LP3985IM5X-2.5 Equivalent & Substitute Parts

Part Overview

The LP3985IM5X-2.5 is a linear voltage regulator IC from Texas Instruments, delivering a fixed 2.5V output at 150mA in a SOT-23-5 surface mount package. This part is classified as obsolete, making equivalent and substitute parts necessary for ongoing design support and production continuity. The device provides positive fixed output regulation with integrated protection features including over-current, over-temperature, and short-circuit protection, suitable for low-power applications requiring stable 2.5V rails.

Key Parameters

Parameter	Value
Manufacturer	Texas Instruments
Output Voltage (Fixed)	2.5V
Output Current	150mA
Input Voltage (Max)	6V
Voltage Dropout (Max)	0.1V @ 150mA
Quiescent Current	150 µA
Package	SOT-23-5 (SC-74A)
Operating Temperature	-40°C to 125°C
Protection Features	Over Current, Over Temperature, Short Circuit
Control Features	Enable

Substitute Part Grouping Explanation

Substitute parts for the LP3985IM5X-2.5 are grouped into three categories based on electrical and mechanical compatibility:

Category 1: Direct Parametric Equivalents (Texas Instruments LP3985 Series) These parts maintain identical electrical specifications: 2.5V fixed output, 150mA output current, 0.1V dropout at 150mA, 150 µA quiescent current, and SOT-23-5 packaging. Substitution is based on matching output voltage, output current rating, maximum input voltage (6V), dropout voltage, and package type. Parts in this category differ only in product status and RoHS compliance.

Category 2: Enhanced Performance Alternatives (Texas Instruments LP5951 Series) These parts provide the same 2.5V output and 150mA current but with improved quiescent current (55 µA vs. 150 µA) and PSRR performance. The trade-off is a higher dropout voltage (0.35V @ 150mA vs. 0.1V). Maximum input voltage is reduced to 5.5V. Substitution is valid when lower quiescent current is beneficial and the reduced input voltage range and higher dropout are acceptable.

Category 3: Cross-Manufacturer Equivalents (STMicroelectronics, Analog Devices, Maxim) These parts from alternative manufacturers provide equivalent 2.5V output and 150mA current in SOT-23-5 packaging. Electrical parameters vary slightly (dropout voltage, quiescent current, PSRR). Substitution is valid when manufacturer diversification or specific performance characteristics are required.

Parameter Comparison

Part Number	Manufacturer	Output Voltage	Output Current	Input Voltage (Max)	Dropout @ 150mA	Quiescent Current	Package	Product Status	RoHS Status
LP3985IM5X-2.5	Texas Instruments	2.5V	150mA	6V	0.1V	150 µA	SOT-23-5	Obsolete	Non-compliant
LP3985IM5-2.5	Texas Instruments	2.5V	150mA	6V	0.1V	150 µA	SOT-23-5	Last Time Buy	ROHS3 Compliant
LP3985IM5-2.5/NOPB	Texas Instruments	2.5V	150mA	6V	0.1V	150 µA	SOT-23-5	Active	ROHS3 Compliant
LP3985IM5X-2.5/NOPB	Texas Instruments	2.5V	150mA	6V	0.1V	150 µA	SOT-23-5	Active	ROHS3 Compliant
LP5951MF-2.5/NOPB	Texas Instruments	2.5V	150mA	5.5V	0.35V	55 µA	SOT-23-5	Active	ROHS3 Compliant
LP5951MFX-2.5/NOPB	Texas Instruments	2.5V	150mA	5.5V	0.35V	55 µA	SOT-23-5	Active	ROHS3 Compliant
LD3985M25R	STMicroelectronics	2.5V	150mA	6V	0.1V	150 µA	SOT-23-5	Active	ROHS3 Compliant
LDS3985M25R	STMicroelectronics	2.5V	300mA	6V	0.25V	150 µA	SOT-23-5	Active	ROHS3 Compliant
LTC1844ES5-2.5#TRMPBF	Analog Devices Inc.	2.5V	150mA	6.5V	0.2V	80 µA	TSOT-23-5	Active	ROHS3 Compliant
LTC1844ES5-2.5#TRPBF	Analog Devices Inc.	2.5V	150mA	6.5V	0.2V	80 µA	TSOT-23-5	Active	ROHS3 Compliant
MAX8868EUK25+T	Analog Devices Inc./Maxim Integrated	2.5V	150mA	6.5V	0.165V	180 µA	SOT-23-5	Active	ROHS3 Compliant

Engineering Selection Recommendations

Primary Recommendation: LP3985IM5X-2.5/NOPB This Texas Instruments part is the direct equivalent with identical electrical specifications and is currently in active production status with ROHS3 compliance. It provides the most straightforward replacement path with no design modifications required.

