Tripath Technology, Inc. - Technical Information
Please see the External Component Description section on page 6 for more details on the above-
mentioned components. The Application/ Test Circuit refers to the low side diodes as DO, and
both supply decoupling capacitors as CSW
.
T A2 0 2 4 C Amp l i f i e r Gai n
The ideal gain of the TA2024C is set by the ratio of two external resistors, RI and RF, and is given
by the following formula:
VO
VI
R F
R I
= −12
where VI is the input signal level and VO is the differential output signal level across the speaker.
Please note that VO is 180° out of phase with VI.
The ideal gain of the TA2024C is 12V/V, whereas typical values are: AV = 11.5V/V for 4Ω and
11.7V/V for 8Ω.
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 TA2024C. 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 TA2024C amplifier, the cause may be other
circuitry external to the TA2024C 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
TA2024C 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.
T u r n -o n an d Tu r n - o ff N o i se
The TA20204C has improved mute-off and mute-on click performance as compared to previous
Tripath devices including TA2024 and TA2024B. The main improvement was related to keeping
the input stage biased up during mute, but other specific circuit details, beyond the scope of the
data sheet, were also improved.
But as with the previous devices, many complaints about turn on and off clicks were not actually
caused by the TA2024C. As noted above, a typical cause of turn off pop is related to the audio
processor that provides the audio input to the TA2024C amplifier. The audio processor used for
most LCD TV’s produces a pop when its power supply collapses. Thus, it is recommended that
the TA2024C mute pin is pulled high before the power supply is removed.
The time that it takes to activate mute has been reduced in the TA2024C as opposed to TA2024
and TA2024B. This allows for the mute to be activated before the audio processor power supply
can collapse. Thus, any possibility of a pop being amplified by the TA2024C can be adverted.
The remaining source of click is the residual output offset. This pop would normally be masked if
the TA2024C is playing music but in some cases, may be undesirable due to application
requirements. The level of the pop is proportional to the offset, which has a specified maximum
of 150mV as stated in the Electrical Characteristics Section.
10
TA2024C –KL/1.0/01.06
TRIPATH [ TRIPATH TECHNOLOGY INC. ]
