LM317AT Linear Voltage Regulator IC Equivalent & Substitute Parts

Part Overview

The LM317AT is a positive adjustable linear voltage regulator IC manufactured by Texas Instruments, rated for 1.5A output current in a TO-220-3 through-hole package. This device is classified as Last Time Buy, indicating limited availability from the original manufacturer. Finding equivalent and substitute parts is necessary to ensure design continuity and maintain supply chain flexibility for applications requiring positive adjustable voltage regulation.

Key Parameters

Parameter	Value
Manufacturer	Texas Instruments
Part Number	LM317AT
Category	Power Management (PMIC)
Package / Case	TO-220-3
Mounting Type	Through Hole
Output Configuration	Positive
Output Type	Adjustable
Voltage - Input (Max)	40V
Voltage - Output (Min/Fixed)	1.25V
Voltage - Output (Max)	37V
Current - Output	1.5A
Current - Quiescent (Iq)	10 mA
Operating Temperature	-40°C ~ 125°C
Protection Features	Over Current, Over Temperature, Short Circuit
RoHS Status	ROHS3 Compliant

Substitute Part Grouping Explanation

Substitution of the LM317AT is determined by the following critical parameters:

Primary Substitution Criteria:

Output Configuration: Positive
Output Type: Adjustable
Voltage - Input (Max): 40V
Voltage - Output Range: 1.25V to 37V minimum
Current - Output: 1.5A minimum
Package / Case: TO-220-3 (through-hole mounting)
Protection Features: Over Current, Over Temperature, Short Circuit

Substitute parts are grouped into two categories:

Category 1: Direct Equivalents (Same Package, Same Current Rating) Parts with identical TO-220-3 packaging and 1.5A output current rating. These provide pin-for-pin compatibility and identical thermal characteristics.

Category 2: Functional Equivalents (Same Package, Reduced Current Rating) Parts with identical TO-220-3 packaging but 500mA output current rating. These are suitable only for applications where the maximum output current requirement does not exceed 500mA.

Category 3: Package Variant (Surface Mount Alternative) Parts with identical electrical specifications but different package types (TO-263 DDPAK). These require PCB redesign and are suitable only when surface-mount technology is preferred.

Category 4: Cross-Manufacturer Alternatives Parts from alternative manufacturers (STMicroelectronics, onsemi, NTE Electronics) with equivalent electrical specifications and TO-220-3 packaging.

Parameter Comparison

Part Number	Manufacturer	Package	Mounting	Output Current	Voltage Input (Max)	Voltage Output (Min)	Operating Temp	Product Status
LM317AT	Texas Instruments	TO-220-3	Through Hole	1.5A	40V	1.25V	-40°C ~ 125°C	Last Time Buy
LM317AT/NOPB	Texas Instruments	TO-220-3	Through Hole	1.5A	40V	1.25V	-40°C ~ 125°C	Active
LM317KTTR	Texas Instruments	TO-263 (DDPAK-3)	Surface Mount	1.5A	40V	1.25V	0°C ~ 125°C	Active
LM217T	STMicroelectronics	TO-220-3	Through Hole	1.5A	40V	1.2V	-25°C ~ 150°C	Active
LM317BTG	onsemi	TO-220-3	Through Hole	1.5A	40V	1.2V	-40°C ~ 125°C	Active
LM317TG	onsemi	TO-220-3	Through Hole	1.5A	40V	1.2V	0°C ~ 125°C	Active
LM317T	NTE Electronics, Inc	TO-220-3	Through Hole	1.5A	37V	1.25V	0°C ~ 125°C	Active
LM317MBTG	onsemi	TO-220-3	Through Hole	500mA	40V	1.2V	-40°C ~ 125°C	Active
LM317MABTG	onsemi	TO-220-3	Through Hole	500mA	40V	1.2V	-40°C ~ 125°C	Active
LM317MTG	onsemi	TO-220-3	Through Hole	500mA	40V	1.2V	0°C ~ 125°C	Active

Engineering Selection Recommendations

Recommended Primary Substitutes (Active Status, Full Compatibility):

LM317AT/NOPB (Texas Instruments) is the direct successor with identical electrical and mechanical specifications. This part maintains Active product status and is the preferred choice for direct replacement.

