FT2045 [FANGTEK]
3W Class-D Audio Power Amplifier with Automatic Level Control;
| 型号： | FT2045 |
| 厂家： | 
Fangtek Ltd. |
| 描述： | 3W Class-D Audio Power Amplifier with Automatic Level Control |
| 文件： | 总22页 (文件大小：1082K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
ft2045
3W Class-D Audio Power Amplifier
with Automatic Level Control
GENERAL DESCRIPTION
FEATURES
The ft2045 is a high efficiency, filterless Class-D
audio power amplifier with automatic level control
(ALC). It operates from 2.7V to 5.5V supply.
When powered with 5V supply voltage, the ft2045
is capable of delivering 3W into a 4Ω load or 1.7W
into an 8Ω load, with 10% THD+D. Other than a
simple one-wire pulse control to set the operating
mode and the ALC function, the ft2045 is pin and
functionality compatible with traditional Class-D
audio amplifiers. Note that, unlike traditional
Class-D audio amplifiers, no external bypass
capacitor for the common-mode bias of audio
inputs is required for ft2045, thus minimizing the
number of the external components (3 capacitors
only) needed for high-quality audio applications.
Filterless Class-D operation
Automatic level control to eliminate output
clipping
No bypass capacitor required for the
common-mode bias of audio inputs
High efficiency up to 90%
Output power at 5V supply (ALC Off, ft2045M)
3.0W (4Ω load, 10% THD+N)
1.7W (8Ω load, 10% THD+N)
2.4W (4Ω load, 1% THD+N)
1.4W (8Ω load, 1% THD+N)
Low THD+N: 0.04%
(VDD=3.6V, f=1kHz, RL=8Ω, PO=0.5W)
Low quiescent current: 2.4mA @ VDD=3.6V
Low shutdown current < 0.1µA
The ft2045 features ALC on the output signals,
which detects the output clipping caused by the
over-level input signal and automatically adjusts
the voltage gain of the amplifier to eliminate the
clipping while maintaining a maximally-allowed
dynamic range of the audio output signals. The
ALC also eliminates the output clipping due to low
battery supply voltage.
High PSRR: 70dB @ 217Hz
One-wire pulse control to configure operating
mode & gain
Two fixed gain settings: 18/24dB
Maximum ALC attenuation: 10dB
Short-circuit & thermal protection
Fast startup time: 5ms
As a Class-D power amplifier, the ft2045 features
high efficiency (up to 90%) and high PSRR (70dB
at 217Hz), which make the device ideal for use in
portable electronic devices. It also features
minimized click-and-pop noise during turn-on and
turn-off transitions.
Available in COL1.5x1.5-9L, MSOP-8L, and
DFN2x2-8L packages
APPLICATIONS
Cellular handsets
Portable navigation devices
Multimedia internet devices
APPLICATION CIRCUIT
VDD
Cs
1uF
VDD
Cin 33nF
INP
VOP
Input
Class-D
Modulator
Output
Buffer
Cin 33nF
Buffer
INN
EN
VON
Mode
Control
Pulse Input
1
2
3
4
Shutdown
Control
BIAS
AGND/PGND
Figure 1: Typical Application Circuit Diagram
Sep, 2012
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ft2045
PIN CONFIGURATION AND DESCRIPTION
EN
VOP
VDD
PGND
VON
EN
VOP
GND
VDD
VON
1
2
3
4
8
7
6
5
VOP
GND
VDD
VON
3
2
1
EN
1
2
3
4
8
7
6
5
NC
INP
INN
NC
INP
INN
NC
INP
A
AGND
INN
C
B
ft2045A
ft2045N
ft2045M
(TOP VIEW)
(TOP VIEW)
(TOP VIEW)
PIN DESIGNATION
ft2045A ft2045M ft2045N
SYMBOL
DESCRIPTION
EN
NC
C2
B2
A1
C1
A3
A2
B1
1
2
3
4
5
6
1
2
3
4
5
6
Enable (active high) & one-wire pulse control.
No internal connection.
INP
Positive audio input terminal.
Negative audio input terminal.
Negative BTL audio output terminal.
Power supply.
INN
VON
VDD
AGND
Analog ground.
Power ground for the output stage. For ft2045M/N, it is internally
shorted to AGND. For ft2045A, it must be externally shorted to
AGND on the system board.
7
8
7
8
PGND
VOP
B3
C3
Positive BTL audio output terminal.
PACKAGE DISSIPATION RATINGS
PACKAGE
COL1.5x1.5-9L
MSOP-8L
PACKAGE DRAWING
Θ JA
190
145
90
UNIT
°C/W
°C/W
°C/W
DFN2x2-8L
ORDERING INFORMATION
PART NUMBER
ft2045A
TEMPERATURE RANGE
PACKAGE
COL1.5x1.5-9L
MSOP-8L
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
ft2045M
ft2045N
DFN2x2-8L
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ft2045
ABSOLUTE MAXIMUM RATINGS
PARAMETER
RATING
Supply Voltage
-0.3V to 6.0V
-45°C to 150°C
-0.3V to VDD+0.3V
Internally Limited
4000V
Storage Temperature
Input Voltage
Power Dissipation
ESD Susceptibility (HBM)
Junction Temperature
Soldering Information
Vapor Phase (60 sec.)
Infrared (15 sec.)
