APA2030/2031
Application Descriptions
A final point to remember about linear amplifiers (either
SE or BTL) is how to manipulate the terms in the effi-
ciency equation to utmost advantage whenpossible.
Note that in equation, VDD is in the dominator. This
indicates that as VDD goes down,efficiency goes up. In
other words, use the efficiency analysis to choose the
correct supply voltage and speaker impedance for the
application.
O
P
P
Efficiency =
(7)
(8)
SUP
Where:
O
×
O
P ×
P
V rms V rms
V
V
L
PO =
=
L
R
2R
P
V
VOrms =
2
Power Dissipation
P
2V
π
Whether the power amplifier is operated in BTL or SE
modes, power dissipation is a major concern. In equa-
tion11 states the maximum power dissipation point
for a SE mode operating at a given supply voltage and
driving a specified load.
Psup = VDD * IDDAVG =
L
R
Efficiency of a BTL configuration:
2
O
P ×
P
P
π
P
P
P
V
V
L
2V
π
V
DD
V
= (
) / (VDD
x
)=
(10)
SE mode : PD,MAX =
(11)
π2
L
SUP
L
R
DD
2R
4V
2 R
Table 2 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 dissipation over the normal operating
range. Note that the internal dissipation at full output
power is less than in the half power range. Calculating
the efficiency for a specific system is the key to proper
power supply design. For a stereo 1W audio system
In BTL mode operation, the output voltage swing is
doubled as in SE mode. Thus the maximum power
dissipation point for a BTL mode operating at the same
given conditions is 4 times as in SE mode.
4V2DD
BTL mode : PD,MAX
=
(12)
2ʌ2R
L
Since the APA2030/1 is a dual channel power
amplifier, the maximum internal power dissipation is
2 times that both of equations depending on the mode
of operation. Even with this substantial increase in
power dissipation, the APA2030/1 does not require
extra heatsink. The power dissipation from equation12,
assuming a 5V-power supply and an 8Ω load, must
not be greater than the power dissipation that results
from the equation13:
with 8Ω loads and a 5V supply, the maximum draw
on the power supply is almost 3W.
Po (W)
0.25
Efficiency (%)
31.25
IDD(A)
0.16
0.21
0.30
0.32
VPP(V)
2.00
2.83
4.00
4.47
PD (W)
0.55
0.55
0.5
0.50
47.62
J.MAX −
A
T
T
PD,MAX =
(13)
θJA
1.00
66.67
For TSSOP-24 (APA2030) and TSSOP-20 (APA2031)
package with and without thermal pad, the thermal
resistance (θJA) is equal to 45oC/W and 48oC/W,
respectively.
1.25
78.13
0.35
**High peak voltages cause the THD to increase.
Since the maximum junction temperature (TJ,MAX) of
APA2030/1 is 150oC and the ambient temperature (TA)
is defined by the power system design, the maximum
Table 2. Efficiency Vs Output Power in 5V/8Ω BTL
Systems
Copyright ANPEC Electronics Corp.
22
www.anpec.com.tw
Rev. A.2 - Apr., 2004
ANPEC [ ANPEC ELECTRONICS COROPRATION ]
