ta104, Elektronika, wzmacniacze
[ Pobierz całość w formacie PDF ]TECHNICAL INFORMATION
CLASS-T DIGITAL AUDIO AMPLIFIER EVALUATION BOARD USING
DIGITAL POWER PROCESSING
TM
TECHNOLOGY
EB-TA0104
February 2000, For Rev. 3.3 Board
General Description
The EB-TA0104 evaluation board is based on the TA0104A digital audio power amplifier from Tripath
Technology. This board is designed to provide a simple and straightforward environment for the
evaluation of the Tripath stereo TA0104A amplifier. This board can also be used in a bridged
configuration for high power mono output.
Note: Although the maximum supply voltage limit for the TA0104A is
+
100V, the supply voltage
for this board is limited because of other component limitations. Do not exceed the following:
+
90V for 4
W
Single Ended Applications
+
75V for 4
W
Bridged or 2
W
Single Ended Applications
Features
Û
2 x 400W rms @ 0.1% THD+N, 4
W
Û
1000W rms bridgeable subwoofer
output, 4
W
@ 0.1% THD+N
Û
Four N-Channel power MOSFETs
Û
Outputs short circuit protected
Benefits
Û
Quick, easy evaluation and testing of the
TA0104A amplifier
Û
Ready to use in many applications:
Û
2 channel stereo systems
Û
Powered 2.1 speaker systems
Û
Powered Subwoofers
EB-TA0104, 02.00 Rev. 4.0
1
TECHNICAL INFORMATION
OPERATING INSTRUCTIONS
Power Supply Description
There are three external power supplies required to operate this board: Vspos, Vsneg and +5V (see
Figures 1 and 2). Vspos and Vsneg power the load and so must each be able to provide half of the
desired output power, plus about 20% for overhead and margin. The TA0104A amplifier also requires a
supply, VN12, that is 12V more positive than Vsneg and tracks Vneg. This evaluation board generates
this VN12 voltage on-board. All input, output and power supply connections are made using tinned wire
or female banana connectors (not shown).
To begin evaluation, the following powering-up sequence is recommended: 1
st
) +5V, 2
nd
) Vsneg and 3
rd
)
Vspos. The positive and negative supply voltages do not have to match or track each other, but
distortion or clipping levels will be determined by the lowest (absolute) supply voltage. For applications
where VN12 is supplied separately, this supply should be sequenced after +5V and before Vsneg.
NOTE: TO AVOID PERMANENT DAMAGE, DO NOT EXCEED THE FOLLOWING:
+
90V FOR 4
W
SINGLE ENDED APPLICATIONS
+
75V FOR 4
W
BRIDGED OR 2
W
SINGLE ENDED APPLICATIONS
Once power is applied to the evaluation board, the green Power light, LED 1, will illuminate. If it does
not, power the unit down and recheck all connections and supplies. If the MUTE jumper is missing, the
LED will not illuminate. We recommend powering-down in the reverse order from power-up.
Input Connections
Audio input to the board is located at IN1 and IN2 (see Figures 1 and 2). The input can be a test signal
or music source. Connections are made using tinned wired to IN1, IN2 and Analog Ground, AGND.
Output Connections
There are four female banana connectors on the evaluation board for speaker outputs OUT1, OUT2,
and Power Grounds, GND1 and GND2 (see Figures 1 and 2). The TA0102A can be operated as a two
channel single-ended amplifier, bridged mono output amplifier (see Figure 8) or with a passive crossover
for a 2.1 channel application (refer to Application Note 13). Outputs can be any passive speaker(s) or
test measurement equipment (see Application Note 4 for more information on bench testing).
Note:
To avoid board damage, the Analog Ground and Power Grounds should be kept separate.
Connector Name Channel
IN1
Channel 1 Input
IN2
Channel 2 Input
OUT1
Channel 1 Output
OUT2
Channel 2 Output
Turn-on/off Pop
To avoid turn-on and turn-off pops, MUTE the amplifier by pulling up the MUTE pin to +12V through a
1M
W
resistor before turning on or off the power supplies. Refer to the MUTE description in the TA0104A
Control Circuitry section on page 5.
