Microchip 93AA66BT-I/SN 16Kb SPI Microwire Serial EEPROM: Features and Application Design Guide
The Microchip 93AA66BT-I/SN is a 16-kilobit (organized as 1024 x 16 or 2048 x 8) serial Electrically Erasable PROM (EEPROM) that utilizes the popular SPI (Serial Peripheral Interface) and Microwire-compatible serial bus. This device is engineered for a broad range of applications requiring reliable non-volatile memory storage in space-constrained and power-sensitive designs. Its combination of performance, durability, and ease of integration makes it a cornerstone component in modern electronics.
Key Features and Specifications
The 93AA66BT-I/SN stands out with a set of robust features designed for system resilience and longevity. It operates across a wide voltage range from 1.8V to 5.5V, making it suitable for both 3.3V and 5V systems, as well as battery-powered applications where voltage can fluctuate. Its low power consumption is critical for energy-efficient designs, featuring a standby current of just 1 µA (max) and an active current of 1 mA during read operations.
Data integrity is paramount, and this EEPROM ensures it with high endurance of 1,000,000 erase/write cycles and a data retention period of over 200 years. It also includes advanced write-protection mechanisms. The `ORG` pin allows the user to select the memory organization (x8 or x16), providing flexibility for different data word lengths. The entire memory array can be protected from writes via software instructions, and the dedicated `HOLD` pin enables pausing a serial communication without resetting the sequence, which is invaluable in noisy multi-device SPI environments.
The device is offered in the compact 8-lead SOIC (SN) package, ideal for applications where board real estate is limited. It supports an extended industrial temperature range from -40°C to +85°C, ensuring reliable operation in harsh environmental conditions.
Application Design Guide
Integrating the 93AA66BT-I/SN into a system requires attention to several key design considerations to ensure optimal performance and reliability.
1. Hardware Interface: The device communicates via a 4-wire SPI bus:
CS (Chip Select): Driven by the host microcontroller to select the EEPROM.
SK (Serial Clock): Provides the synchronization clock for data shifting.
DI (Data In): The line for transmitting instruction and data from the host to the EEPROM.
DO (Data Out): The line for receiving data from the EEPROM by the host.
Proper pull-up resistors may be needed on these signals, and traces should be kept short to minimize noise and signal integrity issues.
2. Software Protocol: Communication is managed by sending specific 16-bit instruction opcodes followed by address and data. Key instructions include:
READ (opcode 1100): Reads data from a specified memory address.
WRITE (opcode 1010): Writes data to a specified address (automatically erases the location first).
EWEN (Erase/Write Enable): Must be issued before any write or erase operation to unlock the memory array.
ERASE (opcode 1100): Erases a specific memory location.
The host must carefully manage the timing between sending the `EWEN` command and subsequent write commands to prevent accidental writes.
3. Write Cycle Timing: After initiating a write sequence (WRITE or ERASE), the internal self-timed write cycle begins, typically taking 5ms maximum. During this time, the device will not respond to any commands. The host can poll the device's status by sending a Read instruction and checking if the DO line has gone high, indicating the write cycle is complete and the device is ready for a new command.
4. Power Supply and Decoupling: Stable power is crucial during write operations. A 0.1µF ceramic decoupling capacitor should be placed as close as possible to the VCC and GND pins of the EEPROM to filter high-frequency noise and provide a stable local charge reservoir, preventing brown-out conditions that could corrupt a write process.
5. PCB Layout: Place the EEPROM close to the host microcontroller to minimize the length of the SPI traces. Avoid routing these high-speed signals near noise sources like switching regulators or clock oscillators.
ICGOODFIND summarizes that the Microchip 93AA66BT-I/SN is an exceptionally versatile and robust serial EEPROM solution. Its low-power operation, high endurance, and flexible Microwire/SPI interface make it an ideal choice for designers needing reliable non-volatile memory in applications such as automotive modules, industrial control systems, smart meters, medical devices, and consumer electronics. Careful attention to hardware layout, write-protection protocols, and power integrity is the key to harnessing its full potential in any design.
Keywords: SPI EEPROM, Non-volatile Memory, Low-Power Design, Microwire Interface, Data Retention.
