LM4818M/NOPB Equivalent & Substitute Parts

Part Overview

The LM4818M/NOPB is a Class AB mono audio amplifier IC manufactured by Texas Instruments, part of the Boomer® series. This device delivers 350mW output power at 16Ohm load in an 8-SOIC surface mount package. The LM4818M/NOPB is classified as obsolete, necessitating identification of active equivalent and substitute components for new designs and production continuity. Substitute parts must maintain functional compatibility while meeting current supply chain requirements and product status criteria.

Key Parameters

Parameter	LM4818M/NOPB
Manufacturer	Texas Instruments
Category	Linear, Amplifiers
Type	Class AB
Output Type	1-Channel (Mono)
Max Output Power @ Load	350mW x 1 @ 16Ohm
Voltage Supply Range	2V ~ 5.5V
Package / Case	8-SOIC (0.154", 3.90mm Width)
Mounting Type	Surface Mount
Operating Temperature	-40°C ~ 85°C (TA)
Features	Depop, Shutdown
RoHS Status	ROHS3 Compliant
Product Status	Obsolete

Substitute Part Grouping Explanation

Substitute parts for the LM4818M/NOPB are selected based on strict compatibility criteria derived from the provided parameters:

Primary Substitution Criteria:

Class AB amplifier topology
1-Channel (Mono) output configuration
8-SOIC package with identical physical dimensions (0.154", 3.90mm Width)
Surface mount mounting type
Operating temperature range -40°C ~ 85°C
Supply voltage compatibility (minimum 2V, maximum 5.5V)
ROHS3 compliance and REACH unaffected status

Output Power Consideration: The LM4818M/NOPB delivers 350mW at 16Ohm. Substitute parts with higher output power ratings (700mW or 1.1W) at lower impedance loads (8Ohm) are functionally compatible for applications requiring equal or greater power delivery. Parts with lower power ratings are not suitable substitutes.

Feature Compatibility: The LM4818M/NOPB includes Depop and Shutdown features. Substitute parts must include Shutdown; Depop is an enhanced feature present in select alternatives.

Product Status: Active substitute parts are preferred for new designs. Last Time Buy status indicates limited availability but continued support.

Parameter Comparison

Part Number	Manufacturer	Type	Output Type	Max Output Power @ Load	Voltage Supply	Package	Operating Temp	Features	Product Status
LM4818M/NOPB	Texas Instruments	Class AB	1-Channel (Mono)	350mW @ 16Ohm	2V ~ 5.5V	8-SOIC	-40°C ~ 85°C	Depop, Shutdown	Obsolete
TPA301DR	Texas Instruments	Class AB	1-Channel (Mono)	700mW @ 8Ohm	2.5V ~ 5.5V	8-SOIC	-40°C ~ 85°C	Short-Circuit and Thermal Protection, Shutdown	Active
TPA301D	Texas Instruments	Class AB	1-Channel (Mono)	700mW @ 8Ohm	2.5V ~ 5.5V	8-SOIC	-40°C ~ 85°C	Short-Circuit and Thermal Protection, Shutdown	Active
TPA321D	Texas Instruments	Class AB	1-Channel (Mono)	700mW @ 8Ohm	2.5V ~ 5.5V	8-SOIC	-40°C ~ 85°C	Differential Inputs, Short-Circuit and Thermal Protection, Shutdown	Active
TPA321DR	Texas Instruments	Class AB	1-Channel (Mono)	700mW @ 8Ohm	2.5V ~ 5.5V	8-SOIC	-40°C ~ 85°C	Differential Inputs, Short-Circuit and Thermal Protection, Shutdown	Active
TPA4861DR	Texas Instruments	Class AB	1-Channel (Mono)	1.1W @ 8Ohm	2.7V ~ 5.5V	8-SOIC	-40°C ~ 85°C	Short-Circuit and Thermal Protection, Shutdown	Active
TPA4861D	Texas Instruments	Class AB	1-Channel (Mono)	1.1W @ 8Ohm	2.7V ~ 5.5V	8-SOIC	-40°C ~ 85°C	Short-Circuit and Thermal Protection, Shutdown	Active
TPA701D	Texas Instruments	Class AB	1-Channel (Mono)	700mW @ 8Ohm	2.5V ~ 5.5V	8-SOIC	-40°C ~ 85°C	Short-Circuit and Thermal Protection, Shutdown	Active
TPA701DR	Texas Instruments	Class AB	1-Channel (Mono)	700mW @ 8Ohm	2.5V ~ 5.5V	8-SOIC	-40°C ~ 85°C	Short-Circuit and Thermal Protection, Shutdown	Active
TPA721DR	Texas Instruments	Class AB	1-Channel (Mono)	700mW @ 8Ohm	2.5V ~ 5.5V	8-SOIC	-40°C ~ 85°C	Depop, Short-Circuit and Thermal Protection, Shutdown	Active
TPA731DR	Texas Instruments	Class AB	1-Channel (Mono)	700mW @ 8Ohm	2.5V ~ 5.5V	8-SOIC	-40°C ~ 85°C	Differential Inputs, Short-Circuit and Thermal Protection, Shutdown	Last Time Buy

