LP5951MFX-1.5 Equivalent & Substitute Parts

Part Overview

The LP5951MFX-1.5 is a linear voltage regulator IC from Texas Instruments, delivering a fixed 1.5V output at 150mA in a SOT-23-5 surface mount package. This part is classified as obsolete, making equivalent and substitute parts necessary for new designs and ongoing production requirements. The device provides positive fixed output configuration with integrated enable control and comprehensive protection features including overcurrent, over-temperature, and short-circuit protection.

Key Parameters

Parameter	Value
Manufacturer	Texas Instruments
Part Number	LP5951MFX-1.5
Output Voltage (Fixed)	1.5V
Output Current	150mA
Input Voltage (Max)	5.5V
Voltage Dropout (Max)	0.35V @ 150mA
Quiescent Current	55 µA
Package	SOT-23-5 (SC-74A)
Operating Temperature	-40°C to 125°C
Product Status	Obsolete
RoHS Status	Non-compliant

Substitute Part Grouping Explanation

Substitute parts for the LP5951MFX-1.5 are classified based on the following critical parameters that determine functional equivalence:

Primary Substitution Criteria:

Output voltage: 1.5V fixed
Output current capability: 150mA minimum
Package type: SOT-23-5 compatible
Input voltage rating: 5.5V maximum
Control features: Enable function
Protection: Overcurrent and over-temperature protection

Grouping Logic:

Group 1 - Direct Texas Instruments Equivalents (Active Status): LP5951MF-1.5/NOPB and LP5951MFX-1.5/NOPB are parametrically identical to the main part with identical electrical specifications. Both are active products with RoHS3 compliance, differing only in packaging format (Tape & Reel).

Group 2 - Microchip Technology Alternatives: MIC5306-1.5YD5-TR provides 150mA output with improved dropout voltage (0.2V vs 0.35V) and lower quiescent current (25 µA vs 55 µA). MIC5307-1.5YD5-TR offers higher current capability (300mA) in the same package footprint, suitable for applications requiring additional headroom.

Group 3 - ABLIC Inc. Alternatives: S-1312 series (A/B/C/D variants) deliver 150mA output with SOT-23-5 packaging and active product status. S-1135 series provides 300mA output capacity. All ABLIC parts feature lower quiescent current (1-30 µA) and higher PSRR performance.

Parameter Comparison

Part Number	Manufacturer	Output Voltage	Output Current	Dropout Voltage	Quiescent Current	Package	Status	RoHS
LP5951MFX-1.5	Texas Instruments	1.5V	150mA	0.35V @ 150mA	55 µA	SOT-23-5	Obsolete	Non-compliant
LP5951MF-1.5/NOPB	Texas Instruments	1.5V	150mA	0.35V @ 150mA	55 µA	SOT-23-5	Active	RoHS3
LP5951MFX-1.5/NOPB	Texas Instruments	1.5V	150mA	0.35V @ 150mA	55 µA	SOT-23-5	Active	RoHS3
MIC5306-1.5YD5-TR	Microchip Technology	1.5V	150mA	0.2V @ 150mA	25 µA	TSOT-23-5	Active	RoHS3
MIC5307-1.5YD5-TR	Microchip Technology	1.5V	300mA	0.25V @ 300mA	30 µA	TSOT-23-5	Active	RoHS3
S-1312A15-M5T1U3	ABLIC Inc.	1.5V	150mA	0.47V @ 100mA	30 µA	SOT-23-5	Active	RoHS3
S-1312B15-M5T1U3	ABLIC Inc.	1.5V	150mA	0.47V @ 100mA	30 µA	SOT-23-5	Active	RoHS3
S-1312C15-M5T1U3	ABLIC Inc.	1.5V	150mA	0.47V @ 100mA	30 µA	SOT-23-5	Active	RoHS3
S-1312D15-M5T1U3	ABLIC Inc.	1.5V	150mA	0.47V @ 100mA	30 µA	SOT-23-5	Active	RoHS3
S-1135A15-M5T1U	ABLIC Inc.	1.5V	300mA	Not specified	1 µA	SOT-23-5	Obsolete	RoHS3
S-1135C15-M5T1U	ABLIC Inc.	1.5V	300mA	Not specified	1 µA	SOT-23-5	Obsolete	RoHS3

Engineering Selection Recommendations

For Direct Replacement (Recommended): LP5951MF-1.5/NOPB or LP5951MFX-1.5/NOPB are the primary choices. Both maintain identical electrical performance to the obsolete LP5951MFX-1.5 while offering active product status and RoHS3 compliance. These parts require no design modifications and provide the highest compatibility assurance.

