LM2940CSX-15 Equivalent & Substitute Parts

Part Overview

The LM2940CSX-15 is a linear voltage regulator IC from Texas Instruments, classified as a positive fixed output power management component. It delivers 1A output current at a fixed 15V output with a maximum dropout voltage of 0.8V at rated load. The device is packaged in TO-263 (DDPAK-3) surface mount configuration and includes integrated protection features for over-current, over-temperature, reverse polarity, and short-circuit conditions.

The LM2940CSX-15 is currently listed as obsolete. Identifying equivalent and substitute parts is necessary to maintain design continuity, ensure supply chain availability, and support ongoing production or maintenance requirements for systems utilizing this regulator.

Substiute Parts

LM2940CSX-15

Texas InstrumentsIn Stock: 5082LM2940CSX-15 Datasheet

Current PartRFQ

UA7815CKTTR

Texas InstrumentsIn Stock: 1981UA7815CKTTR Datasheet

MFR RecommendedRFQ

LM2940CSX-15/NOPB

National SemiconductorIn Stock: 2961LM2940CSX-15/NOPB Datasheet

Parametric EquivalentRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitute parts for the LM2940CSX-15 are identified based on the following critical parameters that determine functional compatibility:

Primary Substitution Criteria:

• Output voltage: 15V fixed
• Package type: TO-263 (DDPAK-3) surface mount
• Output configuration: Positive fixed regulator
• Protection features: Over-current, over-temperature, reverse polarity, and short-circuit protection
• Operating temperature range: 0°C to 125°C

Allowable Parameter Variations:

• Output current: Equal to or greater than 1A
• Input voltage maximum: Equal to or greater than 26V
• Dropout voltage: Equal to or less than 0.8V at rated load
• PSRR: Equal to or greater than 66dB at 120Hz
• Quiescent current: Equal to or less than 10 mA

Two substitute parts meet these criteria and are grouped as follows:

Group 1 - Parametric Equivalent (Recommended for Direct Replacement): LM2940CSX-15/NOPB maintains identical electrical specifications and package configuration, differing only in manufacturer designation (National Semiconductor vs. Texas Instruments).

Group 2 - Functional Substitute (Higher Current Capability): UA7815CKTTR provides equivalent 15V output in the same package with enhanced output current (1.5A) and improved PSRR (78dB), though with increased dropout voltage (2V @ 1A) and higher input voltage rating (30V).

Parameter Comparison

Engineering Selection Recommendations

For Direct Replacement (Preferred): LM2940CSX-15/NOPB is the optimal substitute. It maintains identical electrical performance and package configuration as the original part. Product status is active, ensuring continued availability. This part is recommended when design specifications require exact parameter matching and long-term supply chain stability.

For Applications Requiring Enhanced Current Capability: UA7815CKTTR provides 1.5A output current in the same TO-263 package, suitable for designs where the original 1A specification is marginal or where future current headroom is required. The increased dropout voltage (2V vs. 0.8V) must be evaluated against the application's input voltage margin and thermal dissipation budget. This part carries ROHS3 compliance, addressing regulatory requirements where the original non-compliant part cannot be used.

Compliance Considerations: The original LM2940CSX-15 is RoHS non-compliant. If regulatory compliance is mandatory, UA7815CKTTR (ROHS3 compliant) is the appropriate selection despite the higher dropout voltage penalty.

Frequently Asked Questions (FAQ)

Q: Can LM2940CSX-15/NOPB be used as a direct drop-in replacement? A: Yes. LM2940CSX-15/NOPB is electrically and mechanically identical to the original part. It uses the same TO-263 (DDPAK-3) package and maintains all electrical specifications including 1A output current, 0.8V dropout voltage, and 66dB PSRR. The part is currently in active production status.

Q: What is the key difference between LM2940CSX-15 and UA7815CKTTR? A: Both deliver 15V output in TO-263 packaging. UA7815CKTTR provides higher output current (1.5A vs. 1A) and superior PSRR (78dB vs. 66dB), but exhibits higher dropout voltage (2V vs. 0.8V at 1A). UA7815CKTTR is ROHS3 compliant while the original is not.

Q: Will the higher dropout voltage of UA7815CKTTR affect my circuit? A: The 2V dropout voltage of UA7815CKTTR requires 17V minimum input voltage to maintain 15V output at 1A load, compared to 15.8V for the original part. Verify that your input voltage supply margin accommodates this requirement and that thermal dissipation remains within acceptable limits.

Q: Are all three parts available in the same package? A: Yes. LM2940CSX-15, LM2940CSX-15/NOPB, and UA7815CKTTR are all packaged in TO-263 (DDPAK-3) surface mount configuration with identical pinout and footprint compatibility.

Q: Which substitute should I select for new designs? A: LM2940CSX-15/NOPB is recommended for new designs requiring exact specification matching. If RoHS compliance is mandatory, UA7815CKTTR is the appropriate choice, provided the higher dropout voltage is acceptable for your application.

Q: Can I use UA7815CKTTR in a circuit designed for 1A output? A: Yes. UA7815CKTTR is rated for 1.5A output, so it operates safely at 1A. The higher current rating provides design margin without affecting circuit operation at lower loads.