Renesas AT25DF021-SSHF-B

Overview

AT25DF021-SSHF-B from Adesto Technologies (now part of Dialog Semiconductor) is a 2-Mbit serial SPI Flash memory IC designed for code shadowing and embedded data storage in resource-constrained systems. It operates from a single 2.3V–3.6V supply, supports SPI Modes 0/3 up to 66 MHz, delivers ≤6 ns clock-to-output delay, and features uniform 4/32/64-Kbyte block erase plus full-chip erase - enabling efficient firmware updates and parameter logging in industrial controllers and IoT edge nodes.

For engineers reviewing the AT25DF021-SSHF-B datasheet, AT25DF021-SSHF-B pinout, AT25DF021-SSHF-B application, or AT25DF021-SSHF-B equivalent, key selection criteria include its 2.3V minimum VCC, hardware write-protect via WP pin, 128-byte OTP security register, JEDEC-compliant ID read, and dual green package options (8-lead SOIC and 5×6 mm DFN) - all critical for long-lifecycle, low-power, secure embedded designs.

Technical Context

The AT25DF021-SSHF-B implements a dedicated SPI interface with rising-edge input capture (SI, CS, SCK) and falling-edge output timing (SO), supporting only Modes 0 and 3. Its internal architecture includes a 256-byte page buffer, SRAM-based data latch, and hierarchical protection logic managing four 64-Kbyte sectors with individual software/hardware lock control.

Erase and program operations are fully self-timed and monitored: status register polling reveals BUSY, WEL, and EPE (Erase/Program Error) flags. The device integrates automatic failure detection for both page programming (tPP = 1.0 ms typ.) and block erases (tBLKE = 50–450 ms typ.), eliminating need for external timeout circuits in host firmware.

Key Specifications

Pinout & Package

AT25DF021-SSHF-B is packaged in an industry-standard 8-lead SOIC (150-mil wide), pin-compatible with legacy SPI Flash devices and suitable for reflow soldering in high-volume manufacturing.

Key Features

Applications

Equivalent & Alternatives

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

Compared with W25Q20JVSSIQ and MX25L2006EM1I-12G, AT25DF021-SSHF-B uniquely supports 2.3V operation, includes a dedicated HOLD pin for interrupt-safe SPI pauses, and provides 128-byte OTP for secure device identity - making it preferred for ultra-low-voltage, safety-critical, or anti-counterfeiting applications.

Availability

AT25DF021-SSHF-B is available at Aetrix Electronics and suitable for industrial PLCs, portable medical diagnostics, smart metering infrastructure, and automotive body control modules requiring stable component supply across extended product lifecycles.

Supply support for AT25DF021-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, acquired by Dialog Semiconductor in 2020, specialized in low-power, nonvolatile memory and IoT connectivity solutions for industrial and medical markets.

The AT25DF021 belongs to Adesto's DataFlash® family, engineered specifically for embedded systems demanding reliable, low-voltage, secure serial Flash with flexible erase and robust protection - targeting applications where code integrity and data longevity are mission-critical.

FAQ

What is the minimum supply voltage required for reliable operation of the AT25DF021-SSHF-B?

The AT25DF021-SSHF-B supports a minimum supply voltage of 2.3V across the full industrial temperature range (–40°C to +85°C). This enables direct integration into 2.5V systems without level-shifting circuitry. Operation below 2.3V may result in undefined behavior, including failed program/erase cycles or corrupted status register reads. Always verify VCC stability under load using the 7 mA typical active current spec.

Does the AT25DF021-SSHF-B support Quad SPI mode?

No, the AT25DF021-SSHF-B does not support Quad SPI. It is a standard 4-wire SPI device (CS, SCK, SI, SO) compatible only with SPI Modes 0 and 3. Quad-capable alternatives like the Winbond W25Q20JV require different command sets and pin assignments. The AT25DF021-SSHF-B uses SI/SO for half-duplex communication and relies on its 66 MHz clock rate and 6 ns tV for high-speed throughput instead.

How is hardware write protection implemented on the AT25DF021-SSHF-B?

Hardware write protection on the AT25DF021-SSHF-B is controlled by the WP pin: when driven low, it locks all protected sectors against program and erase commands, regardless of software protection state. The WP pin is internally pulled high, so leaving it unconnected defaults to unprotected operation. For robust security, tie WP to VCC externally unless hardware locking is actively used - this prevents accidental activation during board handling or noise events.

Can the AT25DF021-SSHF-B be used for execute-in-place (XIP) applications?

Yes, the AT25DF021-SSHF-B supports XIP operation due to its ≤6 ns clock-to-output (tV) latency and 66 MHz maximum read speed. When interfaced with an MCU that supports memory-mapped SPI Flash, instructions can be fetched directly from the AT25DF021-SSHF-B without copying to RAM. However, XIP performance depends on host controller capabilities - ensure the MCU's SPI peripheral supports continuous read mode and proper address wraparound handling per the 0Bh/03h opcodes.

What is the function of the HOLD pin on the AT25DF021-SSHF-B?

The HOLD pin on the AT25DF021-SSHF-B temporarily suspends ongoing SPI communication without deselecting the device or resetting internal state. When asserted low (with CS active and SCK low), it places SO in high-impedance and ignores SI/SCK transitions - allowing the host MCU to service higher-priority interrupts while preserving the current command context. This avoids reinitializing sequences after interrupt return, improving real-time responsiveness in multitasking firmware.