Microchip Technology 93LC66A-I/MS

Overview

93LC66A-I/MS from Microchip Technology Inc. is a 4 Kbit (512 × 8-bit) low-voltage serial EEPROM with Microwire-compatible 3-wire interface, operating from 2.5 V to 5.5 V, rated for Industrial temperature range (–40°C to +85°C), and housed in an 8-lead MSOP package. It provides nonvolatile memory storage with self-timed erase/write cycles, automatic ERAL before WRAL, and Ready/Busy status signaling via DO pin - used in embedded system configuration storage and calibration data retention.

For engineers reviewing the 93LC66A-I/MS datasheet, 93LC66A-I/MS pinout, 93LC66A-I/MS application, or 93LC66A-I/MS equivalent, key selection considerations include its fixed 8-bit organization (no ORG pin), 1 million erase/write endurance, >200-year data retention, and compatibility with microcontroller SPI-like serial interfaces requiring minimal external components.

Technical Context

The 93LC66A-I/MS implements a synchronous serial Microwire protocol using CS, CLK, and DI/DO lines - no ORG pin is present, fixing memory organization to 512 × 8-bit. Communication begins with a Start bit (CS high + DI high on CLK rising edge), followed by opcode, address, and data fields clocked on CLK rising edges.

Internal logic includes power-on/off data protection, EWEN/EWDS write-enable control, and automatic erase-before-write. The DO pin serves dual function: serial data output during READ and Ready/Busy status indicator during programming - pulled high when ready, low during active erase/write, and tri-stated when CS is low.

Key Specifications

Pinout & Package

8-lead MSOP (Micro Small Outline Package), 3.0 mm × 4.9 mm body, 0.65 mm pitch, exposed pad optional (VSS or floating), Pb-free Matte Tin finish.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar serial EEPROM applications.

Compared with 93LC66B-I/MS, the 93LC66A-I/MS offers native 8-bit compatibility with legacy Microwire firmware; versus AT25040B-MAU-1.8, it retains pin count and board space parity in MSOP but uses simpler 3-wire signaling - reducing MCU GPIO usage in resource-constrained designs.

Availability

93LC66A-I/MS is available at Aetrix Electronics and suitable for industrial sensor calibration, consumer appliance configuration, and automotive body control modules requiring stable component supply across extended product lifecycles.

Supply support for 93LC66A-I/MS includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Microchip Technology Inc. is a leading provider of microcontrollers, analog, and Flash-IP solutions, headquartered in Chandler, Arizona, serving industrial, automotive, and consumer markets globally.

The 93LC66A-I/MS belongs to Microchip's legacy 93XX serial EEPROM family, designed specifically for cost-sensitive, low-power embedded systems requiring reliable nonvolatile storage with minimal external components and broad voltage compatibility.

FAQ

What is the memory organization of the 93LC66A-I/MS?

The 93LC66A-I/MS has a fixed 512 × 8-bit (4 Kbit) organization. Unlike 'C' variants, it lacks an ORG pin - so word size cannot be configured. This makes it ideal for 8-bit data paths and simplifies PCB layout by removing ORG routing and biasing requirements. The 93LC66A-I/MS delivers deterministic addressing and timing behavior across all operating conditions.

Does the 93LC66A-I/MS require an external pull-up resistor on the DO pin?

No, the 93LC66A-I/MS does not require an external pull-up on DO. During READ, DO actively drives logic levels; during READY/BSY polling, it outputs valid low/high states. When CS is low, DO is tri-stated - a pull-up may be used only if bus-sharing with other open-drain devices, but it is not specified or required for standalone 93LC66A-I/MS operation per DS21795E.

How is write protection implemented on the 93LC66A-I/MS?

Write protection on the 93LC66A-I/MS is enforced through hardware power-on reset (EWDS mode) and explicit EWEN/EWDS commands. The 93LC66A-I/MS powers up locked; an EWEN instruction must precede any ERASE or WRITE. After each write, issuing EWDS restores protection - preventing accidental overwrites during noise events or firmware faults. VCC monitoring below 2.5 V also disables writes automatically.

Can the 93LC66A-I/MS be used with a 3.3 V microcontroller without level shifting?

Yes, the 93LC66A-I/MS operates natively from 2.5 V to 5.5 V, making it fully compatible with 3.3 V MCUs. Its VIH1 threshold is 2.0 V (min) at VCC ≥ 2.7 V, and VOL1 is ≤ 0.4 V at IOL = 2.1 mA - satisfying 3.3 V logic high/low margins. No level shifter is needed when interfacing directly with 3.3 V GPIOs driving CS, CLK, and DI.

What is the maximum clock frequency supported by the 93LC66A-I/MS at 3.3 V?

At VCC = 3.3 V (within 2.5–5.5 V range), the 93LC66A-I/MS supports a maximum clock frequency of 2 MHz, as specified in Table 1-2 (A1: FCLK). This corresponds to minimum TCKH/TCKL of 250 ns/200 ns respectively. Exceeding 2 MHz risks setup/hold violations and unreliable communication - firmware drivers must enforce this limit regardless of MCU clock speed.