TPA2000D2
2-W FILTERLESS STEREO CLASS-D AUDIO POWER AMPLIFIER
SLOS291B – MARCH 2000 – REVISED APRIL 2000
1
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
D
Modulation Scheme Optimized to Operate
Without a Filter
D
2 W Into 3-Ω Speakers (THD+N< 0.4%)
D
< 0.08% THD+N at 1 W, 1 kHz, Into 4-Ω Load
D
Extremely Efficient 3rd Generation 5-V
Class-D Technology:
– Low Supply Current (No Filter) ...8 mA
– Low Supply Current (Filter) ...15 mA
– Low Shutdown Current ...1 µA
– Low Noise Floor ...56 µV
RMS
– Maximum Efficiency into 3 Ω, 65 – 70%
– Maximum Efficiency into 8 Ω, 75 – 85%
– 4 Internal Gain Settings ...8 – 23.5 dB
– PSRR . . . –77 dB
D
Integrated Depop Circuitry
D
Short-Circuit Protection (Short to Battery,
Ground, and Load)
D
–40°C to 85°C Operating Temperature
Range
description
The TPA2000D2 is the third generation 5-V class-D amplifier from Texas Instruments. Improvements to
previous generation devices include: lower supply current, lower noise floor, better ef ficiency, four dif ferent gain
settings, smaller packaging, and fewer external components. The most significant advancement with this device
is its modulation scheme that allows the amplifier to operate without the output filter. Eliminating the output filter
saves the user approximately 30% in system cost and 75% in PCB area.
The TPA2000D2 is a monolithic class-D power IC stereo audio amplifier, using the high switching speed of
power MOSFET transistors. These transistors reproduce the analog signal through high-frequency switching
of the output stage. The TPA2000D2 is configured as a bridge-tied load (BTL) amplifier capable of delivering
greater than 2 W of continuous average power into a 3-Ω load at less than 1% THD+N from a 5-V power supply
in the high fidelity range (20 Hz to 20 kHz). With 1 W being delivered to a 4-Ω load at 1 kHz, the typical THD+N
is less than 0.08%.
A BTL configuration eliminates the need for external coupling capacitors on the output. Low supply current of
8 mA makes the device ideal for battery-powered applications. Protection circuitry increases device reliability:
thermal, over-current, and under-voltage shutdown.
Efficient class-D modulation enables the TPA2000D2 to operate at full power into 3-Ω loads at an ambient
temperature of 85°C.
AVAILABLE OPTIONS
PACKAGED DEVICE
T
A
TSSOP (PWP)
–40°C to 85°C TPA2000D2PWP
NOTE: The PWP package is available taped and reeled. To
order a taped and reeled part, add the suffix R to the
part number (e.g., TPA2000D2PWPR).
Copyright 2000, Texas Instruments Incorporated
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of Texas Instruments
standard warranty. Production processing does not necessarily include
testing of all parameters.
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.
PowerPAD is a trademark of Texas Instruments.
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12
24
23
22
21
20
19
18
17
16
15
14
13
PGND
LOUTN
GAIN0
PV
DD
LINN
AGND
COSC
RINN
PV
DD
SHUTDOWN
ROUTN
PGND
PGND
LOUTP
BYPASS
PV
DD
LINP
V
DD
ROSC
RINP
PV
DD
GAIN1
ROUTP
PGND
PWP PACKAGE
(TOP VIEW)
TPA2000D2
2-W FILTERLESS STEREO CLASS-D AUDIO POWER AMPLIFIER
SLOS291B – MARCH 2000 – REVISED APRIL 2000
2
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
functional block diagram
Gate
Drive
_
+
Gate
Drive
_
+
_
+
_
+
Gain
Adjust
Gain
Adjust
Start-up
Protection
Logic
OC
Detect
OC
Detect
Thermal VDD ok
Ramp
Generator
Biases
and
References
Gate
Drive
_
+
Gate
Drive
_
+
_
+
_
+
Gain
Adjust
Gain
Adjust
Gain
2
AGNDV
DD
V
DD
PV
DD
RINN
ROUTN
PGND
PV
DD
ROUTP
PGND
PV
DD
LOUTP
PGND
PV
DD
LOUTN
PGND
RINP
SHUTDOWN
GAIN1
GAIN0
COSC
ROSC
BYPASS
LINP
LINN
TPA2000D2
2-W FILTERLESS STEREO CLASS-D AUDIO POWER AMPLIFIER
SLOS291B – MARCH 2000 – REVISED APRIL 2000
3
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
Terminal Function
TERMINAL
NAME NO.
