REG103FA-3/500 Equivalent & Substitute Parts

Part Overview

The REG103FA-3/500 is a linear voltage regulator IC from Texas Instruments designed for positive fixed 3V output at 500mA in a TO-263 (DDPAK-5) surface mount package. This device is classified as obsolete, making identification of suitable substitute components essential for ongoing design support and production continuity. The regulator features integrated over-current and over-temperature protection with an enable control function, suitable for applications requiring stable 3V regulation from input sources up to 15V.

Key Parameters

Parameter	Value
Manufacturer	Texas Instruments
Part Number	REG103FA-3/500
Output Voltage (Fixed)	3V
Output Current	500mA
Input Voltage (Max)	15V
Voltage Dropout (Max)	0.28V @ 500mA
Package Type	TO-263 (DDPAK-5)
Mounting Type	Surface Mount
Operating Temperature Range	-40°C to 85°C
Protection Features	Over Current, Over Temperature
Control Features	Enable
Product Status	Obsolete
RoHS Compliance	ROHS3 Compliant

Substitute Part Grouping Explanation

Substitution of the REG103FA-3/500 is determined by the following critical parameters:

Output voltage compatibility (3V fixed output)
Output current capability (minimum 500mA required)
Package type (TO-263 DDPAK-5 surface mount)
Input voltage rating (15V maximum)
Protection features (over-current and over-temperature)
Control features (enable function)
Operating temperature range (-40°C to 85°C)
RoHS compliance status

The REG104FA-3.3/500 qualifies as a direct substitute based on identical package type, matching input voltage rating, equivalent protection and control features, and compatible operating temperature range. While the output voltage differs (3.3V vs 3V) and output current capability is higher (1A vs 500mA), these parameters represent functional improvements that maintain backward compatibility in applications where 3.3V regulation is acceptable.

Parameter Comparison

Parameter	REG103FA-3/500	REG104FA-3.3/500
Manufacturer	Texas Instruments	Texas Instruments
Output Voltage (Fixed)	3V	3.3V
Output Current	500mA	1A
Input Voltage (Max)	15V	15V
Voltage Dropout (Max)	0.28V @ 500mA	0.48V @ 1A
Quiescent Current (Iq)	0.7 mA	0.7 mA
PSRR	65dB (120Hz)	65dB (120Hz)
Package Type	TO-263 (DDPAK-5)	TO-263 (DDPAK-5)
Mounting Type	Surface Mount	Surface Mount
Operating Temperature Range	-40°C to 85°C	-40°C to 85°C
Protection Features	Over Current, Over Temperature	Over Current, Over Temperature
Control Features	Enable	Enable
RoHS Compliance	ROHS3 Compliant	ROHS3 Compliant
Product Status	Obsolete	Last Time Buy

Engineering Selection Recommendations

The REG104FA-3.3/500 is the identified substitute for the obsolete REG103FA-3/500. Selection of this alternative is supported by:

Identical package footprint (TO-263 DDPAK-5) enabling direct PCB compatibility
Matching input voltage specification (15V maximum)
Equivalent protection architecture (over-current and over-temperature)
Identical enable control functionality
Identical operating temperature range (-40°C to 85°C)
ROHS3 compliance maintained
Higher current capability (1A vs 500mA) provides design margin
Last Time Buy status provides extended procurement window compared to the obsolete REG103FA-3/500

The primary design consideration is the output voltage difference (3.3V vs 3V). Applications requiring strict 3V regulation must evaluate circuit tolerance to 3.3V operation. The REG104FA-3.3/500 is available in higher inventory quantities (1631 pcs) compared to the REG103FA-3/500 (844 pcs), supporting production continuity.

Frequently Asked Questions (FAQ)

Q: Can the REG104FA-3.3/500 directly replace the REG103FA-3/500 on the PCB?

A: Yes. Both devices use identical TO-263 (DDPAK-5) package geometry with matching pin assignments, enabling direct PCB substitution without layout modifications.

Q: What is the impact of the 0.3V output voltage difference (3V to 3.3V)?

A: Circuit tolerance to 3.3V operation must be evaluated. Applications designed for 3V nominal operation with adequate voltage margin can typically accommodate 3.3V regulation. Downstream components must be rated for 3.3V maximum input.

Q: Does the higher output current rating (1A vs 500mA) affect compatibility?

A: No. Higher current capability represents a functional improvement. The REG104FA-3.3/500 can supply the same 500mA required by the original design with additional headroom for future requirements.

Q: Are there packaging differences between these parts?

A: Both parts are supplied in TO-263 (DDPAK-5) surface mount packages. The REG104FA-3.3/500 is available in Tape & Reel (TR) packaging, while the REG103FA-3/500 packaging format is not specified in the provided data.

Q: What is the significance of the product status difference?

A: The REG103FA-3/500 is classified as obsolete, indicating end-of-life status with no further production. The REG104FA-3.3/500 is Last Time Buy, indicating limited future availability but extended procurement window compared to obsolete status.

Q: Are there compliance or certification differences?

A: Both parts maintain ROHS3 compliance and identical REACH status (REACH Unaffected). No compliance barriers exist for substitution.

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