SN74LS33D Equivalent & Substitute Parts

Part Overview

The SN74LS33D is a NOR Gate IC featuring 4 channels with 2 inputs per channel and open collector output configuration, packaged in 14-SOIC surface mount format. Manufactured by Texas Instruments, this component operates within the 74LS logic family standard. The main part (SN74LS33D) carries Last Time Buy status, indicating discontinued production. Identifying equivalent substitute parts is necessary to ensure design continuity and maintain supply chain reliability for new production runs and ongoing support.

Key Parameters

Parameter	Value
Logic Type	NOR Gate
Number of Circuits	4
Number of Inputs	2
Features	Open Collector
Voltage - Supply	4.75V ~ 5.25V
Current - Output High, Low	-, 24mA
Input Logic Level - Low	0.8V
Input Logic Level - High	2V
Max Propagation Delay @ V, Max CL	32ns @ 5V, 45pF
Operating Temperature	0°C ~ 70°C
Mounting Type	Surface Mount
Package / Case	14-SOIC (0.154", 3.90mm Width)
Series	74LS
RoHS Status	ROHS3 Compliant
Moisture Sensitivity Level (MSL)	1 (Unlimited)

Substitute Part Grouping Explanation

Substitution eligibility for the SN74LS33D is determined by strict equivalence across the following critical parameters:

Logic function: NOR Gate with identical 4-channel, 2-input configuration
Output type: Open Collector architecture
Electrical specifications: Supply voltage range (4.75V ~ 5.25V), output current (24mA), input logic levels (0.8V low, 2V high), and propagation delay (32ns @ 5V, 45pF)
Package format: 14-SOIC surface mount with identical physical dimensions
Series classification: 74LS logic family
Compliance standards: ROHS3 compliance, MSL Level 1

The substitute part SN74LS33DR meets all these criteria. The primary distinction is packaging configuration: the main part uses Tube packaging while the substitute uses Tape & Reel (TR) format. Both are identical in electrical performance, pinout, and functional operation.

Parameter Comparison

Parameter	SN74LS33D (Main)	SN74LS33DR (Substitute)
Manufacturer	Texas Instruments	Texas Instruments
Logic Type	NOR Gate	NOR Gate
Number of Circuits	4	4
Number of Inputs	2	2
Features	Open Collector	Open Collector
Voltage - Supply	4.75V ~ 5.25V	4.75V ~ 5.25V
Current - Output High, Low	-, 24mA	-, 24mA
Input Logic Level - Low	0.8V	0.8V
Input Logic Level - High	2V	2V
Max Propagation Delay @ V, Max CL	32ns @ 5V, 45pF	32ns @ 5V, 45pF
Operating Temperature	0°C ~ 70°C	0°C ~ 70°C
Mounting Type	Surface Mount	Surface Mount
Package / Case	14-SOIC (0.154", 3.90mm Width)	14-SOIC (0.154", 3.90mm Width)
Series	74LS	74LS
Product Status	Last Time Buy	Active
Packaging Format	Tube	Tape & Reel (TR)
RoHS Status	ROHS3 Compliant	ROHS3 Compliant
Moisture Sensitivity Level (MSL)	1 (Unlimited)	1 (Unlimited)

Engineering Selection Recommendations

The SN74LS33DR is the direct substitute for SN74LS33D. Both parts are manufactured by Texas Instruments and maintain identical electrical and functional specifications. The SN74LS33DR carries Active product status, ensuring continued availability and manufacturing support, whereas the SN74LS33D is designated Last Time Buy.

Both parts satisfy ROHS3 compliance requirements and carry MSL Level 1 rating, indicating no moisture sensitivity constraints during storage and handling. The substitution is electrically and mechanically transparent—no circuit redesign or board layout modification is required.

The only operational difference is packaging format: Tube versus Tape & Reel. This distinction affects handling, automated assembly compatibility, and inventory management but does not impact electrical performance or functional operation.

Frequently Asked Questions (FAQ)

Q: Can SN74LS33DR be used as a direct replacement for SN74LS33D in existing designs?

A: Yes. The SN74LS33DR is electrically and functionally identical to the SN74LS33D. Pinout, logic operation, electrical specifications, and package dimensions are equivalent. No circuit modifications are required.

Q: What is the difference between Tube and Tape & Reel packaging?

A: Tube packaging supplies components in plastic tubes suitable for manual handling and small-quantity applications. Tape & Reel packaging supplies components on continuous carrier tape wound on reels, optimized for automated pick-and-place assembly equipment. Both formats contain identical components with identical specifications.

Q: Why is SN74LS33D marked as Last Time Buy?

A: Last Time Buy status indicates that Texas Instruments has discontinued production of this part number. Existing inventory may be available from distributors, but no new manufacturing runs are planned. The SN74LS33DR (Active status) is the recommended path forward for new designs and ongoing production.

Q: Are there any compliance or certification differences between these parts?

A: No. Both parts carry identical ROHS3 compliance and MSL Level 1 ratings. Regulatory and environmental certifications are equivalent.

Q: What is the maximum output current for the open collector output?

A: The maximum output current (low state) is 24mA per channel. This specification is identical for both the main part and substitute.

Q: Can these parts operate outside the 0°C to 70°C temperature range?

A: No. Both parts are specified for operation within 0°C to 70°C. Operation outside this range is not supported and may result in functional failure or degraded performance.

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