ETC BA20373

2W Stereo Class-D Audio
Power Amplifier
BA20373
Data Sheet
Rev.1.0, 2006.05.19
Biforst Technology Inc.
BA20373
____
2W Stereo Class-D Audio Power Amplifier
2W Stereo Class-D Audio Power Amplifier
BA20373
GENERAL DESCRIPTION
The BA20373 is a 5V class-D amplifier from Biforst Technology. BA20373 provides dc volume
control, lower supply current, high efficiency & few external components for driving speaker directly.
BA20373 also integrates Anti-Pop, Output Short & Over-Heat Protection Circuitry to increase device
reliability. The functionality makes this device ideal for LCD projectors, LCD monitors, powered
speakers & other applications that demand more battery life.
FEATURE
2W Per Channel Into 3-Ω Speakers (THD+N = [email protected])
Operation Voltage From 3.3 To 5.5V
DC Volume Control From –27dB to 20dB
Low Shutdown Control : <10μA
Low Noise Floor, -80dBV
Maximum Efficiency into 3-Ω, 77%
Maximum Efficiency into 8-Ω, 87%
PSRR, -71dB
Filter Free PWM Output Technology without LC Output Filter
Integrated Anti-Pop Circuitry
Integrated Output Short Protection Circuitry
Integrated Over-Heat Protection Circuitry
Provide DC Volume Control
Shipping in Die Form
APPLICATION
LCD Monitors
Powered Speakers
Cellular Phones
PDA
Portable DVD/CD Players
USB Audio
Battery Powered Application
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Biforst Technology, Inc., reserves the right to change product or specifications without notice.
Page 2 of 8
BA20373
____
2W Stereo Class-D Audio Power Amplifier
PAD ASSIGNMENTS, PAD LIST & DESCRIPTION
3
4
46
47
48
VSS
VSS
LINP
VDD
VDD
BA20373
1
2
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
VSS
VSS
VDD
VDD
RINP
RINN
C_BYPASS
SHUTDOWN_B
VSS
VSS
VSS
VSS
VSS
OSC_C
VOLUME
OSC_R
LINN
28
27
30
29
VSS
VSS
VSS
VSS
PAD ASSIGNMENTS
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
VSS
VSS
ROUT_N
ROUT_N
ROUT_N
ROUT_P
ROUT_P
ROUT_P
VDD
VDD
VDD
VDD
VDD
VDD
LOUT_P
LOUT_P
LOUT_P
9
8
7
LOUT_N
LOUT_N
LOUT_N
6
5
VSS
VSS
PAD LIST & DESCRIPTION
Pad
No.
Pad
Type
X
Y
I/O Pad Function
1
176.48
46.50
2
274.48
46.50
1254.47
80.85
4
1354.47
80.85
5
1930.25
83.85
6
1930.25
183.85
7
1930.25
304.20
1930.25
409.20 Left channel negative output
9
1930.25
514.20
10
1930.25
619.20
1930.25
724.20 Left channel positive output
12
1930.25
829.20
13
1930.25
949.55
3
VSS
8
11
14
LOUT_N
LOUT_P
VDD
Power
Output
Output
Power
5V Ground
1930.25 1049.55 5V Power Input
15
1930.25 1149.55
16
1930.25 1597.45
17
18
VDD
Power
1930.25 1697.45 5V Power Input
1930.25 1797.45
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Biforst Technology, Inc., reserves the right to change product or specifications without notice.
Page 3 of 8
BA20373
Pad
No.
