TI TPA2006D1DRBTG4

TPA2006D1
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SLOS498 – SEPTEMBER 2006
1.45-W MONO FILTER-FREE CLASS-D AUDIO POWER AMPLIFIER WITH 1.8-V
COMPATIBLE INPUT THRESHOLDS
FEATURES
APPLICATIONS
•
•
•
•
•
Maximum Battery Life and Minimum Heat
– Efficiency With an 8-Ω Speaker:
• 88% at 400 mW
• 80% at 100 mW
– 2.8-mA Quiescent Current
– 0.5-µA Shutdown Current
Shutdown Pin has 1.8-V Compatible
Thresholds
Only Three External Components
• Optimized PWM Output Stage Eliminates
LC Output Filter
• Internally Generated 250-kHz Switching
Frequency Eliminates Capacitor and
Resistor
• Improved PSRR (–75 dB) and Wide
Supply Voltage (2.5 V to 5.5 V) Eliminates
Need for a Voltage Regulator
• Fully Differential Design Reduces RF
Rectification and Eliminates Bypass
Capacitor
• Improved CMRR Eliminates Two Input
Coupling Capacitors
Space Saving 3 mm x 3 mm QFN Package
(DRB)
Ideal for Wireless or Cellular Handsets and
PDAs
DESCRIPTION
The TPA2006D1 is a 1.45-W high efficiency
filter-free class-D audio power amplifier in a 3 mm ×
3 mm QFN package that requires only three external
components. The SHUTDOWN pin is fully
compatible with 1.8-V logic GPIO, such as are used
on low power cellular chipsets.
Features like 88% efficiency, –75-dB PSRR,
improved RF-rectification immunity, and very small
total PCB footprint make the TPA2006D1 ideal for
cellular handsets. A fast start-up time of 1 ms with
minimal pop makes the TPA2006D1 ideal for PDA
applications.
In cellular handsets, the earpiece, speaker phone,
and melody ringer can each be driven by the
TPA2006D1. The TPA2006D1 allows independent
gain while summing signals from separate sources,
and has a low 36 µV noise floor, A-weighted.
APPLICATION CIRCUIT
To Battery
Internal
Oscillator
+
RI
-
RI
CS
PWM
HBridge
VO+
VO-
INGND
SHUTDOWN
8-PIN QFN (DRB) PACKAGE
(TOP VIEW)
IN+
+
_
Differential
Input
VDD
Bias
Circuitry
TPA2006D1
SHUTDOWN
1
8 V
O−
NC
2
7 GND
IN+
3
6 VDD
IN−
4
5 VO+
NC − No internal connection
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas
Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
Copyright © 2006, Texas Instruments Incorporated
TPA2006D1
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SLOS498 – SEPTEMBER 2006
These devices 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.
ORDERING INFORMATION
(1)
TA
PACKAGE (1)
PART NUMBER
SYMBOL
–40°C to 85°C
8-pin QFN (DRB)
TPA2006D1DRB
BTQ
For the most current package and ordering information, see the Package Option Addendum at the end of this document, or see the TI
Web site at www.ti.com.
ABSOLUTE MAXIMUM RATINGS
over operating free-air temperature range unless otherwise noted (1)
TPA2006D1
VDD
Supply voltage
VI
Input voltage
In active mode
–0.3 V to 6 V
In SHUTDOWN mode
–0.3 V to 7 V
–0.3 V to VDD + 0.3 V
Continuous total power dissipation
See Dissipation Rating Table
TA
Operating free-air temperature
–40°C to 85°C
TJ
Operating junction temperature
–40°C to 125°C
Tstg
Storage temperature
–65°C to 150°C
(1)
Stresses beyond those listed under absolute maximum ratings may cause permanent damage to the device. These are stress ratings
only, and functional operation of the device at these or any other conditions beyond those indicated under recommended operating
conditions is not implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
RECOMMENDED OPERATING CONDITIONS
MIN
NOM
MAX
UNIT
VDD
Supply voltage
2.5
5.5
VIH
High-level input voltage
SHUTDOWN
V
1.3
VDD
V
VIL
Low-level input voltage
SHUTDOWN
RI
Input resistor
Gain ≤ 20 V/V (26 dB)
15
0
0.35
VIC
Common mode input voltage range
VDD = 2.5 V, 5.5 V, CMRR ≤ –49 dB
0.5
VDD–0.8
V
TA
Operating free-air temperature
–40
85
°C
V
kΩ
PACKAGE DISSIPATION RATINGS
(1)
2
PACKAGE
DERATING FACTOR (1)
TA ≤ 25°C
POWER RATING
TA = 70°C
POWER RATING
TA = 85°C
POWER RATING
DRB
21.8 mW/°C
2.7 W
1.7 W
1.4 W
Derating factor measure with High K board.
