78ST105SC DC DC Converter 5V Equivalent & Substitute Parts

Part Overview

The Texas Instruments 78ST105SC is a non-isolated point-of-load (PoL) module DC DC converter delivering 5V output at 1.5A maximum current from a 7V to 30V input range. This surface mount component is classified as obsolete product status, necessitating identification of active equivalent and substitute parts for ongoing design support and procurement requirements. The 78ST105SC operates across the commercial ITE (Information Technology Equipment) application space with integrated over-temperature protection (OTP) and short-circuit protection (SCP) features.

Substiute Parts

78ST105SC

Texas InstrumentsIn Stock: 123678ST105SC Datasheet

Current PartRFQ

R-78B5.0-1.5L

Recom PowerIn Stock: 64916R-78B5.0-1.5L Datasheet

MFR RecommendedRFQ

R-78T5.0-1.0/FC-TRAY

Recom PowerIn Stock: 828R-78T5.0-1.0/FC-TRAY Datasheet

MFR RecommendedRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution of the obsolete 78ST105SC requires evaluation against the following critical electrical and mechanical parameters:

Electrical Compatibility Criteria:

• Output voltage specification of 5V (fixed requirement)
• Maximum output current rating of 1.5A or greater
• Input voltage range overlap with 7V – 30V specification
• Operating temperature range of -40°C to 85°C minimum
• Protection features including OTP and SCP

Mechanical Compatibility Criteria:

• Surface mount or through-hole mounting capability
• Package footprint compatibility or functional equivalence
• Physical dimensions suitable for existing PCB layouts

Compliance and Certification:

• RoHS3 compliance
• Moisture Sensitivity Level 1 classification
• REACH unaffected status

Two active substitute parts meet these criteria with varying trade-offs in input voltage range, output current capacity, and mounting technology.

Parameter Comparison

Engineering Selection Recommendations

R-78T5.0-1.0/FC-TRAY (Recom Power)

This non-isolated PoL module maintains architectural equivalence to the 78ST105SC with surface mount technology. The R-78T5.0-1.0/FC-TRAY operates across an extended input voltage range of 8V to 42V, providing superior headroom for higher input voltage applications. Output current is rated at 1A, which is 33% lower than the original 1.5A specification. This substitute is suitable for applications where the 1A output current ceiling is acceptable and extended input voltage range is beneficial. Efficiency improves to 92% compared to the original 85%. The part is ROHS3 compliant with MSL 1 classification and active product status ensures long-term availability.

R-78B5.0-1.5L (Recom Power)

This linear regulator replacement DC DC converter maintains the full 1.5A output current rating of the original part. The R-78B5.0-1.5L operates across a narrower input voltage range of 6.5V to 18V, which encompasses the lower portion of the original 7V to 30V specification. Mounting technology transitions from surface mount to through-hole right-angle configuration, requiring PCB layout modification. Efficiency reaches 94%, the highest among all options. The part includes both OTP and SCP protection features matching the original specification. ROHS3 compliance and MSL 1 classification are maintained. This substitute is appropriate for designs where output current capacity is critical and input voltage remains below 18V.

Selection Basis:

Both substitute parts maintain ROHS3 compliance, MSL 1 moisture sensitivity classification, and REACH unaffected status. Product status transitions from obsolete to active for both alternatives, ensuring procurement continuity. Selection between the two substitutes depends on application-specific requirements: prioritize R-78T5.0-1.0/FC-TRAY for extended input voltage range with reduced output current; prioritize R-78B5.0-1.5L for full output current capacity with constrained input voltage range and modified mounting approach.

Frequently Asked Questions (FAQ)

Q: Can the R-78T5.0-1.0/FC-TRAY directly replace the 78ST105SC in all applications?

A: The R-78T5.0-1.0/FC-TRAY provides direct electrical substitution for applications requiring maximum output current of 1A or less. The 1A output current rating is 33% lower than the original 1.5A specification. Applications demanding the full 1.5A output current require the R-78B5.0-1.5L alternative. Both parts maintain 5V output voltage, -40°C to 85°C operating temperature range, and surface mount capability for the R-78T5.0-1.0/FC-TRAY.

Q: What are the input voltage compatibility differences between the two substitutes?

A: The R-78T5.0-1.0/FC-TRAY accepts 8V to 42V input, extending the upper limit from the original 30V specification. The R-78B5.0-1.5L accepts 6.5V to 18V input, which covers the lower portion of the original 7V to 30V range but does not extend to 30V. Applications operating above 18V input voltage require the R-78T5.0-1.0/FC-TRAY. Applications operating below 18V input voltage can use either substitute based on output current requirements.

Q: Does the R-78B5.0-1.5L require PCB redesign due to mounting type differences?

A: Yes. The R-78B5.0-1.5L uses through-hole right-angle mounting, whereas the original 78ST105SC and the R-78T5.0-1.0/FC-TRAY use surface mount technology. PCB layout modification is necessary to accommodate the different mounting footprint and component orientation. The R-78B5.0-1.5L dimensions are 17.5mm L × 11.5mm W × 8.5mm H compared to the original 23.9mm L × 22.9mm W × 8.6mm H, potentially offering space advantages in certain layout configurations.

Q: Are both substitute parts compliant with the same regulatory standards as the original?

A: Yes. Both R-78T5.0-1.0/FC-TRAY and R-78B5.0-1.5L maintain ROHS3 compliance, Moisture Sensitivity Level 1 (unlimited), and REACH unaffected status identical to the 78ST105SC. Both parts carry EAR99 ECCN classification and 8504.40.9580 HTSUS code matching the original specification.

Q: Which substitute offers better efficiency?

A: The R-78B5.0-1.5L provides the highest efficiency at 94%, compared to 92% for the R-78T5.0-1.0/FC-TRAY and 85% for the original 78ST105SC. Efficiency improvements reduce thermal dissipation and power loss in the converter circuit.

Q: What protection features are included in each substitute?

A: The R-78T5.0-1.0/FC-TRAY includes short-circuit protection (SCP) only. The R-78B5.0-1.5L includes both over-temperature protection (OTP) and short-circuit protection (SCP), matching the original 78ST105SC feature set. Applications requiring OTP functionality must use the R-78B5.0-1.5L or confirm that SCP-only protection is sufficient.

Q: What is the current inventory status of the substitute parts?

A: The R-78T5.0-1.0/FC-TRAY has 771 pieces in stock. The R-78B5.0-1.5L has 64,845 pieces in stock. Both parts are active products with established supply chains, providing long-term procurement security compared to the obsolete 78ST105SC.