Part A
AT45DB642D-CNU
Adesto Technologies
- Lifecycle
- Active
- Stock
- 3548 PCS
- Package
- CASON-8
- Series
- Memory
Replacement verdict
Not a drop-in replacement
The AT45DB642D-CNU and AT45DB321C-CNC are not drop-in replacements for one another. Although both are DataFlash serial memory devices in the same 8-pin CASON package family, they differ in density, page size, interface clock rate, and command set generation, so a direct board-level swap is not supported without design validation.
Different memory density
Different page size
Different interface speed
Different command set
Parts at a glance
Part B
AT45DB321C-CNC
Công nghệ Microchip
- Lifecycle
- Active
- Stock
- 8247 PCS
- Package
- VDFN-8
- Series
- Memory
Key differences
Rows are prioritized by design impact. Highlighted values require attention during substitution.
Key electrical and mechanical differences between the two devices
| Parameter | AT45DB642D-CNU | AT45DB321C-CNC | Why it matters |
|---|---|---|---|
| Memory Density | 64 Mbit | 32 Mbit | Density determines total storage capacity; a 64 Mbit device holds twice the data of a 32 Mbit device, so they are not drop-in substitutes for capacity-critical designs. |
| Page Size | 1056 bytes (1024 + 32) | 528 bytes (512 + 16) | Page size affects write granularity and buffer requirements; firmware page-addressing logic must match the device page size. |
| Number of Pages | 8192 | 8192 | Page count combined with page size defines total array organization and addressing scheme used by the controller. |
| Supply Voltage Range | 2.7 V to 3.6 V | 2.7 V to 3.6 V | Operating voltage must match the host system rail; identical ranges allow reuse of the same power design. |
| Maximum Clock Frequency (SPI) | 66 MHz | 50 MHz | Clock rate sets maximum throughput; a slower device may bottleneck high-speed read/write operations. |
| Interface Type | SPI (Serial Peripheral Interface) | SPI (Serial Peripheral Interface) | Interface protocol must match the host controller; both use SPI, simplifying bus-level substitution. |
| Package / Mounting | 8-pin CASON, surface mount | 8-pin CASON, surface mount | Package and footprint must be compatible for board-level replacement without layout changes. |
| Operating Temperature Range | -40 °C to +85 °C | -40 °C to +85 °C | Temperature range determines suitability for industrial versus commercial environments. |
| Organization (Sectors) | 64 sectors | 32 sectors | Sector count affects erase-block management and wear-leveling strategy in firmware. |
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Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | AT45DB642D-CNU | AT45DB321C-CNC |
|---|---|---|
| Supplier | - | Microchip Technology |
| Part Status | Obsolete | Obsolete |
| Memory Type | Non-Volatile | Non-Volatile |
| Memory Format | FLASH | FLASH |
| Technology | FLASH | FLASH |
| Memory Size | 64Mb (1056 Bytes x 8192 pages) | 32Mb (528 Bytes x 8192 pages) |
| Memory Interface | SPI | SPI |
| Clock Frequency | 66 MHz | 40 MHz |
| Write Cycle Time - Word Page | 6ms | 15ms |
| Voltage - Supply | 2.7V ~ 3.6V | 2.7V ~ 3.6V |
| Operating Temperature | -40°C ~ 85°C (TC) | 0°C ~ 70°C (TC) |
| Mounting Type | Surface Mount | Surface Mount |
Frequently asked questions
What are the key differences between the AT45DB642D-CNU and the AT45DB321C-CNC?
The AT45DB642D-CNU is a 64-Mbit (8-MByte) DataFlash device organized as 8192 pages of 1056 bytes, while the AT45DB321C-CNC is a 32-Mbit (4-MByte) device organized as 8192 pages of 528 bytes. The AT45DB642D-CNU supports SPI clock frequencies up to 66 MHz, whereas the AT45DB321C-CNC supports up to 50 MHz. Both are offered in 8-pad CASON packages, but they differ in density, page size, and maximum interface speed.
Are the AT45DB642D-CNU and AT45DB321C-CNC pin-compatible?
Both devices are supplied in an 8-pad CASON package with the same serial interface pin functions (SI, SO, SCK, CS, RESET, VCC, GND, and WP). However, pin compatibility alone does not guarantee interchangeability; the designer must confirm package dimensions, land pattern, and signal timing against the respective datasheets before substituting one for the other.
What is the page size and organization of each device?
The AT45DB642D-CNU has 8192 pages of 1056 bytes each (8 MByte total), with two 1056-byte SRAM data buffers. The AT45DB321C-CNC has 8192 pages of 528 bytes each (4 MByte total), with two 528-byte SRAM data buffers. The different page sizes affect programming granularity and buffer usage in firmware.
What SPI clock frequencies do these devices support?
The AT45DB642D-CNU supports a maximum SPI clock frequency of 66 MHz. The AT45DB321C-CNC supports a maximum SPI clock frequency of 50 MHz. System designers should verify the timing specifications in the respective datasheets when operating near these limits.
What are the supply voltage requirements for these devices?
Both the AT45DB642D-CNU and the AT45DB321C-CNC operate from a single 2.7 V to 3.6 V supply. Designs should ensure the supply remains within this range and that decoupling is adequate for the chosen clock frequency.
Can the AT45DB321C-CNC be used as a drop-in replacement for the AT45DB642D-CNU?
No. Although both are 8-pad CASON SPI DataFlash devices, they differ in density (32 Mbit vs 64 Mbit), page size (528 bytes vs 1056 bytes), and maximum SPI clock (50 MHz vs 66 MHz). Firmware page addressing, buffer sizes, and timing must be revalidated, so a direct drop-in replacement is not supported without design changes.
Do both devices support the same command set?
Both devices use the Atmel DataFlash command set for read, program, and erase operations, but command behavior depends on page size and density. For example, page program and buffer write operations reference different byte counts (528 vs 1056 bytes), and address fields differ. Firmware must be adapted to the specific device's organization as documented in each datasheet.