Microchip Technology 93C66A-E/P

Overview

93C66A-E/P from Microchip Technology Inc. is a 4 Kbit (512 × 8-bit) low-voltage serial EEPROM with Microwire-compatible 3-wire interface, 4.5–5.5 V supply range, and industrial/automotive temperature support (−40°C to +125°C). It features self-timed erase/write cycles, automatic ERAL before WRAL, power-on/off data protection, and Ready/Busy status signaling via DO pin - used in embedded system configuration storage and calibration data retention.

For engineers reviewing the 93C66A-E/P datasheet, 93C66A-E/P pinout, 93C66A-E/P application, or 93C66A-E/P equivalent, this page delivers verified electrical specs, package mapping to 8-lead PDIP, functional timing behavior, and real-world selection guidance for nonvolatile memory in automotive control modules, industrial sensors, and legacy Microwire-based microcontroller systems.

Technical Context

The 93C66A-E/P implements a synchronous serial Microwire protocol with CS, CLK, and DI/DO lines - no ORG pin (fixed 8-bit organization). Erase/write initiation differs from 'AA'/'LC' variants: rising edge of CLK on final data bit triggers self-timed programming, not falling CS edge.

It requires VCC ≥ 4.5 V for ERAL and WRAL operations, includes built-in power-on reset detection at 3.8 V, and enforces EWEN/EWDS write-protection sequencing. Standby current is ≤5 µA, and DO provides active-low Ready/Busy status only when CS is reasserted after ≥250 ns low time (TCSL).

Key Specifications

Pinout & Package

8-lead PDIP (P package), through-hole mounting, RoHS-compliant matte tin finish. Pin 1 marked by laser dot or notch; pin 1 ID corner 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 93LC66A-E/P, the 93C66A-E/P offers faster 2 ms writes and tighter 4.5–5.5 V regulation but sacrifices 3.3 V flexibility; versus AT25040B, it retains Microwire compatibility and PDIP-8 drop-in capability for legacy 5 V designs, avoiding SPI migration effort.

Availability

93C66A-E/P is available at Aetrix Electronics and suitable for automotive control units, industrial sensor calibration systems, and legacy Microwire-based HMI designs requiring stable component supply, long-lifecycle support, and RoHS-compliant through-hole packaging.

Supply support for 93C66A-E/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 microcontrollers, analog devices, and memory solutions, headquartered in Chandler, Arizona, with global design and manufacturing operations.

The 93Cxx EEPROM family was designed specifically for cost-sensitive, low-pin-count embedded systems requiring reliable nonvolatile storage with minimal external components - targeting automotive, industrial, and consumer applications where Microwire compatibility and robust data retention are critical.

FAQ

What is the maximum clock frequency supported by the 93C66A-E/P?

The 93C66A-E/P supports up to 3 MHz clock frequency when VCC is 4.5–5.5 V. This is specified in Table 1-2 (Param. A1, FCLK) of DS21795E. Operation above 3 MHz risks setup/hold violations and failed instruction execution. The 93C66A-E/P does not support higher frequencies even at elevated VCC, unlike some later Microwire EEPROMs.

Does the 93C66A-E/P require an external pull-up resistor on the DO pin?

No, the 93C66A-E/P does not require an external pull-up on DO. Its output buffer actively drives high/low during read and Ready/Busy status reporting. However, if DI and DO are shorted (bus-sharing configuration), a series resistor (typically 1–10 kΩ) is required to prevent bus conflict during the dummy zero phase of read operations, as noted in Section 2.2 of DS21795E.

Can the 93C66A-E/P be used in a 3.3 V system?

No, the 93C66A-E/P is not rated for 3.3 V operation. Its absolute minimum VCC is 4.5 V, and its power-on reset threshold is 3.8 V (Table 1-1, D11). Attempting to operate below 4.5 V risks data corruption, failed writes, and undefined DO status behavior. For 3.3 V systems, consider the 93LC66A-E/P or 93AA66A-E/P instead.

What is the function of the NC pins on the 93C66A-E/P PDIP package?

Pins 6 and 7 on the 93C66A-E/P PDIP package are No Connect (NC) terminals - internally unconnected and electrically isolated. They must remain floating; tying them to VCC, VSS, or signals violates the device's electrical specifications and may cause latch-up or parametric failure. Their presence maintains mechanical symmetry and legacy footprint compatibility.

How does the 93C66A-E/P handle power loss during a write operation?

The 93C66A-E/P incorporates hardware power-loss protection: if VCC drops below 3.8 V during erase/write, the internal circuitry aborts the operation and holds memory contents unchanged. This is enforced by the VPOR (VCC voltage detect) circuit (D11 in DS21795E). No external capacitors or supervisors are needed - the 93C66A-E/P guarantees data integrity across brown-out events within its specified VCC range.