Tripath Technology, Inc. - Technical Information
The ideal gain of the TAA2008 is 12V/V, whereas typical values are: AV = 11.7V/V for 8Ω.
The low frequency roll-off characteristic is dictated by the choice of CI and RI.
The –3dB frequency is:
1
f − 3dB =
2Π CI RI
The figure below shows the roll-off characteristic for different values of CI, assuming an RI value
of 20kΩ. As can be seen, the larger the value of CI, the lower the –3dB cutoff point. On the EB-
TAA2008, a value of 2.2µF is used for CI which creates a nearly flat response down to 20Hz. In
many cases, a lower value of CI can be used because the speakers used in LCD TV’s or similar
applications do not have the ability to reproduce low frequency signals.
FrequencyResponse
+1
+0
-1
CI
=
2.2uF
CI 1.0uF
CI 0.47uF
CI 0.22uF
=
d
B
r
-2
-3
-4
=
=
-5
-6
VDD = 12V
PO
RL
=
=
1W
8Ω
20
50
100
200
500
1k
2k
5k
10k
20k
Hz
M u t e P i n
The mute pin must be driven to a logic low or logic high state for proper operation. To enable the
amplifier, connect the mute pin to a logic low. To enable the mute function, connect the mute pin to a
logic high signal. Please note that the mute pin is a 5V CMOS input pin and the mute signal should
be de-bounced to eliminate a possibility of falsely muting.
When in mute, the internal processor bias voltages are still active in the TAA2008. This minimizes
any turn on pop caused by charging the input coupling capacitor. It is recommended that the mute is
held high during power up or power down to eliminate audible transients.
If turn-on and/or turn-off noise is still present with a TAA2008 amplifier, the cause may be other
circuitry external to the TAA2008 such as an audio processor or preamp. Multiple audio processors
used in LCD TV’s create audible pops as their power supply collapses. If the TAA2008 is still active
(mute pin is low), then these audible pops will be amplified and output to the speakers. To eliminate
this problem, simply activate the mute before the power supply collapses. The delay going into mute
is approximately 1us, as compared to several hundred milliseconds on the previous Tripath IC’s such
as TA2024B.
S l e e p P i n
The SLEEP pin is a 5V logic input that when pulled high (>3.5V) puts the part into a low quiescent
current mode. This pin is internally clamped by a zener diode to approximately 6V thus allowing
the pin to be pulled up through a large valued resistor (1MΩ recommended) to VDD. To disable
SLEEP mode, the sleep pin should be grounded.
P r o t ect i o n C i r cu i t s
The TAA2008 is guarded against over-temperature and over-current conditions. When the
device goes into an over-temperature or over-current state, the FAULT pin goes to a logic HIGH
state indicating a fault condition. When this occurs, the amplifier is muted, all outputs are TRI-
11
TAA2008 –KLi/1.0/05.06
TRIPATH [ TRIPATH TECHNOLOGY INC. ]
