LM350T Linear Voltage Regulator IC Equivalent & Substitute Parts

Part Overview

The LM350T is a linear voltage regulator IC manufactured by onsemi, designed for positive adjustable output applications requiring 3A current capacity in a TO-220-3 package. This device is classified as obsolete, making equivalent and substitute parts necessary for ongoing design support and procurement.

The LM350T operates with an input voltage range up to 35V and provides adjustable output from 1.2V to 33V. It includes over temperature and short circuit protection features, with a PSRR of 80dB at 120Hz. The device is RoHS3 compliant and MSL Level 1, suitable for through-hole mounting applications.

Key Parameters

Parameter	Value
Manufacturer	onsemi
Part Number	LM350T
Product Status	Obsolete
Output Configuration	Positive
Output Type	Adjustable
Current - Output	3A
Voltage - Input (Max)	35V
Voltage - Output (Min/Fixed)	1.2V
Voltage - Output (Max)	33V
Package / Case	TO-220-3
Operating Temperature	0°C ~ 125°C
Protection Features	Over Temperature, Short Circuit
RoHS Status	ROHS3 Compliant

Substitute Part Grouping Explanation

Substitution eligibility for the LM350T is determined by the following critical parameters:

Output Configuration & Type: Must be positive adjustable output
Current Rating: Minimum 3A output capacity
Voltage Range: Input maximum ≥35V; output adjustable range covering 1.2V to 33V
Package Compatibility: TO-220-3 form factor for direct pin-compatible replacement
Protection Features: Over temperature protection required; short circuit protection preferred
Compliance: RoHS3 compliance and MSL Level 1 required

The substitute parts identified meet these criteria with the following considerations:

LM350AT/NOPB and LM350T/NOPB (Texas Instruments): Identical base product number (LM350), same TO-220-3 package, matching 3A output, identical voltage ranges, and active product status. Both include enhanced protection (over current, over temperature, short circuit).

LM138K STEEL/NOPB (Texas Instruments): Higher current rating (5A), compatible voltage ranges, and active status. Package is TO-3-2 (TO-204AA, TO-3), which differs from TO-220-3 and requires board layout modification.

Parameter Comparison

Parameter	LM350T (onsemi)	LM350AT/NOPB (TI)	LM350T/NOPB (TI)	LM138K STEEL/NOPB (TI)
Product Status	Obsolete	Active	Active	Active
Output Configuration	Positive	Positive	Positive	Positive
Output Type	Adjustable	Adjustable	Adjustable	Adjustable
Current - Output	3A	3A	3A	5A
Voltage - Input (Max)	35V	35V	35V	40V
Voltage - Output (Min/Fixed)	1.2V	1.25V	1.25V	1.2V
Voltage - Output (Max)	33V	33V	33V	32V
Package / Case	TO-220-3	TO-220-3	TO-220-3	TO-204AA, TO-3
Operating Temperature	0°C ~ 125°C	-40°C ~ 125°C	0°C ~ 125°C	-55°C ~ 150°C
Protection Features	Over Temperature, Short Circuit	Over Current, Over Temperature, Short Circuit	Over Current, Over Temperature, Short Circuit	Over Temperature
PSRR (120Hz)	80dB	86dB ~ 65dB	86dB ~ 65dB	75dB
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant

Engineering Selection Recommendations

Direct Pin-Compatible Replacements (Recommended for Immediate Substitution):

LM350T/NOPB and LM350AT/NOPB (both Texas Instruments) are the primary substitutes. Both maintain active product status, identical TO-220-3 packaging, matching 3A output specifications, and equivalent voltage operating ranges. LM350T/NOPB offers the closest thermal operating range match (0°C ~ 125°C) to the original LM350T. Both include enhanced over current protection compared to the original device. Inventory availability is substantial (16,627 and 2,380 units respectively).

Alternative with Enhanced Specifications:

LM138K STEEL/NOPB provides higher current capacity (5A) and extended temperature range (-55°C ~ 150°C), supporting more demanding applications. However, the TO-3-2 package requires PCB layout modification and is not a direct pin replacement. This substitute is suitable only when board redesign is feasible and higher current capability is beneficial.

Compliance Basis:

All substitute parts maintain RoHS3 compliance and MSL Level 1 rating, ensuring regulatory and environmental compatibility with the original LM350T specification.

Frequently Asked Questions (FAQ)

Q: Can LM350T/NOPB directly replace the onsemi LM350T without PCB modification?

A: Yes. LM350T/NOPB is pin-compatible with identical TO-220-3 packaging, matching lead configuration, and equivalent electrical specifications. No PCB layout changes are required.

Q: What is the difference between LM350AT/NOPB and LM350T/NOPB?

A: Both are Texas Instruments LM350 base products with identical electrical performance and TO-220-3 packaging. The primary difference is operating temperature range: LM350AT/NOPB operates -40°C ~ 125°C, while LM350T/NOPB operates 0°C ~ 125°C. Select based on your application's minimum operating temperature requirement.

Q: Why is LM138K STEEL/NOPB listed as a substitute if it uses a different package?

A: LM138K STEEL/NOPB meets the core electrical substitution criteria (positive adjustable output, 5A capacity, compatible voltage ranges, active status, RoHS3 compliance). However, its TO-3-2 package differs from TO-220-3, requiring board redesign. It is suitable only when higher current capacity justifies layout modification.

Q: Are there any electrical parameter differences that affect circuit design?

A: Minimum output voltage differs slightly: LM350T specifies 1.2V minimum, while LM350AT/NOPB and LM350T/NOPB specify 1.25V minimum. For applications requiring output below 1.25V, verify circuit design compatibility. PSRR performance is comparable across all substitutes (75dB to 86dB at 120Hz).

Q: What inventory status should I consider for procurement?

A: LM350T/NOPB has the highest inventory (16,627 units), followed by LM350AT/NOPB (2,380 units). Both are active products with reliable supply. LM138K STEEL/NOPB has lower inventory (900 units) and should be evaluated for long-term availability if selected.

Q: Are all substitutes RoHS3 compliant?

A: Yes. All listed substitute parts are RoHS3 compliant with MSL Level 1 rating, matching the original LM350T compliance status.

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