T E C H N I C A L I N F O R M A T I O N
Application Information
Figure 1 is a simplified diagram of one channel (Channel 1) of a TA3020 amplifier to assist in
understanding its operation.
22
23
BBM0
BBM1
43 OCS1HP
VPP
OVER
DB
CS
CURRENT
DETECTION
RS
26
OAOUT1
VN10
RB
OCS1HN
40 VBOOT1
44
RI
RF
CI
V5
QO
RG
RG
25
INV1
ROFB
+ CBAUX
+
CB
-
45 HO1
46 HO1COM
0.1uF
+
CHBR
AGND
V5
VN10
OUTPUT
FILTER
QO
RS
Processing
&
ROFB
48 LO1
RL
ROFA
47
LO1COM
Modulation
COF
2.5V
V5
42 OCS1LP
Offset Trim
Circuit
OVER
CURRENT
DETECTION
CA
41 OCS1LN
BIASCAP 19
MUTE 24
VNN
33,37
OCR1
COCR
CS
V5
ROCR
5V
RFBA
RFBA
RFBC
13 FBKOUT1
FBKGND1
14
32
30
REF
RFBC
RREF
CFB
RFBB
RFBB
*RVNN1
VNNSENSE
VNN
VPP
OVER/
UNDER
*RVPP1
VOLTAGE
VPPSENSE 29
DETECTION
15 HMUTE
1
*RVNN2
*RVPP1
V5
V5
VN10
VNN
VN10
CSW
V5
27,35
5V
CS
VNN
39
AGND 28,34
VNN
Analog Ground
Power Ground
F. BEAD
Figure 1: Simplified TA3020 Amplifier
TA3020 Basic Amplifier Operation
The audio input signal is fed to the processor internal to the TA3020, where a switching pattern is
generated. The average idle (no input) switching frequency is approximately 700kHz. With an input
signal, the pattern is spread spectrum and varies between approximately 200kHz and 1.5MHz
depending on input signal level and frequency. Complementary copies of the switching pattern are
level-shifted by the MOSFET drivers and output from the TA3020 where they drive the gates (HO1
and LO1) of external power MOSFETs that are connected as a half bridge. The output of the half
bridge is a power-amplified version of the switching pattern that switches between VPP and VNN.
This signal is then low-pass filtered to obtain an amplified reproduction of the audio input signal.
The processor portion of the TA3020 is operated from a 5-volt supply. In the generation of the
switching patterns for the output MOSFETs, the processor inserts a “break-before-make” dead time
between the turn-off of one transistor and the turn-on of the other in order to minimize shoot-through
currents in the MOSFETs. The dead time can be programmed by setting the break-before-make
control bits, BBM1 and BBM0. Feedback information from the output of the half-bridge is supplied to
TA3020, Rev 2.1, 01.01
15
TRIPATH [ TRIPATH TECHNOLOGY INC. ]
