LM317KCT Equivalent & Substitute Parts

Part Overview

The LM317KCT is a linear voltage regulator IC from Texas Instruments designed for positive adjustable output applications. It delivers 1.5A output current in a TO-220-3 package and is classified as obsolete. Due to its obsolete status, equivalent and substitute parts from active product lines are necessary for new designs and ongoing production requirements. Substitute parts maintain the same functional specifications and package compatibility while offering improved availability and active manufacturer support.

Key Parameters

Parameter	Value
Output Configuration	Positive
Output Type	Adjustable
Number of Regulators	1
Voltage - Input (Max)	40V
Voltage - Output (Min/Fixed)	1.25V
Voltage - Output (Max)	37V
Current - Output	1.5A
Current - Quiescent (Iq)	10 mA
PSRR	80dB ~ 65dB (120Hz)
Protection Features	Over Current, Over Temperature, Short Circuit
Operating Temperature	0°C ~ 125°C
Package / Case	TO-220-3
RoHS Status	ROHS3 Compliant

Substitute Part Grouping Explanation

Substitution for the LM317KCT is determined by strict equivalence across the following critical parameters:

Output configuration (Positive) and type (Adjustable)
Output current rating (1.5A)
Voltage specifications: Input maximum 40V, output adjustable range 1.25V to 37V
Protection features: Over current, over temperature, and short circuit protection
Package type: TO-220-3
RoHS3 compliance and regulatory status

Substitute parts are grouped into two categories based on manufacturer and product status:

Parametric Equivalent (Texas Instruments): LM317T/NOPB maintains identical electrical specifications with active product status and higher inventory availability.

Manufacturer Recommended Alternatives (onsemi): LM317BTG and LM317TG are onsemi equivalents that meet or exceed the original specifications with active product status and extended temperature range options.

Parameter Comparison

Parameter	LM317KCT	LM317T/NOPB	LM317BTG	LM317TG
Manufacturer	Texas Instruments	Texas Instruments	onsemi	onsemi
Product Status	Obsolete	Active	Active	Active
Output Configuration	Positive	Positive	Positive	Positive
Output Type	Adjustable	Adjustable	Adjustable	Adjustable
Voltage - Input (Max)	40V	37V	40V	40V
Voltage - Output (Min/Fixed)	1.25V	1.25V	1.2V	1.2V
Voltage - Output (Max)	37V	37V	37V	37V
Current - Output	1.5A	1.5A	1.5A	1.5A
Current - Quiescent (Iq)	10 mA	10 mA	10 mA	10 mA
PSRR	80dB ~ 65dB (120Hz)	64dB (120Hz)	80dB ~ 65dB (120Hz)	80dB ~ 65dB (120Hz)
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
Operating Temperature	0°C ~ 125°C	0°C ~ 125°C	-40°C ~ 125°C	0°C ~ 125°C
Package / Case	TO-220-3	TO-220-3	TO-220-3	TO-220-3
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant

Engineering Selection Recommendations

LM317T/NOPB (Texas Instruments): This part is the direct parametric equivalent from the original manufacturer. It maintains active product status with significantly higher inventory availability (188,400 pcs). Selection is appropriate for applications requiring continuity with the original Texas Instruments product line. Note that maximum input voltage is specified at 37V compared to the original 40V specification.

LM317BTG (onsemi): This part matches the original 40V maximum input voltage specification and extends the operating temperature range to -40°C ~ 125°C, providing enhanced performance for wider temperature applications. Active product status with substantial inventory (100,099 pcs) ensures supply chain reliability.

LM317TG (onsemi): This part maintains the 40V maximum input voltage and identical PSRR specifications to the original. Operating temperature range matches the original specification (0°C ~ 125°C). Active product status with available inventory (2,344 pcs) supports production requirements.

All substitute parts are ROHS3 compliant and REACH unaffected, maintaining regulatory compliance with the original part.

Frequently Asked Questions (FAQ)

Q: Can LM317T/NOPB be used as a direct replacement for LM317KCT?

A: LM317T/NOPB is a parametric equivalent with identical electrical specifications and TO-220-3 package compatibility. The primary difference is the maximum input voltage specification of 37V versus the original 40V. For applications operating within 37V input limits, this part provides direct substitution with active product status and superior availability.

Q: What is the difference between the onsemi alternatives (LM317BTG and LM317TG)?

A: Both onsemi parts maintain the 40V maximum input voltage specification. LM317BTG extends the operating temperature range to -40°C ~ 125°C, making it suitable for applications requiring enhanced low-temperature performance. LM317TG maintains the original 0°C ~ 125°C operating range. Both are electrically equivalent and use identical TO-220-3 packaging.

Q: Are all substitute parts pin-compatible with the original LM317KCT?

A: All substitute parts use the TO-220-3 package with identical pinout configuration, ensuring direct mechanical and electrical compatibility in existing circuit designs.

Q: Do the substitute parts maintain the same protection features?

A: All substitute parts include over current, over temperature, and short circuit protection features identical to the original LM317KCT specification.

Q: Which substitute part should be selected for new designs?

A: Selection depends on specific application requirements. For standard applications within 37V input limits, LM317T/NOPB offers continuity with the original manufacturer. For applications requiring 40V input capability or extended temperature range, onsemi alternatives (LM317BTG or LM317TG) are appropriate. All parts maintain ROHS3 compliance and active product status.

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