ETC BA16852

3W Mono Filterless Class-D
Audio Power Amplifier
BA16852
Data Sheet
Rev.1.1, 2007.08.28
Biforst Technology Inc.
BA16852 3W Mono Filterless Class-D Audio Power Amplifier
3W Mono Filterless Class-D Audio Power Amplifier
BA16852
GENERAL DESCRIPTION
The BA16852 is a cost-effective mono class-d audio power amplifier that assembles in 1.45mm x
1.45mm wafer chip scale package (CSP). Only three external components offer space and cost saving
for cellular phone or PDA application. The BA16852 provides 3W high performance output capacity at
4-Ω load. Other feature like 90% efficiency, -75dB PSRR, fully differential design reduces RF
rectification, and allows independent gain while summing signals from various audio sources.
BA16852 also integrates Anti-Pop, Output Short & Over-Heat Protection Circuitry to increase device
reliability. The functionality makes this device ideal for cellular phone, PDA, and other applications that
demand more battery life.
FEATURE
Wide Operation Voltage From 2.5 To 5.5V
Efficiency with 8-Ω Speaker
89% at 1.3W
80% at 0.25W
Output Driver Capability, 1.3W With 8-Ω Load And THD+N < 1%
Output Driver Capability, 2.3W With 4-Ω Load And THD+N < 1%
Low 1μA Shutdown Current
Low 5mA Typical Quiescent Current
PSRR, -75dB, No Need For Voltage Regulator
Internally Generated 250KHz Switching Frequency Without External Capacitor And Resistor
External Gain Configuration Capability
Fully Differential Design For Eliminates Two Input Coupling Capacitors And Reduces RF
Rectification
Filterless PWM Output Technology without LC Output Filter
Integrated Anti-Pop Circuitry
Integrated Output Short Protection Circuitry
Integrated Over-Heat Protection Circuitry
Package Type : MSOP 8Pin
APPLICATION
Cellular Phones
PDA and Smart Phones
Portable Electronic Device
Portable Computer
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Page 2 of 24
BA16852 3W Mono Filterless Class-D Audio Power Amplifier
APPLICATION CIRCUIT
-
RI
Internal
Osciliator
To Power Source
VDD
CS
INN
OUTN
Audio
Input
PWM
+
+
RI
SD_B
Driver
OUTP
INP
Bias
Circuitry
GND
BA16852
Figure 1. Typical BA16852 Application Circuit
PIN ASSIGNMENT
MSOP 8Pin
Top View
SD_B
NC
INP
INN
1
2
3
4
8
7
6
5
OUTN
GND
VDD
OUTP
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Page 3 of 24
BA16852 3W Mono Filterless Class-D Audio Power Amplifier
PIN LIST & DESCRIPTION
Pin No.
Pin
1
SD_B
2
NC
3
I/O Pad Function
Type
Input
Shutdown (Active Low Logic)
INP
Input
Positive differential audio input
4
INN
Input
Negative differential audio input
5
OUTP
Output
Positive BTL output
6
VDD
Power
Power supply
7
GND
Power
Power ground
8
OUTN
Output
Negative BTL output
Function Block Diagram
VDD
150KΩ
INP
+
+ - +
+ - +
Data
Processor
INN
Output
Driver
OUTN
+
-
150KΩ
SD_B
OUTP
Shutdown
Control
300KΩ
Bias &
References
Clock
Generator
Startup
Protection
OC
Detect
GND
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Page 4 of 24
BA16852 3W Mono Filterless Class-D Audio Power Amplifier
These device have limited built-in ESD protection. The leads should be shorted together or the device placed
in conductive foam during storage or handling to prevent electrostatic damage to the MOS gates.
