LP3985IM5-2.8 Linear Voltage Regulator — Equivalent & Substitute Parts

Part Overview

The LP3985IM5-2.8 is a linear voltage regulator IC from Texas Instruments, delivering a fixed 2.8V output at 150mA in a SOT-23-5 surface mount package. This part is classified as obsolete, making equivalent and substitute parts necessary for new designs and ongoing production support. The regulator provides positive fixed output configuration with integrated protection features including over-current, over-temperature, and short-circuit protection, operating across the industrial temperature range of -40°C to 125°C.

Key Parameters

Parameter	Value
Output Voltage (Fixed)	2.8V
Output Current	150mA
Input Voltage (Max)	6V
Voltage Dropout (Max)	0.1V @ 150mA
Quiescent Current (Iq)	150 µA
Operating Temperature Range	-40°C to 125°C
Package Type	SOT-23-5 (SC-74A)
Protection Features	Over Current, Over Temperature, Short Circuit
Control Features	Enable

Substitute Part Grouping Explanation

Substitution for the LP3985IM5-2.8 is determined by strict alignment of the following electrical and mechanical parameters:

Fixed output voltage of 2.8V
Output current capability of 150mA minimum
Maximum input voltage of 5.5V to 6.5V
SOT-23-5 package compatibility
Operating temperature range of -40°C to 125°C
Enable control feature
Protection against over-current and over-temperature conditions

Substitute parts are grouped into three categories: direct manufacturer equivalents (identical specifications and packaging), parametric equivalents (functionally compatible with minor specification variations), and manufacturer-recommended alternatives (approved cross-references with acceptable performance trade-offs).

Parameter Comparison

Part Number	Manufacturer	Output Voltage	Output Current	Input Voltage (Max)	Dropout Voltage @ 150mA	Quiescent Current	Package	Product Status	RoHS Compliance
LP3985IM5-2.8	Texas Instruments	2.8V	150mA	6V	0.1V	150 µA	SOT-23-5	Obsolete	Non-compliant
LP3985IM5-2.8/NOPB	Texas Instruments	2.8V	150mA	6V	0.1V	150 µA	SOT-23-5	Active	ROHS3 Compliant
LP3985IM5X-2.8/NOPB	National Semiconductor	2.8V	150mA	6V	0.1V	150 µA	SOT-23-5	Active	Not specified
LP5951MF-2.8/NOPB	Texas Instruments	2.8V	150mA	5.5V	0.35V	55 µA	SOT-23-5	Active	ROHS3 Compliant
LD3985M28R	STMicroelectronics	2.8V	150mA	6V	0.1V	150 µA	SOT-23-5	Active	ROHS3 Compliant
LTC1844ES5-2.8#TRMPBF	Analog Devices Inc.	2.8V	150mA	6.5V	0.165V	80 µA	TSOT-23-5	Active	ROHS3 Compliant
LTC1844ES5-2.8#TRPBF	Analog Devices Inc.	2.8V	150mA	6.5V	0.165V	80 µA	TSOT-23-5	Active	ROHS3 Compliant
MAX8868EUK28+T	Analog Devices Inc./Maxim Integrated	2.8V	150mA	6.5V	0.165V	180 µA	SOT-23-5	Active	ROHS3 Compliant
MAX8877EUK28+T	Analog Devices Inc./Maxim Integrated	2.8V	150mA	6.5V	0.165V	180 µA	SOT-23-5	Active	ROHS3 Compliant
MAX8878EUK28+T	Analog Devices Inc./Maxim Integrated	2.8V	150mA	6.5V	0.165V	180 µA	SOT-23-5	Active	ROHS3 Compliant
MIC5252-2.8YM5-TR	Microchip Technology	2.8V	150mA	6V	0.25V	150 µA	SOT-23-5	Active	ROHS3 Compliant

Engineering Selection Recommendations

For new designs and production applications requiring replacement of the obsolete LP3985IM5-2.8, the following selection criteria apply:

Direct Replacement (Identical Electrical and Mechanical Specifications): LP3985IM5-2.8/NOPB from Texas Instruments is the active production equivalent with identical electrical performance and RoHS3 compliance. This part maintains the original 0.1V dropout voltage and 150 µA quiescent current specifications.