I/O
DESCRIPTION
AGND 6 – Analog ground
BYPASS 22 I Tap to voltage divider for internal midsupply bias generator used for analog reference.
COSC 7 I
A capacitor connected to this terminal sets the oscillation frequency in conjunction with ROSC. For proper
operation, connect a 220 pF capacitor from COSC to ground.
GAIN0 3 I Bit 0 of gain control (TTL logic level)
GAIN1 15 I Bit 1 of gain control (TTL logic level)
LINN 5 I Left channel negative differential audio input
LINP 20 I Left channel positive differential audio input
LOUTN 2 O Left channel negative audio output
LOUTP 23 O Left channel positive audio output
1, 24 – Power ground for left channel H-bridge
PGND
12, 13 – Power ground for right channel H-bridge
4, 21 – Power supply for left channel H-bridge
PV
DD
9, 16 – Power supply for right channel H-bridge
RINN 8 I Right channel negative differential audio input
RINP 17 I Right channel positive differential audio input
ROSC 18 I
A resistor connected to this terminal sets the oscillation frequency in conjunction with COSC. For proper
operation, connect a 120 kΩ resistor from ROSC to ground.
ROUTN 11 O Right channel negative audio output
ROUTP 14 O Right channel positive output
SHUTDOWN 10 I
Places the amplifier in shutdown mode if a TTL logic low is placed on this terminal; normal operation if a TTL
logic high is placed on this terminal.
V
DD
19 – Analog power supply
absolute maximum ratings over operating free-air temperature (unless otherwise noted)
†
Supply voltage, VDD, PVDD –0.3 V to 6 V. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Input voltage, VI –0.3 V to VDD+0.3 V. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Continuous total power dissipation See Dissipation Rating Table. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Operating free-air temperature range, T
A
–40°C to 85°C. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Operating junction temperature range, T
J
–40°C to 150°C. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Storage temperature range, T
stg
–65°C to 150°C. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Lead temperature 1,6 mm (1/16 inch) from case for 10 seconds 260°C. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
†
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.