ABSOLUTE MAXIMUM RATINGS
SYMBOL
VDD
VI
TA
TJ
TSTG
PARAMETER
Supply Voltage Range
Input Voltage Range
Operating Free-Air Temperature Range
Operating Junction Temperature Range
Storage Temperature Range
VALUE
-0.3V to 6V
-0.3V to VDD+0.3V
-40oC to 85oC
-40oC to 125oC
-65oC to 150oC
RECOMMANDED OPERATING CONDITIONS
SYMBOL
VDD
VIH
VIL
RI
fPWM
VIC
TA
PARAMETER
Supply Voltage
High-Level Input Voltage
SHUTDOWN_B
Low-Level Input Voltage
SHUTDOWN_B
Input Resistor
GAIN ≤ 20V/V
PWM Frequency
Common Mode Input Voltage Range
VDD=2.5V, 5.5V, CMRR ≤ -49dB
Operating Free-Air Temperature
MIN
2.5
2
0
15
200
0.5
-40
MAX
5.5
VDD
0.8
300
VDD-0.8
85
UNIT
V
V
V
kΩ
KHz
V
o
C
ELECTRICAL CHARACTERISTICS
TA = 25oC (unless otherwise noted)
SYMBOL
PSRR
CMRR
| IIH |
| IIL |
PARAMETER
Output Offset Voltage
(Measured Differentially)
Power Supply Rejection Ratio
Common Mode Rejection Ratio
High-Level Input Current
Low-Level Input Current
I(Q)
Quiescent Current
I(SD)
Shutdown Current
rDS(ON)
Static Drain-Source On-State
Resistance
| VOS |
F(SW)
TEST CONDITIONS
TYP
MAX
UNIT
VI = 0V, AV = 2V/V, VDD = 2.5 to 5.5V
1
25
mV
VDD = 2.5 to 5.5V
VDD = 2.5 to 5.5V, VIC = 0.5V to VDD-0.8V
VDD = 5.5V, VI = 5.8V
VDD = 5.5V, VI = -0.3V
VDD = 5.5V, no load
VDD = 3.6V, no load
VDD = 2.5V, no load
V(SHUTDOWN_B) = 0.35V, VDD = 2.5 to 5.5V
-75
-68
dB
5.8
4.3
3.1
0.5
-55
-49
100
5
6.2
4.7
3.4
2
450
650
μA
μA
mA
μA
High Side
VDD = 5V, IO = 500mA
mΩ
Low Side
Switching Frequency
VDD = 2.5 to 5.5V
Gain
VDD = 2.5 to 5.5V
Resistance from shutdown to GND
MIN
200
250
300
285kΩ 300kΩ 350kΩ
RI
RI
RI
300
kHz
V
V
kΩ
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Page 5 of 24
BA16852 3W Mono Filterless Class-D Audio Power Amplifier
OPWEATING CHARACTERISTICS
TA = 25oC , Gain = 2V/V, RL = 3 / 4 / 8Ω (unless otherwise noted)
SYMBOL
PARAMETER
TEST CONDITIONS
THD+N = 10%, f = 1KHz, RL = 3Ω
THD+N = 1%, f = 1KHz, RL = 3Ω
THD+N = 10%, f = 1KHz, RL = 4Ω
PO
Output Power
THD+N = 1%, f = 1KHz, RL = 4Ω
THD+N = 10%, f = 1KHz, RL = 8Ω
THD+N = 1%, f = 1KHz, RL = 8Ω
THD+N
Total Harmonic
Distortion Plus Noise
SNR
Supply Ripple
Rejection Ration
Signal-to-noise Ratio
Vn
Output Voltage Noise
KSVR
CMRR
ZI
Common Mode
Rejection Ratio
Input Impedance
Start-up time from
shutdown
MIN
VDD = 5V
VDD = 3.6V
VDD = 2.5V
VDD = 5V
VDD = 3.6V
VDD = 2.5V
VDD = 5V
VDD = 3.6V
VDD = 2.5V
VDD = 5V
VDD = 3.6V
VDD = 2.5V
