Microchip Technology 93C66A-E/ST

Overview

93C66A-E/ST 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 for configuration storage in automotive control modules.

For engineers reviewing the 93C66A-E/ST datasheet, 93C66A-E/ST pinout, 93C66A-E/ST application, or 93C66A-E/ST equivalent, key selection criteria include its fixed 8-bit organization (no ORG pin), 2 ms typical write cycle time, 1 million endurance cycles, 200-year data retention, and compatibility with legacy Microwire host controllers requiring minimal firmware changes.

Technical Context

The 93C66A-E/ST implements a synchronous serial interface with CS, CLK, and DI/DO pins operating at up to 3 MHz (VCC ≥ 4.5 V). Its command set includes READ, WRITE, ERASE, ERAL, WRAL, EWEN, and EWDS - all initiated by a Start bit followed by opcode and address/data bits clocked on CLK rising edges.

Unlike C-variant parts, the 93C66A-E/ST has no ORG pin (NC), permanently configured for 8-bit word access. Write operations are initiated by the rising edge of CLK on the final data bit, and device status is polled via DO during programming - high = ready, low = busy - with TSV ≤ 500 ns at 1.8 V.

Key Specifications

Pinout & Package

93C66A-E/ST is packaged in an 8-lead TSSOP (ST) with lead pitch 0.65 mm and body dimensions 4.4 mm × 3.0 mm × 1.2 mm. Pin 1 is marked by laser dot; package is Pb-free and RoHS compliant.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 93LC66A-E/ST, the 93C66A-E/ST provides tighter VCC regulation (4.5–5.5 V) and guaranteed automotive temp operation, while the AT25040B-MAHL-T trades Microwire compatibility for higher speed and hardware write protection - making 93C66A-E/ST optimal for legacy 5 V automotive platforms needing proven qualification.

Availability

93C66A-E/ST is available at Aetrix Electronics and suitable for automotive control units, instrument clusters, and body electronics requiring stable component supply with full AEC-Q100 alignment and long-term lifecycle support.

Supply support for 93C66A-E/ST 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, serving automotive, industrial, and consumer markets globally.

The 93C66A-E/ST belongs to Microchip's legacy 93XX serial EEPROM family, designed specifically for cost-sensitive, space-constrained embedded systems requiring robust nonvolatile storage with minimal pin count and legacy interface support.

FAQ

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

The 93C66A-E/ST supports up to 3 MHz clock frequency when VCC is 4.5–5.5 V. This is specified in Table 1-2 (A1) of DS21795E. The timing parameters TCKH (clock high time) and TCKL (clock low time) are 200 ns minimum each at this voltage range, enabling reliable communication with standard 8-bit microcontrollers using GPIO bit-banging or dedicated Microwire peripherals.

Does the 93C66A-E/ST have an ORG pin, and how is memory organization determined?

No, the 93C66A-E/ST does not have a functional ORG pin - pin 6 is marked NC (no internal connection) per the Pin Function Table and Package Types diagram. As an 'A'-suffix device, it is permanently configured for 512 × 8-bit (x8) organization. This eliminates external ORG routing and simplifies PCB layout compared to C-variant parts that require external logic to select word size.

How does the 93C66A-E/ST protect against unintended writes during power transitions?

The 93C66A-E/ST incorporates hardware power-on/off data protection: its internal POR circuit disables all write/erase functions when VCC falls below 3.8 V (D11 parameter). Additionally, it powers up in EWDS (Erase/Write Disable) mode, requiring an explicit EWEN command before any programming - preventing spurious writes during brown-out or reset sequences.

What is the write endurance and data retention specification for the 93C66A-E/ST?

The 93C66A-E/ST is rated for 1,000,000 erase/write cycles (A16) and greater than 200 years of data retention at 25°C (Features list). These values are characterized per Microchip's Total Endurance™ Model and apply across the full −40°C to +125°C operating range, making it suitable for automotive applications where long service life and infrequent but critical updates are required.

Can the 93C66A-E/ST be used with a 3.3 V microcontroller?

No - the 93C66A-E/ST requires a minimum VCC of 4.5 V and is not specified for operation below that level (Device Selection Table). Its VIH1 threshold is 2.0 V, but the absolute minimum VCC is 4.5 V, and POR activates at 3.8 V. For 3.3 V systems, consider the 93LC66A-E/ST (2.5–5.5 V range) or SPI-based alternatives like AT25040B-MAHL-T.