DISSIPATION RATING TABLE
PACKAGE
TA ≤ 25°C
POWER RATING
DERATING FACTOR
ABOVE TA = 25°C
TA = 70°C
POWER RATING
TA = 125°C
POWER RATING
PWP 2.7 W 21.8 mW/°C 1.7 W 1.4 W
TPA2000D2
2-W FILTERLESS STEREO CLASS-D AUDIO POWER AMPLIFIER
SLOS291B – MARCH 2000 – REVISED APRIL 2000
4
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
recommended operating conditions
MIN MAX UNIT
Supply voltage, VDD, PV
DD
4.5 5.5 V
High-level input voltage, V
IH
GAIN0, GAIN1, SHUTDOWN 2 V
Low-level input voltage, V
IL
GAIN0, GAIN1, SHUTDOWN 0.8 V
Operating free-air temperature, T
A
–40 85 °C
PWM Frequency 200 300 kHz
electrical characteristics, TA = 25°C, VDD = PVDD = 5 V (unless otherwise noted)
PARAMETER TEST CONDITIONS MIN TYP MAX UNIT
| VOO | Output offset voltage (measured differentially) VI = 0 V 10 mV
PSRR Power supply rejection ratio VDD=PVDD = 4.5 V to 5.5 V –77 dB
I
IH
High-level input current VDD=PVDD = 5.5 V, VI = VDD = PV
DD
1 µA
I
IL
Low-level input current VDD=PVDD = 5.5 V, VI = 0 V –1 µA
I
DD
Supply current No filter (with or without speaker load) 8 10 mA
I
DD
Supply current With filter ,L = 22 µH, C = 1 µF 15 mA
I
DD(SD)
Supply current, shutdown mode 1 10 µA
operating characteristics, TA = 25°C, VDD = PVDD = 5 V, RL = 4 Ω, Gain = –2 V/V (unless otherwise
noted)
PARAMETER TEST CONDITIONS MIN TYP MAX UNIT
P
O
Output power THD = 0.1%, f = 1 kHz, RL = 3 Ω 2 W
THD+N Total harmonic distortion plus noise PO = 1 W, f = 20 Hz to 20 kHz <0.5%
B
OM
Maximum output power bandwidth THD = 5% 20 kHz
k
SVR
Supply ripple rejection ratio f = 1 kHz, C
(BYPASS)
= 0.4 µF –60 dB
SNR Signal-to-noise ratio 87 dBV
Integrated noise floor 20 Hz to 20 kHz, No input 56 µV
Z
I
Input impedance >20 kΩ
Table 1. Gain Settings
GAIN0 GAIN1
AMPLIFIER GAIN
(dB)
INPUT IMPEDANCE
(kΩ)
TYP TYP
0 0 8 104
0 1 12 74
1 0 17.5 44
1 1 23.5 24
TPA2000D2
2-W FILTERLESS STEREO CLASS-D AUDIO POWER AMPLIFIER
SLOS291B – MARCH 2000 – REVISED APRIL 2000
5
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
TYPICAL CHARACTERISTICS
Table of Graphs
FIGURE
η Efficiency vs Output power 2, 3
In-band output spectrum vs Frequency 4
p
vs Output power 5 – 7
THD+N
Total harmonic distortion plus noise
vs Frequency 8, 9
test set-up for graphs
The THD+N measurements shown do not use an LC output filter, but use a low pass filter with a cut-of f frequency
of 20 kHz so the switching frequency does not dominate the measurement. This is done to ensure that the
THD+N measured is just the audible THD+N. The THD+N measurements are shown at the highest gain for
worst case.
The LC output filter used in the efficiency curves (Figure 2 and 3) is shown in Figure 1.
L1 = L2 = 22 µH (DCR = 110 mΩ,
Part Number = SCD0703T–220 M–S,
Manufacturer = GCI)
C1 = C2 = 1 µF
The ferrite filter used in the efficiency curves (Figure 2 and 3) is shown in Figure 1, where L is a ferrite bead.