Parametric Equivalents with Active Status: LP3985IM5X-2.8/NOPB (National Semiconductor) provides identical electrical specifications. LD3985M28R (STMicroelectronics) matches all key electrical parameters with improved PSRR performance and active product status with RoHS3 compliance.

Alternative Solutions with Acceptable Trade-offs: LP5951MF-2.8/NOPB reduces quiescent current to 55 µA but increases dropout voltage to 0.35V and reduces maximum input voltage to 5.5V. This variant is suitable for low-power applications where reduced quiescent current is beneficial.

MIC5252-2.8YM5-TR (Microchip Technology) maintains identical quiescent current but increases dropout voltage to 0.25V. All alternatives maintain the 150mA output current and SOT-23-5 package compatibility.

LTC1844ES5-2.8#TRMPBF and LTC1844ES5-2.8#TRPBF (Analog Devices Inc.) use TSOT-23-5 thin package variant with improved PSRR (50dB @ 120Hz) and lower quiescent current (80 µA), but require PCB layout verification for package compatibility.

MAX8868EUK28+T, MAX8877EUK28+T, and MAX8878EUK28+T (Analog Devices Inc./Maxim Integrated) provide extended input voltage tolerance to 6.5V and improved PSRR performance. Operating temperature range is limited to -40°C to 85°C, which may restrict use in extended industrial applications.

All recommended substitutes maintain RoHS3 compliance and active product status, ensuring long-term availability and regulatory compliance.

Frequently Asked Questions (FAQ)

Q: Can LP3985IM5-2.8/NOPB be used as a direct drop-in replacement for the obsolete LP3985IM5-2.8?

A: Yes. LP3985IM5-2.8/NOPB is the active production equivalent with identical electrical specifications, package type (SOT-23-5), and performance characteristics. The primary difference is RoHS3 compliance status. No circuit modifications are required.

Q: What is the difference between SOT-23-5 and TSOT-23-5 packages?

A: TSOT-23-5 is a thin variant of the SOT-23-5 package with reduced height. While electrically compatible, PCB layout and assembly equipment must accommodate the thinner profile. Verify with your manufacturing partner before substituting LTC1844 variants.

Q: Which substitute offers the lowest quiescent current?

A: LP5951MF-2.8/NOPB provides the lowest quiescent current at 55 µA, compared to 150 µA in the original part. However, this comes with increased dropout voltage (0.35V) and reduced maximum input voltage (5.5V). Evaluate your application's power budget and input voltage requirements before selection.

Q: Are all substitute parts RoHS3 compliant?

A: All recommended active substitutes are RoHS3 compliant except LP3985IM5X-2.8/NOPB, which does not specify RoHS status. For applications requiring RoHS3 certification, select from the remaining alternatives.

Q: What is the maximum operating temperature for each substitute?

A: LP3985IM5-2.8/NOPB, LP3985IM5X-2.8/NOPB, LP5951MF-2.8/NOPB, LD3985M28R, LTC1844ES5-2.8#TRMPBF, LTC1844ES5-2.8#TRPBF, and MIC5252-2.8YM5-TR all support -40°C to 125°C. MAX8868EUK28+T, MAX8877EUK28+T, and MAX8878EUK28+T are limited to -40°C to 85°C.

Q: Can I use a substitute with higher maximum input voltage than the original specification?

A: Yes, if your circuit design does not exceed the original 6V maximum input specification. Substitutes with higher input voltage ratings (6.5V) provide additional design margin and are backward compatible with lower input voltages.

Q: What inventory levels are available for each substitute?

A: Inventory availability varies by part and supplier. LD3985M28R has the highest inventory at 59,700 pieces. LP3985IM5-2.8/NOPB has 2,400 pieces. Verify current stock with your component distributor before finalizing procurement decisions.

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