apa2068ka Anpec Electronics Corporation, apa2068ka Datasheet - Page 22

• Manufacturer Part Number: apa2068ka
• Description: Stereo 2.6w Audio Power Amplifier With Dc_volume Control
• Manufacturer: Anpec Electronics Corporation

APA2068
BTL Amplifier Efficiency (Cont.)
load is increased resulting in a nearly flat internal power
dissipation over the normal operating range.
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 with 8 loads
and a 5V supply, the maximum draw on the power
supply is almost 3W.
A final point to remember about linear amplifiers (either
SE or BTL) is how to manipulate the terms in the
efficiency equation to utmost advantage when possible.
Note that in equation, V
indicates that as V
In other 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
Power Dissipation
Whether the power amplifier is operated in BTL or SE
modes, power dissipation is a major concern. In equa-
Copyright
Rev. A.2 - Jul., 2005
Applicat ion Descript ions ( Cont .)
Po (W) Efficiency (%) I
0.25
0.50
1.00
1.25
ANPEC Electronics Corp.
31.25
47.62
66.67
78.13
DD
goes down, efficiency goes up.
DD
is in the denominator. This
DD
0.16
0.21
0.30
0.32
(A) V
2.00
2.83
4.00
4.47
PP
(V) P
0.55
0.55
0.35
D
0.5
BTL
(W)
22
tion13 states the maximum power dissipation point
for a SE mode operating at a given supply voltage and
driving a specified load.
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.
Since the APA2068 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 APA2068 does not require extra
heatsink. The power dissipation from equation14,
assuming a 5V-power supply and an 8
not be greater than the power dissipation that results
from the equation15 :
For SOP16-P package with thermal pad, the thermal
resistance (
Since the maximum junction temperature (T
APA2068 is 150 C and the ambient temperature (T
is defined by the power system design, the maximum
power dissipation which the IC package is able to
handle can be obtained from equation15.
Once the power dissipation is greater than the maxi-
mum limit (P
be decreased, the load impedance (R
creased or the ambient temperature should be reduced.
Thermal Pad Considerations
The thermal pad must be connected to ground. The
package with thermal pad of the APA2068 requires
special attention on thermal design. If the thermal
SE mode : P
BTL mode : P
P
D,MAX
=
D,MAX
T
JA
J,MAX
) is equal to 45 C/W.
), either the supply voltage (V
D,MAX
JA
D,MAX
- T
A
=
=
2 R
V
4V
2 R
DD
2
2
DD
2
L
L
2
www.anpec.com.tw
L
) must be in-
load, must
(15)
(13)
(14)
DD
J,MAX
) must
) of
A
)