150°C
215°C
220°C
RECOMMENDED OPERATING CONDITIONS
PARAMETER
CONDITIONS
MIN
2.7
TYP
MAX
5.5
UNIT
V
Supply Voltage (VDD)
Operating Free-air Temperature, TA
Speaker Impedance (RLOAD)
-40
3.2
85
°C
Ω
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ft2045
ELECTRICAL CHARACTERISTICS
V
DD=3.6V, CIN=33nF, A
V
=18dB, f=1kHz, T =25°C, unless otherwise specified.
A
SYMBOL
VDD
PARAMETER
Supply Voltage
CONDITIONS
MIN
TYP
MAX
UNIT
2.7
5.5
V
V
VUVLU
Power-up Threshold Voltage
Power-off Threshold Voltage
VDD from Low to High
2.1
VUVLD
VDD from High to Low
VDD=5V, RL=8Ω
1.9
2.7
2.4
0.1
1.4
1.7
2.4
3.0
V
mA
mA
µA
W
1.5
1.2
5.0
4.0
Power Supply Quiescent Current
Inputs AC-Grounded
IDD
ISD
VDD=3.6V, RL=8Ω
Shutdown Current
EN Low
THD+N=1%, Mode 2 & 4
THD+N=10%, Mode 2 & 4
THD+N=1%, Mode 2 & 4
THD+N=10%, Mode 2 & 4
Maximum Output Power (ft2045M)
RL=8Ω, VDD=5V, ALC Off
W
PO, MAX
W
Maximum Output Power (ft2045M)
RL=4Ω, VDD=5V, ALC Off
W
Constant Output Power
RL=8Ω, VDD=3.6V, ALC On
Constant Output Power
RL=4Ω, VDD=3.6V, ALC On
Constant Output Power
RL=8Ω, VDD=5V, ALC On
Constant Output Power
RL=4Ω, VDD=5V, ALC On
Mode 1, Vin=0.6VRMS
Mode 3, Vin=0.3VRMS
Mode 1, Vin=0.6VRMS
Mode 3, Vin=0.3VRMS
Mode 1, Vin=0.6VRMS
Mode 3, Vin=0.3VRMS
Mode 1, Vin=0.6VRMS
Mode 3, Vin=0.3VRMS
0.68
1.2
W
W
W
W
PO, ALC
1.3
2.3
Mode 1 & 2
18
24
dB
dB
%
Closed-loop Voltage Gain
Av
Mode 3 & 4
Po=0.50W, RL=8Ω
Po=0.65W, RL=4Ω
0.04
0.04
30
THD+N
Total Harmonic Distortion + Noise
%
ZIN
Input Impedance @ INP, INN
Pulldown Resistance @ EN
KΩ
ZEN
500
KΩ
f=20Hz ~ 20kHz, Av=18dB
Inputs AC-Grounded
VN
Output Voltage Noise
85
µVRMS
Inputs AC-Grounded, No Load
±10
90
mV
%
VOS
η
Output Offset Voltage
Efficiency
VDD=5V, Po=1W, RL=8Ω+33µH
AMAX
SNR
PSRR
CMRR
fPWM
ILIMIT
Maximum ALC Attenuation
Signal-to-Noise Ratio
Power Supply Rejection Ratio
Common Mode Rejection Ratio
Modulation Frequency
Over-Current Protection
EN High Input Voltage
EN Low Input Voltage
Startup Time
10
dB
dB
dB
dB
kHz
A
85
f=217Hz
70
65
400
1.4
VDD=3.6V
VIH
1.2
V
VIL
0.4
V
TSTUP
TAT
5
ms
ms
s
ALC Attack Time
RL=8Ω+33µH
RL=8Ω+33µH
40
2.0
TRL
ALC Release Time
TLO
Time of EN Low
0.5
0.5
10
µs
µs
µs
µs
C
C
4
THI
Time of EN High
TRST
TSHDN
TOTP
Time for Mode Reset, Active Low
Time for Shutdown, Active Low
Over-Temperature Threshold
Over-Temperature Hysteresis
100
800
200
160
20
THYS
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ft2045
TYPICAL PERFORMANCE CHARACTERISTICS
CIN=33nF, AV=18dB, f=1kHz, ft2045M, TA=25°C, unless otherwise specified.
