Microchip 93LC56/SN Serial EEPROM Memory Chip: Technical Overview and Application Guide

The Microchip 93LC56/SN is a 2K-bit, serial-accessed Electrically Erasable Programmable Read-Only Memory (EEPROM) organized as 128 x 16-bit or 256 x 8-bit. It serves as a fundamental component for non-volatile data storage in a vast array of electronic systems, from consumer appliances to industrial automation. Its reliability, ease of interface, and low power consumption make it a perennial choice for designers.

Technical Overview

The 93LC56 operates on a wide voltage range, typically from 2.5V to 5.5V, accommodating both 3.3V and 5V systems. A key feature is its low power consumption, with a standby current of just 1 µA (max) and an active read current of 500 µA (max), making it ideal for battery-powered applications.

Communication with a microcontroller is achieved via a simple and robust 3-wire serial interface (Clock, Data In, Data Out), which is compatible with Microwire protocols. This minimal pin count allows it to be integrated into designs with limited I/O resources. The chip supports a set of essential instructions including READ, WRITE, ERASE, WREN (Write Enable), and WRDI (Write Disable). A critical operational feature is its self-timed write cycle, which automatically handles the internal programming timing, freeing the host controller for other tasks. The entire memory array can be erased in a single operation using the ERAL (Erase All) instruction, and similarly, all locations can be written with the WRAL (Write All) instruction.

The device offers impressive endurance, capable of 1,000,000 erase/write cycles, and provides exceptional data retention of over 200 years. It is available in industry-standard 8-pin PDIP, SOIC, and TSSOP packages.

Application Guide

Integrating the 93LC56 into a design is straightforward. The primary considerations are proper connection and protocol timing.

1. Hardware Connection: The three essential lines are:

CS (Chip Select): Driven high to select and activate the device.

SK (Serial Clock): Provides the synchronization clock for data shifting.

DI (Data In) & DO (Data Out): For sending instructions and addresses and receiving data.

2. Software Protocol: All operations follow a standard sequence:

Bring CS high to select the chip.

Transmit a start bit (1), followed by the specific opcode (2 bits for the instruction, e.g., 10 for a READ), and then the memory address (7 or 8 bits, depending on org pin configuration).

For a write operation, the address is followed by the 16-bit data word.

The chip will respond during a read operation by outputting the requested data on the DO pin.

3. Key Design Considerations:

Write Protection: The WREN instruction must be issued before any write or erase command to prevent accidental data corruption. The device will automatically disable writes after a successful operation.

Ready/Busy Status: After initiating a write cycle, the chip is busy until the cycle completes. While the datasheet indicates the typical time, the most reliable method is to wait the maximum specified time (e.g., 5 ms) before sending another command. Polling the DO pin can also indicate readiness.

Organization Pin (ORG): The logic state applied to the ORG pin determines the memory organization (x8 or x16), affecting how addresses are interpreted.

Common applications include storing device configuration data, calibration constants, user preference settings, and small lookup tables. It is also widely used for storing identification and serialization data during manufacturing.

ICGOOODFIND

The Microchip 93LC56/SN remains a highly versatile and dependable solution for low-density, non-volatile memory needs. Its simple interface, proven reliability, and ultra-low power profile ensure its continued relevance in modern electronic design, from legacy systems to new, cost-sensitive, and power-constrained applications.

Keywords:

1. Serial EEPROM

2. Non-volatile Memory

3. Microwire Interface

4. Low Power Consumption

5. Data Retention