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ELECTRICAL CHARACTERISTICS
TA = 25°C (unless otherwise noted)
PARAMETER
TEST CONDITIONS
|VOS|
Output offset voltage
(measured differentially)
VI = 0 V, AV = 2 V/V, VDD = 2.5 V to 5.5 V
PSRR
Power supply rejection ratio
VDD = 2.5 V to 5.5 V
CMRR
Common mode rejection ratio
VDD = 2.5 V to 5.5 V, VIC = VDD/2 to 0.5 V,
VIC = VDD/2 to VDD –0.8 V
|IIH|
High-level input current
VDD = 5.5 V, VI = 5.8 V
|IIL|
Low-level input current
VDD = 5.5 V, VI = –0.3 V
I(Q)
Quiescent current
I(SD)
Shutdown current
rDS(on)
f(sw)
Static drain-source on-state
resistance
MIN
TYP
MAX
25
mV
–75
–55
dB
–68
–49
dB
100
µA
5
µA
VDD = 5.5 V, no load
3.4
VDD = 3.6 V, no load
2.8
VDD = 2.5 V, no load
2.2
3.2
V(SHUTDOWN)= 0.35 V, VDD = 2.5 V to 5.5 V
0.5
2
VDD = 2.5 V
770
VDD = 3.6 V
590
VDD = 5.5 V
500
4.9
mA
µA
mΩ
Output impedance in SHUTDOWN
V(SHUTDOWN) = 0.35 V
>1
Switching frequency
VDD = 2.5 V to 5.5 V
200
250
300
Gain
VDD = 2.5 V to 5.5 V
285 kW
RI
300 kW
RI
315 kW
RI
Resistance from shutdown to GND
UNIT
kΩ
300
kHz
V
V
kΩ
OPERATING CHARACTERISTICS
TA = 25°C, Gain = 2 V/V, RL = 8 Ω (unless otherwise noted)
PARAMETER
TEST CONDITIONS
THD + N = 10%, f = 1 kHz, RL = 8 Ω
PO
Output power
THD + N = 1%, f = 1 kHz, RL = 8 Ω
MIN
1.45
VDD = 3.6 V
0.73
VDD = 2.5 V
0.33
VDD = 5 V
1.19
VDD = 3.6 V
0.59
VDD = 2.5 V
THD+N
Total harmonic distortion plus
noise
0.19%
VDD = 3.6 V, PO = 0.5 W, RL = 8 Ω, f = 1 kHz
0.19%
VDD = 2.5 V, PO = 200 mW, RL = 8 Ω, f = 1 kHz
0.20%
f = 217 Hz,
V(RIPPLE) = 200
mVPP
Supply ripple rejection ratio
VDD = 3.6 V, Inputs ac-grounded
with Ci = 2 µF
SNR
Signal-to-noise ratio
VDD = 5 V, PO = 1 W, RL = 8 Ω, A-weighted
Vn
Output voltage noise
VDD = 3.6 V, f = 20 Hz to 20 kHz,
Inputs ac-grounded with Ci = 2 µF
No weighting
CMRR
Common mode rejection ratio
VDD = 3.6 V, VIC = 1 VPP
f = 217 Hz
ZI
Input impedance
W
dB
97
dB
A weighting
36
µVRMS
–63
142
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W
–67
48
VDD = 3.6 V
UNIT
0.26
VDD = 5 V, PO = 1 W, RL = 8 Ω, f = 1 kHz
kSVR
Start-up time from shutdown
TYP MAX
VDD = 5 V
150
1
dB
158
kΩ
ms
3
TPA2006D1
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SLOS498 – SEPTEMBER 2006
Terminal Functions
TERMINAL
NAME
I/O
DRB
DESCRIPTION
IN–
4
I
Negative differential input
IN+
3
I
Positive differential input
VDD
6
I
Power supply
VO+
5
O
Positive BTL output
GND
7
O
High-current ground
VO-
8
O
Negative BTL output
SHUTDOWN
1
I
Shutdown terminal (active low logic)
NC
2
-
No Connect, not connected internal to the device. May be left unconnected
O
Should be soldered to a grounded thermal pad on PCB for best thermal performance
Thermal Pad
FUNCTIONAL BLOCK DIAGRAM
150 kW
150 kW
150 kW
SC
300 kW
150 kW
4
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TYPICAL CHARACTERISTICS
TABLE OF GRAPHS
FIGURE
Efficiency
vs Output power
1
Power dissipation
vs Output power
2
Supply current
vs Output power
3
I(Q)
Quiescent current
vs Supply voltage
4
I(SD)
Shutdown current
vs Shutdown voltage
5
PD
PO
Output power
vs Supply voltage
8
vs Load resistance
6, 7
vs Output power
9
THD+N Total harmonic distortion plus noise vs Frequency
10, 11, 12
vs Common-mode input voltage
KSVR
Supply ripple rejection ratio
vs Frequency
GSM power supply rejection
KSVR
Supply ripple rejection ratio
CMRR
Common-mode rejection ratio
13
14, 15
vs Time
16
vs Frequency
17
vs Common-mode input voltage
18
vs Frequency
19
vs Common-mode input voltage
20
TEST SET-UP FOR GRAPHS
CI
TPA2006D1
RI
IN+
+
Measurement
Output
-
CI
OUT+
Load
RI
INVDD
+
OUT-
30-kHz
Low-Pass
Filter
+
Measurement
Input
-
GND
1 mF
VDD
-
A.