List of Performance Characteristics
DESCRIPTION
CONDITIONS
FIGURE #
R
L
=8Ω+33µH, Mode 1 & Mode 2 (THD+N=10%)
=4Ω+33µH, Mode 1 & Mode 2 (THD+N=10%)
2
Output Power vs. Supply Voltage
RL
3
VDD=5V, R
VDD=5V, R
L
=8Ω+33µH, Mode 1 & Mode 2
=4Ω+33µH, Mode 1 & Mode 2
4
L
5
VDD=3.6V, R
VDD=3.6V, R
L
=8Ω+33µH, Mode 1 & Mode 2
=4Ω+33µH, Mode 1 & Mode 2
6
L
7
Output Power vs. Input Voltage
VDD=5V, R
VDD=5V, R
L
=8Ω+33µH, Mode 3 & Mode 4
=4Ω+33µH, Mode 3 & Mode 4
8
L
9
VDD=3.6V, R
VDD=3.6V, R
L
=8Ω+33µH, Mode 3 & Mode 4
=4Ω+33µH, Mode 3 & Mode 4
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
L
VDD=5V, R
VDD=5V, R
L
=8Ω+33µH, Mode 2
=4Ω+33µH, Mode 2
L
Efficiency vs. Output Power
THD+N vs. Output Power
THD+N vs. Input Voltage
THD+N vs. Input Frequency
PSRR vs. Input Frequency
VDD=3.6V, R
VDD=3.6V, R
L
=8Ω+33µH, Mode 2
=4Ω+33µH, Mode 2
L
VDD=5V, R
VDD=5V, R
L
=8Ω+33µH, Mode 2
=4Ω+33µH, Mode 2
L
VDD=3.6V, R
VDD=3.6V, R
L
=8Ω+33µH, Mode 2
=4Ω+33µH, Mode 2
L
VDD=5V, R
VDD=5V, R
L
=8Ω+33µH, Mode 1
=4Ω+33µH, Mode 1
L
VDD=3.6V, R
VDD=3.6V, R
L
=8Ω+33µH, Mode 1
=4Ω+33µH, Mode 1
L
VDD=5V, Vin=0.35VRMS, R
L
=8Ω+33µH, Mode 1
=4Ω+33µH, Mode 1
VDD=5V, Vin=0.30VRMS, R
L
VDD=3.6V, Vin=0.25VRMS, R
L
=8Ω+33µH, Mode 1
=4Ω+33µH, Mode 1
VDD=3.6V, Vin=0.20VRMS, R
L
VDD=5V, R
VDD=5V, R
L
L
=8Ω+33µH, Input AC-Grounded, Mode 1
=4Ω+33µH, Input AC-Grounded, Mode 1
VDD=3.6V, R
VDD=3.6V, R
L
=8Ω+33µH, Input AC-Grounded, Mode 1
=4Ω+33µH, Input AC-Grounded, Mode 1
L
Quiescent Current vs. Supply Voltage
ALC Attack & Release Time
Input AC-Grounded, No Load, Mode 1
VDD=3.6V, Vin=0.3VRMS ~ 0.95VRMS, R
Mode 1
L
=8Ω+33µH
=8Ω+33µH
33
34
VDD=3.6V, Vin=0.3VRMS ~ 0.95VRMS, R
Mode 1
L
ALC Attack Time
VOP, VON Waveforms
VDD=3.6V, Vin=0.1VRMS , R
L
=8Ω+33µH, Mode 1
35
36
37
(VOP-VON) Startup Waveform
(VOP-VON) Shutdown Waveform
VDD=3.6V, Vin=0.1VRMS, R
L
=8Ω+33µH, Mode 1
=8Ω+33µH, Mode 1
VDD=3.6V, Vin=0.1VRMS, R
L
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ft2045
TYPICAL PERFORMANCE CHARACTERISTICS (Cont’d)
Output Power vs. Supply Voltage
Output Power vs. Supply Voltage
2500
2000
1500
1000
500
4000
3500
3000
2500
2000
1500
1000
500
RL=4Ω+33uH, Mode1
RL=8Ω+33uH, Mode 1
RL=4Ω+33uH, THD+N=10%, Mode 2
RL=8Ω+33uH, THD+N=10%, Mode 2
0
0
2.5
3
3.5
4
4.5
5
5.5
2.5
3
3.5
4
4.5
5
5.5
Supply Voltage (V)
Supply Voltage (V)
Figure 2: Output Power vs. Supply Voltage
Figure 3: Output Power vs. Supply Voltage
Output Power vs. Input Voltage
Output Power vs. Input Voltage
10000
10000
1000
1000
100
100
VDD=5.0V, RL=8Ω+33uH, Mode 1
VDD=5.0V, RL=8Ω+33uH, Mode 2
10
10
VDD=5.0V, RL=4Ω+33uH, Mode 1
VDD=5.0V, RL=4Ω+33uH, Mode 2
1
1
10
100
1000
10000
10
100
1000
10000
Input Voltage (mVrms)
Input Voltage (mVrms)
Figure 4: Output Power vs. Input Voltage
Figure 5: Output Power vs. Input Voltage
Note: The dashed line on the plot indicates the output THD+N
exceeds 10% when the output power is higher than 1.7W.
Note: The dashed line on the plot indicates the output THD+N
exceeds 10% when the output power is higher than 3.0W.
Output Power vs. Input Voltage
Output Power vs. Input Voltage
10000
10000
1000
1000
100
100
VDD=3.6V, RL=4Ω+33uH, Mode 1
VDD=3.6V, RL=4Ω+33uH, Mode 2
VDD=3.6V, RL=8Ω+33uH, Mode 1
VDD=3.6V, RL=8Ω+33uH, Mode 2
10
10
1
1
10
100
1000
10000
10
100
1000
10000
Input Voltage (mVrms)
Input Voltage (mVrms)
Figure 6: Output Power vs. Input Voltage
Figure 7: Output Power vs. Input Voltage
Note: The dashed line on the plot indicates the output THD+N
exceeds 10% when the output power is higher than 0.9W.
Note: The dashed line on the plot indicates the output THD+N
exceeds 10% when the output power is higher than 1.5W.
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ft2045
TYPICAL PERFORMANCE CHARACTERISTICS (Cont’d)
Output Power vs. Input Voltage
Output Power vs. Input Voltage
10000
1000
100
10
10000
1000
100
10
VDD=5.0V, RL=8Ω+33uH, Mode 3
VDD=5.0V, RL=8Ω+33uH, Mode 4
VDD=5.0V, RL=4Ω+33uH, Mode 3
VDD=5.0V, RL=4Ω+33uH, Mode 4
1
1
10
100
1000
10000
10
100
1000
10000
Input Voltage (mVrms)
Input Voltage (mVrms)
Figure 8: Output Power vs. Input Voltage
Figure 9: Output Power vs. Input Voltage
Note: The dashed line on the plot indicates the output THD+N
exceeds 10% when the output power is higher than 1.7W.