Engineering Selection Recommendations

For Direct Replacement (Equivalent Functionality):

TPA721DR is the primary equivalent for LM4818M/NOPB. Both devices include Depop functionality alongside Shutdown, matching the feature set of the original part. TPA721DR is Active status with 700mW output power at 8Ohm, providing increased power delivery capability while maintaining identical package and thermal specifications.

For Higher Power Applications:

TPA4861DR and TPA4861D deliver 1.1W output power at 8Ohm, suitable for applications requiring increased audio amplification. These parts maintain 8-SOIC packaging and -40°C ~ 85°C operating range. Minimum supply voltage is 2.7V (compared to 2V for LM4818M/NOPB), which is compatible with standard 3.3V and 5V supply rails.

For Differential Input Applications:

TPA321D, TPA321DR, and TPA731DR include Differential Inputs feature in addition to standard protection and shutdown functions. These parts are suitable for designs requiring balanced audio signal processing.

Packaging Considerations:

All substitute parts are available in multiple packaging formats (Tube, Cut Tape & Digi-Reel, Tape & Reel). Selection depends on production volume and assembly requirements. TPA701DR and TPA4861DR offer highest inventory availability (20,400 and 31,110 units respectively).

Compliance Status:

All substitute parts maintain ROHS3 compliance and REACH unaffected status, matching the environmental and regulatory requirements of the original LM4818M/NOPB.

Frequently Asked Questions (FAQ)

Q: Can TPA301DR directly replace LM4818M/NOPB in existing designs?

A: TPA301DR is functionally compatible as a Class AB mono amplifier in 8-SOIC package with matching operating temperature range. However, TPA301DR lacks the Depop feature present in LM4818M/NOPB. If Depop functionality is required, TPA721DR is the appropriate substitute. TPA301DR delivers 700mW at 8Ohm compared to 350mW at 16Ohm for the original part, providing increased power capability.

Q: What is the difference between TPA321D and TPA321DR?

A: TPA321D is supplied in Tube packaging, while TPA321DR is supplied in Tape & Reel (TR) format. Both parts are electrically identical Class AB mono amplifiers with Differential Inputs, Short-Circuit and Thermal Protection, and Shutdown features. Selection depends on production volume and assembly line requirements. TPA321DR has higher inventory availability (3,344 units vs. 1,123 units).

Q: Is TPA731DR suitable for new designs despite Last Time Buy status?

A: TPA731DR is functionally suitable for new designs and maintains Active support with 1,640 units in stock. Last Time Buy status indicates limited future availability. For long-term production, TPA321DR or TPA721DR are recommended as Active status alternatives with equivalent or superior specifications and higher inventory levels.

Q: What is the minimum supply voltage requirement for substitute parts?

A: LM4818M/NOPB operates from 2V ~ 5.5V. Most substitute parts (TPA301, TPA321, TPA701, TPA721, TPA731 series) require 2.5V ~ 5.5V minimum. TPA4861 series requires 2.7V ~ 5.5V. All substitute parts are compatible with standard 3.3V and 5V supply rails used in modern audio applications.

Q: Do all substitute parts include thermal protection?

A: LM4818M/NOPB includes Depop and Shutdown features. All substitute parts include Shutdown. Short-Circuit and Thermal Protection is standard across all TPA301, TPA321, TPA4861, TPA701, TPA721, and TPA731 series parts. TPA721DR and TPA731DR additionally include Depop functionality.

Q: What is the package compatibility between LM4818M/NOPB and substitute parts?

A: All substitute parts use 8-SOIC package with identical physical dimensions (0.154", 3.90mm Width). Pin-to-pin compatibility requires verification against specific application schematics, as input/output configurations may differ between base product numbers (TPA301, TPA321, TPA4861, TPA701, TPA721, TPA731).

Q: Which substitute part offers the highest output power?

A: TPA4861D and TPA4861DR deliver 1.1W output power at 8Ohm, the highest among all substitute options. These parts are suitable for applications requiring maximum audio amplification within the 8-SOIC form factor and -40°C ~ 85°C operating range.

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