CI is shorted for any common-mode input voltage measurement.
B.
A 33-µH inductor is placed in series with the load resistor to emulate a small speaker for efficiency measurements.
C.
The 30-kHz low-pass filter is required even if the analyzer has an internal low-pass filter. An RC low-pass filter
(100 Ω, 47 nF) is used on each output for the data sheet graphs.
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EFFICIENCY
vs
OUTPUT POWER
POWER DISSIPATION
vs
OUTPUT POWER
SUPPLY CURRENT
vs
OUTPUT POWER
0.7
90
300
Class-AB, VDD = 5 V, RL = 8 W
VDD = 5 V,
RL = 8 W, 33 mH
0.6
60
50
40
Class-AB,
VDD = 5 V,
RL = 8 W
30
20
250
Class-AB,
VDD = 3.6 V,
RL = 8 W
0.5
0.4
0.3
VDD = 3.6 V,
RL = 8 W, 33 mH
0.2
0
VDD = 5 V,
RL = 8 W, 33 mH
0
0
0.2
0.4
0.6
0.8
1
1.2
0
0.2
0.4
PO - Output Power - W
100
VDD = 3.6 V,
RL = 8 W, 33 mH
0.6
0.8
1
VDD = 2.5 V,
RL = 8 W, 33 mH
0
1.2
0.2
0.4
0.6
0.8
Figure 2.
Figure 3.
QUIESCENT CURRENT
vs
SUPPLY VOLTAGE
SUPPLY CURRENT
vs
SHUTDOWN VOLTAGE
OUTPUT POWER
vs
LOAD RESISTANCE
2
3.6
3.4
RL = 8 W, 33 mH
3.2
3
2.8
No Load
2.6
2.4
1
1.2
PO - Output Power - W
Figure 1.
I (SD) − Shutdown Current − µ A
I(Q) − Quiescent Current − mA
VDD = 5 V,
RL = 8 W, 33 mH
0
1.6
f = 1 kHz
THD+N = 10%
Gain = 2 V/V
1.4
1.5
VDD = 5 V
1
VDD = 3.6 V
VDD = 2.5 V
0.5
1.2
VDD = 5 V
1
VDD = 3.6 V
0.8
VDD = 2.5 V
0.6
0.4
0.2
2.2
0
2
3
3.5
4
4.5
5
0
0
5.5
VDD − Supply Voltage − V
0.1
0.2
0.3
0.4
Shutdown Voltage − V
12
16
20
24
28
32
RL - Load Resistance - W
Figure 4.
Figure 5.
Figure 6.
OUTPUT POWER
vs
LOAD RESISTANCE
OUTPUT POWER
vs
SUPPLY VOLTAGE
TOTAL HARMONIC DISTORTION +
NOISE
vs
OUTPUT POWER
1.4
1.6
f = 1 kHz
THD+N = 1%
Gain = 2 V/V
VDD = 5 V
1
VDD = 3.6 V
0.8
VDD = 2.5 V
0.6
RL = 8 W
f = 1 kHz
Gain = 2 V/V
1.4
PO - Output Power - W
1.2
0.4
1.2
1
THD+N = 10%
0.8
0.6
THD+N = 1%
0.4
0.2
0.2
0
0
8
8
0.5
12
16
20
24
RL - Load Resistance - W
Figure 7.
28
32
2.5
3
3.5
4
4.5
VDD - Supply Voltage - V
Figure 8.
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THD+N − Total Harmonic Distortion + Noise − %
2.5
PO - Output Power - W
150
PO - Output Power - W
3.8
6
200
50
0.1
10
Supply Current - mA
VDD = 2.5 V,
RL = 8 W, 33 mH
PO - Output Power - W
Efficiency - %
70
PD - Power Dissipation - W
80
20
10
RL = 8 W
f = 1 kHz
5V
3.6 V
2.5 V
1
0.1
0.001
0.01
0.1 k
1k
Power Output − W
Figure 9.
