tda2500 Tripath Technology Inc., tda2500 Datasheet - Page 12

• Manufacturer Part Number: tda2500
• Description: Stereo Class-t Digital Audio Amplifier Driver Using Digital Power Processing Dpp
• Manufacturer: Tripath Technology Inc.

R
OFA
Application Information
Figure 1 is a simplified diagram of one channel (Channel 1) of a TDA2500 amplifier to assist in
understanding its operation.
V5
TD A2500 BA SIC AMPLI F I ER O P E R A T ION
The audio input signal is fed to the processor internal to the TDA2500, where a switching pattern is
generated. The average idle (no input) switching frequency is approximately 700kHz and can be adjusted
by changing the C
proper device operation. 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 TDA2500
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 TDA2500 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 the processor via
FBKOUT1. Additional feedback information to account for ground bounce is supplied via FBKGND1.
12
Offset Trim
C
Circuit
I
R
+
OFB
5V
C
S
R
5V
I
R
BBM0
BBM1
MUTE
C
OFB
VN12
VPP 23
VNN 24
OF
IN1 6
V5
19
3
4
7
8
FB
value. The idle switching frequency must be maintained above 575kHz to ensure
AGND
-
+
V5
2.5V
V5
DETECTION
VOLTAGE
Figure 1: Simplified TDA2500 Amplifier
UNDER
OVER/
AGND
1
Processing
Modulation
&
28
PGND
DETECTION
DETECTION
CURRENT
CURRENT
OVER
OVER
VN12
16
15
22
21
20
17
13
14
11
18
37
38
35 HMUTE
9
2
OCS1HN
OCS1LP
VHIGH
VLOW
OVERLOADB
OCS1HP
HO1
HO1COM
LO1
LO1COM
OCS1LN
OCR1
FDBKN1
GNDKELVIN1
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
C
R
VB
AGND
C
OCR
FB
AGND
R
R
G
G
C
R
Q
Q
R
R
VB
R
S
O
O
S
AGND
FB
FB
TDA2500 – KL/ Rev. 0.9/05.05
C
C
0.1uF
C
S
HBR
S
+
+
L
O
C
C
VPP
VNN
S
S
C
O
R
C
Z
Z
R
L