AudioAmp 2 click
PID: MIKROE‐3077
Weight: 26 g
Audio Amp 2 click is a highly efficient class D audio amplifier, using the TDA7491, a dual BTL class‐
D audio amplifier IC, capable of delivering up to 20W to 8Ω load. This amplifier IC features high‐
efficiency output stage drivers and clever design, allowing it to deliver a reasonably high power to
the connected speakers, using only GND polygon on the PCB for heat dissipation. In the BTL
topology, the output DC blocking capacitors are not required. This allows for simpler design and
lower power losses, especially with no input signal. The TDA7491 amplifier IC is equipped with a
set of protection features, that allow reliable operation.
Besides the protection features that include short-circuiting protection and thermal
overload protection, this Click board™ features a few more options that ensure flawless
operation of this amplifier Click board™. Features such as the dedicated diagnostic pin,
reduced pop sound on Power ON/OFF, mute and standby options, four selectable input
gain settings, low noise, and THD, allow a pleasant experience when using the Audio
Amp 2 click. This amplifier Click board™ can be used wherever a quality audio
amplification is required.
How does it work?
The main active component of this Click board™ is the TDA7491, a 20W dual BTL class-D
audio amplifier IC, from STMicroelectronics. This IC uses the bridge tied load (BTL)
topology, which means that the output load is driven by two amplifier stages, one of
them being inverted. This results in twice the voltage swing on the output, or four times
more power. This also means higher power dissipation, but due to the high efficiency of
the TDA7491, the power dissipation is still low enough to be handled by an exposed IC
pad.
This amplifier offers a low noise and good quality audio amplification. The frequency
response of the amplifier goes from under 20Hz to above 20kHz, covering the entire
audio range of the spectrum. Total Harmonic Distortion (THD) 10% at maximum output
power, with the 8Ω load. However, THD decays rapidly as the output power reduces,
and power supply voltage rises, respecting the maximum ratings of this IC. The
datasheet of the TDA7491 IC offers detailed information about technical characteristics
of the amplifier IC itself.
The output modulation scheme of the BTL is the unipolar pulse width modulation
(PWM). The output voltage varies between 0V and +VCC for the positive output driver
and between 0V and -VCC for the negative output driver. For 0V at the input, the
outputs theoretically cancel out each other, resulting with no DC component at the
output. In practice, a small delay is introduced, to avoid both stages switching
simultaneously, when the input is 0V. Using unipolar PWM scheme simplifies
The power amplifier IC has a protection against the pop sounds when powering the
device ON or OFF. However, standby and mute pins provide a way to further reduce the
startup noises. STBY pin of the IC puts the device in the Standby mode. This will turn the
internal power demanding circuitry OFF, reducing the power consumption to a
minimum. MUTE pin allows the inputs to be rerouted internally to GND. By combining
STBY and MUTE modes, it is possible to completely avoid pop sounds at the power up
or shut down. STBY pin is routed to the mikroBUS™ CS pin and it is labeled as STB, while
the MUTE pin is routed to the mikroBUS™ PWM pin, labeled as MUTE.
This Click board™ allows selection of the input gain. Input signal gain staging is
important in order to provide the most adequate input level for the amplifier IC. For
example, if the input signal is too low, the amplifier might not be able to reach the
required output power. Therefore, a corrective gain is applied to the input signal. This is
done by applying logic levels to two GAIN pins of the TDA7491 IC (GAIN0 and GAIN1).
The truth table below describes how to set the logic levels of these pins to achieve the
required signal gain. GAIN0 pin is routed to the mikroBUS™ AN pin, while the GAIN1 pin
is routed to the mikroBUS™ RST pin. Pins are labeled as GN0 and GN1 respectively.
DIAG pin allows monitoring of the fault conditions. When the short-circuit or thermal
overload protection is activated, the DIAG pin will be set to a HIGH logic level by means
of the onboard pull-up resistor, signaling the fault condition to the host MCU. This is an
open drain output, which actively sinks current when no fault condition exists, keeping
this pin to a LOW logic state. This pin is routed to the mikroBUS™ INT pin, labeled as
DIA.
The Click board™ is equipped with 3.5mm stereo jack connector, used to connect the
line level audio input. Besides the input jack, there are also two screw terminals, used for
connecting the output speakers (4Ω to 8Ω).