Note: The dashed line on the plot indicates the output THD+N
exceeds 10% when the output power is higher than 3.0W.
Output Power vs. Input Voltage
Output Power vs. Input Voltage
10000
10000
1000
100
1000
100
VDD=3.6V, RL=4Ω+33uH, Mode 3
VDD=3.6V, RL=4Ω+33uH, Mode 4
10
1
10
1
VDD=3.6V, RL=8Ω+33uH, Mode 3
VDD=3.6V, RL=8Ω+33uH, Mode 4
10
100
1000
10000
10
100
1000
10000
Input Voltage (mVrms)
Input Voltage (mVrms)
Figure 10: Output Power vs. Input Voltage
Figure 11: Output Power vs. Input Voltage
Note: The dashed line on the plot indicates the output THD+N
exceeds 10% when the output power is higher than 0.9W.
Note: The dashed line on the plot indicates the output THD+N
exceeds 10% when the output power is higher than 1.5W.
Efficiencyvs.OutputPower
Efficiencyvs.OutputPower
100
90
80
70
60
50
40
30
100
90
80
70
60
50
40
30
20
20
VDD=5.0V,RL=4Ω+33uH, Mode 2
VDD=5.0V,RL=8Ω+33uH, Mode 2
10
0
10
0
0
500
1000
1500
2000
2500
3000
0
200
400
600
800 1000 1200 1400 1600 1800 2000
Output Power (mW)
Output Power (mW)
Figure 12: Efficiency vs. Output Power
Figure 13: Efficiency vs. Output Power
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ft2045
TYPICAL PERFORMANCE CHARACTERISTICS (Cont’d)
Efficiency vs. Output Power
Efficiency vs. Output Power
100
90
80
70
60
50
40
30
20
10
0
100
90
80
70
60
50
40
30
20
10
0
VDD=3.6V,RL=4Ω+33uH, Mode 2
VDD=3.6V,RL=8Ω+33uH, Mode 2
0
200
400
600
800
1000
1200
1400
1600
0
100 200 300
400 500
600 700 800 900 1000
Output Power (mW)
Output Power (mW)
Figure 14: Efficiency vs. Output Power
Figure 15: Efficiency vs. Output Power
THD+N vs. Output Power
THD+N vs. Output Power
100
100
VDD=5.0V, RL=8Ω+33uH,
f=1KHz, Mode 2
VDD=5.0V, RL=4Ω+33uH,
f=1KHz, Mode 2
10
10
1
1
0.1
0.1
0.01
0.01
10
100
1000
Output Power (mW)
10000
10
100
1000
10000
Output Power (mW)
Figure 16: THD+N vs. Output Power
Figure 17: THD+N vs. Output Power
THD+N vs. Output Power
THD+N vs. Output Power
100
10
100
10
VDD=3.6V, RL=4Ω+33uH,
f=1KHz, Mode 2
VDD=3.6V, RL=8Ω+33uH,
f=1KHz, Mode 2
1
1
0.1
0.01
0.1
0.01
10
100
1000
Output Power (mW)
10000
10
100
1000
Output Power (mW)
10000
Figure 18: THD+N vs. Output Power
Figure 19: THD+N vs. Output Power
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ft2045
TYPICAL PERFORMANCE CHARACTERISTICS (Cont’d)
THD+N vs. Input Voltage
THD+N vs. Input Voltage
100
10
100
10
VDD=5.0V, RL=4Ω+33uH,
f=1KHz, Mode 1
VDD=5.0V, RL=8Ω+33uH,
f=1KHz, Mode 1
1
1
0.1
0.01
0.1
0.01
10
100
1000
10000
10
100
1000
10000
Input Voltage (mVrms)
Input Voltage (mVrms)
Figure 20: THD+N vs. Input Voltage
Figure 21: THD+N vs. Input Voltage
THD+N vs. Input Voltage
THD+N vs. Input Voltage
100
10
100
10
VDD=3.6V, RL=8Ω+33uH,
f=1KHz, Mode 1
VDD=3.6V, RL=4Ω+33uH,
f=1KHz, Mode 1
1
1
0.1
0.01
0.1
0.01
10
100
1000
10000
10
100
1000
10000
Input Voltage (mVrms)
Input Voltage (mVrms)
Figure 22: THD+N vs. Input Voltage
Figure 23: THD+N vs. Input Voltage
THD+N vs. Frequency
THD+N vs. Frequency
100
100
VDD=5.0V, RL=8Ω+33uH,
Vin=350mVrms, Mode 1
VDD=5.0V, RL=4Ω+33uH,
Vin=300mVrms, Mode 1
10
1
10
1
0.1
0.1
0.01
0.001
0.01
0.001
10
100
1000
10000
100000
10
100
1000
10000
100000
Frequency (Hz)
Frequency (Hz)
Figure 24: THD+N vs. Frequency
Figure 25: THD+N vs. Frequency
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ft2045
TYPICAL PERFORMANCE CHARACTERISTICS (Cont’d)
THD+N vs. Frequency
THD+N vs. Frequency
100
10
100
10
VDD=3.6V, RL=8Ω+33uH,
Vin=250mVrms, Mode 1
VDD=3.6V, RL=4Ω+33uH,
Vin=200mVrms, Mode 1
1
1
0.1
0.1
0.01
0.001
0.01
0.001
10
100
1000
10000
100000
10
100
1000
10000
100000
Frequency (Hz)
Frequency (Hz)
Figure 26: THD+N vs. Frequency
Figure 27: THD+N vs. Frequency
PSRR vs. Frequency
PSRR vs. Frequency
0
-10
-20
-30
-40
-50
-60
-70
-80
0
-10
-20
-30
-40
-50
-60
-70
-80
VDD=5.0V, RL=8Ω+33uH, Cin=1uF,
Input AC-ground, Mode 1
VDD=5.0V, RL=4Ω+33uH, Cin=1uF,
Input AC-ground, Mode 1
-90
10
-90
10
100
1000
10000
100000
100
1000
10000
100000
Frequency (Hz)
Frequency (Hz)
Figure 28: PSRR vs. Frequency
Figure 29: PSRR vs. Frequency
PSRR vs. Frequency
PSRRvs.Frequency
0
-10
-20
-30
-40
-50
-60
-70
-80
0
-10
-20
-30
-40
-50
-60
-70
-80
