AN3956
Application note
5 W + 5 W dual BTL class-D audio amplifier demonstration board
based on the TDA7491LP
Introduction
The STEVAL-CCA029V1 is a demonstration board designed for the TDA7491LP dual BTL
class-D audio amplifier. This application note provides the board specifications and a quick-
start list for standalone operation. Also included are the schematic, printed circuit board
layout and bill of material.
Due to its high efficiency, the device assembled in the PSSO36 (slug-down) package is
capable of dissipating heat without any heatsink. Jumpers on the board allow the
configuration of the amplifier in order to verify all the features as single-ended or differential
inputs, fixed gain settings. Microswitches are also provided to enable the standby and mute
functions.
The main features of the TDA7491LP include:
■
■
■
■
■
■
■
■
■
■
5 W +5 W continuous output power at THD =10%, R
L
= 8
Ω,
V
CC
= 9 V
5 W +5 W continuous output power at THD = 10%, R
L
= 4
Ω,
V
CC
=6.5V
Wide-range, single-supply operation (5 V - 14 V)
High efficiency (
η
= 90%)
Four selectable, fixed gain settings (20 dB, 26 dB, 30 dB and 32 dB)
Differential inputs to minimize common-mode noise
Filterless operation
Standby and mute features
Short-circuit and thermal overload protections
Externally synchronizable
STEVAL-CCA029V1
Figure 1.
September 2012
Doc ID 022034 Rev 1
1/14
www.st.com
Contents
AN3956
Contents
1
Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1
1.2
1.3
1.4
1.5
1.6
1.7
Power supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Demonstration board preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Inputs and outputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Powering up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Gain settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Single-ended or differential input . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Board schematic and bill of material . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2
PCB layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.1
2.2
Layout views . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Design guidelines for PCB schematic and layout . . . . . . . . . . . . . . . . . . . . 9
2.2.1
2.2.2
2.2.3
Dumping network . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Filterless operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Layout recommendations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
3
Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
2/14
Doc ID 022034 Rev 1
AN3956
Operation
1
Operation
The TDA7491LP demonstration board specifications are as follows:
●
●
●
●
●
Power supply voltage range: 5 V to 14V
Number of channels: 2 BTL (bridge-tied load) stereo
Load impedance: 4
Ω
to 8
Ω
Gain settings: 20 dB, 26 dB, 30 dB, 32 dB
Undervoltage protection (UVP): 4 V
1.1
Power supply
A single power supply is required to feed the TDA7491LP demonstration board via the
connector J2 (see
Figure 2).
Connect the positive voltage of the 15 V/3 A DC power supply to the +Vcc pin and the
negative to GND.
Note:
Voltage range 5 V to 14 V = 3 A current capability
1.2
Demonstration board preparation
1.
2.
Ensure that the power supply is switched OFF.
Connect the regulated power supply, adjusted in the device operating range, to the
connector J7(Vcc) - J8(GND) (observe the polarity).
1.3
Inputs and outputs
1.
2.
Connect the loads across the connectors J5-J6 (LEFT) and J9-J10 (RIGHT), the
specified impedance ranges from 4 to 8
Ω.
Connect the analog audio inputs, single-ended, to the L-input and R-input RCA plugs
(J1).
Refer to
Figure 2: Demonstration board connections on page 4.
Doc ID 022034 Rev 1
3/14
Operation
Figure 2.
Demonstration board connections
AN3956
1.4
Powering up
Before powering up the demonstration board, ensure that the TDA7491LP is in standby and
mute conditions and the gain is set to the desired value (default 20 dB). Verify also the
dedicated switches and jumpers.
Table 1.
Standby and mute settings
STBY (S1)
L
L
H
H
Mute (S2)
L
H
L
H
Status
STBY
STBY
MUTE
PLAY
Figure 3.
Standby and mute switches
S 1= S T B Y
L
L
H
H
S 2= M UT E
4/14
Doc ID 022034 Rev 1
AN3956
Operation
1.5
Gain settings
Table 2.
Configuration of jumpers J11 and J12
Gain 0 (J11)
Open (L)
Open (L)
Closed (H)
Closed (H)
Gain 1 (J12)
Open (L)
Closed (H)
Open (L)
Closed (H)
Gain (db)
20
26
30
32
Figure 4.
Jumpers J11 and J12
Closed=H
Open=L
J11/J12
J11/J12
J12=G1
J11=G0
1.6
Single-ended or differential input
Although the TDA7491LP can be configured for both input configurations, the STEVAL-
CCA029V1 allows only the single-ended connection.
Doc ID 022034 Rev 1
5/14
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