ETC BA20371

2W Stereo Class-D Audio
Power Amplifier
DiPOP
Only
BA20371
Data Sheet
Rev.1.4, 2007.03.09
Biforst
Biforst Technology Inc.
BA20371
____
2W Stereo Class-D Audio Power Amplifier
2W Stereo Class-D Audio Power Amplifier
BA20371
GENERAL DESCRIPTION
The BA20371 is a 5V class-D amplifier from Biforst Technology. BA20371 provides dc volume
control, lower supply current, high efficiency & few external components for driving speaker directly.
BA20371 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
DiPOP
Only
2.3W Per Channel Into 4-Ω Speakers (THD+N = 10%@5.5V)
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
Package Type: TSSOP28
Biforst
APPLICATION
LCD Monitors
Powered Speakers
Cellular Phones
PDA
Portable DVD/CD Players
USB Audio
_________________________________________________________________________________________________
Biforst Technology, Inc., reserves the right to change product or specifications without notice.
Page 2 of 16
BA20371
____
2W Stereo Class-D Audio Power Amplifier
Battery Powered Application
DiPOP
Only
Biforst
_________________________________________________________________________________________________
Biforst Technology, Inc., reserves the right to change product or specifications without notice.
Page 3 of 16
BA20371
____
2W Stereo Class-D Audio Power Amplifier
OPERATE VOLATGE VS. OUTPUT POWER PER CHANNEL
3.00
2.80
2.60
2.40
2.20
2.00
1.80
1.60
1.40
1.20
1.00
0.80
0.60
0.40
0.20
0.00
THD 1%-3Ohm
THD 10%3Ohm
THD 1%-4Ohm
DiPOP
Only
THD 10%4Ohm
THD 1%-8Ohm
THD 10%8Ohm
3.3
3.4
3.5
3.6
3.7
3.8
3.9
4.0
4.1
4.2
4.3
4.4
4.5
4.6
4.7
4.8
4.9
5.0
5.1
5.2
5.3
5.4
5.5
5.6
5.7
5.8
5.9
6.0
Output Power Per Channel
(W)
Operate Voltage vs Output Power
Operate Voltage (V)
FUNCTION BLOCK DIAGRAM
VDD
VDD
C_BYPASS
Gain
Adj.
RINP
PVDD_A
Driver
ROUTP
PVSS_A
PVDD_A
Driver
Gain
Adj.
RINN
SHUTDOWN_B
VOLUME
OSC_C
OSC_R
LINP
Volume
Control
ROUTN
PVSS_A
Baises &
References
Clock
Generator
Protection
Circuit
Biforst
Gain
Adj.
Driver
PVDD_A
LOUTP
PVSS_A
PVDD_A
Driver
LINN
Gain
Adj.
LOUTN
PVSS_A
VSS
VSS
VSS
_________________________________________________________________________________________________
Biforst Technology, Inc., reserves the right to change product or specifications without notice.
Page 4 of 16
BA20371
____
2W Stereo Class-D Audio Power Amplifier
ABSOLUTE MAXIMUM RATINGS (Note 1)
SYMBOL
PARAMETER
VALUE
UNIT
VDD, PVDD_A
Supply Voltage Range
-0.3 to 6
V
Input Voltage Range
0 to VDD
V
Input Voltage Range
1 to VDD
V
TA
Operating Free-Air Temperature Range
-40 ~ +85
℃
TJ
Operating Junction Temperature Range
-40 to 150
℃
Storage Temperature Range
-65 to 85
℃
VI
(RINP, RINN, LINP, LINN)
VI
(VOLUME)
TSTG
DiPOP
Only
Note 1: Stress beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device.
Exposure to absolute-maximum-rating conditions for extended periods may affect device reliability.