VDD=3.6V, RL=8Ω+33uH, Cin=1uF,
Input AC-ground, Mode 1
VDD=3.6V, RL=4Ω+33uH, Cin=1uF,
Input AC-ground, Mode 1
-90
10
-90
10
100
1000
10000
100000
100
1000
10000
100000
Frequency(Hz)
Frequency (Hz)
Figure 30: PSRR vs. Frequency
Figure 31: PSRR vs. Frequency
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ft2045
TYPICAL PERFORMANCE CHARACTERISTICS (Cont’d)
Quiescent Current vs. Supply Voltage
X: 0.5s/div
Y: 0.2V/div
VDD=3.6V, RL=8Ω+33µH
5
Vin=0.3VRMS ~ 0.95VRMS, 1kHz
4
3
2
X: 0.5s/div
Y: 1V/div
No Load, Input AC-ground, Mode 1
1
VOP-VON (33kHz Lowpass Filer)
Release Time (2s)
0
2.5
3
3.5
4
4.5
5
5.5
Supply Voltage (V)
Figure 32: Quiescent Current vs. Supply Voltage
Figure 33: ALC Operation (Mode 1)
VDD=3.6V, RL=8Ω+33µH
VOP, 0.5V/div
VON, 0.5V/div
Vin=0.3VRMS ~ 0.95VRMS, 1kHz
Vin=0.1VRMS, 1kHz
X: 0.5ms/div
Attack Time (40ms)
VOP-VON (33kHz Lowpass Filer)
X: 5ms/div
VOP-VON, 0.5V/div
(33kHz Lowpass Filer)
Y: 1V/div
Figure 34: ALC Attack Time (Mode 1)
Figure 35: VOP & VON Waveforms
VDD=3.6V, RL=8Ω+33µH
VDD=3.6V, RL=8Ω+33µH
CTRL, 2V/div
CTRL, 2V/div
Vin=0.1VRMS, 1kHz
Vin=0.1VRMS, 1kHz
VOP-VON, 0.5V/div
VOP-VON, 0.5V/div
(33kHz Lowpass Filer)
(33kHz Lowpass Filer)
X: 2ms/div
X: 2ms/div
Figure 36: Startup Waveforms
Figure 37: Shutdown Waveforms
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ft2045
APPLICATION INFORMATION
The ft2045 is a high efficiency, filterless Class-D audio power amplifier with automatic level control (ALC).
It operates from 2.7V to 5.5V supply. When powered with 5V supply voltage, the ft2045 is capable of
delivering 3W into a 4Ω load or 1.7W into an 8Ω load, with 10% THD+D. Other than a simple one-wire
pulse control to set the operating mode and the ALC function, the ft2045 is pin and functionality compatible
with traditional Class-D audio power amplifiers.
The ft2045 features ALC on the output signals, which detects the output clipping caused by the over-level
input signal and automatically adjusts the voltage gain of the amplifier to eliminate the clipping while
maintaining a maximally-allowed dynamic range of the audio output signals. The ALC also eliminates the
output clipping due to low battery supply voltage.
As a Class-D power amplifier, the ft2045 features high efficiency, up to 90%, and high PSRR, 70dB at
217Hz, which make the device ideal for use in battery-powered portable devices. It also features
minimized click-and-pop noise during turn-on and turn-off transitions. Thanks to its proprietary design, the
external bypass capacitor typically required for the common-mode bias of audio inputs to maintain high
PSRR is eliminated in ft2045, thus further reducing the number of the external components needed for use
in high-quality audio applications.
As specifically designed for portable applications, the ft2045 incorporates shutdown mode to minimize the
power consumption by holding the EN pin to ground for more than 800µs. It also includes comprehensive
protection features against various operating faults such as over-current, over-temperature, or
under-voltage lockout for a safe and reliable operation.
AUTOMATIC-LEVEL CONTROL (ALC)
The automatic-level control is to maintain the output signal level for a maximum output swing without
distortion when an excessive input that may cause output clipping is applied. With the ALC function, the
ft2045 lowers the gain of the amplifier to an appropriate value such that the clipping at the outputs is
eliminated. It also eliminates the clipping of the output signal due to the decrease of the power-supply
voltage.
Output Signal when Supply Voltage is Sufficiently Large
Output Signal in ALC Off Mode
Output Signal in ALC On Mode
Attack Time
Release Time
Figure 38: Automatic Level Control Diagram
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ft2045
The attack time is defined as the time interval required for the gain to fall to its steady-state gain less 3dB
approximately, presumed that a sufficiently large input signal is applied. The release time is the time
interval required for the amplifier to exit out of the present mode of operation. See Table 1.
