LM4952 datasheet(12/20 Pages) NSC

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Application Information

HIGH VOLTAGE BOOMER WITH INCREASED OUTPUT

POWER

Unlike previous 5V Boomer® amplifiers, the LM4952 is de-

signed to operate over a power supply voltages range of

9.6V to 16V. Operating on a 12V power supply, the LM4952

will deliver 3.8W into a 4

Ω SE load with no more than 10%

THD+N.

POWER DISSIPATION

Power dissipation is a major concern when designing a

successful single-ended or bridged amplifier. Equation (2)

states the maximum power dissipation point for a single-

ended amplifier operating at a given supply voltage and

driving a specified output load.

DMAX-SE =(VDD)

2 / (2

π2R

L):

Single Ended

(1)

The LM4952’s dissipation is twice the value given by Equa-

tion (2) when driving two SE loads. For a 12V supply and two

Ω SE loads, the LM4952’s dissipation is 1.82W.

The maximum power dissipation point given by Equation (1)

must not exceed the power dissipation given by Equation

(2):

DMAX’= (TJMAX -TA) /

(2)

The LM4952’s T

JMAX = 150˚C. In the TS package, the

LM4952’s

JA is 20˚C/W when the metal tab is soldered to a

copper plane of at least 16in

2. This plane can be split be-

tween the top and bottom layers of a two-sided PCB. Con-

nect the two layers together under the tab with a 5x5 array of

vias. At any given ambient temperature T

A, use Equation (2)

to find the maximum internal power dissipation supported by

the IC packaging. Rearranging Equation (2) and substituting

DMAX for PDMAX’ results in Equation (3). This equation gives

the maximum ambient temperature that still allows maximum

stereo power dissipation without violating the LM4952’s

maximum junction temperature.

A =TJMAX -PDMAX-SE

(3)

For a typical application with a 12V power supply and an SE

Ω load, the maximum ambient temperature that allows

maximum stereo power dissipation without exceeding the

maximum junction temperature is approximately 77˚C for the

TS package.

JMAX =PDMAX-MONOBTL

JA +TA

(4)

Equation (4) gives the maximum junction temperature

JMAX. If the result violates the LM4952’s 150˚C, reduce the

maximum junction temperature by reducing the power sup-

ply voltage or increasing the load resistance. Further allow-

ance should be made for increased ambient temperatures.

The above examples assume that a device is operating

around the maximum power dissipation point. Since internal

200809E8

FIGURE 2. Typical LM4952 SE Application Circuit

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