LP3855ET-1.8 Equivalent & Substitute Parts

Part Overview

The LP3855ET-1.8 is a linear voltage regulator IC from Texas Instruments, classified as a Power Management (PMIC) component. It delivers a fixed 1.8V output at 1.5A in a TO-220-5 package configuration. The device is currently marked as obsolete, which necessitates identification of active equivalent and substitute parts for ongoing design support and procurement.

Key Parameters

Parameter	Value
Manufacturer	Texas Instruments
Part Number	LP3855ET-1.8
Output Voltage (Fixed)	1.8V
Output Current	1.5A
Input Voltage (Max)	7V
Voltage Dropout (Max)	0.38V @ 1.5A
Quiescent Current	3 mA
Package Type	TO-220-5 Formed Leads
Operating Temperature Range	-40°C to 125°C
Protection Features	Over Current, Over Temperature, Short Circuit
Product Status	Obsolete

Substitute Part Grouping Explanation

Substitution for the LP3855ET-1.8 is determined by the following critical parameters:

Fixed output voltage of 1.8V
Output current capability of 1.5A minimum
TO-220-5 package configuration
Operating temperature range of -40°C to 125°C
Enable control feature
Protection against over current, over temperature, and short circuit conditions

Substitute parts are grouped into three categories:

Parametric Equivalents (Texas Instruments): LP3852ET-1.8/NOPB and LP3965ET-1.8/NOPB maintain identical or compatible electrical specifications with the original part.

Direct Equivalent (Texas Instruments): LP3855ET-1.8/NOPB is the active production variant of the original obsolete part, with identical electrical characteristics and RoHS3 compliance.

Manufacturer Recommended Alternatives (Analog Devices Inc.): LT1963ET-1.8#PBF, LT1963AET-1.8#PBF, and LT1963AET-1.8#06PBF are cross-manufacturer alternatives that meet the core functional requirements while offering enhanced input voltage tolerance and improved quiescent current performance.

Parameter Comparison

Parameter	LP3855ET-1.8 (Original)	LP3852ET-1.8/NOPB	LP3965ET-1.8/NOPB	LP3855ET-1.8/NOPB	LT1963ET-1.8#PBF	LT1963AET-1.8#PBF	LT1963AET-1.8#06PBF
Manufacturer	Texas Instruments	Texas Instruments	Texas Instruments	Texas Instruments	Analog Devices Inc.	Analog Devices Inc.	Analog Devices Inc.
Output Voltage	1.8V	1.8V	1.8V	1.8V	1.8V	1.8V	1.8V
Output Current	1.5A	1.5A	1.5A	1.5A	1.5A	1.5A	1.5A
Input Voltage (Max)	7V	7V	7V	7V	20V	20V	20V
Voltage Dropout (Max)	0.38V @ 1.5A	0.38V @ 1.5A	0.55V @ 1.5A	0.38V @ 1.5A	0.55V @ 1.5A	0.55V @ 1.5A	0.55V @ 1.5A
Quiescent Current	3 mA	3 mA	9 mA	3 mA	1.5 mA	1.5 mA	1.5 mA
Package Type	TO-220-5 Formed Leads	TO-220-5 Formed Leads	TO-220-5 Formed Leads	TO-220-5 Formed Leads	TO-220-5	TO-220-5	TO-220-5
Operating Temperature	-40°C to 125°C	-40°C to 125°C	-40°C to 125°C	-40°C to 125°C	-40°C to 125°C	-40°C to 125°C	-40°C to 125°C
Protection Features	Over Current, Over Temperature, Short Circuit	Over Current, Over Temperature, Short Circuit	Over Current, Over Temperature, Short Circuit	Over Current, Over Temperature, Short Circuit	Over Current, Over Temperature, Reverse Polarity	Over Current, Over Temperature, Reverse Polarity	Over Current, Over Temperature, Reverse Polarity
Product Status	Obsolete	Active	Active	Active	Active	Active	Active
RoHS Status	RoHS Non-Compliant	RoHS3 Compliant	RoHS3 Compliant	RoHS3 Compliant	RoHS3 Compliant	RoHS3 Compliant	RoHS3 Compliant

Engineering Selection Recommendations

For Direct Replacement (Preferred): LP3855ET-1.8/NOPB is the recommended primary substitute. It maintains identical electrical specifications to the original obsolete part while offering active product status and RoHS3 compliance. This part provides the most seamless transition with no circuit redesign required.

For Texas Instruments Ecosystem: LP3852ET-1.8/NOPB serves as a parametric equivalent with identical dropout voltage and quiescent current characteristics. LP3965ET-1.8/NOPB is an alternative within the same manufacturer family, though it exhibits higher quiescent current (9 mA versus 3 mA) and increased dropout voltage (0.55V versus 0.38V).

For Cross-Manufacturer Substitution: The LT1963 series from Analog Devices Inc. (LT1963ET-1.8#PBF, LT1963AET-1.8#PBF, LT1963AET-1.8#06PBF) provides functional equivalence with enhanced input voltage tolerance (20V maximum versus 7V). These parts feature lower quiescent current (1.5 mA) and include reverse polarity protection. All substitute options are RoHS3 compliant and carry active product status.

Frequently Asked Questions (FAQ)

Q: Can LP3852ET-1.8/NOPB be used as a direct replacement for LP3855ET-1.8?

A: Yes. Both parts share identical output voltage (1.8V), output current (1.5A), dropout voltage (0.38V @ 1.5A), quiescent current (3 mA), and package configuration (TO-220-5). The primary difference is product status: LP3852ET-1.8/NOPB is active while the original is obsolete.

Q: What is the key difference between LP3965ET-1.8/NOPB and LP3855ET-1.8/NOPB?

A: LP3965ET-1.8/NOPB exhibits higher quiescent current (9 mA versus 3 mA) and increased dropout voltage (0.55V versus 0.38V). Select LP3855ET-1.8/NOPB for applications requiring lower power dissipation and tighter voltage regulation.

Q: Can Analog Devices LT1963 series parts replace the Texas Instruments LP3855ET-1.8?

A: Functional replacement is possible. The LT1963 series maintains the 1.8V output, 1.5A current rating, and TO-220-5 package. However, the LT1963 series supports higher input voltage (20V maximum versus 7V), features lower quiescent current (1.5 mA), and includes reverse polarity protection. Circuit validation is required if the higher input voltage rating or additional protection features affect system design.

Q: Are all substitute parts RoHS3 compliant?

A: All active substitute parts listed (LP3852ET-1.8/NOPB, LP3965ET-1.8/NOPB, LP3855ET-1.8/NOPB, and all LT1963 variants) are RoHS3 compliant. The original LP3855ET-1.8 is RoHS non-compliant.

Q: What is the difference between LT1963ET-1.8#PBF and LT1963AET-1.8#PBF?

A: Both parts are functionally equivalent with identical electrical specifications. The "A" designation in LT1963AET-1.8#PBF indicates an enhanced or selected grade variant. The LT1963AET-1.8#06PBF variant includes flow-specific packaging designation. All three LT1963 variants are suitable for the same applications.

Q: Is package compatibility guaranteed across all substitutes?

A: All substitute parts use the TO-220-5 package configuration. Physical lead formation (Formed Leads designation for Texas Instruments parts versus standard TO-220-5 for Analog Devices parts) is compatible with standard TO-220-5 PCB footprints. Verify PCB layout compatibility with specific lead spacing if required.

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