Secondary Recommendation: LD3985M25R (STMicroelectronics) This STMicroelectronics part matches all electrical parameters of the original LP3985IM5X-2.5 and is actively produced with ROHS3 compliance. Selection is appropriate when manufacturer diversification is required or when STMicroelectronics supply chain advantages apply.

Alternative for Lower Quiescent Current: LP5951MFX-2.5/NOPB When reduced quiescent current (55 µA vs. 150 µA) is a design priority, the LP5951MFX-2.5/NOPB provides active production status and ROHS3 compliance. This selection requires verification that the reduced maximum input voltage (5.5V vs. 6V) and increased dropout voltage (0.35V vs. 0.1V) are acceptable for the application.

Alternative for Enhanced Input Voltage Range: LTC1844ES5-2.5#TRPBF The Analog Devices LTC1844ES5-2.5#TRPBF supports a higher maximum input voltage (6.5V) and lower quiescent current (80 µA). The package is TSOT-23-5 (thin variant), which maintains SOT-23-5 footprint compatibility. This selection is appropriate when higher input voltage capability is required.

Higher Current Option: LDS3985M25R The STMicroelectronics LDS3985M25R provides 300mA output current in the same SOT-23-5 package, suitable for applications requiring higher current delivery. The trade-off is increased dropout voltage (0.25V @ 300mA). Selection requires confirmation that the application can accommodate the higher dropout.

Frequently Asked Questions (FAQ)

Q: Can LP3985IM5-2.5/NOPB directly replace LP3985IM5X-2.5? A: Yes. Both parts deliver 2.5V at 150mA with 0.1V dropout in SOT-23-5 packaging. The primary difference is product status (Last Time Buy vs. Obsolete) and RoHS compliance (ROHS3 Compliant vs. Non-compliant). No design changes are required.

Q: What is the difference between LP3985IM5X-2.5/NOPB and LP3985IM5-2.5/NOPB? A: Both are electrically identical with matching specifications. The difference is in packaging designation and inventory status. LP3985IM5X-2.5/NOPB is currently in active production with higher inventory availability.

Q: Can LP5951MFX-2.5/NOPB replace LP3985IM5X-2.5 in all applications? A: Not universally. While both deliver 2.5V at 150mA in SOT-23-5 packaging, the LP5951MFX-2.5/NOPB has a lower maximum input voltage (5.5V vs. 6V) and higher dropout voltage (0.35V vs. 0.1V). Substitution is valid only when the application input voltage does not exceed 5.5V and the higher dropout is acceptable.

Q: Are TSOT-23-5 and SOT-23-5 packages interchangeable? A: TSOT-23-5 is a thin variant of SOT-23-5 with identical pin pitch and footprint. Parts using TSOT-23-5 (such as LTC1844ES5-2.5#TRPBF) are mechanically compatible with SOT-23-5 PCB layouts. The thinner profile may provide advantages in space-constrained designs.

Q: Why does LDS3985M25R have higher dropout voltage than LP3985IM5X-2.5? A: LDS3985M25R is rated for 300mA output current compared to 150mA for LP3985IM5X-2.5. The increased dropout voltage (0.25V @ 300mA) reflects the higher current capability. When operating at 150mA, the actual dropout may be lower than the specified maximum.

Q: Which substitute part has the best quiescent current performance? A: LTC1844ES5-2.5#TRPBF provides the lowest quiescent current at 80 µA, followed by LP5951MFX-2.5/NOPB at 55 µA. Selection depends on whether the lower input voltage range (5.5V for LP5951) or higher input voltage capability (6.5V for LTC1844) is required.

Q: Is RoHS compliance required for my application? A: The original LP3985IM5X-2.5 is RoHS non-compliant. All listed substitute parts are ROHS3 compliant. If RoHS compliance is a regulatory requirement, any of the substitute parts listed are suitable replacements.

Q: Can I use MAX8868EUK25+T as a direct replacement? A: MAX8868EUK25+T is electrically compatible, delivering 2.5V at 150mA in SOT-23-5 packaging. The operating temperature range is limited to -40°C to 85°C (vs. -40°C to 125°C for LP3985IM5X-2.5). Substitution is valid only if the application does not require operation above 85°C.

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