Microchip Technology 93LC66A-I/P

Overview

93LC66A-I/P from Microchip Technology Inc. is a 4 Kbit (512 × 8-bit) low-voltage serial EEPROM with Microwire-compatible 3-wire interface, operating from 2.5V to 5.5V, rated for industrial temperature range (–40°C to +85°C), and housed in an 8-lead PDIP package. It provides nonvolatile storage for configuration data, calibration parameters, and system settings in embedded microcontroller systems.

For engineers reviewing the 93LC66A-I/P datasheet, 93LC66A-I/P pinout, 93LC66A-I/P application, or 93LC66A-I/P equivalent, key selection considerations include its 8-bit organization (no ORG pin), self-timed erase/write cycles (6 ms typical), Ready/Busy status signaling via DO, and compatibility with legacy Microwire controllers requiring minimal GPIO overhead.

Technical Context

The 93LC66A-I/P implements a synchronous serial interface using CS, CLK, and DI/DO lines with start-bit detection and opcode-driven command execution. It supports READ, WRITE, ERASE, ERAL, WRAL, EWEN, and EWDS instructions - all clocked on the rising edge of CLK, with no external timing components required.

Its internal architecture includes a 512-word × 8-bit memory array, address counter, mode decode logic, and output buffer. Power-on data protection is enforced by a VCC detect circuit (1.5 V threshold), and write operations require explicit Erase/Write Enable (EWEN) before programming - ensuring robust immunity against accidental overwrites during brown-out or noise events.

Key Specifications

Pinout & Package

8-lead PDIP (P package), through-hole mounting, 0.3-inch body width. Pin 1 marked by notch or dot; pin 1 ID confirmed per Microchip DS21795E-page 18.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 93LC66B-I/P, the 93LC66A-I/P offers simpler 8-bit firmware integration and identical pinout; compared with AT25040B-PU, it provides hardware-ready/busy signaling and lower GPIO count, but requires Microwire-compatible controller support.

Availability

93LC66A-I/P is available at Aetrix Electronics and suitable for industrial control systems, smart metering platforms, and medical device design requiring stable component supply, long-term lifecycle support, and RoHS-compliant through-hole packaging.

Supply support for 93LC66A-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, analog, and Flash-IP solutions, headquartered in Chandler, Arizona, with global design and manufacturing operations.

The 93LCxx series was designed specifically for cost-sensitive, low-pin-count embedded systems needing reliable, low-power serial EEPROM - emphasizing ease of integration, robustness under voltage transients, and long-term data integrity.

FAQ

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

The 93LC66A-I/P has a fixed 512 × 8-bit (4 Kbit) organization with no ORG pin - unlike 'C' variants, it does not support configurable word size. This simplifies firmware development by eliminating ORG pin management and ensuring consistent 8-bit data framing across all transactions. The 93LC66A-I/P is optimized for systems where byte-level access suffices and minimal GPIO usage is prioritized.

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

No, the 93LC66A-I/P does not require an external pull-up on DO. Its DO pin is actively driven high or low during read/status operations and enters high-impedance (High-Z) state when CS is low or during idle periods. External pull-ups may interfere with proper Ready/Busy signaling and are unnecessary per Microchip DS21795E electrical specifications and timing diagrams.

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

Write protection on the 93LC66A-I/P is implemented via Erase/Write Enable (EWEN) and Erase/Write Disable (EWDS) commands. The device powers up in EWDS mode, blocking all erase/write operations until EWEN is issued. After any write, executing EWDS restores protection - preventing accidental overwrites due to noise or software faults. This hardware-enforced lock complements VCC-based power-on protection (1.5 V threshold) for comprehensive data integrity.

Can the 93LC66A-I/P operate at 2.5 V while maintaining full timing performance?

Yes, the 93LC66A-I/P is fully specified down to 2.5 V, including AC timing: maximum clock frequency is 2 MHz, TCKH/TCKL minimums are 250 ns/200 ns, and TPD is 250 ns (CL = 100 pF). All DC parameters - including VIH/VIL thresholds, VOL/VOH levels, and ICC - are guaranteed across the full 2.5–5.5 V range, enabling reliable operation in battery-powered or wide-input industrial supplies without derating.

Is the 93LC66A-I/P pin-compatible with other 93LCxxA variants in PDIP packages?

Yes, the 93LC66A-I/P shares identical 8-lead PDIP (P) pinout and footprint with all 93LCxxA/B/C variants in the same package type, including 93LC46A-I/P and 93LC56A-I/P. Pin functions (CS, CLK, DI, DO, VSS, NC, NC, VCC) and physical dimensions are standardized across the family - enabling direct substitution in existing layouts when memory size or voltage range aligns with system requirements.