93LC66XT-I/SN EEPROM Memory IC Equivalent & Substitute Parts

Part Overview

The 93LC66XT-I/SN is a 4Kbit non-volatile EEPROM memory IC manufactured by Microchip Technology, featuring Microwire serial interface protocol and 8-SOIC surface mount packaging. This device operates across a 2.5V to 5.5V supply voltage range with a 2 MHz clock frequency and 10ms write cycle time. The part is currently in active production status with ROHS3 compliance and unlimited moisture sensitivity rating.

Substitute parts are identified when design requirements necessitate alternative sourcing due to inventory constraints, extended lead times, or when enhanced electrical specifications provide operational advantages within the same functional category and package form factor.

Key Parameters

Parameter	Specification
Memory Size	4Kbit
Memory Organization	512 x 8, 256 x 16
Memory Interface	Microwire
Clock Frequency	2 MHz
Write Cycle Time	10ms
Voltage Supply Range	2.5V ~ 5.5V
Operating Temperature	-40°C ~ 85°C
Package / Case	8-SOIC (0.154", 3.90mm Width)
Mounting Type	Surface Mount
RoHS Status	ROHS3 Compliant

Substitute Part Grouping Explanation

Substitution eligibility is determined by strict adherence to the following electrical and mechanical parameters:

Primary Substitution Criteria:

Memory capacity: 4Kbit (non-negotiable)
Memory interface: Microwire protocol compatibility
Package form factor: 8-SOIC (0.154", 3.90mm Width)
Mounting type: Surface Mount
RoHS compliance: ROHS3 Compliant

Secondary Compatibility Parameters:

Voltage supply range must encompass or exceed 2.5V minimum
Clock frequency of 2 MHz or higher
Operating temperature range must support -40°C to 85°C minimum
Write cycle time of 10ms or faster

Substitute parts are grouped into three categories based on interface protocol and electrical performance characteristics:

Group 1: Microwire Interface, 2 MHz Operation — Direct functional equivalents with identical clock frequency and write cycle specifications. These parts maintain full pin-for-pin compatibility and protocol equivalence.

Group 2: Microwire Interface, Enhanced Performance (3 MHz) — Parts with improved clock frequency and faster write cycle times. These provide superior performance while maintaining Microwire protocol compatibility and backward operational compatibility.

Group 3: 3-Wire Serial Interface — Alternative serial protocol implementation with different pin configuration. Requires circuit-level interface verification before substitution.

Parameter Comparison

Part Number	Manufacturer	Memory Interface	Clock Frequency	Write Cycle Time	Voltage Supply	Operating Temperature	Packaging	Product Status
93LC66XT-I/SN	Microchip Technology	Microwire	2 MHz	10ms	2.5V ~ 5.5V	-40°C ~ 85°C	Tape & Reel	Active
93AA66CT-I/SN	Microchip Technology	Microwire	3 MHz	6ms	1.8V ~ 5.5V	-40°C ~ 85°C	Cut Tape & Digi-Reel	Active
93LC66CT-E/SN	Microchip Technology	Microwire	3 MHz	6ms	2.5V ~ 5.5V	-40°C ~ 125°C	Tape & Reel	Active
AT93C66B-SSHM-T	Microchip Technology	3-Wire Serial	2 MHz	5ms	1.7V ~ 5.5V	-40°C ~ 85°C	Cut Tape & Digi-Reel	Active
93LC66X-I/SN	Microchip Technology	Microwire	2 MHz	10ms	2.5V ~ 5.5V	-40°C ~ 85°C	Tube	Active
CAT93C66VI-G	onsemi	Microwire	2 MHz	—	1.8V ~ 5.5V	-40°C ~ 85°C	Tube	Active
CAT93C66VI-GT3	onsemi	Microwire	2 MHz	—	1.8V ~ 5.5V	-40°C ~ 85°C	Tape & Reel	Active
M93C66-RMN3TP/K	STMicroelectronics	Microwire	2 MHz	5ms	1.8V ~ 5.5V	-40°C ~ 125°C	Cut Tape & Digi-Reel	Active
M93C66-WMN6TP	STMicroelectronics	Microwire	2 MHz	5ms	2.5V ~ 5.5V	-40°C ~ 85°C	Cut Tape & Digi-Reel	Active
M93C76-RMN3TP/K	STMicroelectronics	Microwire	2 MHz	5ms	1.8V ~ 5.5V	-40°C ~ 125°C	Tape & Reel	Active

Engineering Selection Recommendations

For Direct Replacement (Identical Electrical Performance):

93LC66X-I/SN serves as a direct functional equivalent with matching 2 MHz clock frequency, 10ms write cycle time, and identical voltage supply specifications. The primary distinction is packaging format (Tube versus Tape & Reel). This substitution is appropriate when packaging compatibility with existing assembly processes is maintained.