Mode
Attack time (ms)
Release time (s)
Mode 1 & 3 (ALC Enabled)
40
2.0
Table 1: Attack Time & Release Time
OPERATING MODE CONTROL AND GAIN SETTING
To support for a wide range of applications, the ft2045 incorporates one-wire pulse control to configure the
operating mode and the voltage gain. By applying a string of pulses to the EN pin, users can enable
(Constant Output Power) or disable (Maximum Output Power) the ALC function and also set the voltage
gain. The operating mode is advanced and updated on each low-to-high transition of the pulses applied
onto the EN pin. The detailed timing diagram of the one-wire pulse control to select the operating mode is
shown in Figure 39.
TLO
SHDN
>0.5us
H
T
RST
T
THI
<
<
TLO 10us
0.5us
EN
L
MODE1
MODE2
MODE3
MODE4
MODE1
MODE1
SHUTDOWN
Figure 39: One-Wire Pulse Control for Operating Mode Selection
Four operating modes are configured by the application of a string of pulses onto the EN pin. After the
application of the power supply, the first low-to-high transition at the EN pin will set the device into Mode 1,
where the voltage gain is set at 18dB with the ALC function enabled. On the next low-to-high transition, the
device advances into Mode 2, where the ALC function is disabled while the voltage gain remains at 18dB.
On the third low-to-high transition, the device advances into Mode 3, where the voltage gain is set at 24dB
with the ALC function enabled. Finally, on the forth low-to-high transition, the device advances into Mode 4,
where the ALC function is disabled while the voltage gain remains at 24dB. The operating modes will be
cycled and repeated in the same manner as described above for consecutive pulses applied.
Note that each individual pulse must be longer than a minimum of 0.5µs to be recognized. Any pulses
shorter than 0.5µs may be ignored. The state of the mode operation can be reset back to Mode 1 by
holding the EN pin low more than 100µs but less than 200µs, regardless of the state it is currently
operating. Whenever the EN pin held low for more than 800µs, the device enters into shutdown mode,
where all the internal circuitry is de-biased. Once the device is forced into shutdown mode, one or multiple
pulses are required for the ft2045 to return to the desired mode of operation.
Mode
Mode 1
Mode 2
Mode 3
Mode 4
# of Pulses
Voltage Gain
18dB (8X)
ALC Function
Enable
1
2
3
4
18dB (8X)
Disable
24dB (16X)
24dB (16X)
Enable
Disable
Table 2: Mode of Operation
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ft2045
CLICK-AND-POP SUPPRESSION
The ft2045 audio power amplifier features comprehensive click-and-pop suppression. During startup, the
click-and-pop suppression circuitry reduces any audible transients internal to the device. When entering
into shutdown, the differential audio outputs ramp down to ground quickly and simultaneously.
PSRR ENHANCEMENT
Contrary to a conventional Class-D amplifier, the ft2045 employs a proprietary circuitry to remove the
requirement for a common-mode bias pin in conjunction with an external bypass capacitor while
maintaining high PSRR, thus further reducing the number of external components required.
PROTECTION FEATURES
The ft2045 incorporates various protection functions against possible operating faults for a safe operation.
It includes Under-voltage Lockout (UVLO), Over-Current Protection (OCP), and Over-Temperature
Shutdown (OTSD).
Under-Voltage Lockout (UVLO)
The ft2045 incorporates a circuitry to detect a low supply voltage for a safe and reliable operation.
When the supply voltage is first applied, the ft2045 will remain inactive until the supply voltage
exceeds 2.2V (VUVLU). When the supply voltage is removed and drops below 2.0V (VUVLD), the
ft2045 enters into shutdown mode immediately.
Over-Current Protection (OCP)
Once an over-current or a short-circuit condition at the differential outputs, either to the power supply
or to ground or to each other, is detected, the ft2045 enters into the over-current protection mode,
where the amplifier output stage is disabled. Note that the over-current detection is a latched
operation. Thus, once the OCP is detected, the ft2045 must undergo a normal power-up sequence;
i.e., pull the EN pin low, followed by a sequence of pulses to return the device to the desired operating
mode.
Over-Temperature Shutdown (OTSD)
When the die temperature exceeds a preset threshold (160C), the device enters into the
over-temperature shutdown mode, where two differential outputs are pulled to ground through an
internal resistor (2KΩ) individually. The device will resume normal operation once the die temperature
returns to a lower temperature, which is about 20C lower than the threshold.
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ft2045
CLASS-D AUDIO AMPLIFIER
The ft2045 filterless Class-D amplifier offers much higher efficiency than Class-AB amplifiers. The high
efficiency of a Class-D amplifier is due to the switching operation of the output stage. Any power loss
associated with the Class-D output stage is mostly due to the I2R loss of the MOSFET on-resistance and
quiescent current overhead.
Fully Differential Amplifier
The ft2045 is a fully differential amplifier with differential inputs and outputs. The fully differential amplifier
consists of a differential amplifier and a common-mode amplifier. The differential amplifier ensures that the
amplifier outputs a differential voltage on the output that is equal to the differential input times the voltage
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 fully differential ft2045 can still be used
with a single-ended input; however, the ft2045 should be used with differential inputs in a noisy
environment, like a wireless handset, to ensure maximum noise rejection.
