93C66CT-I/ST EEPROM 4Kbit Microwire Equivalent & Substitute Parts

Part Overview

The 93C66CT-I/ST is a 4Kbit non-volatile EEPROM memory IC manufactured by Microchip Technology, featuring Microwire serial interface protocol and 8-TSSOP surface mount packaging. This component operates at 3 MHz clock frequency with a 2ms write cycle time and supports dual memory organization (512 x 8 or 256 x 16 bits). The part is ROHS3 compliant and currently active in production with 811 units in stock.

Equivalent and substitute parts are identified when designs require alternative sourcing due to inventory constraints, supply chain disruptions, or specific application requirements while maintaining functional compatibility within defined electrical and mechanical parameters.

Key Parameters

Parameter	Specification
Memory Type	Non-Volatile EEPROM
Memory Size	4Kbit
Memory Organization	512 x 8, 256 x 16
Memory Interface	Microwire
Clock Frequency	3 MHz
Write Cycle Time	2ms
Supply Voltage Range	4.5V ~ 5.5V
Operating Temperature	-40°C ~ 85°C
Package Type	8-TSSOP (0.173", 4.40mm Width)
Mounting Type	Surface Mount
RoHS Status	ROHS3 Compliant

Substitute Part Grouping Explanation

Substitution eligibility for the 93C66CT-I/ST is determined by the following critical parameters:

Memory Capacity & Organization: All substitute parts must provide 4Kbit capacity with 512 x 8 or 256 x 16 organization to ensure data storage compatibility.

Serial Interface Protocol: The Microwire interface is the primary communication standard for this part. Substitutes using Microwire protocol maintain direct pin and protocol compatibility. Parts using alternative serial protocols (such as 3-Wire Serial) may require firmware or hardware interface modifications and are listed as functional alternatives only.

Package & Pinout: All substitutes use 8-TSSOP surface mount packaging with identical physical dimensions (0.173", 4.40mm width), ensuring PCB layout compatibility without redesign.

Voltage Supply Range: Substitutes must operate within overlapping voltage ranges. The main part operates at 4.5V ~ 5.5V. Substitutes with wider ranges (such as 1.8V ~ 5.5V or 2.5V ~ 5.5V) are compatible when the application supplies voltage within the main part's specified range.

Operating Temperature: All substitutes support the -40°C ~ 85°C range, with some offering extended temperature capability to 125°C for automotive applications.

Compliance & Certifications: All substitutes maintain ROHS3 compliance and EAR99 export classification, ensuring regulatory equivalence.

Parameter Comparison

Parameter	93C66CT-I/ST (Main)	AT93C66B-XHM-T	M93C66-RDW3TP/K	M93C66-WDW6TP
Manufacturer	Microchip Technology	Microchip Technology	STMicroelectronics	STMicroelectronics
Memory Size	4Kbit	4Kbit	4Kbit	4Kbit
Memory Organization	512 x 8, 256 x 16	512 x 8, 256 x 16	512 x 8, 256 x 16	512 x 8, 256 x 16
Memory Interface	Microwire	3-Wire Serial	Microwire	Microwire
Clock Frequency	3 MHz	2 MHz	2 MHz	2 MHz
Write Cycle Time	2ms	5ms	5ms	5ms
Supply Voltage Range	4.5V ~ 5.5V	1.7V ~ 5.5V	1.8V ~ 5.5V	2.5V ~ 5.5V
Operating Temperature	-40°C ~ 85°C	-40°C ~ 85°C	-40°C ~ 125°C	-40°C ~ 85°C
Package Type	8-TSSOP	8-TSSOP	8-TSSOP	8-TSSOP
Mounting Type	Surface Mount	Surface Mount	Surface Mount	Surface Mount
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant
Product Status	Active	Active	Active	Active

Engineering Selection Recommendations

AT93C66B-XHM-T (Microchip Technology): This substitute shares the same manufacturer as the main part and maintains identical memory capacity, organization, and package specifications. The primary difference is the 3-Wire Serial interface protocol instead of Microwire. This part is suitable only for applications where the host controller supports 3-Wire Serial protocol or where firmware can be adapted to accommodate the alternative interface. Clock frequency is reduced to 2 MHz and write cycle time extends to 5ms. Supply voltage range is wider (1.7V ~ 5.5V), providing greater flexibility in low-voltage applications.

