AN4170
Application note
20 W + 20 W dual BTL class-D audio amplifier demonstration board
based on the TDA7491HV
Introduction
The STEVAL-CCA042V1 is a demonstration board designed for the evaluation of the
TDA7491HV 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 a heatsink. Jumpers on the board allow the configuration
of the amplifier in order to verify the input signal as single-ended or differential and choose
the fixed gain settings. Microswitches are also provided to enable the standby and mute
functions.
The main features of the TDA7491HV include:
■
■
■
■
■
■
■
■
■
■
20 W + 20 W continuous output power at THD =10%, R
L
= 8
Ω,
V
CC
= 18 V
9.5 W + 9.5 W continuous output power at THD = 10%, R
L
= 8
Ω,
V
CC
=12 V
Wide-range, single-supply operation (5 V - 18 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-CCA042V1
Figure 1.
November 2012
Doc ID 023709 Rev 1
1/15
www.st.com
Contents
AN4170
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
Main filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Layout recommendations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
3
Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
2/15
Doc ID 023709 Rev 1
AN4170
Operation
1
Operation
The TDA7491HV demonstration board specifications are as follows:
●
●
●
●
●
Power supply voltage range: 5 V to 18 V
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): 4.5 V
1.1
Power supply
A single power supply is required to feed the TDA7491HV demonstration board via the
connector J2 (see
Figure 2).
Connect the positive voltage of the 25 V/ 5 A DC power supply to the +Vcc pin and the
negative to GND.
Note:
Voltage range 5 V to 18 V = 5 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 J2 (observe the polarity).
1.3
Inputs and outputs
1.
2.
Connect the loads across the connectors J3 (LEFT) and J4 (RIGHT), the specified
impedance ranges from 6 to 8
Ω.
Connect the analog audio inputs, either differential or single-ended, to the L-input and
R-input RCA plugs (J1).
Input configuration
Input configuration
Differential
Single-ended
Jumper J8 (right)
Open
Closed
Jumper J9 (left)
Open
Closed
Table 1.
Refer to
Figure 2: Demonstration board connections on page 4.
Doc ID 023709 Rev 1
3/15
Operation
Figure 2.
Demonstration board connections
AN4170
STBY
MUTE
Dummy
Load
GND
+VCC
Dummy
Load
Analog
Inputs
1.4
Powering up
Before powering up the demonstration board, ensure that the TDA7491HV 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 2.
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
S1= STBY
L
L
H
H
S2= MUTE
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Doc ID 023709 Rev 1
AN4170
Operation
1.5
Gain settings
Table 3.
Configuration of jumpers J5 and J6
Gain 0 (J5)
Open (L)
Open (L)
Closed (H)
Closed (H)
Gain 1 (J6)
Open (L)
Closed (H)
Open (L)
Closed (H)
Gain (db)
20
26
30
32
Figure 4.
Jumpers J5 and J6
1.6
Single-ended or differential input
Jumpers J8 and J9 are used to modify the input signal configuration.
Table 4.
Configuration of jumpers J8 and J9
Left (J9)
Open
Closed
Right (J8)
Open
Closed
Input configuration
Differential
Single-ended
Figure 5.
Jumpers J8 and J9
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