VDD = 5V
VDD = 3.6V
VDD = 2.5V
VDD = 5V
VDD = 3.6V
VDD = 2.5V
f = 217Hz
W
W
W
W
-67
dB
93
88
63
dB
μVRMS
dB
-63
141
VDD = 3.6V
MAX UNIT
3.6
1.8
0.7
2.8
1.3
0.56
3
1.5
0.66
2.3
1.1
0.48
1.7
0.89
0.4
1.33
0.65
0.3
0.18%
0.16%
0.27%
VDD = 5V, PO = 1W, RL = 8Ω, f = 1KHz
VDD = 3.6V, PO = 0.5W, RL = 8Ω, f = 1KHz
VDD = 3.0V, PO = 0.2W, RL = 8Ω, f = 1KHz
VDD = 3.6V, Input AC-Grounded with
f = 215Hz,
Ci = 2μF
V(RIPPLE) = 0.2VPP
VDD = 5V, PO = 1W, RL = 8Ω
No Weight
VDD = 3.6V, f = 20Hz to 20KHz, Input
AC-Grounded with Ci = 2μF
A Weight
VDD = 3.6V, VIC = 1VPP
TYP
150
30
159
kΩ
ms
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Page 6 of 24
BA16852 3W Mono Filterless Class-D Audio Power Amplifier
TYPICAL CHARACTERISTIC
Table of Graphs
Test Item
Figure
Efficiency vs. Output Power at 8Ω Load
Efficiency vs. Output Power at 4Ω Load
Power Dissipation vs. Output Power at 5.0V
PD
Power Dissipation vs. Output Power at 3.6V
Supply Current vs. Output Power at 8Ω Load
Supply Current vs. Output Power at 4Ω Load
I(Q) Quiescent Current vs. Supply Voltage
I(SD) Shutdown Current vs. Shutdown Voltage
Output Power at 1% THD+N vs. Load Resistance
PO Output Power at 10% THD+N vs. Load Resistance
Output Power vs. Supply Voltage
Total Harmonic Distortion + Noise vs. Output Power at 8Ω Load
Total Harmonic Distortion + Noise vs. Output Power at 4Ω Load
Total Harmonic Distortion + Noise vs. Output Power at 3Ω Load
Total Harmonic Distortion + Noise vs. Frequency at 5.0V & 8Ω Load
Total Harmonic Distortion + Noise vs. Frequency at 3.6V & 8Ω Load
THD+N Total Harmonic Distortion + Noise vs. Frequency at 2.5V & 8Ω Load
Total Harmonic Distortion + Noise vs. Frequency at 5/4/3.6/3/2.5V, 250mW Output, 8Ω Load
Total Harmonic Distortion + Noise vs. Frequency at 5.0V & 4Ω Load
Total Harmonic Distortion + Noise vs. Frequency at 3.6V & 4Ω Load
Total Harmonic Distortion + Noise vs. Frequency at 2.5V & 4Ω Load
Total Harmonic Distortion + Noise vs. Frequency at 5/4/3.6/3/2.5V, 250mW Output, 4Ω Load
Supply Ripple Rejection Ratio vs. Frequency at 8Ω Load
KSVR Supply Ripple Rejection Ratio vs. Frequency at 4Ω Load
Supply Ripple Rejection Ratio vs. Frequency at Input Floating
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
Test Set-Up For Graphs
+
AP
(Analog Generator)
-
CI
RI
CI
RI
INP
INN
OUTP
BA16852
OUTN
+
Load
AP
AUX-0025
AP
-
(Analog Analyzer)
1μF
VDD
Notes:
