Microchip Technology 93C66A-I/SN

Overview

93C66A-I/SN 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 temperature grade (–40°C to +85°C). It features self-timed erase/write cycles, automatic ERAL/WRAL support, and Ready/Busy status signaling via DO pin. Used in embedded system configuration storage, sensor calibration data retention, and firmware parameter backup.

For engineers reviewing the 93C66A-I/SN datasheet, 93C66A-I/SN pinout, 93C66A-I/SN application, or 93C66A-I/SN equivalent, key selection criteria include its fixed 8-bit organization (no ORG pin), 2 ms typical write cycle time, 1 million endurance cycles, and SOIC-8 (SN) package compatibility with legacy board layouts.

Technical Context

The 93C66A-I/SN implements a synchronous serial Microwire protocol with CS, CLK, and DI/DO lines - no ORG pin required, enforcing strict 8-bit word access. Its internal logic executes auto-erase-before-write and supports full-array operations (ERAL, WRAL) only at VCC ≥ 4.5 V.

Timing is tightly coupled to VCC: clock frequency up to 3 MHz at 4.5–5.5 V, TWC = 2 ms for erase/write, and DO provides real-time Ready/Busy polling during programming. Power-on reset protection activates below 3.8 V, preventing inadvertent writes during brown-out conditions.

Key Specifications

Pinout & Package

8-pin SOIC package (SN suffix), 3.9 mm × 4.9 mm body, 1.27 mm pitch, Pb-free Matte Tin finish. Pin 1 marked by laser dot or bevelled corner.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 93LC66A-I/SN, the 93C66A-I/SN trades voltage flexibility for optimized 5 V timing and lower active current; versus AT25040B-MAHL-T, it retains Microwire simplicity and hardware status signaling at the cost of interface universality.

Availability

93C66A-I/SN is available at Aetrix Electronics and suitable for industrial automation, automotive electronics, and medical instrumentation requiring stable component supply, long-lifecycle support, and RoHS-compliant packaging.

Supply support for 93C66A-I/SN 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.

The 93C66A belongs to Microchip's legacy Microwire EEPROM family, designed specifically for cost-sensitive, low-pin-count embedded systems needing reliable nonvolatile storage without complex interface overhead.

FAQ

What is the maximum clock frequency supported by the 93C66A-I/SN?

The 93C66A-I/SN supports up to 3 MHz clock frequency when VCC is between 4.5 V and 5.5 V. This timing is validated per DS21795E AC Characteristics Table 1-2 (Param A1). Operation above this frequency risks command misinterpretation or incomplete data latching. The 93C66A-I/SN does not support higher speeds even with tighter tolerances - the internal state machine is hard-gated to this limit.

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

No, the 93C66A-I/SN does not require an external pull-up on DO. Its output buffer actively drives high/low during READ and Ready/Busy status reporting, and enters high-impedance (High-Z) when CS is low or during non-read states. External pull-ups may cause contention and are explicitly discouraged in DS21795E Section 2.2 and Figure 2-7 timing diagrams.

Can the 93C66A-I/SN be used in place of the 93AA66A-I/SN?

No - the 93C66A-I/SN and 93AA66A-I/SN are not interchangeable. While both are 512×8 EEPROMs in SOIC-8, the 93C66A-I/SN requires minimum 4.5 V VCC and has different timing (e.g., 2 ms TWC vs. 6 ms for 93AA66A), POR threshold (3.8 V vs. 1.5 V), and AC specs. Substituting them risks failed writes or premature lockout in systems operating near 4.5 V.

Is the ORG pin present on the 93C66A-I/SN?

No, the ORG pin is not present on the 93C66A-I/SN. As confirmed in the Device Selection Table and Pin Function Table, 'A'-suffix devices like 93C66A have fixed 8-bit organization and no ORG functionality. Pin 6 on the SOIC-8 package is NC (No Connection), not internally bonded - tying it to any voltage violates the datasheet and may damage the part.

What happens if VCC drops below 3.8 V during a write operation on the 93C66A-I/SN?

If VCC drops below 3.8 V during a write, the 93C66A-I/SN's internal power-on reset (POR) circuit disables all programming functions immediately. The ongoing erase/write cycle halts, and the memory contents remain unchanged or partially written (undefined state). No data corruption occurs, but the operation fails silently - host firmware must detect timeout via DO polling and retry after stable VCC restoration.