LP3990SD-1.8 Linear Voltage Regulator IC Equivalent & Substitute Parts

Part Overview

The LP3990SD-1.8 is a linear voltage regulator IC from Texas Instruments designed for positive fixed 1.8V output applications with 150mA current capacity in a 6-WSON (3x3) surface mount package. This part is classified as obsolete, making equivalent and substitute parts necessary for ongoing production and design requirements. The LP3990SD-1.8 provides regulated 1.8V output with integrated over-temperature and short-circuit protection, suitable for low-power applications requiring stable voltage regulation.

Key Parameters

Parameter	Value
Manufacturer	Texas Instruments
Category	Power Management (PMIC)
Output Voltage (Fixed)	1.8V
Output Current	150mA
Input Voltage (Max)	6V
Voltage Dropout (Max)	0.2V @ 150mA
Quiescent Current	80 µA
Operating Temperature Range	-40°C ~ 85°C
Package Type	6-WDFN Exposed Pad
Mounting Type	Surface Mount
Protection Features	Over Temperature, Short Circuit
Control Features	Enable

Substitute Part Grouping Explanation

Substitution for the LP3990SD-1.8 is determined by the following critical parameters that must remain constant across all equivalent parts:

Output voltage fixed at 1.8V
Output current capacity of 150mA
Surface mount 6-WDFN package with exposed pad
Enable control feature
Over-temperature and short-circuit protection
Operating temperature range of -40°C to 85°C

The substitute parts are grouped into two categories:

Direct Equivalent (Packaging Variant): LP3990SD-1.8/NOPB maintains identical electrical specifications and package dimensions (6-WSON 3x3) with the primary difference being packaging format (Tape & Reel) and product status (Active vs. Obsolete).

Parametric Equivalents (Improved Performance): LP5900SD-1.8/NOPB and LP5900SDX-1.8/NOPB are from the LP5900 series with enhanced electrical characteristics including lower dropout voltage, reduced quiescent current, and improved PSRR, while maintaining the same output voltage, current capacity, and package footprint compatibility.

Parameter Comparison

Parameter	LP3990SD-1.8	LP3990SD-1.8/NOPB	LP5900SD-1.8/NOPB	LP5900SDX-1.8/NOPB
Manufacturer	Texas Instruments	Texas Instruments	Texas Instruments	Texas Instruments
Product Status	Obsolete	Active	Active	Active
Output Voltage	1.8V	1.8V	1.8V	1.8V
Output Current	150mA	150mA	150mA	150mA
Input Voltage (Max)	6V	6V	5.5V	5.5V
Voltage Dropout (Max)	0.2V @ 150mA	0.2V @ 150mA	0.15V @ 150mA	0.15V @ 150mA
Quiescent Current	80 µA	80 µA	50 µA	50 µA
PSRR	55dB ~ 35dB (1kHz ~ 10kHz)	55dB ~ 35dB (1kHz ~ 10kHz)	85dB ~ 40dB (100Hz ~ 100kHz)	85dB ~ 40dB (100Hz ~ 100kHz)
Operating Temperature	-40°C ~ 85°C	-40°C ~ 85°C	-40°C ~ 85°C	-40°C ~ 85°C
Package / Case	6-WDFN Exposed Pad	6-WDFN Exposed Pad	6-WDFN Exposed Pad	6-WDFN Exposed Pad
Supplier Device Package	6-WSON (3x3)	6-WSON (3x3)	6-WSON (2.2x2.5)	6-WSON (2.2x2.5)
RoHS Status	RoHS non-compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant
Protection Features	Over Temperature, Short Circuit	Over Temperature, Short Circuit	Over Temperature, Short Circuit	Over Temperature, Short Circuit
Control Features	Enable	Enable	Enable	Enable

Engineering Selection Recommendations

LP3990SD-1.8/NOPB is the direct equivalent for applications currently using LP3990SD-1.8. This part maintains identical electrical performance and package dimensions while offering the advantage of active product status and ROHS3 compliance. The primary distinction is packaging format (Tape & Reel), making it suitable for production environments requiring standard component packaging.

LP5900SD-1.8/NOPB and LP5900SDX-1.8/NOPB are parametric equivalents offering improved electrical characteristics. These parts feature lower dropout voltage (0.15V vs. 0.2V), reduced quiescent current (50 µA vs. 80 µA), and superior PSRR performance (85dB ~ 40dB across 100Hz ~ 100kHz). Both maintain ROHS3 compliance and active product status. The LP5900 series operates with a maximum input voltage of 5.5V compared to 6V for the LP3990 series. Package footprint compatibility is maintained with the 6-WDFN exposed pad configuration, though the physical dimensions differ slightly (2.2x2.5 vs. 3x3).

Selection between LP5900SD-1.8/NOPB and LP5900SDX-1.8/NOPB depends on packaging requirements: LP5900SD-1.8/NOPB is available in Cut Tape and Digi-Reel formats, while LP5900SDX-1.8/NOPB is supplied in Tape & Reel format.

Frequently Asked Questions (FAQ)

Q: Can LP3990SD-1.8/NOPB be used as a direct replacement for LP3990SD-1.8?

A: Yes. LP3990SD-1.8/NOPB is a direct equivalent with identical electrical specifications and package footprint. The primary difference is packaging format (Tape & Reel) and active product status versus obsolete status.

Q: What are the advantages of using LP5900 series parts over LP3990SD-1.8?

A: The LP5900 series offers improved performance characteristics: lower dropout voltage (0.15V vs. 0.2V), reduced quiescent current (50 µA vs. 80 µA), and significantly better PSRR performance across a wider frequency range. Both series maintain the same 1.8V output voltage and 150mA current capacity.

Q: Are there any input voltage limitations when switching to LP5900 series?

A: Yes. LP5900 series parts have a maximum input voltage of 5.5V compared to 6V for LP3990 series. Applications requiring input voltages above 5.5V must remain on the LP3990 series or LP3990SD-1.8/NOPB.

Q: Do the LP5900 series parts fit the same PCB footprint as LP3990SD-1.8?

A: Both use the 6-WDFN exposed pad package type with identical pin configuration. However, the physical die size differs (2.2x2.5 vs. 3x3). PCB layout compatibility depends on specific footprint design; consult component datasheets for precise dimensional requirements.

Q: What is the difference between LP5900SD-1.8/NOPB and LP5900SDX-1.8/NOPB?

A: Both parts have identical electrical specifications. The difference is packaging format: LP5900SD-1.8/NOPB is available in Cut Tape and Digi-Reel formats, while LP5900SDX-1.8/NOPB is supplied in Tape & Reel format.

Q: Are all substitute parts RoHS compliant?

A: LP3990SD-1.8 is RoHS non-compliant. LP3990SD-1.8/NOPB, LP5900SD-1.8/NOPB, and LP5900SDX-1.8/NOPB are all ROHS3 compliant, meeting current environmental regulations.

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