L1 = L2 = ferrite bead (part number = 2512067007Y3, manufacturer = Fair-Rite)
C1 = C2 = 1 nF
C2
C1
L1
L2
OUT–
OUT+
Figure 1. Class-D Output Filter
TPA2000D2
2-W FILTERLESS STEREO CLASS-D AUDIO POWER AMPLIFIER
SLOS291B – MARCH 2000 – REVISED APRIL 2000
6
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
TYPICAL CHARACTERISTICS
Figure 2
0
10
20
30
40
50
60
70
80
90
0 0.2 0.4 0.6 0.8 1 1.2
No Filter
Ferrite Bead Filter
LC Filter
Class–AB
RL = 8 Ω, Multimedia Speaker
VDD = 5 V
Efficiency – %
EFFICIENCY
vs
OUTPUT POWER
PO – Output Power – W
Figure 3
0
10
20
30
40
50
60
70
80
0 0.5 1 1.5 2
Ferrite Bead Filter
Notebook Speaker
Class–AB
Efficiency – %
EFFICIENCY
vs
OUTPUT POWER
PO – Output Power – W
LC Filter
RL = 3 Ω, Notebook PC Speaker
VDD = 5 V
–140
+0
–120
–100
–80
–60
–40
–20
0 24k2k 4k 6k 8k 10k 12k 14k 16k 18k 20k 22k
Gain – dB
f – Frequency – Hz
IN-BAND OUTPUT SPECTRUM
VDD = 5 V,
Gain = 8 dB,
fIN = fO = 1 kHz,
PO = 1.5 W,
Bandwidth = 20 Hz to 22 kHz,
16386 Frequency Bins
Figure 4
TPA2000D2
2-W FILTERLESS STEREO CLASS-D AUDIO POWER AMPLIFIER
SLOS291B – MARCH 2000 – REVISED APRIL 2000
7
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
TYPICAL CHARACTERISTICS
Figure 5
0.01
0.1
1
10
10 m
THD+N – Total Harmonic Distortion – %
TOTAL HARMONIC DISTORTION PLUS NOISE
vs
OUTPUT POWER
100 m 1 2 3
PO – Output Power – W
VDD = 5 V
Gain = 23.5 dB
RL = 3 Ω
1 kHz
20 kHz
20 Hz
Figure 6
1 kHz
20 kHz
20 Hz
0.1
0.01
10 m 100 m
1
10
123
THD+N – Total Harmonic Distortion – %
TOTAL HARMONIC DISTORTION PLUS NOISE
vs
OUTPUT POWER
PO – Output Power – W
VDD = 5 V
Gain = 23.5 dB
RL = 4 Ω
Figure 7
1 kHz
0.1
0.01
10 m 100 m
1
10
123
THD+N – Total Harmonic Distortion – %
TOTAL HARMONIC DISTORTION PLUS NOISE
vs
OUTPUT POWER
PO – Output Power – W
VDD = 5 V
Gain = 23.5 dB
RL = 8 Ω
20 Hz
20 kHz
Figure 8
0.1
0.01
20 100 1 k
f – Frequency – Hz
10
10 k 20 k
0.2 W
0.75 W
1.5 W
THD+N – Total Harmonic Distortion – %
TOTAL HARMONIC DISTORTION PLUS NOISE
vs
FREQUENCY
VDD = 5 V
Gain = 23.5 dB
RL = 4 Ω
1
TPA2000D2
2-W FILTERLESS STEREO CLASS-D AUDIO POWER AMPLIFIER
SLOS291B – MARCH 2000 – REVISED APRIL 2000
8
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
TYPICAL CHARACTERISTICS
0.1
0.009
20 100 1 k
1
10
20 k
f – Frequency – Hz
0.1 W
1 W
0.5 W
THD+N – Total Harmonic Distortion – %
TOTAL HARMONIC DISTORTION PLUS NOISE
vs
FREQUENCY
VDD = 5 V
Gain = 23.5 dB
RL = 8 Ω
Figure 9
TPA2000D2
2-W FILTERLESS STEREO CLASS-D AUDIO POWER AMPLIFIER
SLOS291B – MARCH 2000 – REVISED APRIL 2000
9
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
APPLICATION INFORMATION
eliminating the output filter with the TPA2000D2
This section will focus on why the user can eliminate the output filter with the TPA2000D2.
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, V
DD
. 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 10. Note that even at an average of 0 volts across the load (50% duty cycle), the current to the load
is high causing high loss thus causing a high supply current.
O V
–5 V
+5 V
Current
OUT+
Differential Voltage
Across Load
OUT–
Figure 10. Traditional Class-D Modulation Scheme’s Output Voltage and Current Waveforms Into an
Inductive Load With no Input
TPA2000D2 modulation scheme
The TPA2000D2 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 OUT–
is 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 I
2
R losses in the load.
