Renesas AT25DN256-SSHF-B

Overview

AT25DN256-SSHF-B from Adesto Technologies is a 256-Kbit serial SPI Flash memory IC optimized for code shadowing and mixed code/data storage in embedded systems. It operates from 2.3V–3.6V, supports SPI Modes 0/3 and Dual-Output Read up to 50 MHz, delivers 6 ns clock-to-output timing, and features uniform 4-Kbyte and 32-Kbyte block erase plus 256-byte page erase - enabling efficient firmware updates and data logging in space-constrained industrial controllers.

For engineers reviewing the AT25DN256-SSHF-B datasheet, AT25DN256-SSHF-B pinout, AT25DN256-SSHF-B application, or AT25DN256-SSHF-B equivalent, key selection criteria include its dual-output read throughput, ultra-low 350 nA deep power-down current, OTP security register with factory-programmed unique ID, JEDEC-standard device ID support, and hardware write protection via WP pin.

Technical Context

The AT25DN256-SSHF-B implements a flexible SPI interface with dedicated SI (I/O0) and SO (I/O1) pins supporting standard single-output and dual-output read modes - where both pins output bits simultaneously on each SCK falling edge. Its command set includes opcodes for fast 256-byte page programming (1.25 ms typical), 4-Kbyte block erase (35 ms), and 32-Kbyte block erase (250 ms), all internally self-timed and verified via status register polling.

Erase architecture is segmented into 1024 × 256-byte pages, 64 × 4-Kbyte blocks, and 8 × 32-Kbyte blocks - allowing precise allocation of code modules and data segments without wasted erase-region overhead. The integrated 128-byte OTP security register contains 64 bytes of factory-unique identifier and 64 bytes user-programmable for ESN or cryptographic key storage.

Key Specifications

Pinout & Package

AT25DN256-SSHF-B uses an 8-lead SOIC (150-mil) package - RoHS-compliant, surface-mountable, and compatible with standard reflow profiles. Pin functions are fully SPI-compatible with hardware write protection and hold functionality.

Key Features

Applications

Equivalent & Alternatives

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

Compared with W25Q20EW and MX25U25635F, the AT25DN256-SSHF-B uniquely balances compact 256-Kbit density, dual-output read acceleration, ultra-low power consumption, and integrated OTP security - making it optimal for resource-constrained, security-aware, and battery-operated industrial endpoints where pin count, power budget, and device identity are critical.

Availability

AT25DN256-SSHF-B is available at Aetrix Electronics and suitable for industrial PLCs, medical sensor loggers, smart meter bootloaders, automotive telematics modules, and battery-powered IoT gateways requiring stable component supply, long-lifecycle assurance, and RoHS-compliant packaging.

Supply support for AT25DN256-SSHF-B 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

Adesto Technologies (now part of Dialog Semiconductor, part of Renesas Electronics since 2021) specialized in low-power, nonvolatile memory and IoT connectivity solutions for industrial and medical applications.

The AT25DN256-SSHF-B belongs to Adesto's DataFlash® family - designed specifically for embedded systems requiring reliable, low-energy, and secure serial flash storage with flexible erase granularity and integrated security features.

FAQ

What is the maximum clock frequency supported by AT25DN256-SSHF-B for Dual-Output Read operations?

The AT25DN256-SSHF-B supports Dual-Output Read at up to 50 MHz, as specified in the DS-25DN256–039G–02/2022 datasheet. This mode uses both SI and SO pins to output two bits per SCK falling edge, effectively doubling read throughput compared to standard SPI Read Array (0Bh/03h). The 50 MHz limit ensures setup/hold timing margins are maintained under worst-case voltage and temperature conditions. AT25DN256-SSHF-B does not support Dual-Output Read above this frequency.

Does AT25DN256-SSHF-B include factory-programmed unique identification data?

Yes, the AT25DN256-SSHF-B includes a 128-byte One-Time Programmable (OTP) Security Register, of which 64 bytes are factory-programmed with a unique device identifier. This identifier is laser-trimmed during wafer sort and cannot be altered post-manufacture. The remaining 64 bytes are user-programmable for system-level ESN, keys, or calibration data. This feature is confirmed in Section 1 and Table 2-1 of the official datasheet and is accessible via the 77h Read OTP Security Register command.

What erase block sizes are available on AT25DN256-SSHF-B, and how are they used in practice?

The AT25DN256-SSHF-B supports four erase granularities: 256-byte page, 4-Kbyte block, 32-Kbyte block, and full-chip erase. These map directly to real-world use cases - 256-byte pages allow patching individual configuration variables; 4-Kbyte blocks suit firmware function modules; 32-Kbyte blocks align with OTA update packets; and full-chip erase is reserved for factory initialization. All erase operations are internally self-timed and verified, with status reported via the EPE bit in the Status Register.

Can AT25DN256-SSHF-B operate reliably across the full industrial temperature range?

Yes, the AT25DN256-SSHF-B is explicitly rated for the full industrial temperature range of –40°C to +85°C, as stated in the "Features" section of the datasheet. All specifications - including 104 MHz max clock, 6 ns tV, 100,000 endurance cycles, and 20-year data retention - are guaranteed across this range. The SOIC package (SSHF-B suffix) is qualified for industrial thermal cycling and humidity exposure, making AT25DN256-SSHF-B suitable for deployment in harsh environments like factory automation and outdoor metering.

How does hardware write protection work on AT25DN256-SSHF-B, and is it enabled by default?

Hardware write protection on AT25DN256-SSHF-B is controlled by the WP (Write Protect) pin, which is internally pulled-high and defaults to inactive (unprotected) when left floating or tied to VCC. When WP is driven low, it locks protected sectors as defined by status register bits SRP0/SRP1 - preventing program and erase commands regardless of Write Enable Latch (WEL) state. This pin-based protection operates independently of software commands and remains active even after power cycles, providing robust defense against accidental or malicious writes. AT25DN256-SSHF-B requires explicit WP assertion to activate hardware locking.