Open Loop

Frequency Response

Supply Current vs

Supply Voltage

20008938

20008944

Application Information

MICRO-POWER SHUTDOWN

The voltage applied to the SHUTDOWN pin controls the

LM4810’s shutdown function. Activate micro-power shut-

down by applying a logic high voltage to the SHUTDOWN

pin. The logic threshold is typically V

LM4810’s micro-power shutdown feature turns off the ampli-

fier’s bias circuitry, reducing the supply current. The low

0.4µA typical shutdown current is achieved by applying a

voltage that is as near as V

DOWN pin. A voltage that is less than V

shutdown current.

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 between the

SHUTDOWN pin and V

SHUTDOWN pin and GND. Select normal amplifier opera-

tion by closing the switch. Opening the switch connects the

SHUTDOWN pin to V

ing micro-power shutdown. The switch and resistor guaran-

tee 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

(LD) 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 LD package should have its DAP soldered to a copper

pad on the PCB. The DAP’s PCB copper pad may be con-

nected 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 ap-

plications, connecting a copper plane to the DAP’s PCB

copper pad is not required. The LM4810’s Power Dissipation

vs Output Power Curve in the Typical Performance Char-

acteristics 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 LD (LLP) package is

available from National Semiconductor’s Package Engineer-

ing 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.

P

(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 tem-

perature. From Equation 1, assuming a 5V power supply and

a32

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:

P

θ

JA

(2)

For package MUA08A,

θ

the LM4810. Depending on the ambient temperature, T

the system surroundings, Equation 2 can be used to find the

maximum internal power dissipation supported by the IC

packaging. If the result of Equation 1 is greater than that of

Equation 2, then either the supply voltage must be de-

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