LP5951MFX-3.3 Equivalent & Substitute Parts

Part Overview

The LP5951MFX-3.3 is a linear voltage regulator IC manufactured by Texas Instruments, designed to deliver a fixed 3.3V output at 150mA with a maximum dropout voltage of 0.35V. This device operates across an input voltage range up to 5.5V and includes integrated protection features for overcurrent, overtemperature, and short circuit conditions. The part is classified as obsolete, which necessitates identification of active equivalent and substitute components for new designs and ongoing production requirements. Equivalent parts maintain identical electrical and mechanical specifications, while substitute parts provide functional alternatives with modified performance characteristics suitable for specific application requirements.

Key Parameters

Parameter	Value	Unit
Output Voltage (Fixed)	3.3	V
Output Current	150	mA
Input Voltage (Maximum)	5.5	V
Dropout Voltage (Maximum)	0.35	V @ 150mA
Quiescent Current	55	µA
Package Type	SOT-23-5	—
Operating Temperature Range	-40 to 125	°C
Protection Features	Over Current, Over Temperature, Short Circuit	—
Control Features	Enable	—

Substitute Part Grouping Explanation

Substitute parts are classified into two categories based on their relationship to the LP5951MFX-3.3:

Parametric Equivalents maintain identical electrical specifications including output voltage (3.3V), output current (150mA), dropout voltage (0.35V @ 150mA), quiescent current (55µA), operating temperature range (-40°C to 125°C), and SOT-23-5 packaging. These parts differ only in product status (active versus obsolete) or packaging configuration (Tape & Reel versus Cut Tape). Parametric equivalents are direct replacements with no circuit redesign required.

Manufacturer Recommended Substitutes provide functional alternatives with modified electrical characteristics. These parts maintain the 3.3V fixed output voltage and SOT-23-5 package family but differ in one or more of the following parameters: output current capability (200mA to 500mA), dropout voltage (0.15V to 0.22V), quiescent current (16µA to 90µA), or operating temperature range (-40°C to 85°C or 105°C). Selection of manufacturer recommended substitutes depends on application-specific requirements for current capacity, thermal performance, and power efficiency.

Parameter Comparison

Manufacturer Part Number	Manufacturer	Output Voltage (V)	Output Current (mA)	Dropout Voltage (V)	Quiescent Current (µA)	Package	Operating Temp (°C)	Product Status
LP5951MFX-3.3	Texas Instruments	3.3	150	0.35 @ 150mA	55	SOT-23-5	-40 to 125	Obsolete
LP5951MF-3.3	Texas Instruments	3.3	150	0.35 @ 150mA	55	SOT-23-5	-40 to 125	Active
LP5951MF-3.3/NOPB	Texas Instruments	3.3	150	0.35 @ 150mA	55	SOT-23-5	-40 to 125	Active
LP5951MFX-3.3/NOPB	Texas Instruments	3.3	150	0.35 @ 150mA	55	SOT-23-5	-40 to 125	Active
BU33SD2MG-MTR	Rohm Semiconductor	3.3	200	0.15 @ 100mA	80	5-SSOP	-40 to 105	Active
BU33SD5WG-TR	Rohm Semiconductor	3.3	500	0.15 @ 100mA	80	5-SSOP	-40 to 105	Active
BU33UC3WG-TR	Rohm Semiconductor	3.3	300	0.22 @ 300mA	90	5-SSOP	-40 to 85	Not For New Designs
MIC5365-3.3YD5-T5	Microchip Technology	3.3	150	0.31 @ 150mA	39	TSOT-23-5	-40 to 125	Active
MIC5365-3.3YD5-TR	Microchip Technology	3.3	150	0.31 @ 150mA	39	TSOT-23-5	-40 to 125	Active
NCP702SN33T1G	onsemi	3.3	200	Not Specified	16	5-TSOP	-40 to 125	Active
NCV8702SN33T1G	onsemi	3.3	200	0.2 @ 200mA	16	5-TSOP	-40 to 125	Active

Engineering Selection Recommendations

Direct Replacement (Parametric Equivalents):

For applications requiring identical electrical and thermal performance with no circuit modifications, select from the active parametric equivalents: LP5951MF-3.3, LP5951MF-3.3/NOPB, or LP5951MFX-3.3/NOPB. All three parts are manufactured by Texas Instruments and maintain the original specifications of the obsolete LP5951MFX-3.3. The LP5951MF-3.3/NOPB variant offers the highest inventory availability (35,100 units) and carries RoHS3 compliance certification. The /NOPB designation indicates lead-free, halogen-free manufacturing in compliance with current environmental standards.

Higher Current Capacity Substitutes:

Applications requiring output current exceeding 150mA should consider the Rohm Semiconductor BU33SD2MG-MTR (200mA) or BU33SD5WG-TR (500mA). Both devices maintain the 3.3V output voltage and feature improved dropout voltage performance (0.15V @ 100mA). The BU33SD2MG-MTR carries AEC-Q100 automotive qualification and operates to 105°C. The BU33SD5WG-TR provides maximum current capacity with 20,200 units in stock. Operating temperature range is limited to -40°C to 105°C, which is acceptable for most industrial and commercial applications.