10 k
TPA2006D1
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SLOS498 – SEPTEMBER 2006
RL = 8 W
PO = 0.25 W
PO = 0.5 W
1
0.1
PO = 1 W
0.01
20
100
1k
f − Frequency − Hz
10 k 20 k
10
VDD = 3.6 V
RL = 8 W
PO = 0.25 W
PO = 0.125 W
1
0.1
PO = 0.5 W
0.01
0.001
20
100
1k
f − Frequency − Hz
10 k 20 k
TOTAL HARMONIC DISTORTION +
NOISE
vs
FREQUENCY
THD+N − Total Harmonic Distortion + Noise − %
VDD = 5 V
THD+N − Total Harmonic Distortion + Noise − %
10
TOTAL HARMONIC DISTORTION +
NOISE
vs
FREQUENCY
10
VDD = 2.5 V
PO = 0.2 W
RL = 8 W
1
PO = 0.015 W
0.1
PO = 0.075 W
0.01
0.001
20
100
1k
f − Frequency − Hz
10 k 20 k
Figure 10.
Figure 11.
Figure 12.
TOTAL HARMONIC DISTORTION +
NOISE
vs
COMMON MODE INPUT VOLTAGE
SUPPLY RIPPLE REJECTION RATIO
vs
FREQUENCY
SUPPLY RIPPLE REJECTION RATIO
vs
FREQUENCY
−30
VDD = 2.5 V
1
VDD = 5 V
−30
Inputs ac-grounded
CI = 2 mF
RL = 8 W
Gain = 2 V/V
−40
−50
VDD = 2. 5 V
VDD = 3.6 V
−60
−70
−80
0
0.5
1
1.5 2
2.5
3
3.5
4 4.5
5
−50
VDD = 5 V
−60
−70
VDD = 3.6 V
−80
VDD = 2.5 V
VDD = 5 V
VDD = 3.6 V
0.1
Inputs floating
RL = 8 W
−40
−90
−90
20
VIC − Common Mode Input Voltage − V
100
1k
20
10 k 20 k
100
Figure 13.
Figure 14.
Figure 15.
GSM POWER SUPPLY REJECTION
vs
TIME
GSM POWER SUPPLY REJECTION
vs
FREQUENCY
0
C1 − High
3.6 V
−50
C1 − Amp
512 mV
−100
C1 − Duty
12%
VOUT
20 mV/div
VO − Output Voltage − dBV
VDD
200 mV/div
10 k 20 k
1k
f − Frequency − Hz
f − Frequency − Hz
0
VDD Shown in Figure 22
CI = 2 µF,
Inputs ac-grounded
Gain = 2V/V
−50
−150
V DD − Supply Voltage − dBV
f = 1 kHz
PO = 200 mW
Sopply Ripple Rejection Ratio − dB
10
Supply Ripple Rejection Ratio − dB
THD+N − Total Harmonic Distortion + Noise − %
THD+N − Total Harmonic Distortion + Noise − %
TOTAL HARMONIC DISTORTION +
NOISE
vs
FREQUENCY
−100
−150
0
t − Time − 2 ms/div
400
800
1200
1600
2000
f − Frequency − Hz
Figure 16.
Figure 17.
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−10
−20
−30
−40
VDD = 3.6 V
VDD = 2. 5 V
−50
VDD = 5 V
−60
−70
−80
0
0.5
1
1.5
2
2.5
3
3.5 4
DC Common Mode Voltage − V
Figure 18.
8
4.5 5
−50
VIC = 200 mVPP
RL = 8 Ω
Gain = 2 V/V
−55
−60
VDD = 3.6 V
−65
−70
−75
20
100
1k
f − Frequency − Hz
10 k 20 k
Figure 19.
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COMMON-MODE REJECTION RATIO
vs
COMMON-MODE INPUT VOLTAGE
CMRR − Common Mode Rejection Ratio − dB
Sopply Ripple Rejection Ratio − dB
0
COMMON-MODE REJECTION RATIO
vs
FREQUENCY
CMRR − Common Mode Rejection Ratio − dB
SUPPLY RIPPLE REJECTION RATIO
vs
DC COMMON MODE VOLTAGE
0
−10
−20
−30
−40
VDD = 3.6 V
VDD = 2.5 V
−50
−60
−70
−80
VDD = 5 V,
Gain = 2
−90
−100
0
1
2
3
4
VIC − Common Mode Input Voltage − V
Figure 20.
5
TPA2006D1
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SLOS498 – SEPTEMBER 2006
APPLICATION INFORMATION
FULLY DIFFERENTIAL AMPLIFIER
The TPA2006D1 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 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 TPA2006D1 can still be used with a
single-ended input; however, the TPA2006D1 should be used with differential inputs when in a noisy
environment, like a wireless handset, to ensure maximum noise rejection.
Advantages of Fully Differential Amplifiers
• Input-coupling capacitors not required:
– The fully differential amplifier allows the inputs to be biased at voltage other than mid-supply. For example,
if a codec has a mid-supply lower than the mid-supply of the TPA2006D1, the common-mode feedback
circuit will adjust, and the TPA2006D1 outputs will still be biased at mid-supply of the TPA2006D1. The
inputs of the TPA2006D1 can be biased from 0.5 V to VDD – 0.8 V. If the inputs are biased outside of that
range, input-coupling capacitors are required.
