Microchip 93LC86B-I/SN 1K SPI Serial EEPROM: Features and Application Design Guide
The Microchip 93LC86B-I/SN is a 16-Kbit (organized as 1024 x 16) SPI Serial EEPROM memory device renowned for its reliability, low power consumption, and ease of integration into a wide array of embedded systems. It serves as a non-volatile storage solution for everything from small consumer electronics to sophisticated industrial equipment. This article explores its key features and provides essential guidance for its application in circuit design.
A primary advantage of the 93LC86B is its simple 4-wire SPI-compatible serial interface. This interface, comprising Chip Select (CS), Serial Clock (SCK), Serial Data Input (DI), and Serial Data Output (DO), allows for efficient communication with virtually any modern microcontroller (MCU), minimizing the number of I/O pins required and simplifying board layout.
The device is engineered for low-power operation, making it ideal for battery-powered and portable applications. It features a low standby current and an active current of just 3 mA during write operations. Furthermore, it supports a wide voltage range from 2.5V to 5.5V, providing significant flexibility for designs operating on different power rails.
Data integrity is paramount, and the 93LC86B incorporates several features to ensure it. It includes built-in hardware and software write protection mechanisms. The `~WP` pin, when held low, prevents any write operations to the status register or memory array. This is crucial for safeguarding critical data from accidental corruption. Internally, the device features a self-timed erase/write cycle with a typical duration of 5 ms, freeing the MCU from busy-wait loops and improving system efficiency. The memory array is rated for 1,000,000 erase/write cycles and offers over 200 years of data retention.
From a packaging perspective, the I/SN suffix denotes an 8-lead SOIC package, which is compact and suitable for automated assembly processes.
Application Design Guide:
1. Hardware Connection: The interface with an MCU is straightforward. Connect the SCK, DI, DO, and CS lines to the MCU's SPI peripheral pins. While the MCU's SPI controller can often be used in any general-purpose I/O mode, it is critical to ensure the clock polarity and phase (CPOL and CPHA) are configured to match the EEPROM's timing requirements as specified in the datasheet. A pull-up resistor on the `~WP` pin is recommended if software write protection will be used.
2. Power Decoupling: Place a 100nF ceramic decoupling capacitor as close as possible to the VCC and GND pins of the 93LC86B. This is essential to filter high-frequency noise on the power supply line, which ensures stable operation during read and write cycles.
3. Sequential Read Operation: For reading large blocks of data, utilize the sequential read command. After providing the initial address, the device will automatically increment the internal address counter, allowing subsequent bytes to be read with a single command, drastically increasing data throughput.
4. Write Cycle Management: The microcontroller must poll the device's ready status after issuing a write command. Attempting to read the device immediately after a write will be unsuccessful as the device is busy. The recommended method is to read the status register until the Write-In-Progress (WIP) bit clears.
5. Noise Immunity: In electrically noisy environments (e.g., industrial settings), keep SPI trace lengths short and consider using a series resistor (e.g., 100Ω) on the SCK line to dampen ringing and improve signal integrity.
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Keywords: SPI Interface, Low-Power Operation, Write Protection, Non-Volatile Memory, Data Retention.
