LP3985IM5X-2.8 Linear Voltage Regulator Equivalent & Substitute Parts

Part Overview

The LP3985IM5X-2.8 is a linear voltage regulator IC from Texas Instruments designed to deliver a fixed 2.8V output at 150mA in a compact SOT-23-5 surface mount package. This device is classified as obsolete, making equivalent and substitute parts necessary for ongoing production and maintenance applications. The regulator provides positive fixed output 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	150 µA
Operating Temperature	-40°C to 125°C
Package Type	SOT-23-5 (SC-74A)
Control Features	Enable
Protection Features	Over Current, Over Temperature, Short Circuit

Substitute Part Grouping Explanation

Substitute parts for the LP3985IM5X-2.8 are classified based on strict parametric equivalence. The primary substitution criteria are:

Fixed output voltage of 2.8V
Output current capability of 150mA
Maximum input voltage of 5.5V to 6.5V
Voltage dropout specifications compatible with 0.1V to 0.35V @ 150mA
Operating temperature range of -40°C to 125°C (or subset thereof)
Surface mount SOT-23-5 package configuration
Enable control feature and protection against over-current and over-temperature conditions

Substitutes are grouped into two categories: parametric equivalents (identical electrical specifications) and manufacturer-recommended alternatives (functionally equivalent with minor specification variations).

Parameter Comparison

Part Number	Manufacturer	Output Voltage	Output Current	Input Voltage (Max)	Dropout @ 150mA	Quiescent Current	Operating Temp	Package	Product Status	RoHS Status
LP3985IM5X-2.8	Texas Instruments	2.8V	150mA	6V	0.1V	150 µA	-40°C to 125°C	SOT-23-5	Obsolete	Non-compliant
LP3985IM5-2.8/NOPB	Texas Instruments	2.8V	150mA	6V	0.1V	150 µA	-40°C to 125°C	SOT-23-5	Active	ROHS3 Compliant
LP3985IM5X-2.8/NOPB	National Semiconductor	2.8V	150mA	6V	0.1V	150 µA	-40°C to 125°C	SOT-23-5	Active	Not specified
LP5951MF-2.8/NOPB	Texas Instruments	2.8V	150mA	5.5V	0.35V	55 µA	-40°C to 125°C	SOT-23-5	Active	ROHS3 Compliant
LD3985M28R	STMicroelectronics	2.8V	150mA	6V	0.1V	150 µA	-40°C to 125°C	SOT-23-5	Active	ROHS3 Compliant
LTC1844ES5-2.8#TRMPBF	Analog Devices Inc.	2.8V	150mA	6.5V	0.165V	80 µA	-40°C to 125°C	TSOT-23-5	Active	ROHS3 Compliant
LTC1844ES5-2.8#TRPBF	Analog Devices Inc.	2.8V	150mA	6.5V	0.165V	80 µA	-40°C to 125°C	TSOT-23-5	Active	ROHS3 Compliant
MAX8868EUK28+T	Analog Devices Inc./Maxim Integrated	2.8V	150mA	6.5V	0.165V	180 µA	-40°C to 85°C	SOT-23-5	Active	ROHS3 Compliant
MAX8877EUK28+T	Analog Devices Inc./Maxim Integrated	2.8V	150mA	6.5V	0.165V	180 µA	-40°C to 85°C	SOT-23-5	Active	ROHS3 Compliant
MAX8878EUK28+T	Analog Devices Inc./Maxim Integrated	2.8V	150mA	6.5V	0.165V	180 µA	-40°C to 85°C	SOT-23-5	Active	ROHS3 Compliant
MIC5252-2.8YM5-TR	Microchip Technology	2.8V	150mA	6V	0.25V	150 µA	-40°C to 125°C	SOT-23-5	Active	ROHS3 Compliant

Engineering Selection Recommendations

For direct replacement of the obsolete LP3985IM5X-2.8, the LP3985IM5-2.8/NOPB from Texas Instruments is the primary choice. This part maintains identical electrical specifications while offering active product status and ROHS3 compliance, eliminating the need for design modifications.

The LD3985M28R from STMicroelectronics provides an alternative with equivalent specifications and active status. This option is suitable when supply chain diversification is required.

For applications where lower quiescent current is beneficial, the LP5951MF-2.8/NOPB offers reduced Iq (55 µA versus 150 µA) at the cost of higher dropout voltage (0.35V versus 0.1V). This substitution is valid only when the higher dropout voltage does not compromise system performance.

The LTC1844ES5-2.8#TRMPBF and LTC1844ES5-2.8#TRPBF from Analog Devices provide functionally equivalent performance with enhanced input voltage tolerance (6.5V maximum) and lower quiescent current (80 µA). These parts use a thin SOT-23-5 package variant (TSOT-23-5) and are suitable for space-constrained applications.

The MAX8868EUK28+T, MAX8877EUK28+T, and MAX8878EUK28+T from Analog Devices/Maxim Integrated are functionally equivalent alternatives with the limitation of reduced operating temperature range (-40°C to 85°C). These parts are suitable only for applications not requiring the full -40°C to 125°C temperature range.

The MIC5252-2.8YM5-TR from Microchip Technology maintains full specification compatibility with moderate dropout voltage (0.25V @ 150mA) and is suitable for general-purpose replacement applications.

All recommended substitutes are ROHS3 compliant and carry 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 LP3985IM5X-2.8?

A: Yes. Both parts share identical electrical specifications including output voltage, current rating, dropout voltage, and operating temperature range. The primary difference is product status (active versus obsolete) and RoHS compliance. 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. Both packages are mechanically and electrically compatible for standard PCB assembly. TSOT-23-5 is preferred for space-constrained applications. Verify PCB footprint compatibility before substitution.

Q: Why does LP5951MF-2.8/NOPB have higher dropout voltage than the original part?

A: The LP5951MF-2.8/NOPB is designed for lower quiescent current operation (55 µA versus 150 µA), which results in higher dropout voltage (0.35V versus 0.1V). This trade-off is inherent to the device architecture. Substitution is valid only when the application can tolerate the higher dropout voltage without performance degradation.

Q: Are MAX8868EUK28+T, MAX8877EUK28+T, and MAX8878EUK28+T suitable for all applications?

A: These parts are functionally equivalent but operate only to 85°C maximum, compared to 125°C for the original part. They are suitable only for applications with operating temperature limits of -40°C to 85°C. Verify thermal requirements before selection.

Q: What is the significance of RoHS3 compliance for substitute parts?

A: RoHS3 compliance indicates the part meets current environmental and hazardous substance restrictions. All recommended active substitutes carry ROHS3 compliance, ensuring regulatory compliance for new designs and long-term supply chain viability.

Q: Can I use MIC5252-2.8YM5-TR as a substitute if dropout voltage is critical?

A: The MIC5252-2.8YM5-TR has 0.25V dropout at 150mA, which is higher than the original 0.1V specification. Substitution is valid only when the application circuit can accommodate this higher dropout voltage without affecting system performance.

Q: What packaging options are available for substitutes?

A: All substitutes are available in SOT-23-5 or TSOT-23-5 surface mount packages. Packaging variants (Cut Tape, Tape & Reel, Bulk) affect ordering and handling but do not impact electrical or mechanical compatibility. Select packaging based on procurement and assembly requirements.

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