LM4810

www.ti.com

SNAS125D – FEBRUARY 2001 – REVISED APRIL 2013

APPLICATION INFORMATION

MICRO-POWER SHUTDOWN

The voltage applied to the SHUTDOWN pin controls the LM4810's shutdown function. Activate micro-power

active, the LM4810's micro-power shutdown feature turns off the amplifier's bias circuitry, reducing the supply

There are a few ways to control the micro-power shutdown. These include using a single-pole, single-throw

switch, a microprocessor, or a microcontroller. When using a switch, connect an external 100k

Ω pull-up resistor

through the pull-up resistor, activating micro-power shutdown. The switch and resistor ensure that the

SHUTDOWN pin will not float. This prevents unwanted state changes. In a system with a microprocessor or a

microcontroller, use a digital output to apply the control voltage to the SHUTDOWN pin. Driving the SHUTDOWN

pin with active circuitry eliminates the pull-up resistor.

EXPOSED-DAP PACKAGE PCB MOUNTING CONSIDERATION

The LM4810's exposed-Dap (die attach paddle) package (NGL0008B) provides a low thermal resistance

between the die and the PCB to which the part is mounted and soldered. This allows rapid heat transfer from the

die to the surrounding PCB copper traces, ground plane, and surrounding air.

The NGL0008B package should have its DAP soldered to a copper pad on the PCB. The DAP's PCB copper pad

may be connected to a large plane of continuous unbroken copper. This plane forms a thermal mass, heat sink,

and radiation area.

However, since the LM4810 is designed for headphone applications, connecting a copper plane to the DAP's

PCB copper pad is not required. Figure 33 in Typical Performance Characteristics shows that the maximum

power dissipated is just 45mW per amplifier with a 5V power supply and a 32

Ω load.

Further detailed and specific information concerning PCB layout, fabrication, and mounting an NGL0008B

(WSON) package is available from Texas Instruments' Package Engineering Group under application note

AN1187.

POWER DISSIPATION

Power dissipation is a major concern when using any power amplifier and must be thoroughly understood to

ensure a successful design. Equation 1 states the maximum power dissipation point for a single-ended amplifier

operating at a given supply voltage and driving a specified output load.

(1)

Since the LM4810 has two operational amplifiers in one package, the maximum internal power dissipation point

is twice that of the number which results from Equation 1. Even with the large internal power dissipation, the

LM4810 does not require heat sinking over a large range of ambient temperature. From Equation 1, assuming a

5V power supply and a 32

Ω load, the maximum power dissipation point is 40mW per amplifier. Thus the

maximum package dissipation point is 80mW. The maximum power dissipation point obtained must not be

greater than the power dissipation that results from Equation 2:

(2)

For package DGK0008A,

dissipation supported by the IC packaging. If the result of Equation 1 is greater than that of Equation 2, then

application of a 5V power supply, with a 32

Ω load, the maximum ambient temperature possible without violating

the maximum junction temperature is approximately 133.2°C provided that device operation is around the

maximum power dissipation point. Power dissipation is a function of output power and thus, if typical operation is

not around the maximum power dissipation point, the ambient temperature may be increased accordingly. Refer

to Typical Performance Characteristics for power dissipation information for lower output powers.

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