By default, the Click board™ is powered via the mikroBUS™ 5V rail. This will allow the
amplifier to work with limited power. Therefore, an external header is provided, which
allows the external power supply to be used, with up to 18V. To select the external
power supply, a SMD jumper labeled as AMP VCC needs to be placed to the EXT
position.
Specifications
Type
Audio
High output power with low dissipation, requiring no heat sinks, low
Key
Features
Interface
Input
Voltage
Click board
size
THD and SNR, integrated short circuit detection, undervoltage, and
overtemperature protection
GPIO
3.3V,5V
L (57.15 x 25.4 mm)
Pinout diagram
This table shows how the pinout on AudioAmp 2 click corresponds to the pinout on the
mikroBUS™ socket (the latter shown in the two middle columns).
Notes
Pin
Pin
Gain Setup Pin 0
GN0
1
AN
PWM
16
MUTE
Gain Setup Pin 1
GN1
2
RST
INT
15
DIA
Standby Function
STB
3
CS
RX
14
NC
NC
4
SCK
TX
13
NC
Notes
Mute Function
Diagnostic
Interrupt
NC
5
MISO
SCL
12
NC
NC
6
MOSI
SDA
11
NC
3.3V
7
3.3V
5V
10
5V
GND
8
GND
GND
9
GND
Power
supply
Ground
Power Supply
Ground
Truth table
Gain Setup
20dB
26dB
30dB
32dB
GN0
L
L
H
L
GN1
L
H
L
H
On-board jumpers and indicators
Label
LD1
AMP
VCC
N1X2
Name
Default
PWR
-
AMP VCC
Right
EXT VCC
-
Description
Power LED indicator
Power supply source selection: left position
external PSU, right position 5V
External power supply connector
LINE IN
LINE IN
-
3.5mm stereo audio input jack
LEFT
LEFT
-
Lef speaker connector
RIGHT
RIGHT
-
Right speaker connector
Software support
We provide a library for the AudioAmp 2 Click on our LibStock page, as well as a demo
application (example), developed using MikroElektronika compilers. The demo can run
on all the main MikroElektronika development boards.
Library Description
Library offers a choice to put the device in desired mode (Standby, Mute or Play Mode)
and to select the gain to the desired value (20, 26, 30 or 32dB).
For more details check the documentation.
Key functions :
uint8_t audioamp2_setMode( uint8_t selMode ) - The function puts the device in the
uint8_t audioamp2_setGain( uint8_t selGain ) - The function performs the gain
uint8_t audioamp2_checkDiagnostic( void )- The function checks are undervoltage,
desired mode.
selection.
overcurrent or thermal protection activated.
Example description
The application is composed of three sections :
System Initialization - Initializes peripherals and pins.
Application Initialization - Initializes GPIO driver and puts the device in Standby Mode as
default
operation mode and selects 20dB as default gain selection.
Application Task - (code snippet) - Activates Mute operation mode for 4 seconds and
after that activates Play mode.
When the device is in Play mode then changes the gain selection, first sets the minimum
gain (20dB) for 8 seconds
and then sets the maximum gain (32dB) for 8 seconds too.
Note: Internally, the gain is set by changing the feedback resistors of the amplifier.
void applicationTask()
{
audioamp2_setMode( _AUDIOAMP2_MUTE_MODE );
Delay_ms( 4000 );
audioamp2_setGain( _AUDIOAMP2_20DB_GAIN );
audioamp2_setMode( _AUDIOAMP2_PLAY_MODE );
Delay_ms( 8000 );
audioamp2_setGain( _AUDIOAMP2_32DB_GAIN );
Delay_ms( 8000 );
}
The full application code, and ready to use projects can be found on our
LibStock page.
Other mikroE Libraries used in the example:
UART
Additional notes and information
Depending on the development board you are using, you may need USB UART
click, USB UART 2 click or RS232 click to connect to your PC, for development systems
with no UART to USB interface available on the board. The terminal available in all
MikroElektronika compilers, or any other terminal application of your choice, can be
used to read the message.
https://www.mikroe.com/audioamp‐2‐click?search_query=MIKROE‐3077&results=1 7‐11‐18