Low-EMI Filterless Output Stage
Traditional Class-D amplifiers require the use of external LC filters, or shielding, to meet EN55022B
electromagnetic-interference (EMI) regulation standards. The ft2045 uses edge-rate-controlled circuitry to
reduce EMI emissions, while maintaining up to 90% efficiency. Above 10MHz, the wideband spectrum
looks like noise for EMI purposes.
Filterless Design
Traditional Class-D amplifiers require an output filter to recover the audio signal from the amplifier’s output.
The filter adds cost, increases the solution size of the amplifier, and can decrease efficiency and THD+N
performance. The traditional PWM scheme uses large differential output swings (with its peak-to-peak
equal to two times of the supply voltage) and causes large ripple currents. Any parasitic resistance in the
filter components results in a loss of power and lowers the efficiency.
The ft2045 does not require an output filter. The device relies on the inherent inductance of the speaker
coil and the natural filtering of both the speaker and the human ear to recover the audio component of the
square-wave output. Eliminate the output filter results in a smaller, less costly, and more efficient solution.
Because the frequency of the ft2045 output is well beyond the bandwidth of most speakers, voice coil
movement due to the square-wave frequency is very small. Although this movement is small, a speaker
not designed to handle the additional power can be damaged. For optimum results, use a speaker with a
series inductance > 10µH. Typical 8Ω speakers exhibit a series inductance in range of the 20µH to 100µH.
How to Reduce EMI
The ft2045 does not require an LC output filter for short connections from the amplifier to the speaker.
However, additional EMI suppressions can be made by use of a ferrite bead in conjunction with a
capacitor, as shown in Figure 40. Choose a ferrite bead with low DC resistance (DCR) and high
impedance (100Ω ~ 330Ω) at high frequencies (>100MHz). The current flowing through the ferrite bead
must be also taken into consideration. The effectiveness of ferrites can be greatly aggravated at much
lower than the rated current values. Choose a ferrite bead with a rated current value no less than 2A. The
capacitor value varies based on the ferrite bead chosen and the actual speaker lead length. Choose a
capacitor less than 1nF based on EMI performance.
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ft2045
Ferrite
Chip Bead
VOP
VON
FB1 220Ω/2A
C1
1nF
Ferrite
Chip Bead
FB2 220Ω/2A
C2
1nF
Figure 40: Ferrite Bead Filter to Reduce EMI
Decoupling Capacitor (CS)
The ft2045 is a high-performance Class-D audio amplifier that requires adequate power supply
decoupling. Adequate power supply decoupling to ensures that the efficiency is high and total harmonic
distortion (THD) is low.
Place a low equivalent-series-resistance (ESR) ceramic capacitor (X7R or X5R), typically 1µF, within
2mm of the VDD pin. This choice of capacitor and placement helps with higher frequency transients,
spikes, or digital hash on the line. Additionally, placing this decoupling capacitor close to the ft2045 is
important, as any parasitic resistance or inductance between the device and the capacitor causes
efficiency loss. In addition to the 1µF ceramic capacitor, place a 4.7µF to 22µF capacitor on the VDD
supply trace. This larger capacitor acts as a charge reservoir, providing energy faster than the board
supply, thus helping to prevent any droop in the supply voltage.
Input Capacitors (Cin)
Input audio DC decoupling capacitors are recommended. The input audio DC decoupling capacitors will
remove the DC bias from an incoming analog signal. The input capacitors (Cin) and internal input resistors
(Rin) form a highpass filter with the corner frequency, fc, determined by Equation 1.
Any mismatch in capacitance between the two inputs will cause a mismatch in the corner frequencies.
Severe mismatch may also cause turn-on pop noise, PSRR, CMRR. Choose capacitors with a tolerance
of ±5% or better.
fc = 1 / (2 x π x Rin x Cin)
(1)
For best audio quality, use capacitors whose dielectrics have low-voltage coefficients, such as tantalum or
aluminum electrolytic. Capacitors with high-voltage coefficients, such as ceramics, could result in
increased distortion at low frequencies.
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ft2045
TYPICAL APPLICATION CIRCUITS
VDD
C3
Cs
+
47UF
1uF
Differential Inputs
C1 33nF
A1
INP
INN
INP
INN
EN
C3
A3
VON
C1
C2
B2
LS1
C2 33nF
ft2045A
SPEAKER
EN
VOP
NC
Figure 41: Differential Audio Inputs with One-Wire Pulse Control
VDD
C3
Cs
+
47UF
1uF
Single-Ended Input
C1 33nF
A1
C1
C2
B2
INPUT
INP
INN
EN
C3
A3
VON
LS1
C2 33nF
ft2045A
SPEAKER
VOP
NC
EN
Figure 42: Single-Ended Audio Input with One-Wire Pulse Control
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ft2045
TYPICAL APPLICATION CIRCUITS (Cont’d)
VDD
C3
Cs
+
47UF
1uF
Single-Ended Input
C1 33nF
C2 33nF
A1
C1
C2
B2
INPUT
INP
INN
EN
C3
A3
VON
LS1
ft2045A
SPEAKER
VOP
NC
EN
Rctrl 47K
C4
0.1uF
Figure 43: Single-Ended Audio Input with EN High/Low Control
for 2-Mode Operation (Mode1 & Shutdown)
VDD
C3
Cs
+
EN
47UF
1uF
L+R Inputs
1
2
3
4
8
7
6
5
EN
VOP
GND
VDD
VON
R1 2K
R2 2K
R3 1K
C1
C2
C3
33nF
33nF
66nF
LS1
L-IN
NC
INP
INN
ft2045M
R-IN
SPEAKER
R3=R1*R2/(R1+R2)
C3=C1+C2
Figure 44: Dual Channel Audio Inputs with One-Wire Pulse Control (ft2045M)
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ft2045
PACKAGE PHYSICAL DIMENSION
COL1.5X1.5-9L PACKAGE OUTLINE DIMENSIONS
e:0.50
D:1.50± 0.05
E：1.50± 0.05
PIN1 DOT BY
MARKING
d::0.275± 0.025
Top View
Bottom View
A1：0.00-0.05
A:0.55± 0.05
A3：0.152
Side View
All dimensions are in millimeters
Dimensions in Millimeters
Symbol
Min.