RECOMMENDED OPERATING CONDITIONS
SYMBOL
PARAMETER
SPECIFICATION
MIN
TYP
MAX
UNIT
VDD,
Supply Voltage
3.3
5.5
V
PVDD_A
Volume Terminal Voltage
0
VDD
V
VIH
Input High Voltage (SHUTDOWN_B)
2.0
VIL
Input Low Voltage (SHUTDOWN_B)
FPWM
PWM Frequency
TA
Operating Free-Air Temperature
TJ
Operating Junction Temperature
V
0.8
V
200
300
KHz
-40
85
℃
125
℃
Biforst
_________________________________________________________________________________________________
Biforst Technology, Inc., reserves the right to change product or specifications without notice.
Page 5 of 16
BA20371
____
2W Stereo Class-D Audio Power Amplifier
ELECTRICAL CHARACTERISTICS (TA=25℃, VDD=PVDD_A =5V; unless otherwise specified)
SPECIFICATION
SYMBOL
PARAMETER
TEST CONDITIONS
| VOS |
Output Offset Voltage
(Measured Differentially)
VI = 0V, AV = 20dB,
RL = 8Ω
PSRR
Power supply rejection ratio
｜IIH｜
High-level input current
｜IIL｜
Low –level input current
IDD
Supply Current
No Filter (No Load)
10
IDD(MAX)
RMS Supply Current
At Max Power
RL = 3Ω, PO =
2.5W/Channel (Stereo)
1.8
IDD(SD)
Supply Current
In Shutdown Mode
SHUTDOWN_B = 0V
1
10
rds(on)
Drain-Source On-State
Resistance
VDD = 5V, High Side
IO=500mA,
TJ = 25℃ Low Side
550
700
550
700
MIN
VDD=PVDD_A =
TYP
MAX
15
25
-70
4.5V to 5.5V
VDD=PVDD_A =5.5V,
DiPOP
Only
VI = VDD=PVDD_A =0V
VDD=PVDD_A =5.5V,
VI = 0V
UNIT
mV
dB
1
uA
1
uA
20
mA
A
uA
mΩ
OPERATING CHARACTERISTICS (TA=25℃, VDD=PVDD_A=5.5V, RL=4Ω, Gain=0dB; unless
otherwise specified)
SYMBOL
PO
PARAMETER
TEST CONDITIONS
Output Power
F = 1KHz, THD+N =
RL = 4Ω,
1%
Stereo
THD+N =
Operation
10%
SPECIFICATION
MIN
Biforst
TYP
MAX
UNIT
1.7
W
2.3
W
THD+N
Total Harmonic Distortion
Plus Noise
PO = 2W, f= 20Hz to
20KHz
<0.3%
BOM
Maximum Output Power
Bandwidth
THD = 5%
20
KHz
SNR
Signal-to-Noise Rate
Maximum Output at
THD+N < 0.5%
96
dB
TTP
Thermal Trip Point
150
℃
TH
Thermal Hystersis
20
℃
Vn
Integrated Noise Floor
45
uVrms
20Hz to 20KHz, Input
_________________________________________________________________________________________________
Biforst Technology, Inc., reserves the right to change product or specifications without notice.