• Mid-supply bypass capacitor, C(BYPASS), not required:
– The fully differential amplifier does not require a bypass capacitor. This is because any shift in the
midsupply affects both positive and negative channels equally and cancels at the differential output.
• Better RF-immunity:
– GSM handsets save power by turning on and shutting off the RF transmitter at a rate of 217 Hz. The
transmitted signal is picked-up on input and output traces. The fully differential amplifier cancels the signal
much better than the typical audio amplifier.
COMPONENT SELECTION
Figure 21 shows the TPA2006D1 typical schematic with differential inputs and Figure 22 shows the TPA2006D1
with differential inputs and input capacitors, and Figure 23 shows the TPA2006D1 with single-ended inputs.
Differential inputs should be used whenever possible because the single-ended inputs are much more
susceptible to noise.
Table 1. Typical Component Values
(1)
REF DES
VALUE
EIA SIZE
MANUFACTURER
RI
150 kΩ (±0.5%)
0402
Panasonic
PART NUMBER
ERJ2RHD154V
CS
1 µF (+22%, -80%)
0402
Murata
GRP155F50J105Z
CI (1)
3.3 nF (±10%)
0201
Murata
GRP033B10J332K
CI is only needed for single-ended input or if VICM is not between 0.5 V and VDD– 0.8 V. CI = 3.3 nF
(with RI = 150 kΩ) gives a high-pass corner frequency of 321 Hz.
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Input Resistors (RI)
The input resistors (RI) set the gain of the amplifier according to Equation 1.
V
Gain + 2 x 150 kW
R
V
I
ǒǓ
(1)
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. CMRR, PSRR, and cancellation of the second harmonic
distortion diminish if resistor mismatch occurs. Therefore, it is recommended to use 1% tolerance resistors or
better to keep the performance optimized. Matching is more important than overall tolerance. Resistor arrays
with 1% matching can be used with a tolerance greater than 1%.
Place the input resistors very close to the TPA2006D1 to limit noise injection on the high-impedance nodes.
For optimal performance the gain should be set to 2 V/V or lower. Lower gain allows the TPA2006D1 to operate
at its best, and keeps a high voltage at the input making the inputs less susceptible to noise.
Decoupling Capacitor (CS)
The TPA2006D1 is a high-performance class-D audio amplifier that requires adequate power supply decoupling
to ensure the efficiency is high and total harmonic distortion (THD) is low. For higher frequency transients,
spikes, or digital hash on the line, a good low equivalent-series-resistance (ESR) ceramic capacitor, typically
1 µF, placed as close as possible to the device VDD lead works best. Placing this decoupling capacitor close to
the TPA2006D1 is very important for the efficiency of the class-D amplifier, because any resistance or
inductance in the trace between the device and the capacitor can cause a loss in efficiency. For filtering
lower-frequency noise signals, a 10 µF or greater capacitor placed near the audio power amplifier would also
help, but it is not required in most applications because of the high PSRR of this device.
Input Capacitors (CI)
The TPA2006D1 does not require input coupling capacitors if the design uses a differential source that is biased
from 0.5 V to VDD – 0.8 V (shown in Figure 21). If the input signal is not biased within the recommended
common-mode input range, if needing to use the input as a high pass filter (shown in Figure 22), or if using a
single-ended source (shown in Figure 23), input coupling capacitors are required.
The input capacitors and input resistors form a high-pass filter with the corner frequency, fc, determined in
Equation 2.
1
fc +
ǒ2p RICIǓ
(2)
The value of the input capacitor is important to consider as it directly affects the bass (low frequency)
performance of the circuit. Speakers in wireless phones cannot usually respond well to low frequencies, so the
corner frequency can be set to block low frequencies in this application.
Equation 3 is reconfigured to solve for the input coupling capacitance.
1
C +
I
ǒ2p RI f cǓ
(3)
If the corner frequency is within the audio band, the capacitors should have a tolerance of ±10% or better,
because any mismatch in capacitance causes an impedance mismatch at the corner frequency and below.
For a flat low-frequency response, use large input coupling capacitors (1 µF). However, in a GSM phone the
ground signal is fluctuating at 217 Hz, but the signal from the codec does not have the same 217-Hz fluctuation.
The difference between the two signals is amplified, sent to the speaker, and heard as a 217-Hz hum.
