74LCX646MTC Equivalent & Substitute Parts

Part Overview

The 74LCX646MTC is a non-inverting transceiver IC manufactured by onsemi, designed for 8-bit bidirectional data transfer with 3-state output capability. Operating across a 2V to 3.6V supply range, this component is classified as obsolete, making equivalent substitutes necessary for new designs and ongoing production requirements. The 74LVC series from Texas Instruments provides direct functional equivalents with enhanced specifications and active product status.

Key Parameters

Parameter	Value
Logic Type	Transceiver, Non-Inverting
Number of Elements	1
Number of Bits per Element	8
Output Type	3-State
Current - Output High, Low	24mA, 24mA
Voltage - Supply	2V ~ 3.6V
Operating Temperature	-40°C ~ 85°C (TA)
Mounting Type	Surface Mount
Moisture Sensitivity Level (MSL)	1 (Unlimited)

Substitute Part Grouping Explanation

Substitution of the 74LCX646MTC is determined by the following critical parameters:

Logic Function: Transceiver, Non-Inverting with 1 Element and 8 Bits per Element
Output Configuration: 3-State output capability
Current Drive: 24mA output current (high and low)
Supply Voltage Compatibility: Minimum 1.65V to 3.6V (substitute parts support lower minimum voltage while maintaining 3.6V maximum)
Operating Temperature Range: -40°C to 85°C
Package Type: 24-pin surface mount (TSSOP or SSOP variants)
Moisture Sensitivity: MSL 1 (Unlimited)

The 74LVC646 series from Texas Instruments meets all functional and electrical requirements. Substitutes differ only in packaging format (TSSOP vs. SSOP) and product status (active vs. discontinued), with no impact on core electrical performance.

Parameter Comparison

Parameter	74LCX646MTC (onsemi)	SN74LVC646ADBR (TI)	SN74LVC646APW (TI)	SN74LVC646APWR (TI)	SN74LVC646APWT (TI)
Manufacturer	onsemi	Texas Instruments	Texas Instruments	Texas Instruments	Texas Instruments
Series	74LCX	74LVC	74LVC	74LVC	74LVC
Logic Type	Transceiver, Non-Inverting	Transceiver, Non-Inverting	Transceiver, Non-Inverting	Transceiver, Non-Inverting	Transceiver, Non-Inverting
Number of Elements	1	1	1	1	1
Number of Bits per Element	8	8	8	8	8
Output Type	3-State	3-State	3-State	3-State	3-State
Current - Output High, Low	24mA, 24mA	24mA, 24mA	24mA, 24mA	24mA, 24mA	24mA, 24mA
Voltage - Supply	2V ~ 3.6V	1.65V ~ 3.6V	1.65V ~ 3.6V	1.65V ~ 3.6V	1.65V ~ 3.6V
Operating Temperature	-40°C ~ 85°C (TA)	-40°C ~ 85°C (TA)	-40°C ~ 85°C (TA)	-40°C ~ 85°C (TA)	-40°C ~ 85°C (TA)
Package / Case	24-TSSOP (0.173", 4.40mm Width)	24-SSOP (0.209", 5.30mm Width)	24-TSSOP (0.173", 4.40mm Width)	24-TSSOP (0.173", 4.40mm Width)	24-TSSOP (0.173", 4.40mm Width)
Product Status	Obsolete	Active	Active	Active	Discontinued at DiGi Electronics
RoHS Status	REACH Unaffected	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant
Moisture Sensitivity Level (MSL)	1 (Unlimited)	1 (Unlimited)	1 (Unlimited)	1 (Unlimited)	1 (Unlimited)

Engineering Selection Recommendations

Primary Substitutes (Active Status)

SN74LVC646APW and SN74LVC646APWR are the preferred substitutes. Both are manufactured by Texas Instruments with active product status and ROHS3 compliance. SN74LVC646APW is supplied in tube packaging, while SN74LVC646APWR is supplied in tape and reel format. Both use the 24-TSSOP package, maintaining identical footprint compatibility with the original 74LCX646MTC.

Secondary Substitute (Package Variant)

SN74LVC646ADBR provides functional equivalence with a 24-SSOP package (0.209" width vs. 0.173" for TSSOP). This variant requires PCB layout modification due to increased package width but maintains all electrical specifications and active product status.

Discontinued Variant

SN74LVC646APWT shares identical electrical and package specifications with the active variants but is discontinued at DiGi Electronics. Selection should prioritize actively available parts.

Voltage Specification Enhancement

All Texas Instruments substitutes support a lower minimum supply voltage (1.65V vs. 2V), providing improved operational margin in low-voltage applications while maintaining full compatibility with 3.6V maximum specifications.

Frequently Asked Questions (FAQ)

Q: Can SN74LVC646ADBR replace 74LCX646MTC directly on the PCB?

A: Electrical substitution is complete. However, the SN74LVC646ADBR uses a 24-SSOP package (5.30mm width) compared to the 24-TSSOP package (4.40mm width) of the original part. PCB footprint modification is required.

Q: What is the key difference between SN74LVC646APW and SN74LVC646APWR?

A: Both parts are electrically identical with matching 24-TSSOP packages. The difference is packaging format: APW is supplied in tube, while APWR is supplied in tape and reel. Selection depends on assembly process requirements.

Q: Are the Texas Instruments substitutes backward compatible with 74LCX646MTC designs?

A: Yes. The 74LVC series substitutes maintain identical logic function, output drive capability (24mA), operating temperature range (-40°C to 85°C), and MSL rating. The 74LVC variants support an extended lower voltage range (1.65V minimum vs. 2V), ensuring compatibility across all specified operating conditions.

Q: Why is the 74LCX646MTC listed as obsolete?

A: The 74LCX series has been superseded by the 74LVC series, which offers improved specifications and continued manufacturing support. Texas Instruments maintains active production of equivalent 74LVC646 variants.

Q: Does ROHS3 compliance affect substitution suitability?

A: ROHS3 compliance of the Texas Instruments substitutes ensures environmental and regulatory alignment with modern manufacturing standards. The original 74LCX646MTC is REACH Unaffected, indicating no conflict with substitute compliance status.

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