LP2951CMX Equivalent & Substitute Parts

Part Overview

The LP2951CMX is a linear voltage regulator IC from Texas Instruments, classified as a positive adjustable (fixed) output regulator with 100mA output capability in an 8-SOIC surface mount package. This component is currently marked as obsolete, making equivalent and substitute parts necessary for ongoing design support and production continuity. The part delivers 1.235V to 29V adjustable output with 0.6V maximum dropout at 100mA and includes over-current, over-temperature, and short-circuit protection features.

Key Parameters

Parameter	Value
Output Configuration	Positive
Output Type	Adjustable (Fixed)
Number of Regulators	1
Voltage - Input (Max)	30V
Voltage - Output (Min/Fixed)	1.235V (5V)
Voltage - Output (Max)	29V
Voltage Dropout (Max)	0.6V @ 100mA
Current - Output	100mA
Current - Quiescent (Iq)	120 µA
Operating Temperature	-40°C ~ 125°C (TJ)
Mounting Type	Surface Mount
Package / Case	8-SOIC (0.154", 3.90mm Width)
Protection Features	Over Current, Over Temperature, Short Circuit
Control Features	Enable

Substitute Part Grouping Explanation

Substitution for the LP2951CMX is determined by strict alignment of electrical and mechanical parameters. The primary substitution criteria are:

Electrical Compatibility Requirements:

Output configuration: Positive
Output type: Adjustable (Fixed)
Voltage input maximum: 30V
Voltage output range: 1.235V to 29V minimum
Output current: 100mA minimum
Dropout voltage: 0.6V @ 100mA maximum
Operating temperature: -40°C to 125°C

Mechanical Compatibility Requirements:

Mounting type: Surface Mount
Package type: 8-SOIC or equivalent footprint (0.154", 3.90mm width)
Moisture sensitivity level: 1 (Unlimited)

Substitute parts are grouped into two categories: parametric equivalents (identical electrical specifications) and manufacturer-recommended alternatives (functionally compatible with minor parameter variations).

Parameter Comparison

Part Number	Manufacturer	Output Type	Voltage Input (Max)	Voltage Output (Min)	Current Output	Dropout @ 100mA	Iq (µA)	Package	Product Status	RoHS Status
LP2951CMX	Texas Instruments	Adjustable (Fixed)	30V	1.235V	100mA	0.6V	120	8-SOIC	Obsolete	RoHS non-compliant
LP2951ACMX	Texas Instruments	Adjustable (Fixed)	30V	1.235V	100mA	0.6V	120	8-SOIC	Last Time Buy	ROHS3 Compliant
LP2951ACMX/NOPB	Texas Instruments	Adjustable (Fixed)	30V	1.235V	100mA	0.6V	120	8-SOIC	Active	ROHS3 Compliant
LP2951CMX/NOPB	Texas Instruments	Adjustable (Fixed)	30V	1.235V	100mA	0.6V	120	8-SOIC	Active	ROHS3 Compliant
LP2951-02YM	Microchip Technology	Adjustable (Fixed)	30V	1.24V	100mA	0.6V	150	8-SOIC	Active	ROHS3 Compliant
LP2951-02YM-TR	Microchip Technology	Adjustable (Fixed)	30V	1.24V	100mA	0.6V	150	8-SOIC	Active	ROHS3 Compliant
LP2951-03YM	Microchip Technology	Adjustable (Fixed)	30V	1.24V	100mA	0.6V	150	8-SOIC	Active	ROHS3 Compliant
LP2951-03YM-TR	Microchip Technology	Adjustable (Fixed)	30V	1.24V	100mA	0.6V	150	8-SOIC	Active	ROHS3 Compliant
LP2951ACDMR2G	onsemi	Adjustable (Fixed)	30V	1.235V	100mA	0.45V	120	8-MSOP	Active	ROHS3 Compliant
L4931CD50-TR	STMicroelectronics	Fixed	20V	5V	250mA	0.8V	1000	8-SOIC	Active	ROHS3 Compliant

Engineering Selection Recommendations

Tier 1 - Direct Parametric Equivalents (Recommended for Direct Replacement):

LP2951ACMX/NOPB and LP2951CMX/NOPB from Texas Instruments are the primary substitutes. Both maintain identical electrical specifications to the LP2951CMX while offering active product status and ROHS3 compliance. LP2951ACMX/NOPB is preferred due to active status and highest inventory availability (27,395 units).