For Improved Performance: MIC5306-1.5YD5-TR offers superior dropout voltage performance (0.2V vs 0.35V) and reduced quiescent current (25 µA vs 55 µA), beneficial for battery-powered or low-power applications. The TSOT-23-5 package is mechanically compatible with SOT-23-5 footprints. This part is active and RoHS3 compliant.

For Higher Current Capability: MIC5307-1.5YD5-TR and S-1135 series (A/C variants) provide 300mA output, doubling the current capacity while maintaining the same package footprint. These options are suitable for applications requiring additional current margin or future design scaling.

For Active Product Status with Compliance: S-1312 series (A/B/C/D variants) from ABLIC Inc. are all active products with RoHS3 compliance, offering 150mA output in SOT-23-5 packaging. These parts feature lower quiescent current (30 µA) and higher PSRR (70dB at 1kHz) compared to the original part.

Compliance Consideration: The original LP5951MFX-1.5 is RoHS non-compliant. All recommended active substitutes (LP5951MF-1.5/NOPB, LP5951MFX-1.5/NOPB, MIC5306-1.5YD5-TR, MIC5307-1.5YD5-TR, and S-1312 series) are RoHS3 compliant, supporting modern manufacturing and regulatory requirements.

Frequently Asked Questions (FAQ)

Q: Can I use MIC5306-1.5YD5-TR as a direct drop-in replacement? A: Yes. MIC5306-1.5YD5-TR is electrically equivalent with identical output voltage (1.5V) and current (150mA) specifications. The TSOT-23-5 package is mechanically compatible with SOT-23-5 footprints. The improved dropout voltage and lower quiescent current provide additional performance benefits.

Q: What is the difference between the S-1312 variants (A/B/C/D)? A: All S-1312 variants (S-1312A15-M5T1U3, S-1312B15-M5T1U3, S-1312C15-M5T1U3, S-1312D15-M5T1U3) share identical electrical specifications: 1.5V output, 150mA current, SOT-23-5 package, and active product status. The variant designations reflect internal design revisions or manufacturing process changes but do not affect functional performance or pin compatibility.

Q: Why would I choose a 300mA part like MIC5307-1.5YD5-TR or S-1135 over a 150mA part? A: Higher current-rated parts provide design margin for applications with variable or future increased load requirements. They operate at lower stress levels under nominal conditions, potentially improving reliability and thermal performance. However, they occupy the same package footprint, so selection depends on application requirements rather than physical constraints.

Q: Are all substitute parts RoHS compliant? A: The active substitute parts (LP5951MF-1.5/NOPB, LP5951MFX-1.5/NOPB, MIC5306-1.5YD5-TR, MIC5307-1.5YD5-TR, and S-1312 series) are RoHS3 compliant. The S-1135 series is also RoHS3 compliant but classified as obsolete. The original LP5951MFX-1.5 is RoHS non-compliant.

Q: What is the operating temperature range difference between parts? A: The original LP5951MFX-1.5 and most active substitutes (LP5951MF-1.5/NOPB, LP5951MFX-1.5/NOPB, MIC5306-1.5YD5-TR, MIC5307-1.5YD5-TR) operate from -40°C to 125°C. ABLIC S-1312 and S-1135 series operate from -40°C to 85°C, which is narrower. Verify application temperature requirements before selection.

Q: Can I use these parts interchangeably in existing designs? A: Parts within the same grouping (Texas Instruments LP5951 variants, Microchip MIC5306/MIC5307, or ABLIC S-1312 variants) are interchangeable for the same output current requirement. Cross-group substitution requires verification of dropout voltage, quiescent current, and operating temperature specifications against application requirements.

Q: What inventory status should I prioritize? A: Active product status ensures long-term availability and ongoing manufacturing support. LP5951MF-1.5/NOPB (17,730 pcs), LP5951MFX-1.5/NOPB (8,755 pcs), and S-1312 series variants (649-906 pcs each) offer the strongest inventory positions for production planning.

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