1. CI was shorted for any Common-Mode input voltage measurement.
2. A 22μH inductor was placed in series with the load resistor to emulate a small speaker for efficiency measurement.
3. The AP AUX-0025 low-pass filter is required.
4. The 22-KHz or 30-KHz low-pass filter is required even if the AP analyzer has an internal low-pass filter.
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Page 7 of 24
BA16852 3W Mono Filterless Class-D Audio Power Amplifier
Figure 2. Efficiency vs. Output Power at 8Ω Load
Figure 3. Efficiency vs. Output Power at 4Ω Load
Figure 4. Power Dissipation vs. Output Power at 5.0V
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Page 8 of 24
BA16852 3W Mono Filterless Class-D Audio Power Amplifier
Figure 5. Power Dissipation vs. Output Power at 3.6V
Figure 6. Supply Current vs. Output Power at 8Ω Load
Figure 7. Supply Current vs. Output Power at 4Ω Load
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Page 9 of 24
BA16852 3W Mono Filterless Class-D Audio Power Amplifier
Figure 8. Quiescent Current vs. Supply Voltage
Figure 9. Shutdown Current vs. Shutdown Voltage
Figure 10. Output Power at 1% THD+N vs. Load Resistance
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BA16852 3W Mono Filterless Class-D Audio Power Amplifier
Figure 11. Output Power at 10% THD+N vs. Load Resistance
Figure 12. Output Power vs. Supply Voltage
Figure 13. Total Harmonic Distortion + Noise vs. Supply Voltage at 8Ω Load
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Page 11 of 24
BA16852 3W Mono Filterless Class-D Audio Power Amplifier
Figure 14. Total Harmonic Distortion + Noise vs. Supply Voltage at 4Ω Load
Figure 15. Total Harmonic Distortion + Noise vs. Supply Voltage at 3Ω Load
Figure 16. Total Harmonic Distortion + Noise vs. Frequency at 5.0V & 8Ω Load
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BA16852 3W Mono Filterless Class-D Audio Power Amplifier
Figure 17. Total Harmonic Distortion + Noise vs. Frequency at 3.6V & 8Ω Load
Figure 18. Total Harmonic Distortion + Noise vs. Frequency at 2.5V & 8Ω Load
Figure 19. Total Harmonic Distortion + Noise vs. Frequency at 5/4/3.6/3/2.5V,
250mW Output, 8Ω Load
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Page 13 of 24
BA16852 3W Mono Filterless Class-D Audio Power Amplifier
Figure 20. Total Harmonic Distortion + Noise vs. Frequency at 5.0V & 4Ω Load
Figure 21. Total Harmonic Distortion + Noise vs. Frequency at 3.6V & 4Ω Load
Figure 22. Total Harmonic Distortion + Noise vs. Frequency at 2.5V & 4Ω Load
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BA16852 3W Mono Filterless Class-D Audio Power Amplifier
Figure 23. Total Harmonic Distortion + Noise vs. Frequency at 5/4/3.6/3/2.5V,
250mW Output, 4Ω Load
Figure 24. Supply Ripple Rejection Ration vs. Frequency at 8Ω Load
Figure 25. Supply Ripple Rejection Ration vs. Frequency at 4Ω Load
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Page 15 of 24
BA16852 3W Mono Filterless Class-D Audio Power Amplifier
Figure 26. Supply Ripple Rejection Ration vs. Frequency at Input Floating
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Page 16 of 24
BA16852 3W Mono Filterless Class-D Audio Power Amplifier
Function Description
The basic structure of BA16852 is a differential amplifier with differential inputs and outputs. The
BA16852 has one differential amplifier and one common-mode amplifier inside. The differential
amplifier output a differential voltage that is equal to the differential input times the gain. The
common-mode feedback ensures that the common-mode voltage at the output is biased around VDD/2
regardless of the common-mode voltage at the input. The BA16852 can still be used with a single
ended input. The BA16852 should be used with differential inputs when in a noisy environment, like a
wireless handset, to ensure maximum noise rejection.
Input Resistors (RI)
The gain of BA16852 is set by external resistors RI show in Figure 1. Set the gain of the amplifier
according to Equation (1)
2× 150kΩ V
Gain =
( )
(1)
V
RI
The gain should be set to 2 V/V or lower for best performance. Lower gain allows the BA16852 use a
high voltage at input and make the input less susceptible to noise.
Resistor matching is very important in fully differential amplifiers. The balance of the output on the
reference voltage depends on matched ratios of the resistors. It is recommended to use 1% tolerance
resistor or better for best performance. Matching is more important than overall tolerance. Resistor
arrays with 1% matching can be used with a tolerance greater than 1%.
The RI resistor should be placed close to the BA16852 and keep the input traces close to each other
with the same length in high noise environment. It can limit noise injection on the high-impedance
nodes.
Power Supply Decoupling Capacitor (CS)
As with any power amplifier, proper power supply decoupling capacitor is critical for low noise
performance and high power supply rejection ration (PSRR). A good low equivalent-series-resistance
(ESR) ceramic capacitor, typically 1μF, placed as close as possible to the device VDD lead works best.
Placing this decoupling capacitor close to the BA16852 is very important for the efficiency of the
class-d amplifier, because any resistance or inductance in the trace between the device and capacitor
can cause a loss in efficiency.