Pad
Type
X
2W Stereo Class-D Audio Power Amplifier
Y
ROUT_P
Output
1930.25 2022.80 Right channel positive output
21
1930.25 2127.80
22
1930.25 2232.80
23
ROUT_N
Output
1930.25 2337.80 Right channel negative output
24
1930.25 2442.80
25
1930.25 2563.15
26
1930.25 2663.15
1354.47 2666.15
27
28
I/O Pad Function
1930.25 1917.80
19
20
____
VSS
Power
1254.47 2666.15
29
274.48 2699.70
30
176.48 2699.70
5V Ground
46.50 2437.45
31
VDD
Power
5V Power Input
46.50 2339.45
32
33
RINP
Input
46.50 2241.45 Right channel positive differential audio input
34
RINN
Input
46.50 2143.45 Right channel negative differential audio input
35
C_BYPASS
Input
36
SHUTDOWN_B
Input
Connect a 10-uF capacitor from C_BYPASS to ground for internal
46.50 2045.45 bias reference
Shut down control for CS3006, Logic low is placed on this terminal
for shut down mode, Logic high is placed on this terminal for normal
operation (Recommend Connect 100K Ohm To VDD & Connect 1uF
46.50 1947.45 To Ground In Application Circuit)
37
46.50 1849.45
38
46.50 1751.45
39
VSS
Power
46.50 1653.45 5V Ground
40
46.50 1081.95
41
46.50
Input
983.95
A capacitor connected to this terminal sets the oscillation in
conjunction with OSC_C. For proper operation, connect a 220-pF
885.95 capacitor from OSC_C to ground
DC volume control for setting the gain on the internal amplifier. The
787.95 dc voltage range is 0 to VDD
A resistor connected to this terminal sets the oscillation in
689.95 conjunction with OSC_R. For proper operation, connect a 120-kΩ
resistor from OSC_R to ground
42
OSC_C
43
VOLUME
Input
46.50
44
OSC_R
Input
46.50
45
LINN
Input
46.50
591.95 Left channel negative differential audio input
46
LINP
Input
46.50
493.95 Left channel positive differential audio input
47
VSS
46.50
395.95
46.50
297.95
46.50
Power
48
VSS
5V Ground
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Biforst Technology, Inc., reserves the right to change product or specifications without notice.
Page 4 of 8
BA20373
____
2W Stereo Class-D Audio Power Amplifier
FUNCTION DESCRIPTION
Output Power Efficiency
The output transistors of BA20373 act as switches. The amount of power dissipated in the
speaker may be estimated by first considering the overall efficiency of the system. The on-resistance
of the output transistors is considered to cause the dominant loss in the system, the on-resistance of
output transistors is small that the power loss is small and the power efficiency is high. When BA20373
is with 8-ohm load, the power efficiency can be better than 87%.
Shutdown Mode
The BA20373 provides a shutdown mode to reduce supply current to the absolute minimum level
during periods of non-use for battery-power conservation. The SHUTDOWN_B input pin should be
held high during normal operation when the amplifier is in use. Pulling SHUTDOWN_B low causes the
outputs to mute and the amplifier to enter a low-current state. SHUTDOWN_B should never be left
unconnected because the amplifier state would be unpredictable.
Recommend connecting SHUTDOWN_B pin with 100K Ohm To VDD & Connect 1uF To Ground.
Differential Input
The differential input stage of the amplifier cancels any noise that appears on both input lines of
the channel. To use the BA20373 with a differential source, connect the positive lead of the audio
source to the LINP/RINP input and the negative lead from the audio source to the LINN/RINN input. To
use the BA20373 with a single-ended source, ac ground either input through a capacitor and apply the
audio signal to the remaining input. In a single-ended input application, the un-used input should be
ac-grounded at the audio source instead of at the device input for best noise performance.
Single-end stereo input application circuit shows in Figure 1. It’s recommended LINN & RINN
connect 1uF to ground. & Left/Right analog audio signal series connect 1uF to LINP & RINP.
Left Channel
Input
1uF
1uF
Right Channel
Input
1uF
1uF
LINP
LINN
BA20373
RINP
RINN
Figure 1. Single-end stereo input application circuit
Volume Control
The VOLUME pin controls the volume of the BA20373. It is controlled with a dc voltage, which
should not exceed VDD. Table 1 lists the voltage on the VOLUME pin and the corresponding gain.
The volume control circuitry of the BA20373 is internally referenced to the VDD and 1V. Any
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Biforst Technology, Inc., reserves the right to change product or specifications without notice.
Page 5 of 8
BA20373
____
2W Stereo Class-D Audio Power Amplifier
common-mode noise between the VOLUME terminal and these terminals will be sensed by the
volume control circuitry. If the noise exceeds the step size voltage, the gain will change. In order to
minimize this effect, care must be taken to ensure the signal driving the VOLUME terminal is
referenced to the VDD and 1V of the BA20373.