M93C66-RDW3TP/K (STMicroelectronics): This substitute maintains Microwire protocol compatibility with the main part, ensuring direct interface compatibility without firmware modification. It is qualified to AEC-Q100 automotive standards and supports extended operating temperature to 125°C, making it suitable for automotive and high-temperature applications. Clock frequency is 2 MHz and write cycle time is 5ms. Supply voltage range is 1.8V ~ 5.5V. This part is available in Tape & Reel packaging.

M93C66-WDW6TP (STMicroelectronics): This substitute provides Microwire protocol compatibility and is verified as DiGi-Electronics programmable. It offers the highest inventory availability (105,200 units) among all substitutes. Clock frequency is 2 MHz and write cycle time is 5ms. Supply voltage range is 2.5V ~ 5.5V. This part is available in Cut Tape & Digi-Reel packaging and is suitable for high-volume production environments.

Frequently Asked Questions (FAQ)

Q: Can AT93C66B-XHM-T be used as a direct replacement for 93C66CT-I/ST?

A: AT93C66B-XHM-T uses 3-Wire Serial protocol instead of Microwire. While both are serial EEPROM interfaces, they employ different communication protocols. Direct replacement requires the host controller to support 3-Wire Serial protocol. If the application is designed exclusively for Microwire, firmware or hardware interface modifications are necessary.

Q: What is the difference between Microwire and 3-Wire Serial protocols?

A: Microwire and 3-Wire Serial are distinct serial communication protocols with different command structures and timing requirements. Microwire uses a specific instruction set and timing sequence defined by the Microwire standard. 3-Wire Serial uses an alternative protocol. Compatibility depends on the host controller's interface capabilities.

Q: Are M93C66-RDW3TP/K and M93C66-WDW6TP interchangeable?

A: Both parts use Microwire protocol and share identical memory specifications (4Kbit, 512 x 8 or 256 x 16 organization). The primary differences are packaging format (Tape & Reel vs. Cut Tape & Digi-Reel) and supply voltage range (1.8V ~ 5.5V vs. 2.5V ~ 5.5V). They are functionally interchangeable in applications where the supply voltage falls within both specified ranges and the packaging format is acceptable for the assembly process.

Q: Why does M93C66-RDW3TP/K have an extended operating temperature range to 125°C?

A: M93C66-RDW3TP/K is qualified to AEC-Q100 automotive standards, which require extended temperature capability. This qualification is relevant only for automotive applications. For non-automotive applications operating within -40°C ~ 85°C, this extended capability provides no functional advantage.

Q: What is the impact of reduced clock frequency (2 MHz vs. 3 MHz) on system performance?

A: All substitute parts operate at 2 MHz compared to the main part's 3 MHz. This results in proportionally longer data transfer times. For most applications, this difference is negligible because EEPROM access is typically not a performance bottleneck. The impact is measurable only in applications requiring high-frequency sequential memory access.

Q: Are all substitute parts ROHS3 compliant?

A: Yes. All substitute parts listed (AT93C66B-XHM-T, M93C66-RDW3TP/K, and M93C66-WDW6TP) are ROHS3 compliant, matching the compliance status of the main part 93C66CT-I/ST.

Q: Can I use a substitute part with a wider supply voltage range in a 4.5V ~ 5.5V application?

A: Yes. Substitutes with wider voltage ranges (such as 1.8V ~ 5.5V or 2.5V ~ 5.5V) are compatible with applications supplying 4.5V ~ 5.5V, as the application voltage falls within the substitute's specified range. The wider range provides additional flexibility for future applications but does not affect current operation.

Request Quote (Ships tomorrow)

Part Number

Quantity

Company

Contact Name

E-mail

Message