2
EB-TA0104, 02.00 Rev. 4.0
TECHNICAL INFORMATION
EB-TA0104 Board
Output Transistors
Power
LED
Mute
Jumper
Input
Connections
CONNECTIONS
Vspos (+V)
+5V
AGND
DGND
NC
Vsneg (-V)
Voltage Offset
Adjust
Break Before
Make Jumpers
Output
Connections
Output Transistors
Figure 1
N-Channel
MOSFETs, M1-M4
M1
MUTE
M2
MUTE
LED
+V
IN2
+5
AGND
IN1
TA0104A
AG
DG
NC
+
+
-V
OUT1
GND1
GND2
OUT2
M3
Tripath Class-T Audio
Amplifier Board
EB-TA0104, Rev. 3.3
M4
*Please note the Break-Before-Make labels on the PC Board are incorrect and are reversed.
Figure 2
EB-TA0104, 02.00 Rev. 4.0
3
TECHNICAL INFORMATION
ARCHITECTURE
A block diagram of one channel of the evaluation board is shown in Figure 3. The major functional
blocks of the amplifier are described below.
In
Output
Section
Out
Input Stage
TA0104A
VN12
Figure 3
Input Stage
Figure 4 shows one channel of the Input Stage. The TA0104A amplifier is designed to accept
unbalanced inputs and provide an overall gain of 14, or approximately 23 dB.
49.9K
W
1u, 6.3V
Input to TA0104A
R
IN
C
IN
+5V
1M
W
1M
W
10K
W
0.1u, 50V
Figure 4
4
EB-TA0104, 02.00 Rev. 4.0
TECHNICAL INFORMATION
The gain of each channel of the TA0104A amplifier is set by the value of resistor R
IN
in Figure 4 (labeled
R8 and R9 on the schematic), according to the following equation:
In this design, R
IN
is 49.9K
W
, which yields an Av of 14 (23 dB). This value is a good compromise
between gain and noise, as decreasing the gain further results in a negligible increase in noise margin.
The values of the input capacitor, C
IN
in Figure 4 (labeled C13 and C16 on the schematic), and the input
resistor, R
IN
, set the –3dB point of the input high-pass filter. The frequency of the input high pass pole,
F
P
, of the –3dB point can then be calculated as follows:
F
P
= 1/(2
p
x C
IN
)(R
IN
+ 5000)
where: C
IN
= input capacitor value in Farads
R
IN
= input resistor value in Ohms
Output offset voltages are nulled in the input stage potentiometers provided here for this purpose. Once
set, the offset does not typically drift with temperature, so no tracking circuitry is required. Offsets can
typically be set to +/- 25 mV.
TA0104A Control Circuitry
Voltage +5V drives the power light, LED 1, directly to indicate a “good” status. If the LED 1 is off, the
amplifier is in HMUTE (see Figure 5). If this is caused by a fault condition (i.e. over-current, over or
under voltage), the cause of the fault must be cleared and the AC power must be cycled before normal
operation can resume.
The MUTE pin is brought out to an external 3-pin header, JP5 (Figure 5). When a jumper is installed
from Pin 4 to ground, the MUTE line is pulled to ground and the outputs are enabled. If the MUTE
jumper is connected from the external MUTE connection to Pin 4 and pulled high to +12V through 1M
W
,
the outputs are muted. Note that if the MUTE jumper is removed, then MUTE pin floats high, the
amplifier is muted and the power LED will not be lit. This is done to remind the user of a possible
“jumper off” condition if there is no output.
+5V
+5V
10
R10
BBM0
7
JP3
JP5
OCR2
MUTE
4
R
OCR
LED 1
+5V
11
8
OCR1
JP4
HMUTE
35
BBM1
R11
Figure 5
EB-TA0104, 02.00 Rev. 4.0
5
Av = 800 x 10
3
/ (R
IN
+ 5000)
where R
IN
is in Ohms
[ Pobierz całość w formacie PDF ]