-page writes?

The SST25WF040B-40E/SN has a fixed 256-byte page size for Page-Program operations. If fewer than 256 bytes are sent, only whole bytes are accepted; partial-byte inputs are ignored. If the target address is not page-aligned (A[7:0] ≠ 00H) and more than remaining bytes in the page are sent, excess data wraps to the start of the same page-not the next page. This wrap behavior is explicitly described in Section 5.5 of DS20005193E and ensures predictable programming within page boundaries. The SST25WF040B-40E/SN requires prior erasure (FFH state) of target bytes and WREN execution before each Page-Program command.