LP5951MFX-1.3 Equivalent & Substitute Parts

Part Overview

The LP5951MFX-1.3 is a linear voltage regulator IC from Texas Instruments designed for positive fixed 1.3V output at 150mA in SOT-23-5 surface mount packaging. This part is classified as obsolete, making equivalent and substitute parts necessary for new designs and ongoing production support. The device provides regulated 1.3V output with integrated protection features including overcurrent, over-temperature, and short-circuit protection, suitable for low-power applications requiring stable voltage regulation.

Key Parameters

Parameter	Value
Manufacturer	Texas Instruments
Part Number	LP5951MFX-1.3
Category	Power Management (PMIC)
Output Voltage (Fixed)	1.3V
Output Current	150mA
Input Voltage (Max)	5.5V
Dropout Voltage (Max)	0.35V @ 150mA
Quiescent Current	55 µA
Package	SOT-23-5 (SC-74A)
Operating Temperature	-40°C ~ 125°C
Product Status	Obsolete
RoHS Status	RoHS non-compliant

Substitute Part Grouping Explanation

Substitute parts for the LP5951MFX-1.3 are grouped based on the following critical parameters that determine functional equivalence:

Primary Substitution Criteria:

Output voltage: 1.3V fixed
Output current capability: 150mA minimum
Input voltage range: 5.5V maximum
Package type: SOT-23-5 surface mount
Output configuration: Positive fixed regulator
Control features: Enable function
Protection features: Overcurrent and thermal protection

Substitution Groups:

Group 1 - Direct Parametric Equivalents (Texas Instruments): LP5951MF-1.3/NOPB and LP5951MFX-1.3/NOPB are direct parametric equivalents with identical electrical specifications to the main part. These differ only in packaging format (Tape & Reel) and product status (Active vs. Obsolete). Both maintain the same 0.35V dropout voltage at 150mA and 55 µA quiescent current.

Group 2 - Manufacturer Recommended Alternatives (ABLIC Inc. S-1312 Series): S-1312A13-M5T1U3, S-1312B13-M5T1U3, S-1312C13-M5T1U3, and S-1312D13-M5T1U3 are ABLIC equivalents with identical output voltage and current ratings. These parts feature lower quiescent current (30 µA vs. 55 µA) and higher PSRR (70dB at 1kHz). Dropout voltage is 0.56V @ 100mA, which is higher than the main part. Operating temperature range is -40°C ~ 85°C.

Group 3 - Higher Current Alternatives (ABLIC Inc. S-1313 Series): S-1313A13-M5T1U3, S-1313B13-M5T1U3, S-1313C13-M5T1U3, and S-1313D13-M5T1U3 provide 175mA output current capability with 1.3V fixed output. These parts feature significantly lower quiescent current (1.35 µA) and higher dropout voltage (1.11V @ 100mA). Operating temperature range is -40°C ~ 85°C.

Parameter Comparison

Parameter	LP5951MFX-1.3	LP5951MF-1.3/NOPB	LP5951MFX-1.3/NOPB	S-1312 Series	S-1313 Series
Manufacturer	Texas Instruments	Texas Instruments	Texas Instruments	ABLIC Inc.	ABLIC Inc.
Output Voltage	1.3V	1.3V	1.3V	1.3V	1.3V
Output Current	150mA	150mA	150mA	150mA	175mA
Input Voltage (Max)	5.5V	5.5V	5.5V	5.5V	5.5V
Dropout Voltage (Max)	0.35V @ 150mA	0.35V @ 150mA	0.35V @ 150mA	0.56V @ 100mA	1.11V @ 100mA
Quiescent Current	55 µA	55 µA	55 µA	30 µA	1.35 µA
PSRR	60dB ~ 50dB (100Hz ~ 10kHz)	60dB ~ 50dB (100Hz ~ 10kHz)	60dB ~ 50dB (100Hz ~ 10kHz)	70dB (1kHz)	Not specified
Operating Temperature	-40°C ~ 125°C	-40°C ~ 125°C	-40°C ~ 125°C	-40°C ~ 85°C	-40°C ~ 85°C
Package	SOT-23-5	SOT-23-5	SOT-23-5	SOT-23-5	SOT-23-5
Product Status	Obsolete	Active	Active	Active	Active
RoHS Status	RoHS non-compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant

Engineering Selection Recommendations

For Direct Replacement (Identical Specifications): LP5951MF-1.3/NOPB and LP5951MFX-1.3/NOPB are the primary choices for direct substitution. Both are active products with ROHS3 compliance, addressing the obsolescence and compliance issues of the original LP5951MFX-1.3. These maintain identical electrical performance including 0.35V dropout voltage and 55 µA quiescent current. The only difference is packaging format (Tape & Reel vs. standard packaging).

