78ST112TC DC DC Converter Equivalent & Substitute Parts

Part Overview

The 78ST112TC is a non-isolated Point-of-Load (PoL) module DC DC converter manufactured by Texas Instruments, part of the 78ST100 series. This component delivers a fixed 12V output at 1.5A maximum current from a 14.5V to 30V input range, designed for commercial ITE applications. The 78ST112TC is classified as obsolete, necessitating identification of active substitute components that maintain functional compatibility while meeting current procurement and compliance requirements.

Substiute Parts

78ST112TC

Texas InstrumentsIn Stock: 73478ST112TC Datasheet

Current PartRFQ

PTN78000WAZ

Texas InstrumentsIn Stock: 2307PTN78000WAZ Datasheet

MFR RecommendedRFQ

TPS84250RKGT

Texas InstrumentsIn Stock: 1480TPS84250RKGT Datasheet

MFR RecommendedRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution of the 78ST112TC requires identification of non-isolated PoL module DC DC converters capable of delivering 12V output at 1.5A or greater from an input range encompassing 14.5V to 30V. The following criteria determine substitution validity:

Critical Substitution Parameters:

• Output voltage must support 12V operation (fixed or adjustable to 12V)
• Maximum output current must equal or exceed 1.5A
• Input voltage range must fully contain 14.5V to 30V
• Operating temperature range must match or exceed -40°C to 85°C
• Product status must be Active (to ensure continued availability)
• RoHS3 compliance required for regulatory alignment

Identified Substitute Parts:

The PTN78000WAZ and TPS84250RKGT both satisfy these substitution criteria. The PTN78000WAZ provides adjustable output voltage (2.5V to 12.6V) with 1.5A output current and extended input range (7V to 36V). The TPS84250RKGT offers adjustable output voltage (2.5V to 15V) with increased output current capacity (2.5A) and wider input range (7V to 50V).

Parameter Comparison

Engineering Selection Recommendations

PTN78000WAZ Selection Criteria:

The PTN78000WAZ is suitable for direct substitution in applications where the 78ST112TC through-hole form factor can be adapted to surface mount assembly. This part maintains identical output current capacity (1.5A) and operating temperature range. The adjustable output voltage (2.5V to 12.6V) accommodates 12V operation through external resistor configuration. Extended input range (7V to 36V) provides margin beyond the original 14.5V to 30V specification. Active product status ensures long-term availability. Enhanced feature set (OCP, OTP, UVLO) provides additional protection compared to the original part (OTP, SCP). ROHS3 compliance and Active status support current procurement workflows.

TPS84250RKGT Selection Criteria:

The TPS84250RKGT provides the highest performance margin among available substitutes. Increased output current capacity (2.5A versus 1.5A) accommodates future design headroom. Adjustable output voltage (2.5V to 15V) supports 12V operation. Significantly wider input range (7V to 50V) exceeds original specifications. Superior efficiency (96% versus 90%) reduces thermal dissipation. Active product status and ROHS3 compliance ensure regulatory alignment and procurement continuity. Compact 41-BQFN package (11.0mm x 9.0mm x 2.8mm) enables space-constrained applications. Enhanced protection features (OCP, OTP, UVLO) exceed original capabilities.

Packaging Transition Consideration:

Both substitute parts require transition from through-hole (3-SIP) to surface mount assembly. The PTN78000WAZ uses 5-SMD Module packaging, while the TPS84250RKGT uses 41-BQFN Module packaging. PCB layout and assembly process modifications are necessary for either substitute.

Frequently Asked Questions (FAQ)

Q: Can the PTN78000WAZ directly replace the 78ST112TC without circuit modifications?

A: The PTN78000WAZ requires external resistor configuration to set output voltage to 12V, as it provides adjustable output (2.5V to 12.6V) versus the fixed 12V output of the 78ST112TC. Additionally, the transition from through-hole to surface mount packaging requires PCB redesign. Electrical compatibility is confirmed for the specified input and output current ranges.

Q: What is the primary advantage of selecting TPS84250RKGT over PTN78000WAZ?

A: The TPS84250RKGT offers increased output current capacity (2.5A versus 1.5A), superior efficiency (96% versus 91%), and wider input voltage range (7V to 50V versus 7V to 36V). These characteristics provide enhanced performance margin and thermal efficiency for the same 12V output application.

Q: Are both substitute parts RoHS3 compliant?

A: Yes, both PTN78000WAZ and TPS84250RKGT are ROHS3 compliant, matching the compliance status of the original 78ST112TC.

Q: What is the impact of MSL rating differences between the main part and substitutes?

A: The 78ST112TC has MSL rating 1 (Unlimited moisture sensitivity), while both substitutes have MSL rating 3 (168 Hours). Substitute parts require moisture control during storage and handling per IPC-A-610 standards for MSL 3 components. This represents a more stringent handling requirement than the original part.

Q: Can output voltage be adjusted on substitute parts to match the original 12V specification?

A: Yes, both PTN78000WAZ and TPS84250RKGT support external resistor configuration for output voltage adjustment. The PTN78000WAZ adjustable range (2.5V to 12.6V) and TPS84250RKGT adjustable range (2.5V to 15V) both encompass 12V operation. Specific resistor values must be determined from manufacturer datasheets.

Q: What protection features do the substitute parts provide compared to the original?

A: The 78ST112TC provides OTP (Over-Temperature Protection) and SCP (Short Circuit Protection). Both substitutes provide OCP (Over-Current Protection), OTP (Over-Temperature Protection), and UVLO (Under-Voltage Lockout), representing enhanced protection capability.

Q: Is the input voltage range of substitutes compatible with the original 14.5V to 30V specification?

A: Yes, both substitutes fully contain the original input range. PTN78000WAZ input range is 7V to 36V, and TPS84250RKGT input range is 7V to 50V. Both ranges encompass the original 14.5V to 30V specification with additional margin.