Microchip 93LC86C-I/P: A Comprehensive Overview of the 16K Microwire Serial EEPROM

The Microchip 93LC86C-I/P is a 16K-bit (organized as 1024 x 16 or 2048 x 8) serial Electrically Erasable Programmable Read-Only Memory (EEPROM) that utilizes the simple and efficient 4-wire Microwire serial interface. This device is designed for applications requiring non-volatile memory storage with low power consumption, high reliability, and a compact footprint. Housed in an 8-pin PDIP package, it is a versatile solution for a wide array of consumer, industrial, and automotive electronics.

Key Features and Electrical Characteristics

The 93LC86C operates over a broad voltage range (2.5V to 6.0V), making it suitable for both 5V and 3.3V systems. It features a low-power CMOS technology, with a standby current of just 1 µA (max) and an active read current of 500 µA (max), which is critical for battery-powered and portable devices. Its endurance is specified at 1,000,000 erase/write cycles per cell, and data retention is guaranteed for over 200 years, ensuring long-term data integrity.

The core of its functionality is the Microwire interface, consisting of three input signals: Chip Select (CS), Serial Clock (SK), and Data Input (DI), along with one output signal: Data Output (DO). This simple bus structure allows for communication with a microcontroller using only a few I/O pins, simplifying board design and reducing system cost.

Internal Organization and Instruction Set

The memory array can be configured via the ORG pin. Tying the ORG pin to VCC sets the organization to 16-bit words, resulting in 1024 addressable locations. Connecting it to GND sets the organization to 8-bit words, providing 2048 addressable locations. This flexibility allows designers to optimize the memory for their specific data width requirements.

Communication is command-driven. The host controller initiates a transaction by bringing CS high. A start bit ('1') followed by a 2- or 3-bit opcode defines the operation. The fundamental instruction set includes:

READ (OPCODE 10): Reads data from a specified memory address.

WRITE (OPCODE 01): Programs a specific memory location. This operation automatically erases the location before writing.

WREN (OPCODE 00 11): Sets the Write Enable Latch (required before every write or erase operation).

WRDI (OPCODE 00 10): Resets the Write Enable Latch.

ERASE (OPCODE 11): Erases a specific memory location (sets all bits to '1').

ERAL (OPCODE 00 01): Erases the entire memory array.

WRAL (OPCODE 00 00): Writes to the entire memory array.

A critical feature for data protection is the built-in software and hardware write protection. The WREN instruction must be issued before any modify operation, preventing accidental data corruption. Furthermore, a full reset of the write enable latch occurs upon power-up and after the completion of any write cycle.

Application Notes and Circuit Considerations

Integrating the 93LC86C into a design is straightforward. Decoupling capacitors (0.1 µF to 10 µF) should be placed close to the VCC and GND pins to suppress power supply noise. The pull-up resistor on the DO line is typically internal to the microcontroller; if not, an external resistor is required.

For robust performance in electrically noisy environments, such as industrial settings, best practices include:

Keeping the communication traces between the MCU and the EEPROM as short as possible.

Ensuring clean and sharp clock transitions.

Following a precise sequential protocol: Set Write Enable, then issue the Program/Erase command. The device features self-timed write cycles, meaning the MCU only needs to monitor the ready/busy status by polling the DO pin after initiating a write command; DO goes low during the internal write process and returns high upon completion.

Typical applications extend to storing calibration data, device configuration parameters, security codes, and user settings in systems such as:

Automotive modules (e.g., dashboards, sensors)

Smart meters

Medical devices

Printers and consumables

Gaming peripherals

Appliances

ICGOOODFIND: The Microchip 93LC86C-I/P stands out as a highly reliable and flexible non-volatile memory solution. Its simple 4-wire Microwire interface, low power consumption, exceptional endurance and retention, and configurable organization make it an excellent choice for designers seeking to add robust data storage capabilities to their embedded systems efficiently. Its ease of use and proven reliability have cemented its place across countless applications for decades.

Keywords: Microwire Serial Interface, Non-volatile Memory, EEPROM, Low-power CMOS, Data Retention