M93C66-WMN6TP provides equivalent electrical performance with improved write cycle time (5ms versus 10ms) while maintaining the 2.5V to 5.5V supply voltage range. This part is suitable for applications where faster write operations provide operational benefit without circuit modification.

For Enhanced Performance Applications:

93AA66CT-I/SN and 93LC66CT-E/SN offer improved clock frequency (3 MHz) and faster write cycle times (6ms). The 93LC66CT-E/SN extends operating temperature range to 125°C, making it suitable for industrial and automotive temperature environments. Both parts maintain Microwire protocol compatibility.

For Automotive and Extended Temperature Requirements:

M93C66-RMN3TP/K and M93C76-RMN3TP/K are qualified to AEC-Q100 automotive standards with extended operating temperature range (-40°C to 125°C). These parts are appropriate for automotive applications requiring formal qualification documentation.

For Alternative Serial Protocol Applications:

AT93C66B-SSHM-T implements 3-Wire Serial interface protocol instead of Microwire. This part requires circuit-level interface redesign and is not a pin-compatible substitute. Selection of this part is appropriate only when 3-Wire Serial protocol is specified in the system design.

Compliance and Certification Status:

All listed substitute parts maintain ROHS3 compliance and REACH unaffected status, matching the regulatory compliance profile of the primary part. All parts are in active production status with established supply chain availability.

Frequently Asked Questions (FAQ)

Q: Can 93AA66CT-I/SN be used as a direct replacement for 93LC66XT-I/SN?

A: Yes, with operational advantages. Both parts implement Microwire protocol in 8-SOIC packaging. The 93AA66CT-I/SN operates at 3 MHz with 6ms write cycle time versus 2 MHz and 10ms for the original part. The voltage supply range of 93AA66CT-I/SN (1.8V to 5.5V) encompasses the original specification (2.5V to 5.5V). Pin-for-pin compatibility is maintained.

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

A: Microwire and 3-Wire Serial are distinct serial communication protocols with different pin configurations and timing requirements. Parts implementing 3-Wire Serial protocol (such as AT93C66B-SSHM-T) are not pin-compatible with Microwire devices and require circuit redesign for substitution.

Q: Are STMicroelectronics M93C66 parts compatible with Microchip 93LC66 parts?

A: Yes, STMicroelectronics M93C66 and M93C76 series parts are functionally compatible with Microchip 93LC66 series when both implement Microwire protocol and share identical memory organization (512 x 8, 256 x 16). Pin configuration and protocol timing are equivalent. Verify write cycle time specifications for application-specific timing requirements.

Q: What packaging options are available for 4Kbit Microwire EEPROM devices?

A: Available packaging formats include Tape & Reel (TR), Cut Tape with Digi-Reel (CT), and Tube. All substitute parts listed maintain 8-SOIC form factor (0.154", 3.90mm Width). Packaging selection depends on assembly process requirements and volume specifications.

Q: Can onsemi CAT93C66 parts substitute for Microchip 93LC66 parts?

A: Yes, onsemi CAT93C66VI-G and CAT93C66VI-GT3 parts implement Microwire protocol with 2 MHz clock frequency and 8-SOIC packaging, providing functional equivalence. The voltage supply range (1.8V to 5.5V) encompasses the original specification. Primary distinction is manufacturer and packaging format (Tube versus Tape & Reel).

Q: What is the significance of AEC-Q100 qualification?

A: AEC-Q100 qualification indicates the part meets automotive industry reliability and quality standards established by the Automotive Electronics Council. Parts with AEC-Q100 qualification (M93C66-RMN3TP/K and M93C76-RMN3TP/K) are appropriate for automotive applications requiring formal qualification documentation and extended temperature operation (-40°C to 125°C).

Q: Are there voltage supply differences between substitute parts?

A: Yes. The original 93LC66XT-I/SN operates at 2.5V to 5.5V. Some substitutes (93AA66CT-I/SN, CAT93C66VI-G, CAT93C66VI-GT3, M93C66-RMN3TP/K, M93C76-RMN3TP/K) support lower minimum voltage (1.8V). Applications operating at 2.5V or higher are compatible with all listed parts. Applications requiring 1.8V operation must select parts with 1.8V minimum specification.

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