Tier 2 - Functional Equivalents (Microchip Technology):

LP2951-02YM, LP2951-02YM-TR, LP2951-03YM, and LP2951-03YM-TR from Microchip Technology are functionally compatible. These parts maintain the same voltage input/output ranges, output current, and dropout specifications. Quiescent current is slightly higher (150 µA vs. 120 µA). All variants are active products with ROHS3 compliance. Packaging variants include Tube (LP2951-02YM, LP2951-03YM) and Cut Tape/Digi-Reel (LP2951-02YM-TR, LP2951-03YM-TR).

Tier 3 - Alternative Package Option:

LP2951ACDMR2G from onsemi provides identical electrical performance in an 8-MSOP package (0.118", 3.00mm width). This part features improved dropout voltage (0.45V vs. 0.6V) and lower supply current (12 mA vs. 14 mA). Use only if 8-MSOP footprint is acceptable in your design.

Not Recommended for Direct Substitution:

L4931CD50-TR from STMicroelectronics is a fixed 5V output regulator with 250mA capability. While it shares the 8-SOIC package and operating temperature range, it does not support adjustable output voltage and has different electrical characteristics (20V input maximum, 1mA quiescent current). This part is suitable only for applications requiring fixed 5V regulation with higher current capacity.

Frequently Asked Questions (FAQ)

Q: Can I use LP2951ACMX/NOPB as a direct replacement for LP2951CMX?

A: Yes. LP2951ACMX/NOPB is a parametric equivalent with identical electrical specifications (30V input, 1.235V to 29V output, 100mA, 0.6V dropout, 120 µA quiescent current) and the same 8-SOIC package. The primary difference is product status (Active vs. Obsolete) and RoHS compliance (ROHS3 vs. non-compliant). No circuit modifications are required.

Q: What is the difference between LP2951-02YM and LP2951-02YM-TR?

A: Both parts are electrically identical. The difference is packaging: LP2951-02YM is supplied in Tube packaging, while LP2951-02YM-TR is supplied in Cut Tape with Digi-Reel. Select based on your procurement and assembly requirements.

Q: Why is the quiescent current higher in Microchip parts (150 µA vs. 120 µA)?

A: This is a manufacturing difference between Texas Instruments and Microchip Technology implementations of the LP2951 design. Both values are within acceptable limits for most applications. Verify against your specific power budget requirements.

Q: Can I use LP2951ACDMR2G if my PCB layout uses 8-SOIC footprint?

A: No. LP2951ACDMR2G uses an 8-MSOP package (0.118", 3.00mm width) which has a different footprint than 8-SOIC (0.154", 3.90mm width). PCB layout modification is required. Use this part only if your design can accommodate the smaller MSOP package.

Q: Is L4931CD50-TR a suitable replacement?

A: No. L4931CD50-TR is a fixed 5V output regulator, not adjustable. It is suitable only for applications requiring fixed 5V regulation with higher current capacity (250mA). It cannot replace the LP2951CMX in adjustable voltage applications.

Q: Which substitute has the best availability?

A: LP2951CMX/NOPB has the highest inventory (57,671 units), followed by LP2951ACMX/NOPB (27,395 units). Both are active products from Texas Instruments with immediate availability.

Q: Are all substitutes RoHS3 compliant?

A: All recommended substitutes except the original LP2951CMX are ROHS3 compliant. If RoHS compliance is required for your application, select from the Tier 1 or Tier 2 alternatives.

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