TMPA421DS Datasheet, PDF (10/20 Pages) List of Unclassifed Manufacturers – 15W + 6W x2 2.1 Channel CLASS-D AUDIO POWER AMPLIFIER

Tai-1 Microelectronics
www.taimec.com.tw / www.class-d.com.tw
Preliminary
that is
t = - RC In（0.5）= （320k × 10u）（0.693） = 2.2 seconds
TMPA421DS
Rev.2.0 December 20, 2005
The delay time changes linearly with capacitance at HFRC. So a 10uF capacitance will provide
about 2.2 seconds delay.
Differential input VS single ended input
Differential input offers better noise immunity over single ended input. A differential input
amplifier suppresses common noise and amplifies the difference voltage at the inputs. For
single ended applications just tie the negative input end of the balanced input structure to
ground. If external input resistors are used, the negative input has to be grounded with a
series resistor of the same value as the positive input to reduce common noise.
Band pass filter for frequency separation of bass and R/L channels
For best sound effect the frequency of bass and R/L channels has to be separated. The bass
channel amplifies the lower frequencies while the R/L channels amplify the higher frequencies.
The power is saved not to drive bass speaker with high frequencies and not to drive R/L
channel speakers with low frequencies. The noise level can be reduced as well. Typically the
frequency boundary of bass and R/L channels is set 500 Hz and the output power of bass is
set around 3~5 times of the R/L channels. Note that different applications may have different
requirement for these values. Please refer to EVM documentation if the separation frequency
is 200 Hz instead.
Bass channel filter
If the audio source is stereo (right channel signal and left channel signal) one can generate
audio source for bass amplifier by mixing right and left signals and in the mean time filter out
frequencies above 500 Hz. A typical application is shown below. Note that Zin=15k ohms is the
internal resistance of the class-D amplifier when gain0=gain1=High.
Copyright ©2005,Tai-1 Microelectronics Corp.
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