Input Capacitor (CI)
The input capacitor may be needed for some applications or when the source is single-ended (See
Figure 28). This capacitor can block the DC voltage at the amplifier input terminal and create a
high-pass filter with the input resistor RI. The cut-off frequency of high-pass filter is according to
Equation (2)
1
(Hz)
(2)
fC =
2π × R I × C I
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BA16852 3W Mono Filterless Class-D Audio Power Amplifier
The value of the input capacitor affects the low frequency performance of the circuit directly. Speakers
in wireless phone can’t respond well to low frequency, so the cut-off frequency can be set to block low
frequency in this application. For example, power supply noise is at 217Hz in a GSM phone. Setting
cut-off frequency of high-pass filter above 217Hz can filter out this noise that it is not amplified and
heard on the output. Capacitor has 10% tolerance or better is recommended for impedance matching.
Differential Circuit Configurations
The BA16852 can be used in many different circuit configurations. The simplest and best performing is
the DC coupled, differential input configuration show in Figure 27. The resistor RI can set the amplifier
output gain. Set the gain of the amplifier according to Equation (1).
The input capacitors can be used in a differential configure as show in Figure 28. The input capacitor
CI with input resistor RI can create a high-pass filter. The cut-off frequency of high-pass filter is
according to Equation (2). Equation (1) above is used to determine the value of the RI resistors for a
desired gain.
The BA16852 can be used to amplify more than one audio source. Figure 29 shows a dual differential
input configuration. The gain for each input source can be set independently according to Equation (3)
and (4).
2× 150kΩ V
( )
(3)
Gain 1 =
V
R I1
Gain 2 =
2 × 150kΩ V
( )
R I2
V
(4)
The input capacitors can be used with one or more input source as well to have different frequency
responses depending on the source or if a DC voltage needs to be blocked from the source.
Differential
Input
Internal
Osciliator
RI
To Power Source
VDD
CS
INN
OUTN
+
RI
PWM
Driver
OUTP
INP
SD_B
Bias
Circuitry
GND
BA16852
Shutdown
Control
Figure 27. Differential Input Configuration
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BA16852 3W Mono Filterless Class-D Audio Power Amplifier
Differential
Input
CI
RI
Internal
Osciliator
VDD
To Power Source
CS
INN
OUTN
+
CI
RI
PWM
Driver
OUTP
INP
Bias
Circuitry
SD_B
GND
BA16852
Shutdown
Control
Figure 28. Differential Input Configuration with Input Capacitors
Differential
Input 1
RI1
RI1
Differential
Input 2
Internal
Osciliator
RI2
VDD
To Power Source
CS
INN
OUTN
+
RI2
PWM
Driver
OUTP
INP
SD_B
Bias
Circuitry
GND
BA16852
Shutdown
Control
Figure 29. Dual Differential Input Configuration
Single-Ended Circuit Configurations
The BA16852 can also be used with single-ended sources, but input capacitors will be needed to block
any DC at the input terminals. The typical single-ended application configuration shows in Figure 30.
The equation of gain is Equation (1) and the equation of frequency response is Equation (2), hold for
the single-ended configuration as shown in Figure 30.
When using more than one single-ended source as shown in Figure 31. The gain and cut-off
frequency (fC1 and fC2) for each input source can be set independently, shows in Equation (5) ~
Equation (8). Resistor, RI3, and capacitor, CI3, are needed on the INP terminal to match the impedance
on the INN terminal. Equation (9) and Equation (10) shows how to calculate CI3 and RI3 value. The
single-ended inputs must be driven by low impedance source even if one of the inputs is not outputting
an ac signal.
