KA78RM33RTM Linear Voltage Regulator 3.3V 500mA Equivalent & Substitute Parts

Part Overview

The KA78RM33RTM is a linear voltage regulator IC manufactured by onsemi, designed to provide a fixed 3.3V positive output at 500mA maximum current in a surface-mount DPAK package. This device is classified as obsolete, making equivalent and substitute parts necessary for ongoing design support and production continuity. The part operates across an industrial temperature range of -40°C to 125°C and includes integrated protection features for over-current, over-temperature, and short-circuit conditions.

Substiute Parts

KA78RM33RTM

onsemiIn Stock: 10334KA78RM33RTM Datasheet

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BA033CC0FP-E2

Rohm SemiconductorIn Stock: 35204BA033CC0FP-E2 Datasheet

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BD3570YFP-ME2

Rohm SemiconductorIn Stock: 4216BD3570YFP-ME2 Datasheet

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KF33BDT-TR

STMicroelectronicsIn Stock: 37445KF33BDT-TR Datasheet

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L4931ABDT33-TR

STMicroelectronicsIn Stock: 4565L4931ABDT33-TR Datasheet

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L4931CDT33-TR

STMicroelectronicsIn Stock: 10373L4931CDT33-TR Datasheet

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UA78M33IKVURG3

Texas InstrumentsIn Stock: 16712UA78M33IKVURG3 Datasheet

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Key Parameters

Substitute Part Grouping Explanation

Substitution eligibility for the KA78RM33RTM is determined by the following critical parameters:

• Fixed output voltage of 3.3V
• Surface-mount DPAK package (TO-252-3)
• Output current capability of 500mA or greater
• Maximum input voltage of 20V or greater
• Operating temperature range of -40°C to 125°C
• Positive fixed output configuration
• Single regulator topology

Substitute parts must maintain compatibility across these parameters to ensure functional equivalence in existing circuit designs. Parts with lower output current ratings (250mA) are listed for reference but represent downrated alternatives suitable only for reduced-load applications.

Parameter Comparison

Engineering Selection Recommendations

Primary Equivalents (Full 500mA Capability)

KF33BDT-TR (STMicroelectronics) and UA78M33IKVURG3 (Texas Instruments) provide direct functional equivalence to the KA78RM33RTM with identical 500mA output current and matching input voltage specifications. Both devices are active products with RoHS3 compliance and full protection feature sets. KF33BDT-TR maintains the lowest quiescent current at 1mA and offers superior PSRR performance. UA78M33IKVURG3 supports higher input voltage (25V) but exhibits higher dropout voltage at 350mA load conditions.

BD3570YFP-ME2 (Rohm Semiconductor) offers enhanced input voltage tolerance (36V maximum) and exceptional quiescent current performance (50µA), making it suitable for battery-powered or low-standby-current applications while maintaining full 500mA output capability.

BA033CC0FP-E2 (Rohm Semiconductor) provides increased output current capacity (1A) in the same package footprint, offering design margin for future load expansion while maintaining active product status and RoHS3 compliance.

Downrated Alternative (250mA Capability)

L4931ABDT33-TR and L4931CDT33-TR (STMicroelectronics) are suitable only for applications where maximum load current does not exceed 250mA. These parts offer superior PSRR performance and lower quiescent current but represent a 50% reduction in output current capability compared to the original specification.

Frequently Asked Questions (FAQ)

Q: Can BA033CC0FP-E2 be used as a direct replacement for KA78RM33RTM?

A: Yes. BA033CC0FP-E2 is a direct functional equivalent with identical output voltage (3.3V), matching package (TO-252-3), and compatible operating temperature range (-40°C to 125°C). The higher output current rating (1A versus 500mA) provides additional design margin without affecting circuit operation at the original 500mA specification.

Q: What is the difference between KF33BDT-TR and BD3570YFP-ME2?

A: Both devices provide 500mA output current and 3.3V fixed output in TO-252-3 packages. KF33BDT-TR matches the original 20V maximum input voltage specification with 0.7V dropout at 500mA. BD3570YFP-ME2 supports higher input voltage (36V maximum) and features significantly lower quiescent current (50µA versus 1mA), making it preferable for low-power standby applications.

Q: Why are L4931ABDT33-TR and L4931CDT33-TR listed if they only provide 250mA?

A: These parts are included for reference in applications where load current does not exceed 250mA. They offer superior PSRR performance and lower quiescent current but cannot support the full 500mA specification of the original part. Use only if circuit design permits reduced output current.

Q: Are all substitute parts RoHS compliant?

A: All active substitute parts listed (BA033CC0FP-E2, BD3570YFP-ME2, KF33BDT-TR, L4931ABDT33-TR, L4931CDT33-TR, and UA78M33IKVURG3) are RoHS3 compliant. The original KA78RM33RTM is classified as REACH Unaffected.

Q: Can I use UA78M33IKVURG3 in high-current applications?

A: UA78M33IKVURG3 supports the full 500mA output specification. However, note the higher dropout voltage (2V @ 350mA) compared to alternatives. This may impact efficiency in applications with tight input-to-output voltage margins. Verify dropout voltage performance against your specific input voltage and load current requirements.

Q: What is the package compatibility across all parts?

A: All listed parts use the TO-252-3 (DPAK) surface-mount package with identical pinout and footprint. Direct PCB layout substitution is possible without redesign.