Microchip Technology 93C66AT-I/OT

Overview

93C66AT-I/OT from Microchip Technology Inc. is a 4 Kbit (512 × 8-bit) low-voltage serial EEPROM with Microwire-compatible 3-wire interface, operating at 4.5–5.5 V, rated for industrial temperature (−40°C to +85°C), and packaged in 6-lead SOT-23. It features self-timed erase/write cycles, automatic ERAL before WRAL, and power-on/off data protection - used in embedded system configuration storage, sensor calibration retention, and firmware parameter backup.

For engineers reviewing the 93C66AT-I/OT datasheet, 93C66AT-I/OT pinout, 93C66AT-I/OT application, or 93C66AT-I/OT equivalent, key selection considerations include its fixed 8-bit organization (no ORG pin), SOT-23 footprint constraints, 2 ms write cycle time, 1 million endurance cycles, and VCC-dependent Ready/Busy signaling via DO pin.

Technical Context

This device implements a synchronous serial Microwire interface with CS, CLK, and DI/DO pins - no internal ORG pin (dedicated x8 mode). Communication requires a start condition (CS high + DI high on first CLK rising edge), followed by opcode, address, and data bits clocked on CLK rising edges. The DO pin serves dual function: serial data output during READ and Ready/Busy status indicator during erase/write operations.

Write and erase operations are fully self-timed: for 93C66A/B variants, the rising edge of CLK on the final data bit initiates auto-erase-and-write; VCC ≥ 4.5 V is mandatory for ERAL and WRAL commands. Power-down protection activates below 3.8 V, preventing inadvertent writes during brown-out conditions.

Key Specifications

Pinout & Package

6-lead SOT-23 package (OT), with pin 1 marked by laser dot. Pin 1 = DO, pin 2 = VSS, pin 3 = DI, pin 4 = VCC, pin 5 = CS, pin 6 = CLK. No ORG or NC pins - consistent with 'A'-suffix fixed-x8 architecture.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 93LC66AT-I/OT and AT25040B-MAHL-T, the 93C66AT-I/OT provides optimal fit for cost-sensitive, 5 V-only industrial systems needing guaranteed write integrity at VCC ≥ 4.5 V and minimal PCB real estate - without sacrificing endurance or data retention.

Availability

93C66AT-I/OT is available at Aetrix Electronics and suitable for industrial sensor calibration, consumer appliance settings, and medical device configuration requiring stable component supply, long-lifecycle support, and RoHS-compliant sourcing.

Supply support for 93C66AT-I/OT 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 components, and memory solutions, headquartered in Chandler, Arizona, with global design and manufacturing operations.

The 93Cxx series was designed specifically for low-pin-count, low-power serial EEPROM applications in cost-sensitive embedded systems - emphasizing simplicity, reliability, and compatibility with legacy Microwire controllers.

FAQ

What is the memory organization of the 93C66AT-I/OT?

The 93C66AT-I/OT is a fixed 512 × 8-bit (4 Kbit) EEPROM with no ORG pin - it operates exclusively in x8 mode. Unlike 'C' variants, it does not support runtime word-size switching; this simplifies hardware design and eliminates external ORG pull-up/pull-down requirements. The 93C66AT-I/OT matches the timing and instruction set of the 93C66A family as defined in DS21795E.

Does the 93C66AT-I/OT support the ERAL (Erase All) command?

Yes, the 93C66AT-I/OT supports ERAL, but only when VCC is ≥ 4.5 V. The ERAL cycle is self-timed and takes up to 6 ms to complete. During execution, the DO pin outputs low (busy) until completion, then goes high (ready). The 93C66AT-I/OT requires an EWEN command before ERAL, and the device must be in the enabled state - confirmed in Section 2.5 and Table A14 of DS21795E.

What is the maximum clock frequency supported by the 93C66AT-I/OT?

The 93C66AT-I/OT supports up to 3 MHz clock frequency when VCC is 4.5–5.5 V (Table 1-2, A1). At this rate, the minimum clock high/low times are 200 ns/100 ns respectively. This allows high-speed parameter updates while maintaining compatibility with standard 5 V microcontroller GPIO toggle rates - verified across AC characteristics in DS21795E.

How is data protection implemented in the 93C66AT-I/OT?

Data protection in the 93C66AT-I/OT operates at three levels: (1) hardware POR at 3.8 V blocks writes during brown-out; (2) EWEN/EWDS commands require explicit enable before erase/write; (3) power-on default is EWDS state. These mechanisms prevent accidental overwrites - detailed in Sections 2.3 and 2.6 of DS21795E, with electrical validation in D11 and functional flow in Figure 2-5/2-6.

Is the 93C66AT-I/OT pin-compatible with other 93XX66 variants in SOT-23?

Yes - the 93C66AT-I/OT shares identical 6-lead SOT-23 pinout (OT package) with 93AA66AT-I/OT and 93LC66AT-I/OT per Table 3-1 and Package Types diagram on DS21795E-page 2. All use DO/VSS/DI/VCC/CS/CLK mapping; no ORG or NC pins are present in 'A' versions. Mechanical compatibility is confirmed in Microchip's packaging specification.