10
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To Battery
Internal
Oscillator
RI
INPWM
_
Differential
Input
RI
VDD
HBridge
CS
VO+
VO-
+
IN+
GND
Bias
Circuitry
SHUTDOWN
TPA2006D1
Filter-Free Class D
Figure 21. Typical TPA2006D1 Application Schematic With Differential Input for a Wireless Phone
To Battery
CI
Differential
Input
Internal
Oscillator
RI
IN_
CI
RI
VDD
PWM
HBridge
CS
VO+
VO-
+
IN+
GND
SHUTDOWN
Bias
Circuitry
TPA2006D1
Filter-Free Class D
Figure 22. TPA2006D1 Application Schematic With Differential Input and Input Capacitors
SHUTDOWN
TPA2006D1
Filter-Free Class D
Figure 23. TPA2006D1 Application Schematic With Single-Ended Input
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TPA2006D1
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SLOS498 – SEPTEMBER 2006
SUMMING INPUT SIGNALS WITH THE TPA2006D1
Most wireless phones or PDAs need to sum signals at the audio power amplifier or just have two signal sources
that need separate gain. The TPA2006D1 makes it easy to sum signals or use separate signal sources with
different gains. Many phones now use the same speaker for the earpiece and ringer, where the wireless phone
would require a much lower gain for the phone earpiece than for the ringer. PDAs and phones that have stereo
headphones require summing of the right and left channels to output the stereo signal to the mono speaker.
Summing Two Differential Input Signals
Two extra resistors are needed for summing differential signals (a total of 5 components). The gain for each
input source can be set independently (see Equation 4 and Equation 5, and Figure 24).
V
V
Gain 1 + O + 2 x 150 kW
V
R
V
I1
I1
(4)
V
V
Gain 2 + O + 2 x 150 kW
V
R
V
I2
I2
(5)
ǒǓ
ǒǓ
If summing left and right inputs with a gain of 1 V/V, use RI1 = RI2 = 300 kΩ.
SHUTDOWN
Filter-Free Class D
Figure 24. Application Schematic With TPA2006D1 Summing Two Differential Inputs
12
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SLOS498 – SEPTEMBER 2006
Summing a Differential Input Signal and a Single-Ended Input Signal
Figure 25 shows how to sum a differential input signal and a single-ended input signal. Ground noise can couple
in through IN+ with this method. It is better to use differential inputs. The corner frequency of the single-ended
input is set by CI2, shown in Equation 8. 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
V
V
Gain 1 + O + 2 x 150 kW
V
R
V
I1
I1
(6)
V
V
Gain 2 + O + 2 x 150 kW
V
R
V
I2
I2
(7)
1
C +
I2
ǒ2p RI2 f c2Ǔ
(8)
ǒǓ
ǒǓ
If summing a ring tone and a phone signal, the phone signal should use a differential input signal while the ring
tone might be limited to a single-ended signal.
The high pass corner frequency of the single-ended input is set by CI2. If the desired corner frequency is less
than 20 Hz:
1
C u
I2
ǒ2p 150kW 20HzǓ
(9)
CI2 > 53 nF
(10)
RI1
Differential
Input 1
Single-Ended
Input 2
RI1
CI2 R
I2
To Battery
Internal
Oscillator
CS
IN_
RI2
VDD
PWM
HBridge
VO+
VO-
+
IN+
CI2
SHUTDOWN
GND
Bias
Circuitry
Filter-Free Class D
Figure 25. Application Schematic With TPA2006D1 Summing Differential Input and Single-Ended Input
Signals
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TPA2006D1
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SLOS498 – SEPTEMBER 2006
Summing Two Single-Ended Input Signals
Four resistors and three capacitors are needed for summing single-ended input signals. The gain and corner
frequencies (fc1 and fc2) for each input source can be set independently (see Equation 11 through Equation 14,
and Figure 26). Resistor, RP, and capacitor, CP, are needed on the IN+ terminal to match the impedance on the
IN- terminal. The single-ended inputs must be driven by low impedance sources even if one of the inputs is not
outputting an ac signal.
V
V
Gain 1 + O + 2 x 150 kW
V
R
V
I1
I1
(11)
V
V
Gain 2 + O + 2 x 150 kW
V
R
V
I2
I2
(12)
1
C +
I1
ǒ2p RI1 f c1Ǔ
(13)
1
C +
I2
ǒ2p RI2 f c2Ǔ
(14)
C +C ) C
P
I1
I2
(15)
R
R
I2
R + I1
P
ǒRI1 ) RI2Ǔ
(16)
ǒǓ
ǒǓ
Single-Ended
Input 1
CI1 R
I1
To Battery
CI2 R
I2
Single-Ended
Internal
Oscillator
CS
IN-
Input 2
_
RP
VDD
PWM
HBridge
VO+
VO-
+
IN+
CP
GND
SHUTDOWN
Bias
Circuitry
Filter-Free Class D
Figure 26. Application Schematic With TPA2006D1 Summing Two Single-Ended Inputs
Component Location
Place all the external components very close to the TPA2006D1. The input resistors need to be very close to the
TPA2006D1 input pins so noise does not couple on the high impedance nodes between the input resistors and
the input amplifier of the TPA2006D1. Placing the decoupling capacitor, CS, close to the TPA2006D1 is
important for the efficiency of the class-D amplifier. Any resistance or inductance in the trace between the device
and the capacitor can cause a loss in efficiency.
