AT45DB641E-SHN2B-T

The AT45DB641E from Renesas Electronics is a 64-Mbit (8 MByte) DataFlash serial NOR Flash memory with an additional 2-Mbit extra array, designed for code and data storage applications that require sequential access, low pin count, and low power consumption. The AT45DB641E-SHN2B-T is the 8-lead SOIC-W tape-and-reel version.

The DataFlash architecture differs from standard SPI NOR Flash by incorporating two independent 256/264-byte SRAM data buffers. These buffers allow the device to receive data while simultaneously reprogramming the main memory array, enabling continuous data streaming for data logging applications. The buffers can also serve as scratch pad memory, and EEPROM emulation (bit or byte alterability) is supported through a self-contained read-modify-write operation.

The device operates from a single 1.7V to 3.6V supply, covering the full range of battery-powered and low-voltage systems. The SPI-compatible serial interface supports modes 0 and 3 with clock frequencies up to 85 MHz, providing fast data throughput. The RapidS serial interface mode is also supported for applications requiring very high speed operation.

The memory array is organized as 32,768 pages of 256 or 264 bytes each (user configurable, 264 bytes default). Flexible erase options include page erase (256/264 bytes), block erase (2 KB), sector erase (256 KB), and chip erase (64 Mbit). Program and erase operations are self-timed with suspend/resume capability, allowing the system to perform other operations during long erase cycles.

Security features include individual sector protection (prevent program/erase), individual sector lockdown (permanently read-only), and a 128-byte OTP security register with 64 bytes factory-programmed unique identifier and 64 bytes user-programmable space. JEDEC standard manufacturer and device ID read is supported.

The AT45DB641E offers excellent low-power performance: 400 nA ultra-deep power-down, 5 uA deep power-down, 25 uA standby, and 7 mA active read current (all typical). Endurance is rated at 100,000 program/erase cycles per page minimum with 20-year data retention.

Note: The AT45DB641E was originally designed by Atmel, later acquired by Adesto Technologies (2017), which was in turn acquired by Dialog Semiconductor (2020), and subsequently became part of Renesas Electronics (2021). The product is currently listed under Renesas with product longevity guaranteed through 2034.

**DataFlash Architecture:** Unlike standard SPI NOR Flash that uses random-access addressing, the AT45DB641E uses sequential (page-based) access. Data is first written to one of the two SRAM buffers, then the buffer contents are programmed into the main memory array. This buffer-to-main-memory transfer is self-timed and does not require external clocking.

**Dual SRAM Buffer Operation:** The two independent buffers (Buffer 1 and Buffer 2) enable continuous data streaming. While Buffer 1 is being programmed into the main array, Buffer 2 can receive new data from the SPI interface. Once Buffer 1 programming completes, the roles can swap, creating a ping-pong buffer arrangement that never loses data. This is critical for data logging applications where data arrives continuously.

**SPI Interface:** The 3-wire SPI interface (CS, SCK, SI/SO) reduces pin count compared to parallel Flash. Commands, addresses, and data are shifted in on SI on the rising edge of SCK; data is shifted out on SO on the falling edge. The device supports SPI modes 0 (CPOL=0, CPHA=0) and 3 (CPOL=1, CPHA=1).

**Configurable Page Size:** The page size can be set to 256 bytes (binary boundary, simplifies addressing calculations) or 264 bytes (default, includes 8 extra bytes for ECC or metadata). Factory pre-configuration to 256-byte mode is available.

**RapidS Mode:** In RapidS mode, the device eliminates the need to wait for the buffer-to-main-memory transfer before starting the next operation. This is achieved by automatically switching between buffers, maximizing throughput for continuous write operations.