LM317BTG (onsemi) and LM317TG (onsemi) are functionally equivalent alternatives with Active status. Both maintain the TO-220-3 package, 1.5A output current, and identical voltage specifications. Operating temperature ranges differ slightly; LM317BTG supports -40°C to 125°C, matching the original LM317AT specification.

LM217T (STMicroelectronics) is an alternative from a different manufacturer with Active status. It maintains TO-220-3 packaging and 1.5A output current. The minimum output voltage is 1.2V (versus 1.25V for LM317AT), and the operating temperature range extends to 150°C maximum.

LM317T (NTE Electronics, Inc) is available with Active status in TO-220-3 packaging and 1.5A output current. Maximum input voltage is specified as 37V (versus 40V for LM317AT), which may limit applications requiring higher input voltages.

Surface Mount Alternative:

LM317KTTR (Texas Instruments) provides equivalent electrical specifications in a TO-263 (DDPAK-3) surface-mount package. This substitution requires PCB redesign and is suitable only when surface-mount technology is the design requirement. Operating temperature range is 0°C to 125°C.

Reduced Current Alternatives (500mA Rating):

LM317MBTG, LM317MABTG, and LM317MTG (onsemi) are suitable only for applications where maximum output current does not exceed 500mA. These parts maintain TO-220-3 packaging and identical voltage specifications but are not suitable for applications requiring the full 1.5A output current of the LM317AT.

All recommended substitutes maintain ROHS3 compliance and REACH Unaffected status, consistent with the original LM317AT specification.

Frequently Asked Questions (FAQ)

Q: Can LM317AT/NOPB be used as a direct replacement for LM317AT?

A: Yes. LM317AT/NOPB is the direct equivalent with identical electrical specifications, package type (TO-220-3), and current rating (1.5A). The /NOPB designation indicates lead-free plating and RoHS compliance. This is the recommended substitute.

Q: What is the difference between LM317BTG and LM317TG?

A: Both are onsemi products in TO-220-3 packaging with 1.5A output current. The primary difference is operating temperature range: LM317BTG operates from -40°C to 125°C, while LM317TG operates from 0°C to 125°C. Select LM317BTG for applications requiring extended low-temperature operation.

Q: Can LM317MBTG replace LM317AT?

A: LM317MBTG is not a suitable replacement for applications requiring 1.5A output current. This part is rated for 500mA maximum output current. Use LM317MBTG only in designs where the maximum required output current does not exceed 500mA.

Q: Is LM317KTTR compatible with existing PCB layouts designed for LM317AT?

A: No. LM317KTTR uses a TO-263 (DDPAK-3) surface-mount package, while LM317AT uses a TO-220-3 through-hole package. PCB redesign is required. LM317KTTR is suitable only when surface-mount technology is the design requirement.

Q: What is the minimum output voltage difference between LM317AT and LM217T?

A: LM317AT specifies 1.25V minimum output voltage, while LM217T specifies 1.2V minimum output voltage. This 0.05V difference is negligible for most applications. Both parts maintain identical maximum output voltage (37V) and input voltage (40V) specifications.

Q: Are all substitute parts RoHS compliant?

A: Yes. All substitute parts listed maintain ROHS3 compliance, consistent with the original LM317AT specification.

Q: Which substitute offers the widest operating temperature range?

A: LM217T (STMicroelectronics) offers the widest operating temperature range, from -25°C to 150°C, compared to LM317AT's -40°C to 125°C range. This extended high-temperature capability may be beneficial for applications in elevated ambient conditions.

Q: Can LM317T (NTE Electronics) be used in applications requiring 40V input?

A: LM317T (NTE Electronics) specifies a maximum input voltage of 37V, which is lower than the LM317AT specification of 40V. This part is not suitable for applications requiring the full 40V input voltage capability.

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