APA2120(2013) Просмотр технического описания (PDF) - Anpec Electronics

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APA2120
(Rev.:2013)

Stereo 2-W Audio Power Amplifier (with DC_Volume Control)

Anpec Electronics 

APA2120/2121

Application Information (Cont.)

Power Dissipation

Whether the power amplifier is operated in BTL or SE

modes, power dissipation is a major concern. Equation13

states the maximum power dissipation point for a SE

mode operating at a given supply voltage and driving a

specified load.

SE

mode

:

PD,MAX=

VDD2

2π2RL

(13)

In BTL mode operation, the output voltage swing is

doubled as in SE mode. Thus, the maximum power dis-

sipation point for a BTL mode operating at the same given

conditions is 4 times as in SE mode.

BTL

mode

:

PD,MAX=

4VDD2

2π 2RL

(14)

Since the APA2120/1 are dual channel power amplifiers,

the maximum internal power dissipation is 2 times that

both of equations depend on the mode of operation. Even

this substantial increase in power dissipation, the

APA2120/1 do not require extra heatsink. The power dis-

sipation from equation14, assuming a 5V-power supply

and an 8Ω load, must not be greater than the power dis-

sipation that results from the equation15 :

PD,MAX=

TJ,MAX -

θJA

TA

(15)

The thermal pad on the bottom of the APA2120/1 should

be soldered down to a copper pad on the circuit board.

Heat can be conducted away from the thermal pad through

the copper plane to ambient. If the copper plane is not on

the top surface of the circuit board, 8 to 10 vias of 13 mil or

smaller in diameter should be used to thermally couple

the thermal pad to the bottom plane.

For good thermal conduction, the vias must be plated

through and solder filled. The copper plane used to con-

duct heat away from the thermal pad should be as large

as practical.

If the ambient temperature is higher than 25°C, a larger

copper plane or forced-air cooling will be required to keep

the APA2120/1 junction temperature below the thermal

shutdown temperature (150°C). In higher ambient

temperature, higher airflow rate and/or larger copper area

will be required to keep the IC out of the thermal shutdown.

Recommended Minmum Footprint

Via diameter

=0.3mm X10

1.7mm

3mm

4.7mm

Via diameter

=0.3mm X8

1.7mm

For TSSOP-24 package with thermal pad, the thermal

resistance (θJA) is equal to 45οC/W.

Since the maximum junction temperature (TJ,MAX) of

APA2120/1 are 150οC and the ambient temperature (TA)

are defined by the power system design, the maximum

power dissipation which the IC package is able to handle

can be obtained from equation16.

Once the power dissipation is greater than the maximum

limit (P ), either the supply voltage (V ) must be

D,MAX

DD

decreased, the load impedance (R ) must be increased

L

or the ambient temperature should be reduced.

Thermal Pad Consideration

The thermal pad must be connected to the ground. The

package with thermal pad of the APA2120/1 require spe-

cial attention on thermal design. If the thermal design

issues are not properly addressed, the APA2120/1 4Ω

will go into thermal shutdown when driving a 4Ω load.

0.35mm

0.65mm

Ground plane

for ThermalPAD

Exposed for

thermal PAD

connected

TSSOP-24P

Copyright © ANPEC Electronics Corp.

22

Rev. A.4 - Jul., 2013

www.anpec.com.tw

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