DC volume application circuit shows in Figure 2. It’s recommended to connect 10K VR series to
2.2 K resister to ground or 50K VR series to 11 K resister to ground.
VDD
VDD
50K VR
Volume
10K VR
Volume
2.2K
11K
Figure 2. DC Volume Application Circuit
Table 1. Typical DC Volume Control
Voltage On Volume Pin
0.97 - 0.87
1.08 - 0.98
1.19 - 1.09
1.32 - 1.20
1.42 - 1.33
1.53 - 1.43
1.63 - 1.54
1.75 - 1.64
1.84 - 1.76
1.96 - 1.85
2.09 - 1.97
2.19 - 2.10
2.33 - 2.20
2.43 - 2.34
2.49 - 2.44
2.62 - 2.50
2.75 - 2.63
2.85 - 2.76
2.99 - 2.86
3.12 - 3.00
3.25 - 3.13
3.36 - 3.26
3.48 - 3.37
3.64 - 3.49
VDD - 3.65
Typical Gain Of Amplifier
(dB)
-27
-25
-23
-21
-19
-17
-15
-13
-12
-10
-8
-6
-4
-2
0
2
4
6
8
10
12
14
16
18
20
OSC_C & OSC_R Pin
The switching frequency is determined using the values of the components connected to OSC_R
and OSC_C
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Biforst Technology, Inc., reserves the right to change product or specifications without notice.
Page 6 of 8
BA20373
____
2W Stereo Class-D Audio Power Amplifier
The frequency may be varied from 200 kHz to 300 kHz by adjusting the values chosen for OSC_R
and OSC_C. The recommended values are OSC_C = 220 pF, OSC_R= 120 kΩ for a switching
frequency of 250 kHz.
Over-Heat Protection
Over-Heat protection on the BA20373 prevents damage to the device when the internal die
temperature exceeds 125°C. Once the die temperature exceeds the thermal set point, the device
enters the shutdown state and the outputs are disabled. The device will back to normal operation when
die temperature is reduced without external system interaction.
Output Short Protection
The BA20373 has output short circuit protection circuitry on the outputs that prevents damage to
the device during output-to-output short, output-to-GND short, and output-to-VDD short. BA20373
enters the shutdown state and the outputs are disabled when detects output short. The device will
back to normal operation automatically after 2 ~ 3 minute.
Anti-Pop
A soft start capacitor must be added to the C_BYPASS pin. It recommends connecting a capacitor
of 1uF from C_BYPASS pin to Ground. BA20373 provides fade-in function when power-on or
SHUTDOWN_B input voltage level from 0V to VDD, and fade-out function when SHUTDOWN_B input
voltage level from VDD to 0V. The pop noise can be eliminated by fade-in/fade-out function.
Output Filter Application Note
Design the BA20373 without the filter if the traces from amplifier to speaker are short (< 1 inch).
Where the speaker is in the same enclosure as the amplifier is a typical application for class-D without
a filter.
Many applications require a ferrite bead filter. The ferrite filter reduces EMI around 30 MHz. When
selecting a ferrite bead, choose one with high impedance at high frequencies, but low impedance at
low frequencies.
Use an LC output filter if there are low frequency (<1 MHz) EMI sensitive circuits and/or there are
long wires from the amplifier to the speaker.
22uH
OUTP
0.1uF
0.47uF
22uH
0.1uF
OUTN
Figure 3. Typical LC Output Filter
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Biforst Technology, Inc., reserves the right to change product or specifications without notice.
Page 7 of 8
BA20373
____
2W Stereo Class-D Audio Power Amplifier
BEAD (600R)
OUTP
330pF
470pF
BEAD (600R)
330pF
OUTN
Figure 4. Typical Ferrite Chip Bead Output Filter
C_BYPASS Pin
It’s recommended to connect a 10-uF capacitor from C_BYPASS pin to ground for internal bias
reference & provide high power supply rejection ratio (PSRR).
CONTACT INFORMATION
Biforst Technology Inc.
8F-3, No.26, Tai Yuen St., Jubei City, Hsin-Chu, Taiwan, R.O.C.
Tel: 886-3-552-6521; Fax: 886-3-552-6558; Email: [email protected]
Version History
Version
Date
1.0
2006.05.19
Page
Description
First Release
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Biforst Technology, Inc., reserves the right to change product or specifications without notice.
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