apa3010 Anpec Electronics Corporation, apa3010 Datasheet - Page 12

• Manufacturer Part Number: apa3010
• Description: 3w Mono Low-voltage Audio Power Amplifier
• Manufacturer: Anpec Electronics Corporation

Application Information (Cont.)
BTL Amplifier Efficiency (Cont.)
The following equations are the basis for calculating
amplifier efficiency.
Where :
Efficiency of a BTL configuration :
Table 1 calculates efficiencies for four different output
power levels.
Note that the efficiency of the amplifier is quite low for
lower power levels and rises sharply as power to the load
is increased resulting in a nearly flat internal power dissi-
pation over the normal operating range.
Note that the internal dissipation at full output power is
less than in the half power range. Calculating the effi-
ciency for a specific system is the key to proper power
supply design.
A final point to remember about linear amplifiers (either
SE or BTL) is how to manipulate the terms in the effi-
ciency equation to an utmost advantage when possible.
Note that in equation, V
cates that as V
words, use the efficiency analysis to choose the correct
supply voltage and speaker impedance for the application.
** High peak voltages cause the THD to increase.
Table 1. Efficiency Vs Output Power in 5-V/8
Systems.
Copyright
Rev. A.6 - Jun., 2009
APA3010/1
V
P
P
Orms
SUP
0.25
0.50
1.00
1.25
Efficiency =
O
P
P
(W)
=
O
SUP
=
V
DD
=
(
x
V
ANPEC Electronics Corp.
V
Efficiency (%)
2
P
I
2R
P
P
DDAVG
DD
x V
O
L
goes down, efficiency goes up. In other
31.25
47.62
66.67
78.13
=
P
P
P
=
) / (
V
SUP
O
Orms
V
DD
DD
V
DD
R
x
is in the denominator. This indi-
x
L
x
V
Orms
2V
R
I
DD
0.16
0.21
0.30
0.32
2V
P
L
R
(A)
) =
P
L
=
V
4V
V
2.00
2.83
4.00
4.47
PP
2R
P
V
DD
x V
P
(V) P
L
P
BTL
(7)
(8)
0.55
0.55
0.35
(6)
D
0.5
(9)
(W)
12
Power Dissipation
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.
Even with this substantial increase in power dissipation,
the APA3010/1 do not require extra heatsink. The power
dissipation from equation11, assuming a 5V-power sup-
ply and an 8
dissipation that results from the equation11 :
For MSOP-8P package with thermal pad, the thermal re-
sistance (
Since the maximum junction temperature (T
APA3010/1 is 150 C and the ambient temperature (T
defined by the power system design, the maximum power
dissipation which the IC package is able to handle can be
obtained from equation11.
Once the power dissipation is greater than the maximum
limit (P
decreased, the load impedance (R
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 APA3010/1 requires spe-
cial attention on thermal design. If the thermal design
issues are not properly addressed, the APA3010/1 4
will go into thermal shutdown when driving a 4
The thermal pad must be connected to the ground. The
package with thermal pad of the APA3010/1 requires spe-
cial attention on thermal design.
The thermal pad on the bottom of the APA3010/1 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 12 vias of 15 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.
BTL mode : P
P
D,MAX
D,MAX
=
JA
), either the supply voltage (V
) is equal to 48 C/W.
T
load, must not be greater than the power
J,MAX
D,MAX
JA
- T
=
A
2
4V
2
R
DD
L
2
L
) must be increased
www.anpec.com.tw
DD
) must be
J,MAX
(11)
load.
(10)
A
) of
) is