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BA16852 3W Mono Filterless Class-D Audio Power Amplifier
Gain 1 =
2× 150kΩ V
( )
V
R I1
(5)
Gain 2 =
2 × 150kΩ V
( )
R I2
V
(6)
fC1 =
1
(Hz)
2π × R I1 × C I1
(7)
fC2 =
1
(Hz)
2π × R I2 × C I2
(8)
C I3 = C I1 + C I2
R I3 =
(9)
1
R × R I2
= I1
1
1
+
(
) R I1 + R I2
R I1 R I2
Single-Ended
Input
CI
RI
(10)
Internal
Osciliator
To Power Source
VDD
CS
INN
OUTN
+
CI
RI
PWM
Driver
OUTP
INP
Bias
Circuitry
SD_B
GND
BA16852
Shutdown
Control
Figure 30. Single-Ended Input Configuration
Single-Ended
Input 1
Single-Ended
Input 2
CI1
CI2
RI1
RI2
Internal
Osciliator
VDD
To Power Source
CS
INN
OUTN
CI3
+
RI3
SD_B
PWM
Driver
OUTP
INP
Bias
Circuitry
GND
BA16852
Shutdown
Control
Figure 31. Dual Single-Ended Input Configuration
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Page 20 of 24
BA16852 3W Mono Filterless Class-D Audio Power Amplifier
Combine Single-Ended & Differential Circuit Configurations
A typical application with one single-ended source and one differential source shows in Figure 32.
Ground noise can couple in through INP terminal with this method. It is better to use dual differential
inputs. The cut-off frequency of the single-ended input is set by CI shows in Equation (13). To assure
that each input is balanced, the single-ended input must be driven by a low-impedance source even if
the input is not in use.
2 × 150kΩ V
( )
(11)
Gain 1 =
V
R I1
Gain 2 =
fC2 =
2 × 150kΩ V
( )
R I2
V
(12)
1
(Hz)
2π × R I2 × C I
(13)
Differential
Input 1
RI1
RI1
Single-Ended
Input 2
CI
Internal
Osciliator
RI2
VDD
To Power Source
CS
INN
OUTN
CI
+
RI2
PWM
Driver
OUTP
INP
SD_B
Bias
Circuitry
GND
BA16852
Shutdown
Control
Figure 32. Dual Input with a Single-Ended Input and a Differential Input Configuration
Shutdown Mode
The BA16852 provides a shutdown mode for reduce supply current to the absolute minimum level
during periods of nonuse for battery-power conservation. The BA16852 has an internal 300kΩ resistor
connected between GND and SD_B pins. The purpose of this resistor is to eliminate any unwanted
state changes when shutdown pin is floating. The SD_B input pin should be held high during normal
operation when the amplifier is in use. Pulling SD_B low or left floating causes the outputs to mute and
the amplifier to enter a low-current state. During the shutdown mode, the DC quiescent current of the
circuit does not exceed 0.5μA.
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Page 21 of 24
BA16852 3W Mono Filterless Class-D Audio Power Amplifier
Output Filter Application Note
Design the BA16852 without the filter if the traces from amplifier to speaker are short (<100mm).
Where the speaker is in the same enclosure as the amplifier is a typical application for class-d without
a filter. Like wireless handsets and PDAs are great applications 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 there are long
wires from the amplifier to the speaker.
Figure 33 & 34 show typical LC and ferrite bead output filters.
22uH
OUTP
0.1uF
0.47uF
22uH
0.1uF
OUTN
Figure 33. Typical LC Output Filter
BEAD (600R)
OUTP
330pF
470pF
BEAD (600R)
330pF
OUTN
Figure 34. Typical Ferrite Chip Bead Output Filter
(Chip bead example : Queen Core / TI321611U601)
Board Layout Considerations
Place all the external components very close to the BA16852. Placing the decoupling capacitor, CS,
close to the BA16852 VDD terminal is very important for the efficiency of the class-d amplifier. Any
resistance and inductance in the trace between the device and the capacitor can cause a loss in
efficiency. Additionally, the input resistors need to be very close to the BA16852 input terminal, so
noise does not couple on the high-impedance nodes between the input resistors and the input
amplifier of the BA16852.
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Page 22 of 24
BA16852 3W Mono Filterless Class-D Audio Power Amplifier
PACKAGE DIMENSION
8PIN MSOP PACKAGE
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]
[email protected]________________________________
Biforst Technology, Inc., reserves the right to change product or specifications without notice.
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BA16852 3W Mono Filterless Class-D Audio Power Amplifier
Version History
Version
Date
1.0
1.1
2007.08.23
2007.08.28
Page
2
Description
First Release
Modify Package Type in Feature
_________________________________________________________________________________________________
Biforst Technology, Inc., reserves the right to change product or specifications without notice.
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