Page 6 of 16
BA20371
____
2W Stereo Class-D Audio Power Amplifier
88
AC Grounded
TYPICAL CHARACTERISTICS
Frequency Response at 3ohm Load, 5V, 1W
Frequency Response at 4ohm Load, 5V, 1W
Output
Output
Biforst Technology Inc.,
BA2037 Frequency Response
(3ohm Load, 5V 1W Output)
05/09/06 18:41:52
+0
-0.1
-0.1
-0.2
-0.2
-0.2
-0.3
-0.3
-0.3
-0.4
-0.4
-0.5
-0.5
-0.6
-0.6
-0.6
-0.7
-0.7
-0.7
-0.8
-0.8
-0.8
-0.9
-0.9
-0.9
-0.1
-0.2
DiPOP
Only
-0.4
-0.4
d
B
r
d
B
r
-0.5
-0.5
B
A
-0.6
-0.7
-0.8
-0.9
50
100
200
500
+0.1
-0.1
+0
-0.3
1k
2k
Hz
BA2037 at 5.0V, 3 ohm Load, VOLUME 2.5V
5k
-1
20
50
d
B
r
B
A
-1
10k
05/09/06 14:57:48
+0
+0
-1
20
BA2037 Frequency Response
(4ohm Load, 5V 1W Output)
+0.1
+0.1
+0.1
d
B
r
Biforst Technology Inc.,
100
200
500
1k
2k
5k
-1
10k
Hz
BA2037 at 5.0V, 4 ohm Load, VOLUME 2.5V
00_Frequency Response_at 1w Output.at27
00_Frequency Response_at 1w Output.at27
THD+N vs. Frequency at 3ohm Load, 5V, 0.6W
THD+N vs. Frequency at 4ohm Load, 5V, 0.6W
& 1W Output
& 1W Output
Biforst Technology Inc.,
BA2037 THD+N vs Frequency
(at 0.6W & 1W Output)
05/10/06 11:38:19
Biforst Technology Inc.,
0.6
0.5
0.5
0.4
0.3
BA2037 THD+N vs Frequency
(at 0.6W & 1W Output)
05/09/06 15:07:26
0.4
0.3
0.2
0.2
0.1
%
%
0.1
0.08
0.06
0.05
0.08
0.04
0.06
0.03
0.05
0.04
0.02
0.03
0.02
20
50
100
200
500
1k
Hz
BA2037 at 5.0V, 3 ohm Load, VOLUME 2.5V
Yellow : 1W Output, Green : 0.6W Output
Biforst
2k
01_THD+N vs Frequency_at 0.6 1W Output.at27
5k
10k
20k
0.01
20
50
100
200
500
1k
2k
5k
10k
20k
Hz
BA2037 at 5.0V, 4 ohm Load, VOLUME 2.5V
Yellow : 1W Output, Green : 0.6W Output
01_THD+N vs Frequency_at 0.6 1W Output.at27
_________________________________________________________________________________________________
Biforst Technology, Inc., reserves the right to change product or specifications without notice.
Page 7 of 16
BA20371
____
2W Stereo Class-D Audio Power Amplifier
THD+N vs. Output Power at 3ohm Load, 5V
Biforst Technology Inc.,
BA2037 THD+N vs Output Power
05/09/06 15:46:03
THD+N vs. Output Power at 4ohm Load, 5V
Biforst Technology Inc.,
BA2037 THD+N vs Output Power
05/09/06 15:08:24
20
20
10
10
5
5
2
2
1
1
%
0.5
0.5
%
0.2
0.2
0.1
0.1
0.05
0.05
0.02
DiPOP
Only
0.02
0.01
200m
400m
600m
800m
1
1.2
1.4
W
BA2037 at 5.0V, 3 ohm Load, VOLUME 2.5V
Red : 20KHz, Green : 1KHz, Yellow : 20Hz
02_THD+N vs Output Power.at27
1.6
1.8
2
-30
T
T
T
T
400m
600m
800m
1
1.2
1.4
1.6
1.8
2
W
05/09/06 15:46:43
02_THD+N vs Output Power.at27
Crosstalk at 4ohm Load, 5V, 1.8W Output
Biforst Technology Inc.,
T
-30
T
-40
T
T
T
T
BA2037 Crosstalk vs Frequency
(1.8W Output)
05/09/06 15:09:36
T
-40
-50
-50
-60
-60
-70
d
B
200m
BA2037 at 5.0V, 4 ohm Load, VOLUME 2.5V
Red : 20KHz, Green : 1KHz, Yellow : 20Hz
Crosstalk at 3ohm Load, 5V, 1.8W Output
Biforst Technology Inc.,
0.01
2.2
-70
-80
d
B
-90
-80
-90
-100
-100
-110
-110
-120
-120
-130
20
50
100
200
500
1k
2k
5k
10k
-130
20
50
100
200
Hz
BA2037 at 5.0V, 3ohm Load, VOLUME at 2.5V
500
1k
2k
5k
10k
Hz
BA2037 at 5.0V, 4ohm Load, VOLUME at 2.5V
03_Crosstalk vs Frequency.at27
03_Crosstalk vs Frequency.at27
Biforst
_________________________________________________________________________________________________
Biforst Technology, Inc., reserves the right to change product or specifications without notice.
