TDA2075A Datasheet, PDF (12/24 Pages) Tripath Technology Inc. – STEREO CLASS-T DIGITAL AUDIO AMPLIFIER DRIVER USING DIGITAL POWER PROCESSINGTM TECHNOLOGY

Tripath Technology, Inc. - Technical Information
Application Information
Figure 1 is a simplified diagram of one channel (Channel 1) of a TDA2075A amplifier to assist in
understanding its operation.
TDA2075A
OAOUT1 45
OVER
CURRENT
DETECTION
10 OCSN1
9 OCSP1
C_I
R_I
+
V5
R_OFA
Offset Trim
Circuit
R_F
V5
INV1 46 _-
R _OFB
+
AGND
C _OF
C_A
BIASCAP 3
2.5V
Y1B
Processing
&
Modulation
V10
C_G
15 HO1
IN1
FET
CONTROLLER
V10
C_G
17 LO1
R_G
Q_P
R_G
Q_N
25 ^V10
10V
C_S
13,24
PGND
VNN
VPP
V5
V5
R _VNN1
R _REF
REF 34
VNNSENSE 38
R _VPP1
R _VNN2
VPPSENSE 40
OVER/
UNDER
VOLTAGE
DETECTION
R _VPP2
5V
C_S
V5 32,43,44
AGND 41,42
6 ^V5
5V
C_S
5
AGND
V5
12 FBKOUT1
11 FBKGND1
C
FB
R _FBA
R _FBA
R_FBC
R _FBB
R _FBB
R _FBC
Analog Ground
Power Ground
VPP
C_S
C _HBR
OUTPUT
FILTER
VNN
C_S
R_S
R_L
Figure 1: Simplified TDA2075A Amplifier
TDA2075A Basic Amplifier Operation
The audio input signal is fed to the processor internal to the TDA2075A, 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. These switching patterns are inputted to a MOSFET driver and then
outputted to HO1 and LO1 which are ac-coupled to a complementary pair of power MOSFETs. The
output of the MOSFETs 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 is operated from a 5-volt supply while the FET driver is operated from a 10-volt supply.
The FET driver 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 external MOSFETs. The dead time
can be programmed by adjusting RBBMSET. Feedback information from the output of the complementary
FETs is supplied to the processor via FBKOUT1. Additional feedback information to account for ground
bounce is supplied via FBKGND1.
Complementary MOSFETs are used to formulate a half-bridge configuration for the power stage of the
amplifier. The gate capacitors, C_G, are used to ac-couple the FET driver to the complementary
MOSFETs. The gate resistors, R_G, are used to control MOSFET slew rate and thereby minimize voltage
overshoots.
12
TDA2075A – Rev. 0.9/KLi/10.05