Low Quiescent Current Substitutes:

Applications prioritizing power efficiency and low standby current consumption should select the Microchip Technology MIC5365-3.3YD5-TR or onsemi NCV8702SN33T1G. The MIC5365 series maintains 150mA output current with reduced quiescent current (39µA) and improved PSRR performance (80dB to 65dB across 1kHz to 10kHz). The NCV8702SN33T1G provides the lowest quiescent current (16µA) at 200mA output capacity with AEC-Q100 automotive qualification. Both parts maintain the full -40°C to 125°C operating range.

Compliance and Certification:

All recommended active substitutes carry RoHS3 compliance certification. The BU33SD2MG-MTR and NCV8702SN33T1G include AEC-Q100 automotive qualification for applications requiring automotive-grade reliability. The BU33UC3WG-TR is designated "Not For New Designs" and should be avoided for new product development.

Frequently Asked Questions (FAQ)

Q: Can LP5951MF-3.3 be used as a direct replacement for LP5951MFX-3.3?

A: Yes. The LP5951MF-3.3 is a parametric equivalent with identical electrical specifications (3.3V output, 150mA current, 0.35V dropout, 55µA quiescent current) and SOT-23-5 packaging. The primary difference is product status: LP5951MF-3.3 is active while LP5951MFX-3.3 is obsolete. No circuit modifications are required.

Q: What is the difference between LP5951MF-3.3 and LP5951MF-3.3/NOPB?

A: Both parts are parametric equivalents with identical electrical performance. The /NOPB designation indicates lead-free, halogen-free manufacturing. LP5951MF-3.3/NOPB carries RoHS3 compliance certification and is recommended for new designs. Inventory availability is significantly higher for the /NOPB variant (35,100 units versus 3,200 units).

Q: Can I use MIC5365-3.3YD5-TR as a direct replacement?

A: MIC5365-3.3YD5-TR is functionally compatible with identical output voltage (3.3V), output current (150mA), and operating temperature range (-40°C to 125°C). The package type differs (TSOT-23-5 versus SOT-23-5), requiring PCB layout verification. Dropout voltage is slightly lower (0.31V versus 0.35V), and quiescent current is reduced (39µA versus 55µA), resulting in improved power efficiency. No circuit modifications are required if PCB footprint accommodates the TSOT-23-5 package.

Q: When should I select BU33SD5WG-TR over the original LP5951MFX-3.3?

A: Select BU33SD5WG-TR when application requirements exceed 150mA output current. This device provides 500mA capacity with improved dropout voltage (0.15V @ 100mA) and is suitable for applications requiring higher power delivery. Operating temperature range is -40°C to 105°C, which is acceptable for most industrial applications. The 5-SSOP package requires PCB layout modification.

Q: What is the advantage of NCV8702SN33T1G over LP5951MFX-3.3?

A: NCV8702SN33T1G provides 200mA output current (versus 150mA) with significantly reduced quiescent current (16µA versus 55µA), resulting in lower power consumption during standby operation. The device includes AEC-Q100 automotive qualification and maintains the full -40°C to 125°C operating range. Dropout voltage is 0.2V @ 200mA. The 5-TSOP package requires PCB layout verification.

Q: Are all substitute parts RoHS compliant?

A: All active substitute parts listed carry RoHS3 compliance certification. The original LP5951MFX-3.3 is RoHS non-compliant. For applications requiring RoHS compliance, select from the active parametric equivalents (LP5951MF-3.3/NOPB, LP5951MFX-3.3/NOPB) or manufacturer recommended substitutes (all Rohm, Microchip, and onsemi variants).

Q: Can I use BU33UC3WG-TR as a substitute?

A: BU33UC3WG-TR is designated "Not For New Designs" and should not be selected for new product development. This part is retained in inventory for legacy system support only. Select alternative active parts such as BU33SD2MG-MTR or BU33SD5WG-TR for new designs.

Q: What package considerations apply when selecting substitutes?

A: The original LP5951MFX-3.3 uses SOT-23-5 packaging. Parametric equivalents (LP5951MF-3.3, LP5951MF-3.3/NOPB, LP5951MFX-3.3/NOPB) maintain identical SOT-23-5 packaging and require no PCB modification. Rohm Semiconductor substitutes use 5-SSOP packaging. Microchip MIC5365 variants use TSOT-23-5 (thin SOT-23-5) packaging. onsemi NCP702 and NCV8702 variants use 5-TSOP packaging. PCB footprint verification is required for all non-SOT-23-5 substitutes.

Q: Which substitute offers the best power efficiency?

A: NCV8702SN33T1G provides the lowest quiescent current (16µA) for minimal standby power consumption. MIC5365-3.3YD5-TR offers moderate quiescent current reduction (39µA) with improved PSRR performance. For applications prioritizing efficiency during active operation, BU33SD2MG-MTR and BU33SD5WG-TR feature lower dropout voltage (0.15V @ 100mA) compared to the original part (0.35V @ 150mA).

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