14
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TPA2006D1
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SLOS498 – SEPTEMBER 2006
EFFICIENCY AND THERMAL INFORMATION
The maximum ambient temperature depends on the heat-sinking ability of the PCB system. The derating factor
for the DRB package is shown in the dissipation rating table. Converting this to θJA:
1
1
o
qJA =
=
0.0218 = 45.9 C/W
Derating Factor
(17)
Given θJA of 45.9°C/W, the maximum allowable junction temperature of 125°C, and the maximum internal
dissipation of 0.2 W (Po=1.45 W, 8-Ω load, 5-V supply, from Figure 2), the maximum ambient temperature can
be calculated with the following equation.
TAMax = TJMax - qJAPDmax = 125 - 45.9(0.2) = 115.8oC
(18)
Equation 18 shows that the calculated maximum ambient temperature is 115.8°C at maximum power dissipation
with a 5-V supply and 8-Ω a load, see Figure 2. The TPA2006D1 is designed with thermal protection that turns
the device off when the junction temperature surpasses 150°C to prevent damage to the IC.
ELIMINATING THE OUTPUT FILTER WITH THE TPA2006D1
This section focuses on why the user can eliminate the output filter with the TPA2006D1.
Effect on Audio
The class-D amplifier outputs a pulse-width modulated (PWM) square wave, which is the sum of the switching
waveform and the amplified input audio signal. The human ear acts as a band-pass filter such that only the
frequencies between approximately 20 Hz and 20 kHz are passed. The switching frequency components are
much greater than 20 kHz, so the only signal heard is the amplified input audio signal.
Traditional Class-D Modulation Scheme
The traditional class-D modulation scheme, which is used in the TPA005Dxx family, has a differential output
where each output is 180 degrees out of phase and changes from ground to the supply voltage, VDD. Therefore,
the differential pre-filtered output varies between positive and negative VDD, where filtered 50% duty cycle yields
0 volts across the load. The traditional class-D modulation scheme with voltage and current waveforms is shown
in Figure 27. Note that even at an average of 0 volts across the load (50% duty cycle), the current to the load is
high causing a high loss and thus causing a high supply current.
OUT+
OUT+5 V
Differential Voltage
Across Load
0V
-5 V
Current
Figure 27. Traditional Class-D Modulation Scheme's Output Voltage and Current Waveforms Into an
Inductive Load With no Input
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TPA2006D1
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SLOS498 – SEPTEMBER 2006
TPA2006D1 Modulation Scheme
The TPA2006D1 uses a modulation scheme that still has each output switching from 0 to the supply voltage.
However, OUT+ and OUT- are now in phase with each other with no input. The duty cycle of OUT+ is greater
than 50% and OUT- is less than 50% for positive voltages. The duty cycle of OUT+ is less than 50% and OUTis greater than 50% for negative voltages. The voltage across the load sits at 0 volts throughout most of the
switching period greatly reducing the switching current, which reduces any I2R losses in the load.
OUT+
OUTDifferential
Voltage
Across
Load
Output = 0 V
+5 V
0V
-5 V
Current
OUT+
OUTDifferential
+5 V
Voltage
Across
0V
Load
Output > 0 V
-5 V
Current
Figure 28. The TPA2006D1 Output Voltage and Current Waveforms Into an Inductive Load
Efficiency: Why You Must Use a Filter With the Traditional Class-D Modulation Scheme
The main reason that the traditional class-D amplifier needs an output filter is that the switching waveform
results in maximum current flow. This causes more loss in the load, which causes lower efficiency. The ripple
current is large for the traditional modulation scheme because the ripple current is proportional to voltage
multiplied by the time at that voltage. The differential voltage swing is 2 × VDD and the time at each voltage is
half the period for the traditional modulation scheme. An ideal LC filter is needed to store the ripple current from
each half cycle for the next half cycle, while any resistance causes power dissipation. The speaker is both
resistive and reactive, whereas an LC filter is almost purely reactive.
The TPA2006D1 modulation scheme has very little loss in the load without a filter because the pulses are very
short and the change in voltage is VDD instead of 2 × VDD. As the output power increases, the pulses widen
making the ripple current larger. Ripple current could be filtered with an LC filter for increased efficiency, but for
most applications the filter is not needed.
An LC filter with a cutoff frequency less than the class-D switching frequency allows the switching current to flow
through the filter instead of the load. The filter has less resistance than the speaker that results in less power
dissipated, which increases efficiency.