For Designs with Extended Temperature Requirements: The LP5951MFX-1.3 operates to 125°C, while ABLIC alternatives operate to 85°C maximum. If the full -40°C ~ 125°C range is required, Texas Instruments parts (LP5951MF-1.3/NOPB or LP5951MFX-1.3/NOPB) are necessary.

For Low-Power Applications (S-1312 Series): ABLIC S-1312 variants offer reduced quiescent current (30 µA) and improved PSRR (70dB at 1kHz) compared to the original part. These are suitable when lower standby power consumption is beneficial. The higher dropout voltage (0.56V @ 100mA) must be evaluated against application requirements.

For Current Margin Applications (S-1313 Series): ABLIC S-1313 variants provide 175mA output current with ultra-low quiescent current (1.35 µA). These are appropriate for designs requiring additional current headroom or where minimizing quiescent current is critical. The significantly higher dropout voltage (1.11V @ 100mA) requires careful thermal and power budget analysis.

For Compliance-Critical Applications: All active substitute parts (Texas Instruments and ABLIC) are ROHS3 compliant, addressing regulatory requirements that the obsolete LP5951MFX-1.3 does not meet.

Frequently Asked Questions (FAQ)

Q: Can I use LP5951MF-1.3/NOPB as a direct drop-in replacement for LP5951MFX-1.3?

A: Yes. LP5951MF-1.3/NOPB is a parametric equivalent with identical electrical specifications. The primary difference is packaging format (Tape & Reel). Both are SOT-23-5 surface mount packages with identical pinout, output voltage, current rating, and protection features. Verify your assembly process accommodates the Tape & Reel format.

Q: What is the key difference between the S-1312 and S-1313 series?

A: The S-1312 series maintains 150mA output current with 30 µA quiescent current and 0.56V dropout voltage. The S-1313 series increases output current to 175mA with ultra-low 1.35 µA quiescent current but has significantly higher dropout voltage (1.11V @ 100mA). Select based on current requirements and acceptable voltage drop in your application.

Q: Why is the operating temperature range different for ABLIC parts?

A: ABLIC S-1312 and S-1313 series are rated to -40°C ~ 85°C, while Texas Instruments LP5951 variants extend to 125°C. If your application requires operation above 85°C, use Texas Instruments parts. For applications within -40°C ~ 85°C, ABLIC parts are suitable.

Q: Are all substitute parts RoHS compliant?

A: All active substitute parts (LP5951MF-1.3/NOPB, LP5951MFX-1.3/NOPB, and all ABLIC S-1312/S-1313 variants) are ROHS3 compliant. The original LP5951MFX-1.3 is RoHS non-compliant. Use active substitutes for new designs and applications with RoHS requirements.

Q: What is the impact of higher dropout voltage in ABLIC parts?

A: Dropout voltage determines the minimum input-to-output voltage differential required for regulation. The S-1312 series (0.56V @ 100mA) and S-1313 series (1.11V @ 100mA) require higher input voltages compared to the original part (0.35V @ 150mA). Verify your input voltage supply can accommodate the higher dropout voltage without exceeding maximum input voltage (5.5V) or causing output voltage sag.

Q: Can I substitute S-1313 for applications originally designed for LP5951MFX-1.3?

A: S-1313 variants are functionally compatible for 1.3V output regulation in SOT-23-5 packages. However, the higher dropout voltage (1.11V @ 100mA) and lower operating temperature maximum (85°C vs. 125°C) must be evaluated. Use S-1313 only if your application can tolerate these parameter differences and does not require the full -40°C ~ 125°C temperature range.

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

A: LP5951MFX-1.3/NOPB has 2,459 pieces in stock. LP5951MF-1.3/NOPB has 2,359 pieces. ABLIC S-1312 variants range from 791 to 3,809 pieces. ABLIC S-1313 variants range from 793 to 21,156 pieces. Verify current availability with your supplier for production requirements.

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