Microchip Technology 93LC66-I/P

Overview

93LC66-I/P from Microchip Technology Inc. is a 4K-bit serial EEPROM with configurable 512×8 or 256×16 organization, implemented in low-power CMOS and communicating via industry-standard 3-wire Microwire interface. It operates from 2.5V to 5.5V, supports self-timed erase/write cycles, and delivers 1 million endurance cycles with >200-year data retention - used for nonvolatile parameter storage in embedded control systems.

For engineers reviewing the 93LC66-I/P datasheet, 93LC66-I/P pinout, 93LC66-I/P application, or 93LC66-I/P equivalent, key selection criteria include ORG-pin-selectable memory width, industrial temperature range (–40°C to +85°C), PDIP-8 package compatibility, and power-on/off data protection circuitry essential for reliable boot configuration and calibration storage.

Technical Context

The 93LC66-I/P implements a synchronous serial Microwire interface with CS, CLK, DI, and DO signals, where instruction execution begins on detection of a Start condition (CS high and DI high on CLK rising edge). Memory organization is dynamically selected by the ORG pin: VCC enables 256×16 mode; VSS enables 512×8 mode.

It features hardware-level data protection including automatic EWEN/EWDS gating, power-up/down voltage threshold lockout at 1.4V, and status polling via DO pin during erase/write operations. All programming cycles (ERASE, WRITE, ERAL, WRAL) are fully self-timed and require no external timing control beyond minimum CS low time (250 ns).

Key Specifications

Pinout & Package

8-pin Plastic Dual In-line Package (PDIP), 300 mil body width, JEDEC MS-001 compliant, with through-hole mounting and standard lead spacing (0.100" pitch).

Key Features

Applications

Equivalent & Alternatives

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

Compared with 93LC66C-I/P, the 93LC66-I/P lacks updated ESD hardening and newer qualification but retains identical pinout, timing, and instruction behavior - making it viable for legacy repair or cost-sensitive replacements. Versus AT25040B-MAU-1.8, it offers Microwire compatibility and simpler timing but lower maximum clock rate and no daisy-chain capability.

Availability

93LC66-I/P is available at Aetrix Electronics and suitable for industrial sensor calibration, consumer appliance configuration, and automotive body control module applications requiring stable component supply and long-term obsolescence management.

Supply support for 93LC66-I/P 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 microcontroller, mixed-signal, analog, and Flash-IP solutions, headquartered in Chandler, Arizona, with global design, manufacturing, and sales operations.

The 93LC66-I/P belongs to Microchip's legacy 93LC serial EEPROM family, designed specifically for cost-sensitive, low-power embedded systems requiring simple, robust nonvolatile storage with minimal external components and broad voltage compatibility.

FAQ

What memory organization options does the 93LC66-I/P support?

The 93LC66-I/P supports two memory organizations selected by the ORG pin: when tied to VCC, it configures as 256 words × 16 bits; when tied to VSS, it configures as 512 words × 8 bits. This dual-mode capability allows the same 93LC66-I/P device to serve both byte-addressable and word-addressable architectures without redesign. The ORG pin must be fixed - not left floating - for clock frequencies above 1 MHz.

How does the 93LC66-I/P protect against unintended writes during power transitions?

The 93LC66-I/P incorporates hardware-level power-on/power-off data protection that inhibits all programming operations until VCC rises above 1.4V and disables them again when VCC falls below 1.4V. Additionally, it powers up in Erase/Write Disable (EWDS) mode, requiring an explicit EWEN command before any ERASE or WRITE instruction can execute - preventing accidental writes during MCU initialization or noise events. This dual-layer protection is intrinsic to the 93LC66-I/P silicon design.

What is the maximum clock frequency supported by the 93LC66-I/P?

The 93LC66-I/P supports a maximum clock frequency of 2 MHz when VCC ≥ 4.5V, and 1 MHz when VCC < 4.5V. These limits are specified in the AC Characteristics table (DS21712C, page 3) and apply across the full industrial temperature range (–40°C to +85°C). Exceeding these frequencies may result in unreliable instruction decoding or data corruption, as verified in characterization testing for the 93LC66-I/P.

Can the 93LC66-I/P be used in a shared-data-bus configuration with DI and DO connected together?

Yes, the 93LC66-I/P supports a shared-data-bus configuration where DI and DO are connected to the same line, but caution is required: during the dummy-zero phase preceding a READ operation, a "bus conflict" may occur if address bit A0 is high, causing undefined voltage levels on the shared line. To avoid this, ensure strong pull-down/pull-up biasing or use separate lines in noise-sensitive or high-reliability applications. This behavior is documented in Section 2.2 of the 93LC66-I/P datasheet.

Is the 93LC66-I/P still recommended for new designs?

No - Microchip explicitly states "Not recommended for new designs" in the DS21712C datasheet (page 1), advising migration to the enhanced 93LC66C-I/P variant. While the 93LC66-I/P remains fully functional and supported for legacy repair and continuity, the 93LC66C-I/P offers improved ESD robustness (≥4 kV HBM), updated process technology, and extended qualification. Aetrix Electronics maintains inventory of the 93LC66-I/P for backward compatibility, but recommends evaluating 93LC66C-I/P for new projects.