16
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TPA2006D1
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SLOS498 – SEPTEMBER 2006
Effects of Applying a Square Wave Into a Speaker
If the amplitude of a square wave is high enough and the frequency of the square wave is within the bandwidth
of the speaker, a square wave could cause the voice coil to jump out of the air gap and/or scar the voice coil. A
250-kHz switching frequency, however, is not significant because the speaker cone movement is proportional to
1/f2 for frequencies beyond the audio band. Therefore, the amount of cone movement at the switching frequency
is very small. However, damage could occur to the speaker if the voice coil is not designed to handle the
additional power. To size the speaker for added power, the ripple current dissipated in the load needs to be
calculated by subtracting the theoretical supplied power, PSUP THEORETICAL, from the actual supply power, PSUP, at
maximum output power, POUT. The switching power dissipated in the speaker is the inverse of the measured
efficiency, ηMEASURED, minus the theoretical efficiency, ηTHEORETICAL.
P
+P
–P
(at max output power)
SPKR
SUP SUP THEORETICAL
(19)
P
P
P
+ SUP – SUP THEORETICAL (at max output power)
SPKR
P
P
OUT
OUT
(20)
P
SPKR
+P
ǒ
Ǔ
1
1
*
(at max output power)
OUT h MEASURED h THEORETICAL
(21)
R
hTHEORETICAL +
R
L
(at max output power)
) 2r
L
DS(on)
(22)
The maximum efficiency of the TPA2006D1 with a 3.6 V supply and an 8-Ω load is 86% from Equation 22. Using
equation Equation 21 with the efficiency at maximum power (84%), we see that there is an additional 17 mW
dissipated in the speaker. The added power dissipated in the speaker is not an issue as long as it is taken into
account when choosing the speaker.
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TPA2006D1
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SLOS498 – SEPTEMBER 2006
When to Use an Output Filter
Design the TPA2006D1 without an output filter if the traces from amplifier to speaker are short. The TPA2006D1
passed FCC and CE radiated emissions with no shielding with speaker trace wires 100 mm long or less.
Wireless handsets and PDAs are great applications for class-D without a filter.
A ferrite bead filter can often be used if the design is failing radiated emissions without an LC filter, and the
frequency sensitive circuit is greater than 1 MHz. This is good for circuits that just have to pass FCC and CE
because FCC and CE only test radiated emissions greater than 30 MHz. If choosing a ferrite bead, choose one
with high impedance at high frequencies, but very 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 leads
from amplifier to speaker.
Figure 29 and Figure 30 show typical ferrite bead and LC output filters.
Ferrite
Chip Bead
VO+
1 nF
Ferrite
Chip Bead
VO1 nF
Figure 29. Typical Ferrite Chip Bead Filter (Chip bead example: NEC/Tokin: N2012ZPS121)
33 mH
VO+
0.47 mF
VO-
0.1 mF
33 mH
0.1 mF
Figure 30. Typical LC Output Filter, Cutoff Frequency of 27 kHz
18
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PACKAGE OPTION ADDENDUM
www.ti.com
2-Oct-2006
PACKAGING INFORMATION
Orderable Device
Status (1)
Package
Type
Package
Drawing
Pins Package Eco Plan (2)
Qty
TPA2006D1DRBR
ACTIVE
SON
DRB
8
3000 Green (RoHS &
no Sb/Br)
CU NIPDAU
Level-2-260C-1 YEAR
TPA2006D1DRBRG4
ACTIVE
SON
DRB
8
3000 Green (RoHS &
no Sb/Br)
CU NIPDAU
Level-2-260C-1 YEAR
TPA2006D1DRBT
ACTIVE
SON
DRB
8
250
Green (RoHS &
no Sb/Br)
CU NIPDAU
Level-2-260C-1 YEAR
TPA2006D1DRBTG4
ACTIVE
SON
DRB
8
250
Green (RoHS &
no Sb/Br)
CU NIPDAU
Level-2-260C-1 YEAR
Lead/Ball Finish
MSL Peak Temp (3)
(1)
The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in
a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
(2)
Eco Plan - The planned eco-friendly classification: Pb-Free (RoHS), Pb-Free (RoHS Exempt), or Green (RoHS & no Sb/Br) - please check
http://www.ti.com/productcontent for the latest availability information and additional product content details.
TBD: The Pb-Free/Green conversion plan has not been defined.
Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements
for all 6 substances, including the requirement that lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered
at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes.
Pb-Free (RoHS Exempt): This component has a RoHS exemption for either 1) lead-based flip-chip solder bumps used between the die and
package, or 2) lead-based die adhesive used between the die and leadframe. The component is otherwise considered Pb-Free (RoHS
compatible) as defined above.
Green (RoHS & no Sb/Br): TI defines "Green" to mean Pb-Free (RoHS compatible), and free of Bromine (Br) and Antimony (Sb) based flame
retardants (Br or Sb do not exceed 0.1% by weight in homogeneous material)
(3)
MSL, Peak Temp. -- The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder
temperature.
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Addendum-Page 1
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