LP3981IMMX-3.3 Linear Voltage Regulator IC Equivalent & Substitute Parts

Part Overview

The LP3981IMMX-3.3 is a linear voltage regulator IC from Texas Instruments designed for positive fixed 3.3V output applications with 300mA current capacity in an 8-VSSOP surface mount package. This part is classified as Obsolete, making identification of equivalent and substitute parts essential for ongoing design support and production continuity. The substitute parts listed maintain identical electrical specifications and mechanical compatibility while offering improved product status and compliance certifications.

Key Parameters

Parameter	Value
Output Voltage (Fixed)	3.3V
Output Current	300mA
Input Voltage (Max)	6V
Voltage Dropout (Max)	0.2V @ 300mA
Quiescent Current	120 µA
PSRR	50dB ~ 55dB (1kHz ~ 10kHz)
Operating Temperature Range	-40°C ~ 125°C
Package Type	8-VSSOP (8-TSSOP, 8-MSOP, 0.118" / 3.00mm Width)
Protection Features	Over Current, Over Temperature, Short Circuit
Control Features	Enable

Substitute Part Grouping Explanation

Substitution of the LP3981IMMX-3.3 is based on strict equivalence across the following critical parameters:

Output voltage configuration: Positive fixed 3.3V output
Output current capacity: 300mA
Maximum input voltage: 6V
Voltage dropout specification: 0.2V @ 300mA
Quiescent current: 120 µA
PSRR performance: 50dB ~ 55dB (1kHz ~ 10kHz)
Operating temperature range: -40°C ~ 125°C
Package type: 8-VSSOP surface mount
Protection and control features: Over Current, Over Temperature, Short Circuit protection with Enable control

All substitute parts maintain these electrical and mechanical specifications. Differences exist only in product status, packaging format, and RoHS/REACH compliance certifications.

Parameter Comparison

Part Number	Manufacturer	Output Voltage	Output Current	Input Voltage (Max)	Dropout Voltage	Quiescent Current	PSRR	Operating Temp	Package	Product Status	RoHS Status
LP3981IMMX-3.3	Texas Instruments	3.3V	300mA	6V	0.2V @ 300mA	120 µA	50dB ~ 55dB	-40°C ~ 125°C	8-VSSOP	Obsolete	RoHS non-compliant
LP3981IMM-3.3	Texas Instruments	3.3V	300mA	6V	0.2V @ 300mA	120 µA	50dB ~ 55dB	-40°C ~ 125°C	8-VSSOP	Last Time Buy	ROHS3 Compliant
LP3981IMM-3.3/NOPB	Texas Instruments	3.3V	300mA	6V	0.2V @ 300mA	120 µA	50dB ~ 55dB	-40°C ~ 125°C	8-VSSOP	Active	ROHS3 Compliant
LP3981IMMX-3.3/NOPB	Texas Instruments	3.3V	300mA	6V	0.2V @ 300mA	120 µA	50dB ~ 55dB	-40°C ~ 125°C	8-VSSOP	Active	ROHS3 Compliant

Engineering Selection Recommendations

For applications currently using the LP3981IMMX-3.3 (Obsolete, RoHS non-compliant), the following selection criteria apply:

Active Product Status Priority: LP3981IMM-3.3/NOPB and LP3981IMMX-3.3/NOPB are both classified as Active products and represent the primary substitution path. These parts maintain full electrical equivalence while providing current manufacturing support and availability.

RoHS3 Compliance: All substitute parts listed are ROHS3 Compliant, addressing regulatory requirements that the original LP3981IMMX-3.3 does not meet. This compliance is mandatory for applications subject to RoHS directives.

Packaging Format Considerations: LP3981IMM-3.3 is available in Cut Tape and Digi-Reel packaging, while LP3981IMM-3.3/NOPB and LP3981IMMX-3.3/NOPB are supplied in Tape & Reel format. Selection depends on procurement volume and assembly line requirements.

Last Time Buy Status: LP3981IMM-3.3 carries Last Time Buy status, indicating limited future availability. For new designs or long-term production, Active status parts (LP3981IMM-3.3/NOPB or LP3981IMMX-3.3/NOPB) are preferred.

Frequently Asked Questions (FAQ)

Q: Can LP3981IMM-3.3/NOPB directly replace LP3981IMMX-3.3 in existing designs?

A: Yes. Both parts are electrically and mechanically identical across all specified parameters: 3.3V fixed output, 300mA current capacity, 0.2V dropout voltage, 120 µA quiescent current, and 8-VSSOP package. The /NOPB suffix indicates lead-free plating and RoHS3 compliance, which are improvements over the original part.

Q: What is the difference between LP3981IMM-3.3 and LP3981IMMX-3.3?

A: Both variants are electrically equivalent with identical electrical specifications. The primary differences are product status (Last Time Buy vs. Obsolete) and packaging format (Cut Tape/Digi-Reel vs. standard). The IMMX variant is the extended temperature or extended feature variant designation, but electrical performance is identical.

Q: Are there any compatibility issues with the 8-VSSOP package across these part numbers?

A: No. All substitute parts use the identical 8-VSSOP package (8-TSSOP, 8-MSOP, 0.118" / 3.00mm Width). PCB footprints, pin assignments, and mechanical dimensions are fully compatible.

Q: Which substitute part should be selected for new production designs?

A: LP3981IMM-3.3/NOPB or LP3981IMMX-3.3/NOPB are recommended for new designs. Both are Active products with ROHS3 compliance and guaranteed long-term availability. Selection between these two depends on packaging requirements and supplier availability.

Q: Does the /NOPB designation affect electrical performance?

A: No. The /NOPB suffix indicates lead-free plating and RoHS3 compliance only. All electrical specifications, performance characteristics, and operating parameters remain identical to non-/NOPB variants.

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

A: LP3981IMM-3.3: 17,354 Pcs; LP3981IMM-3.3/NOPB: 16,280 Pcs; LP3981IMMX-3.3/NOPB: 16,380 Pcs. All parts are available as new original stock.

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