78ST133SC DC DC Converter 3.3V Equivalent & Substitute Parts

Part Overview

The Texas Instruments 78ST133SC is a non-isolated point-of-load (PoL) module DC DC converter delivering 3.3V at 1.5A output from a 7V to 26V input range. This component is classified as obsolete, necessitating identification of active equivalent and substitute parts for new designs and ongoing production requirements. The 78ST133SC operates across the commercial ITE (Information Technology Equipment) application space with integrated over-temperature protection (OTP) and short-circuit protection (SCP) features.

Substiute Parts

78ST133SC

Texas InstrumentsIn Stock: 79478ST133SC Datasheet

Current PartRFQ

R-78B3.3-1.5L

Recom PowerIn Stock: 12496R-78B3.3-1.5L Datasheet

MFR RecommendedRFQ

R-78T3.3-1.0/FC-TRAY

Recom PowerIn Stock: 770R-78T3.3-1.0/FC-TRAY Datasheet

MFR RecommendedRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution of the 78ST133SC is determined by alignment across the following critical parameters:

Output Specification Alignment: All substitute parts must deliver 3.3V output at current levels compatible with or exceeding the 1.5A maximum output requirement of the original part.

Input Voltage Compatibility: Substitute parts must accept the 7V to 26V input range specified for the 78ST133SC. Parts with narrower input ranges or lower maximum input voltages are not direct substitutes.

Topology and Protection: The original part is a non-isolated PoL module with OTP and SCP protection. Substitute parts must maintain equivalent protection features and topology classification.

Operating Temperature Range: All substitute parts must support the -40°C to 85°C operating temperature range.

Compliance and Regulatory Status: Substitute parts must maintain ROHS3 compliance and REACH unaffected status to ensure regulatory continuity.

Mounting and Package Considerations: While the original part uses surface mount 3-SMD packaging, substitute parts may employ alternative mounting technologies (through-hole or surface mount) provided they are physically compatible with the target application.

Parameter Comparison

Engineering Selection Recommendations

R-78B3.3-1.5L (Recom Power): This substitute part is classified as active and maintains full compliance with ROHS3 and REACH requirements. It delivers the identical 3.3V output at 1.5A maximum current, matching the original part's output specification. The R-78B3.3-1.5L incorporates both OTP and SCP protection features. The input voltage range (4.75V to 18V) is narrower than the original part; applications requiring operation above 18V input are not suitable for this substitute. The through-hole, right-angle mounting configuration differs from the original surface-mount package, requiring PCB layout modification. Efficiency is improved at 91% compared to the original 80%.

R-78T3.3-1.0/FC-TRAY (Recom Power): This substitute part is classified as active and maintains full compliance with ROHS3 and REACH requirements. It maintains the non-isolated PoL module topology and surface-mount configuration of the original part. The R-78T3.3-1.0/FC-TRAY accepts a wider input voltage range (7V to 42V), extending the upper operating limit beyond the original specification. The maximum output current is reduced to 1.0A, which is lower than the original 1.5A specification. This part incorporates SCP protection but does not include OTP protection. Efficiency is 88%, representing an 8% improvement over the original part.

Compliance Continuity: Both substitute parts maintain ROHS3 compliance and REACH unaffected status, ensuring regulatory alignment with the original 78ST133SC across commercial ITE applications.

Frequently Asked Questions (FAQ)

Q: Can the R-78B3.3-1.5L replace the 78ST133SC in all applications?

A: The R-78B3.3-1.5L provides identical output specifications (3.3V at 1.5A) and includes both OTP and SCP protection. However, its input voltage range (4.75V to 18V) is narrower than the original part (7V to 26V). Applications requiring input voltages above 18V must use an alternative substitute. Additionally, the through-hole mounting configuration requires PCB redesign compared to the original surface-mount package.

Q: What is the key difference between the two substitute parts?

A: The R-78B3.3-1.5L is a linear regulator replacement with through-hole mounting and full 1.5A output current capability. The R-78T3.3-1.0/FC-TRAY is a non-isolated PoL module with surface-mount configuration, wider input voltage range (7V to 42V), but reduced output current (1.0A maximum). The R-78B3.3-1.5L includes OTP protection; the R-78T3.3-1.0/FC-TRAY does not.

Q: Which substitute part maintains the closest physical compatibility with the original 78ST133SC?

A: The R-78T3.3-1.0/FC-TRAY maintains surface-mount configuration and non-isolated PoL module topology identical to the original part. The R-78B3.3-1.5L requires through-hole mounting, necessitating PCB layout changes.

Q: Can I use the R-78T3.3-1.0/FC-TRAY if my application requires 1.5A output?

A: No. The R-78T3.3-1.0/FC-TRAY is rated for 1.0A maximum output current, which is insufficient for applications requiring the full 1.5A specification of the original 78ST133SC. The R-78B3.3-1.5L provides the required 1.5A output capacity.

Q: Are both substitute parts suitable for the -40°C to 85°C operating temperature range?

A: Yes. Both the R-78B3.3-1.5L and R-78T3.3-1.0/FC-TRAY support the full -40°C to 85°C operating temperature range specified for the original 78ST133SC.

Q: What protection features does each substitute part provide?

A: The R-78B3.3-1.5L includes both over-temperature protection (OTP) and short-circuit protection (SCP), matching the original part. The R-78T3.3-1.0/FC-TRAY includes short-circuit protection (SCP) only and does not include OTP protection.

Q: Do both substitute parts maintain regulatory compliance with the original part?

A: Yes. Both the R-78B3.3-1.5L and R-78T3.3-1.0/FC-TRAY are ROHS3 compliant and REACH unaffected, maintaining regulatory continuity with the original 78ST133SC for commercial ITE applications.