Part A
AT45DB642D-CNU
Adesto Technologies
- Lifecycle
- Active
- Stock
- 3548 PCS
- Package
- CASON-8
- Series
- Memória
Replacement verdict
Compatible functional replacement candidate
The AT45DB321C-CNU is a lower-density member of the same DataFlash family as the AT45DB642D-CNU, sharing the identical 8-pin CASON package, SPI interface, and 2.7V–3.6V supply range. It can serve as a functional substitute where 32 Mbit of density is sufficient, but the reduced page size, lower clock rate, and smaller sector-erase granularity require firmware and timing validation before adoption.
Memory Density
Not compatible
Package Type
High match
Supply Voltage Range
High match
Interface Speed
Validation required
Parts at a glance
Part B
AT45DB321C-CNU
Tecnologia Microchip
- Lifecycle
- Active
- Stock
- 9187 PCS
- Package
- VDFN-8
- Series
- Memória
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-CNU | 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 directly interchangeable in capacity-critical designs. |
| Page Size | 1056 bytes (1024 + 32) | 528 bytes (512 + 16) | Page size affects write granularity and buffer usage; firmware page-addressing logic must match the device page size for correct programming. |
| Number of Pages | 8192 | 8192 | Page count combined with page size defines total array organization; matching page counts with different page sizes changes the overall memory map. |
| Maximum Clock Frequency | 66 MHz | 50 MHz | Clock frequency sets maximum SPI throughput; a slower-rated device may not sustain the same data rate in high-speed applications. |
| 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 here mean both are compatible with 3.3 V systems. |
| Interface Type | SPI (Serial Peripheral Interface) | SPI (Serial Peripheral Interface) | Both use SPI, so bus-level compatibility is maintained, though command sets and timing may still differ between generations. |
| Package | 8-lead CASON | 8-lead CASON | Package and pinout determine PCB footprint compatibility; identical packages allow drop-in board placement. |
| Operating Temperature Range | -40 °C to +85 °C | -40 °C to +85 °C | Temperature range confirms suitability for industrial environments; matching ranges mean equivalent environmental tolerance. |
Need help validating a replacement?
Send your BOM and application constraints for technical and sourcing review.
Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | AT45DB642D-CNU | AT45DB321C-CNU |
|---|---|---|
| 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) | -40°C ~ 85°C (TC) |
| Mounting Type | Surface Mount | Surface Mount |
Frequently asked questions
What are the key differences between the AT45DB642D-CNU and the AT45DB321C-CNU?
The AT45DB642D-CNU is a 64-Mbit (8-Mbyte) DataFlash device organized as 8192 pages of 1056 bytes, while the AT45DB321C-CNU is a 32-Mbit (4-Mbyte) device organized as 8192 pages of 528 bytes. Both are 3.3 V devices in 8-lead CASON packages, but they differ in density, page size, and command set generation.
Are the AT45DB642D-CNU and AT45DB321C-CNU pin-compatible?
Both devices are offered in an 8-lead CASON package with the same pin functions (SI, SO, SCK, CS, RESET, VCC, GND, WP). However, pin compatibility alone does not guarantee functional interchangeability; the command set and page addressing must be validated against the respective datasheets.
Can the AT45DB321C-CNU be used as a drop-in replacement for the AT45DB642D-CNU?
No. The AT45DB642D-CNU has twice the density and a different page size (1056 bytes vs. 528 bytes) and uses an extended command set. A direct drop-in replacement is not possible without firmware and design changes validated against the manufacturer datasheets.
What is the page size and organization of each device?
The AT45DB642D-CNU has 8192 pages of 1056 bytes each (8 Mbytes total). The AT45DB321C-CNU has 8192 pages of 528 bytes each (4 Mbytes total). Both support page and block erase operations, but the differing page sizes affect buffer and addressing requirements.
Do both devices operate at the same supply voltage?
Yes. Both the AT45DB642D-CNU and AT45DB321C-CNU are specified for a 2.7 V to 3.6 V supply range, making them suitable for 3.3 V system designs.
What SPI interface and clock rates do these devices support?
Both devices use a standard SPI interface (Mode 0 and Mode 3) and support clock frequencies up to 66 MHz for the AT45DB642D-CNU and up to 50 MHz for the AT45DB321C-CNU, per their respective datasheets. The maximum SCK frequency should be confirmed against the specific datasheet revision.
Are both devices available in the same package type?
Both the AT45DB642D-CNU and AT45DB321C-CNU are offered in an 8-lead CASON package. Designers should verify the exact package drawing and land pattern from the manufacturer datasheet before layout.
Which device should be selected for a new design requiring 4 Mbytes of DataFlash storage?
The AT45DB321C-CNU provides 4 Mbytes (32 Mbits) of storage and is the appropriate choice when 4 Mbytes is sufficient. The AT45DB642D-CNU provides 8 Mbytes and should be selected only if the larger density is required, with firmware updated for its page size and command set.