Page 7 of 16
BA20371
____
2W Stereo Class-D Audio Power Amplifier
Frequency Response at 3ohm Load, 3.9V,
Frequency Response at 4ohm Load, 3.9V,
0.5W Output
0.5W Output
Biforst Technology Inc.,
BA2037 Frequency Response
(3ohm Load, 3.9V 0.5W Output)
05/10/06 11:34:27
+0.1
d
B
r
Biforst Technology Inc.,
+0.1
BA2037 Frequency Response
(4ohm Load, 3.9V 0.5W Output)
05/09/06 18:53:44
+0.1
+0.1
+0
+0
+0
+0
-0.1
-0.1
-0.1
-0.1
-0.2
-0.2
-0.2
-0.2
-0.3
-0.3
-0.3
-0.3
-0.4
-0.4
-0.4
-0.4
-0.5
d
B
r
d
B
r
DiPOP
Only
-0.5
A
-0.5
-0.5
-0.6
-0.6
-0.6
-0.7
-0.8
-0.7
-0.7
-0.7
-0.8
-0.8
-0.9
-0.8
-0.9
-0.9
-1
20
50
100
200
500
1k
2k
Hz
5k
-1
20
-1
10k
B
A
B
-0.6
50
d
B
r
-0.9
100
200
500
1k
2k
5k
-1
10k
Hz
BA2037 at 3.9V, 4 ohm Load, VOLUME 1.95V
BA2037 at 3.9V, 3 ohm Load, VOLUME 1.95V
00_Frequency Response_at 0.5W Output.at27
00_Frequency Response_at 0.5W Output.at27
THD+N vs. Frequency at 3ohm Load, 3.9V,
THD+N vs. Frequency at 4ohm Load, 3.9V,
0.25W & 0.5W Output
0.25W & 0.5W Output
Biforst Technology Inc.,
BA2037 THD+N vs Frequency
(at 0.25W & 0.5W Output)
05/09/06 15:40:07
Biforst Technology Inc.,
BA2037 THD+N vs Frequency
(at 0.25W & 0.5W Output)
05/09/06 15:42:17
0.6
1
0.5
0.4
0.5
0.3
0.2
%
0.2
0.1
%
0.1
0.05
0.07
0.06
0.05
0.02
0.04
0.01
20
50
100
200
500
1k
2k
5k
10k
20k
0.03
20
50
100
200
Hz
500
1k
2k
5k
10k
20k
Hz
BA2037 at 3.9V, 3 ohm Load, VOLUME 1.95V
Yellow : 0.5W Output, Green : 0.25W Output
BA2037 at 3.9V, 4 ohm Load, VOLUME 1.95V
Yellow : 0.5W Output, Green : 0.25 Output
01_THD+N vs Frequency_at 0.25 0.5W Output.at27
01_THD+N vs Frequency_at 0.25 0.5W Output.at27
Biforst
_________________________________________________________________________________________________
Biforst Technology, Inc., reserves the right to change product or specifications without notice.
