tda2075a Tripath Technology Inc., tda2075a Datasheet - Page 12

• Manufacturer Part Number: tda2075a
• Description: Stereo Class-t Digital Audio Amplifier Driver Using Digital Power Processingtm
• Manufacturer: Tripath Technology Inc.

Application Information
Figure 1 is a simplified diagram of one channel (Channel 1) of a TDA2075A amplifier to assist in
understanding its operation.
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 R
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
MOSFETs. The gate resistors, R
overshoots.
VNN
VPP
V5
V5
Offset Trim
12
Circuit
C
I
R
+
OFA
R
R
R
R
VNN2
VNN1
VPP2
VPP1
V5
R
I
5V
R
C
REF
S
R
C
VNNSENSE
VPPSENSE
F
A
BIASCAP
OAOUT1
R
AGND
C
OFB
INV1
REF
OF
V5
46
34
38
40
32,43,44
41,42
45
3
AGND
-
+
V5
2.5V
DETECTION
VOLTAGE
UNDER
OVER/
Processing
Modulation
Figure 1: Simplified TDA2075A Amplifier
&
G
G
, are used to ac-couple the FET driver to the complementary
, are used to control MOSFET slew rate and thereby minimize voltage
BBMSET
TDA2075A
Y1B
Power Ground
Analog Ground
12
11
. Feedback information from the output of the complementary
FBKOUT1
FBKGND1
IN1
C
FB
CONTROLLER
DETECTION
CURRENT
OVER
FET
R
R
FBB
V5
FBA
T r i p a t h T e c h n o l o g y , I n c . - T e c h n i c a l I n f o r m a t i o n
13,24
V10
V10
R
R
25
FBB
6
5
FBA
10
15
17
R
9
FBC
PGND
V10
AGND
HO1
LO1
V5
OCSN1
OCSP1
R
FBC
C
C
G
G
C
C
S
S
R
R
G
G
5V
10V
T D A 2 0 7 5 A – R e v . 0 . 9 / K L i / 1 0 . 0 5
Q
Q
P
N
C
C
S
HBR
C
S
VNN
OUTPUT
FILTER
VPP
R
S
R
L