Part A
AT25DF321A-SH-T
Technologie adesto
- Lifecycle
- Active
- Stock
- 6999 PCS
- Package
- SOIC-W-8
- Series
- Mémoire
Replacement verdict
Not a drop-in replacement
The AT25DF321A-SH-T and AT25DF021-SSHF-T are not drop-in replacements for one another. Although both are single-voltage SPI serial flash memories from the same manufacturer family, they differ in density, package and pinout, and operating voltage range, so a direct board-level substitution is not possible without design changes.
Different memory density
Different package and pinout
Different supply voltage range
Different interface mode support
Parts at a glance
Part B
AT25DF021-SSHF-T
Technologie adesto
- Lifecycle
- Active
- Stock
- 5344 PCS
- Package
- SOIC-8
- Series
- Mémoire
Key differences
Rows are prioritized by design impact. Highlighted values require attention during substitution.
Key electrical and mechanical differences between the two devices
| Parameter | AT25DF321A-SH-T | AT25DF021-SSHF-T | Why it matters |
|---|---|---|---|
| Memory Density | 32 Mbit (4 MB) | 2 Mbit (256 KB) | Density determines storage capacity; a 16x difference means the parts are not drop-in substitutes for firmware or data storage. |
| Organization | 4,194,304 x 8 bits | 262,144 x 8 bits | Byte organization affects addressing and memory map; different sizes require firmware and address range changes. |
| Package / Case | 8-SOIC (0.209", 5.30mm width) | 8-SOIC (0.154", 3.90mm width) | Different SOIC body widths affect PCB footprint and land pattern, so the parts are not mechanically interchangeable without layout changes. |
| Supply Voltage Range | 2.7 V to 3.6 V | 2.3 V to 3.6 V | The wider low-voltage range of the 2 Mbit part allows operation in lower-voltage systems where the 32 Mbit part may not function. |
| Maximum Clock Frequency | 100 MHz | 70 MHz | Clock frequency determines read/program throughput; a slower maximum clock can affect boot time and data transfer performance. |
| Operating Temperature Range | -40°C to +85°C | -40°C to +85°C | Both parts share the same industrial temperature range, so thermal environment is not a differentiator between them. |
| Interface Type | SPI (Dual/Quad capable) | SPI (Single/Dual capable) | Interface capability affects achievable bandwidth and host controller compatibility; the 32 Mbit part supports Quad I/O while the 2 Mbit part does not. |
| Page Size | 256 bytes | 256 bytes | Identical page size simplifies firmware page-buffer handling, so this parameter does not block substitution. |
| Sector Size | 4 KB (uniform) | 4 KB (uniform) | Matching uniform 4 KB sectors means erase granularity is the same, easing firmware portability between the two parts. |
| Endurance | 100,000 program/erase cycles | 100,000 program/erase cycles | Equal endurance ratings indicate comparable write-cycle lifetime, so reliability under repeated updates is similar. |
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Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | AT25DF321A-SH-T | AT25DF021-SSHF-T |
|---|---|---|
| Supplier | - | Dialog Semiconductor GmbH |
| Part Status | Not For New Designs | Obsolete |
| Memory Type | Non-Volatile | Non-Volatile |
| Memory Format | FLASH | FLASH |
| Technology | FLASH | FLASH |
| Memory Size | 32Mb (256 Bytes x 16384 pages) | 2Mb (256K x 8) |
| Memory Interface | SPI | SPI |
| Clock Frequency | 100 MHz | 50 MHz |
| Write Cycle Time - Word Page | 7µs, 3ms | 7µs, 5ms |
| Voltage - Supply | 2.7V ~ 3.6V | 2.3V ~ 3.6V |
| Operating Temperature | -40°C ~ 85°C (TC) | -40°C ~ 85°C (TC) |
| Mounting Type | Surface Mount | Surface Mount |
Frequently asked questions
What are the key differences between the AT25DF321A-SH-T and the AT25DF021-SSHF-T?
The AT25DF321A-SH-T is a 32-Mbit (4 MB) SPI serial flash memory, while the AT25DF021-SSHF-T is a 2-Mbit (256 KB) SPI serial flash memory. Both are single-voltage devices from the Adesto (formerly Atmel) AT25DF series, but they differ in density, package, and operating voltage range.
What package types do the AT25DF321A-SH-T and AT25DF021-SSHF-T use?
The AT25DF321A-SH-T is supplied in an 8-lead SOIC package (208-mil body width). The AT25DF021-SSHF-T is supplied in an 8-lead SOIC package (150-mil body width). The different body widths mean the PCB land patterns are not identical.
What are the operating voltage ranges for these two devices?
The AT25DF321A-SH-T operates from 2.7 V to 3.6 V. The AT25DF021-SSHF-T operates from 2.3 V to 3.6 V, giving it a wider low-voltage margin suitable for 2.5 V systems.
Are the AT25DF321A-SH-T and AT25DF021-SSHF-T pin-compatible?
Both devices use the standard 8-lead SPI flash pinout (CS, SO, WP, GND, SI, SCLK, HOLD, VCC), so the signal assignments are compatible. However, the package body widths differ (208-mil vs 150-mil SOIC), so the PCB footprint must be verified before substitution.
Can the AT25DF021-SSHF-T be used as a drop-in replacement for the AT25DF321A-SH-T?
No. Although the pinout is compatible, the AT25DF021-SSHF-T has only 2 Mbit of density versus 32 Mbit for the AT25DF321A-SH-T, and the package body width differs. A drop-in replacement requires matching density, package footprint, and voltage requirements, so the design must be revalidated.
What SPI interface and clock speeds do these devices support?
Both devices use a standard SPI interface supporting SPI modes 0 and 3. The AT25DF321A-SH-T supports clock frequencies up to 100 MHz for fast read operations. The AT25DF021-SSHF-T supports clock frequencies up to 85 MHz. Exact timing limits should be confirmed in the respective manufacturer datasheets.
Do both devices support sector and block erase operations?
Yes. Both the AT25DF321A-SH-T and AT25DF021-SSHF-T support flexible erase options including 4-KB sectors, 32-KB blocks, 64-KB blocks, and full-chip erase. The erase granularity is consistent across the AT25DF family, but the total number of sectors differs with density.
What are the typical applications for each density variant?
The AT25DF321A-SH-T (32 Mbit) is suited to code storage, firmware updates, and data logging in embedded systems requiring larger non-volatile memory. The AT25DF021-SSHF-T (2 Mbit) is suited to compact designs with smaller code or parameter storage needs, such as sensors, small MCU boot memory, and configuration data.