Page 8 of 15
BA20371
____
2W Stereo Class-D Audio Power Amplifier
THD+N vs. Output Power at 3ohm Load, 3.9V
Biforst Technology Inc.,
BA2037 THD+N vs Output Power
05/09/06 15:32:50
THD+N vs. Output Power at 4ohm Load, 3.9V
Biforst Technology Inc.,
BA2037 THD+N vs Output Power
05/09/06 15:14:57
30
10
20
5
10
5
2
1
2
0.5
1
%
%
0.5
0.2
0.2
0.1
0.1
0.05
0.05
0.02
0.01
100m
200m
300m
400m
500m
600m
700m
W
800m
.9
1
1.1
02_THD+N vs Output Power.at27
-30
T
T
200m
300m
DiPOP
Only
Crosstalk at 3ohm Load, 3.9V, 1W Output
Biforst Technology Inc.,
0.02
100m
1.2
400m
500m
600m
700m
800m
.9
1
1.1
1.2
W
BA2037 at 3.9V, 4 ohm Load, VOLUME 1.95V
Red : 20KHz, Green : 1KHz, Yellow : 20Hz
BA2037 at 3.9V, 3 ohm Load, VOLUME 1.95V
Red : 20KHz, Green : 1KHz, Yellow : 20Hz
BA2037 Crosstalk vs Frequency
(1W Output)
T
Crosstalk at 4ohm Load, 3.9V, 1W Output
05/09/06 18:55:13
Biforst Technology Inc.,
-30
T
-40
02_THD+N vs Output Power.at27
T
T
BA2037 Crosstalk vs Frequency
(1W Output)
05/09/06 18:54:30
T
-40
-50
-50
-60
-60
-70
d
B
-70
d
B
-80
-80
-90
-90
-100
-100
-110
-110
-120
20
50
100
200
500
1k
Hz
2k
5k
10k
-120
20
50
100
200
03_Crosstalk vs Frequency.at27
500
1k
2k
5k
10k
Hz
BA2037 at 3.9V, 3ohm Load, VOLUME at 1.95V
BA2037 at 3.9V, 4ohm Load, VOLUME at 1.95V
03_Crosstalk vs Frequency.at27
Biforst
_________________________________________________________________________________________________
Biforst Technology, Inc., reserves the right to change product or specifications without notice.
Page 9 of 15
BA20371
____
2W Stereo Class-D Audio Power Amplifier
PIN ASSIGNMENTS
1
28
VDD
PVSS_A
2
27
VSS
PVSS_A
3
26
LINP
PVSS_A
4
25
LINN
LOUTN
5
24
OSC_R
LOUTP
6
PVDD_A
7
PVDD_A
8
ROUTP
9
ROUTN
10
PVSS_A
11
18
RINP
PVSS_A
12
17
VSS
PVSS_A
13
16
VSS
PVSS_A
14
15
VDD
BA20371
PVSS_A
23
VOLUME
22
OSC_C
21
SHUTDOWN_B
20
C_BYPASS
19
RINN
DiPOP
Only
PIN LIST & DESCRIPTION
Pin No.
Pin
1
PVSS_A
2
PVSS_A
3
PVSS_A
4
PVSS_A
5
I/O Pad Function
Type
Power
5V ground
LOUTN
Output
Left channel negative output
6
LOUTP
Output
Left channel positive output
7
PVDD_A
8
PVDD_A
Power
5V power supply
9
ROUTP
Output
Right channel positive output
10
ROUTN
Output
Right channel negative output
11
PVSS_A
12
PVSS_A
13
PVSS_A
Power
5V ground
14
PVSS_A
15
VDD
Power
5V power supply
16
VSS
17
VSS
Power
5V ground
18
RINP
19
RINN
20
C_BYPASS
Input
Right channel positive differential audio input
Input
Right channel negative differential audio input
Input
Connect a 10-uF capacitor from C_BYPASS to ground for internal bias
reference
Biforst
Shut down control for BA20371, Logic low is placed on this terminal for
21
SHUTDOWN_B
Input
shut down mode, Logic high is placed on this terminal for normal
operation (Recommend Connect 100K Ohm To VDD & Connect 1uF To
Ground In Application Circuit)
_________________________________________________________________________________________________
Biforst Technology, Inc., reserves the right to change product or specifications without notice.
