dm00034744

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 quickstart 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%, RL = 8 Ω, VCC = 9 V
■
5 W +5 W continuous output power at THD = 10%, RL = 4 Ω, VCC =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
Figure 1.
September 2012
STEVAL-CCA029V1
Doc ID 022034 Rev 1
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www.st.com
Contents
AN3956
Contents
1
2
3
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Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1
Power supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.2
Demonstration board preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.3
Inputs and outputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.4
Powering up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.5
Gain settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.6
Single-ended or differential input . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.7
Board schematic and bill of material . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
PCB layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.1
Layout views . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.2
Design guidelines for PCB schematic and layout . . . . . . . . . . . . . . . . . . . . 9
2.2.1
Dumping network . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.2.2
Filterless operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.2.3
Layout recommendations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
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1
Operation
Operation
The TDA7491LP demonstration board specifications are as follows:
1.1
●
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
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
1.3
1.
Ensure that the power supply is switched OFF.
2.
Connect the regulated power supply, adjusted in the device operating range, to the
connector J7(Vcc) - J8(GND) (observe the polarity).
Inputs and outputs
1.
Connect the loads across the connectors J5-J6 (LEFT) and J9-J10 (RIGHT), the
specified impedance ranges from 4 to 8 Ω.
2.
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.
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Operation
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Figure 2.
Demonstration board connections
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.
Figure 3.
Standby and mute settings
STBY (S1)
Mute (S2)
Status
L
L
STBY
L
H
STBY
H
L
MUTE
H
H
PLAY
Standby and mute switches
S 1= S T B Y
L
H
L
H
S 2= M UT E
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1.5
Operation
Gain settings
Table 2.
Figure 4.
Configuration of jumpers J11 and J12
Gain 0 (J11)
Gain 1 (J12)
Gain (db)
Open (L)
Open (L)
20
Open (L)
Closed (H)
26
Closed (H)
Open (L)
30
Closed (H)
Closed (H)
32
Jumpers J11 and J12
Closed=H
Open=L
J11/J12
J11/J12
J12=G1
1.6
J11=G0
Single-ended or differential input
Although the TDA7491LP can be configured for both input configurations, the STEVALCCA029V1 allows only the single-ended connection.
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Operation
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1.7
Board schematic and bill of material
Figure 5.
STEVAL-CCA029V1 schematic
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Table 3.
Type
Operation
Bill of material
Footprint
Description
Qty
Reference
Manufacturer
CCAP
CAP0603
330 pF 50 V NPO ±5%
2
C21, C27
Murata
CCAP
CAP0603
2200 pF 50 V X7R
4
C18, C22,
C24, C28
Murata
CCAP
CAP0603
1 nF 50 V ±10%
4
C3, C4, C13,
C14
Murata
CCAP
CAP0603
100 nF 50 V ±10%
7
C5, C6, C8,
C9,
C10, C19, C25
Murata
CCAP
CAP0603
220 nF 50 V ±10%
4
C1, C2, C11,
C12
Murata
CCAP
CAP0603
2.2 µF, 16 V ±10%
1
C29
Murata
ECAP
CAP0603
2.2 µF, 16 V, ±10%
2
C7, C15
Murata
ECAP
CAP0603
1 µF, 16 V, ±10%
2
C16, C17
Murata
ECAP
D < 12.0 mm
1000 µF, 25 V, ±10%, pitch = 5.0 mm
1
C23
Rubicon
SMD
tantalum
CAP1206
10 µF, 25 V, ±10%, tantalum
4
C31, C32,
C33, C34
Rubicon
RES
R0603
22 ohm, ±10%, 1/16 W
3
R5, R6, R7
Murata
RES
R0603
2.2k ohm, ±10%, 1/16 W
1
R8
Murata
RES
R0603
9.1k ohm, ±10%, 1/16 W
1
R13
Murata
RES
R0603
33k ohm, ±10%, 1/16 W
2
R2, R4
Murata
RES
R0603
39k ohm, ±10%, 1/16 W
1
R3
Murata
RES
R0603
100k ohm, ±10%, 1/16 W
1
R1
Murata
Terminal
Through-hole
2P, pitch = 5 mm connector terminal
3
J2, J3, J4
Any source
Jumper
2-way jumper
2P, pitch = 2.5 mm jumper
4
J5, J6, J8, J9
Any source
Switch
Slide
3P, pitch = 2.5 mm
2
S1, S2
Any source
Bead
SMD
0R
1
L1
Any source
Jumper
3-way jumper
3P, pitch = 2.5 mm jumper
2
J11, J12
Any source
IC
TDA7491LP
TDA7491LP (SSO36) slug-down
1
IC1
Bead
SMD
BLM41PG471SN1
4
L2, L3, L4, L7
Connector
RCA-2P
RCA socket 2Px2, type AV2-8.4-12
1
J1
Songcheng
Regulator
TO92
L4931CZ33, 3V3 regulator
1
IC2
STMicroelectronics
PCB
75 x 50 mm
TDA7491P filterless PCB
1
Doc ID 022034 Rev 1
STMicroelectronics
Murata
King Brother
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PCB layout
AN3956
2
PCB layout
2.1
Layout views
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Figure 6.
Top view of PCB layout
Figure 7.
Bottom view of PCB layout
Doc ID 022034 Rev 1
AN3956
PCB layout
Figure 8.
Top view of PCB layout - with dimensions
2.2
Design guidelines for PCB schematic and layout
2.2.1
Dumping network
The capacitor is mainly intended for high inductive loads and for common-mode noise
attenuation.
Figure 9.
2.2.2
Dumping network (for one channel)
Filterless operation
The TDA7491LP can avoid using the main filter (LC Butterworth-based filter) if the speakers
are placed at a distance within 50 cm. In order to improve the EMI performance ferrite beads
are used (see Figure 5 and Table 3 for details).
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PCB layout
2.2.3
AN3956
Layout recommendations
The following figures illustrate layout recommendations.
Solder 100 nF bypass capacitors (X7R) as close as possible to the IC VCC pins
(recommended distance to be within 3 mm) in order to avoid spikes generated by the stray
inductance caused by the copper supply lines.
Figure 10. Capacitors soldered as close as possible to VCC pins
Ground pin and VCC pin of
100nF capacitor shouldbe
directly connected to the
IC related pin
Solder the snubber networks as close as possible to the IC related pin.
A voltage spike dangerous for device operation could occur if the snubber network is far
from the output pins. It is recommended that the distance between the snubber network and
the output pins be within 5 mm.
Figure 11. Snubber networks soldered as close as possible to relevant IC pin
Snubbers
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PCB layout
Put the RC filter for the ROSC pin close to the IC.
Figure 12. RC filter
Put the filter capacitor for SVR, VREF, SVCC, VSS and VDDPW close to the IC.
Figure 13. Filter capacitor
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PCB layout
AN3956
Signal ground should be directly connected to the negative terminal of the bulk capacitor.
Figure 14. Signal ground routing
Signal gnd
C23 gnd pin
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3
Revision history
Revision history
Table 4.
Document revision history
Date
Revision
21-Sep-2012
1
Changes
Initial release.
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AN3956
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