0.50
0.00
Max.
0.60
0.05
A
A1
A3
D
0.152REF.
1.45
1.45
1.55
1.55
E
0.50TYP
e
d
0.25
0.30
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ft2045
PACKAGE PHYSICAL DIMENSION (Cont’d)
MSOP-8 PACKAGE OUTLINE DIMENSIONS
D:3.00± 0.10
E1:3.00± 0.10
E:4.90± 0.20
B
B
e:0.65± 0.10
A3:0.35± 0.10
A2:0.85± 0.10
All dimensions are in millimeters
Dimensions in Millimeters
Symbol
A:0.00-1.10
Min.
—
Max.
1.10
0.15
0.95
0.39
0.37
0.33
0.20
0.16
3.10
5.10
3.10
0.75
0.80
A
A1
A2
A3
b
0
A1:0.00-0.15
0.75
0.25
0.28
0.27
0.15
0.14
2.90
4.70
2.90
0.55
0.40
WITH PLATING
BASE METAL
b1
c
c1
D
E
E1
e
c1：0.15± 0.01
c:0.175± 0.025
θ1:12° ± 3°
b1：0.30± 0.03
b:0.325± 0.045
L
R1
0.95REF.
0.25BSC.
L1
L2
R
R1
θ
θ1
R
0.07
0.07
0°
—
—
8°
15°
L2：0.25
L：0.60± 0.20
L1：0.95
θ：0° -8°
9°
θ1:12° ± 3°
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ft2045
PACKAGE PHYSICAL DIMENSION (Cont’d)
DFN2X2-8L PACKAGE OUTLINE DIMENSIONS
e：0.500
D:2.000± 0.100
L:0.350± 0.100
E1：0.600± 0.100
E:2.000± 0.100
D1：1.200± 0.100
b:0.24± 0.06
Top View
Bottom View
A1:0.000-0.050
A:0.800± 0.100
A3:0.203
Side View
All dimensions are in millimeters
Dimensions in Millimeters
Dimensions in Inches
Symbol
Min.
0.700/0.800
0.000
Max.
0.800/0.900
0.050
Min.
0.028/0.031
0.000
Max.
0.031/0.035
0.002
A
A1
A3
D
0.203REF
0.008REF
1.900
1.900
1.100
0.500
2.100
2.100
1.300
0.700
0.075
0.075
0.043
0.020
0.083
0.083
0.051
0.028
E
D1
E1
k
0.200MIN.
0.008MIN.
b
e
L
0.180
0.250
0.300
0.450
0.007
0.010
0.012
0.018
0.500TYP
0.020TYP.
Sep, 2012
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ft2045
IMPORTANT NOTICE
1. Disclaimer: The information in document is intended to help you evaluate this product. Fangtek, LTD.
makes no warranty, either expressed or implied, as to the product information herein listed, and reserves
the right to change or discontinue work on this product without notice.
2. Life support policy: Fangtek’s products are not authorized for use as critical components in life support
devices or systems without the express written approval of the president and general counsel of Fangtek
Inc. As used herein
Life support devices or systems are devices or systems which, (a) are intended for surgical implant into
the body, or (b) support or sustain life, and whose failure to perform when properly used in accordance
with instructions for use provided in the labeling, can be reasonably expected to result in a significant
injury to the user.
A critical component is any component of a life support device or system whose failure to perform can be
reasonably expected to cause the failure of the life support device or system, or to affect its safety or
effectiveness.
3. Fangtek assumes no liability for incidental, consequential or special damages or injury that may result
from misapplications or improper use or operation of its products
4. Fangtek makes no warranty or representation that its products are subject to intellectual property
license from Fangtek or any third party, and Fangtek makes no warranty or representation of
non-infringement with respect to its products. Fangtek specifically excludes any liability to the customer or
any third party arising from or related to the products’ infringement of any third party’s intellectual property
rights, including patents, copyright, trademark or trade secret rights of any third party.
5. The information in this document is merely to indicate the characteristics and performance of Fangtek
products. Fangtek assumes no responsibility for any intellectual property claims or other problems that
may result from applications based on the document presented herein. Fangtek makes no warranty with
respect to its products, express or implied, including, but not limited to the warranties of merchantability,
fitness for a particular use and title.
6. Trademarks: The company and product names in this document may be the trademarks or registered
trademarks of their respective manufacturers. Fangtek is trademark of Fangtek, LTD.
CONTACT INFORMATION
Fangtek Electronics (Shanghai) Co., Ltd
Room 503&504, Lane 198, Zhangheng Road
Zhangjiang Hi-tech Park, Pudong District
Shanghai, P. R. China, 201204
Tel: +86-21-61631978
Fax: +86-21-61631981
Website: www.fangtek.com.cn
Sep, 2012
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22
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