Microchip 93LC86/SN Serial EEPROM Memory Chip: Datasheet, Pinout, and Circuit Application Guide

The Microchip 93LC86 is a 16K-bit (2048 x 8 or 1024 x 16) serial Electrically Erasable Programmable Read-Only Memory (EEPROM) that serves as a reliable non-volatile storage solution for a vast array of electronic devices. Housed in an 8-pin SN (SOIC) package, this chip is prized for its low power consumption, ease of interfacing with microcontrollers, and robust performance. This guide provides a detailed overview of its datasheet specifications, pinout configuration, and a fundamental circuit application.

Datasheet Overview and Key Specifications

The 93LC86 operates on a wide voltage range, typically from 2.5V to 5.5V, making it suitable for both 3.3V and 5V systems. Its key specifications include:

Organization: Can be configured for 8-bit or 16-bit memory organization via the ORG pin.

Interface: Utilizes a simple Microwire serial interface, which is a 4-wire protocol comprising Chip Select (CS), Serial Clock (SK), Data Input (DI), and Data Output (DO).

Write Protection: Features a built-in software write protection mechanism. A specific instruction sequence must be issued to enable write operations, preventing accidental data corruption.

Endurance: Rated for 1,000,000 erase/write cycles, ensuring long-term data retention and reliability.

Data Retention: Guarantees data integrity for over 200 years.

Low Power: Consumes very low current in both active and standby modes, which is critical for battery-powered applications.

Pinout Configuration

Understanding the pinout is crucial for correct circuit design. The 93LC86/SN in an 8-pin SOIC package has the following pins:

1. CS (Chip Select): Active-high input that initiates and enables a communication session with the chip. Must be held high for the duration of any operation.

2. SK (Serial Clock): Input pin that provides the synchronization clock for data shifting in and out of the EEPROM. Data is sampled on the rising edge of the clock.

3. DI (Data Input): The pin through which the microcontroller sends opcodes, addresses, and data to be written to the memory array.

4. DO (Data Output): The pin used by the EEPROM to send data back to the microcontroller during a read operation. It enters a high-impedance state when not active.

5. GND (Ground): Circuit ground reference (0V).

6. ORG (Memory Organization): This pin dictates the word width. Tying it to VCC selects a 16-bit organization; tying it to GND selects an 8-bit organization.

7. NC (No Connect): This pin is not internally connected and can be left floating.

8. VCC (Power Supply): Positive power supply input (2.5V to 5.5V).

Basic Circuit Application Guide

A typical application circuit for interfacing the 93LC86 with a microcontroller (MCU) is straightforward. The following steps outline the fundamental connections and operational flow:

1. Hardware Connections:

Connect the VCC and GND pins of the EEPROM to the MCU's power and ground rails, ensuring stable power.

Connect the CS, SK, and DI pins of the EEPROM to any digital I/O pins of the MCU.

Connect the DO pin of the EEPROM to another digital I/O pin on the MCU.

Connect the ORG pin based on your desired data width: to VCC for 16-bit mode or to GND for 8-bit mode.

Use pull-up resistors (e.g., 10kΩ) on the CS, SK, and DI lines if necessary, though many modern MCUs have configurable internal pull-ups.

2. Software Protocol (Microwire):

The communication is driven by the MCU. The basic sequence for any operation involves:

Initiating Communication: Set the CS pin high.

Sending Instruction: The MCU sends a Start bit ('1') followed by a specific opcode (e.g., READ, WRITE, ERASE, EWEN) through the DI line, synchronized by pulses on the SK line.

Sending Address: The appropriate memory address is sent (7 bits for 16-bit mode, 8 bits for 8-bit mode).

Data Transfer:

For a Write: The MCU sends the 8 or 16 bits of data to be written.

For a Read: The MCU continues toggling the SK pin and reads the data back from the DO line bit-by-bit.

Terminating Communication: Set the CS pin low to complete the operation. After a write command, the chip will be busy for a few milliseconds internally programming the data; during this time, it will not respond to new commands.

ICGOODFIND: The Microchip 93LC86/SN stands out as an industry-standard serial EEPROM due to its extreme reliability, simple 4-wire interface, and flexible memory organization. Its ease of use with virtually any microcontroller and its excellent endurance make it a perfect choice for storing calibration data, user settings, and other critical information in applications ranging from industrial automation and automotive electronics to consumer gadgets and smart sensors.

Keywords: Serial EEPROM, Microwire Interface, Non-volatile Memory, 93LC86 Pinout, Microcontroller Interfacing