Page 10 of 15
BA20371
Pin No.
____
Pin
2W Stereo Class-D Audio Power Amplifier
I/O Pad Function
Type
A capacitor connected to this terminal sets the oscillation in conjunction
22
OSC_C
Input
with OSC_C. For proper operation, connect a 220-pF capacitor from
OSC_C to ground
DC volume control for setting the gain on the internal amplifier. The dc
23
VOLUME
Input
24
OSC_R
Input
25
LINN
Input
Left channel negative differential audio input
26
LINP
Input
Left channel positive differential audio input
voltage range is 0 to VDD
A resistor connected to this terminal sets the oscillation in conjunction
with OSC_R. For proper operation, connect a 120-kΩ resistor from
OSC_R to ground
27
VSS
28
VDD
DiPOP
Only
Power
5V ground
Power
5V power supply
FUNCTION DESCRIPTION
Output Power Efficiency
The output transistors of BA20371 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 BA20371
is with 8-ohm load, the power efficiency can be better than 87%.
Shutdown Mode
The BA20371 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.
Biforst
Differential Input
The differential input stage of the amplifier cancels any noise that appears on both input lines of
the channel. To use the BA20371 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 BA20371 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.
_________________________________________________________________________________________________
Biforst Technology, Inc., reserves the right to change product or specifications without notice.
Page 11 of 15
BA20371
____
2W Stereo Class-D Audio Power Amplifier
Left Channel
Input
1uF
1uF
Right Channel
Input
1uF
1uF
LINP
LINN
BA20371
RINP
RINN
Figure 1. Single-end stereo input application circuit
DiPOP
Only
Volume Control
The VOLUME pin controls the volume of the BA20371. 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 BA20371 is internally referenced to the VDD and 1V. Any
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 BA20371.
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
50K VR
11K
VDD
Volume
10K VR
Volume
2.2K
Biforst
Figure 2. DC Volume Application Circuit
_________________________________________________________________________________________________
Biforst Technology, Inc., reserves the right to change product or specifications without notice.
Page 12 of 15
BA20371
____
2W Stereo Class-D Audio Power Amplifier
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
DiPOP
Only
OSC_C & OSC_R Pin
The switching frequency is determined using the values of the components connected to OSC_R
and OSC_C
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.
Biforst
Over-Heat Protection
Over-Heat protection on the BA20371 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 BA20371 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. BA20371
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
_________________________________________________________________________________________________
Biforst Technology, Inc., reserves the right to change product or specifications without notice.
Page 13 of 15
BA20371
____
2W Stereo Class-D Audio Power Amplifier
of 1uF from C_BYPASS pin to Ground. BA20371 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 BA20371 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.
DiPOP
Only
22uH
OUTP
0.1uF
0.47uF
22uH
0.1uF
OUTN
Figure 3. Typical LC Output Filter
BEAD (600R)
OUTP
330pF
470pF
Biforst
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).
_________________________________________________________________________________________________
Biforst Technology, Inc., reserves the right to change product or specifications without notice.
Page 14 of 15
BA20371
____
2W Stereo Class-D Audio Power Amplifier
PACKAGE DIMENSION
TSSOP28
DiPOP
Only
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
2005.12.15
1.1
2006.01.26
Page
Description
Biforst
First Release
2
Add features of DC Volume Control, Low Shutdown Control, Low Noise
Floor, Max. Efficiency & PSRR.
Update Graph “Output Voltage vs. Output Power”
1.2
2006.04.07
2 – 5, 7 – 10 Update Feature, Add Electrical Parameters and Function Description
1.3
2006.07.04
6-9
1.4
2007.03.09
3
Add Typical Characteristics Charts
Modify Function Block Diagram Error
_________________________________________________________________________________________________
Biforst Technology, Inc., reserves the right to change product or specifications without notice.
Page 15 of 15