TPA2000D2
2-W FILTERLESS STEREO CLASS-D AUDIO POWER AMPLIFIER
SLOS291B – MARCH 2000 – REVISED APRIL 2000
10
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
APPLICATION INFORMATION
0 V
–5 V
+5 V
Current
OUT+
OUT–
Differential
Voltage
Across
Load
0 V
–5 V
+5 V
Current
OUT+
OUT–
Differential
Voltage
Across
Load
Output = 0 V
Output > 0 V
Figure 11. The TPA2000D2 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 ef ficiency. 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 TP A2000D2 modulation scheme has very little loss in the load without a filter because the pulses are very
short and the change in voltage is V
DD
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 ef ficiency , but for
most applications the filter is not needed.
An LC filter with a cut-off 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.
TPA2000D2
2-W FILTERLESS STEREO CLASS-D AUDIO POWER AMPLIFIER
SLOS291B – MARCH 2000 – REVISED APRIL 2000
11
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
APPLICATION INFORMATION
effects of applying a square wave into a speaker
Audio specialists have said for years not to apply a square wave to speakers. If the amplitude of the waveform
is high enough and the frequency of the square wave is within the bandwidth of the speaker, the 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/f
2
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, P
SUP THEORETICAL
, from the actual supply power, P
SUP
, at maximum output power,
P
OUT
. The switching power dissipated in the speaker is the inverse of the measured efficiency, η
MEASURED
,
minus the theoretical efficiency, η
THEORETICAL
.
(1)P
SPKR
= P
SUP
– P
SUP THEORETICAL
(at max output power)
(2)P
SPKR
= P
SUP
/ P
OUT
– P
SUP THEORETICAL
/ P
OUT
(at max output power)
(3)P
SPKR
= 1/η
MEASURED
– 1/η
THEORETICAL
(at max output power)
The maximum efficiency of the TPA2000D2 with an 8-Ω load is 85%. Using equation 3 with the efficiency at
maximum power from Figure 2 (78%), we see that there is an additional 106 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.
when to use an output filter
Design the TPA2000D2 without the filter if the traces from amplifier to speaker are short. The TPA2000D2
passed FCC and CE radiated emissions with no shielding with speaker wires 8 inches long or less. Notebook
PCs and powered speakers where the speaker is in the same enclosure as the amplifier are good applications
for class-D without a filter.
A ferrite bead filter can often be used if the design is failing radiated emissions without a 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 output filter if there are low frequency (< 1 MHz) EMI sensitive circuits and/or there are long leads from
amplifier to speaker.
gain setting via GAIN0 and GAIN1 inputs
The gain of the TPA2000D2 is set by two input terminals, GAIN0 and GAIN1.
The gains listed in Table 2 are realized by changing the taps on the input resistors inside the amplifier. This
causes the input impedance, ZI, to be dependent on the gain setting. The actual gain settings are controlled
by ratios of resistors, so the actual gain distribution from part-to-part is quite good. However, the input
impedance may shift by 30% due to shifts in the actual resistance of the input resistors.
For design purposes, the input network (discussed in the next section) should be designed assuming an input
impedance of 20 kΩ, which is the absolute minimum input impedance of the TPA2000D2. At the higher gain
settings, the input impedance could increase as high as 115 kΩ.
TPA2000D2
2-W FILTERLESS STEREO CLASS-D AUDIO POWER AMPLIFIER
SLOS291B – MARCH 2000 – REVISED APRIL 2000
12
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
APPLICATION INFORMATION
Table 2. Gain Settings
GAIN0 GAIN1
AMPLIFIER GAIN
(dB)
INPUT IMPEDANCE
(kΩ)
TYP TYP
0 0 8 104
0 1 12 74
1 0 17.5 44
1 1 23.5 24
input resistance
Each gain setting is achieved by varying the input resistance of the amplifier, which can range from its smallest
value to over 6 times that value. As a result, if a single capacitor is used in the input high pass filter, the –3 dB
or cut-off frequency will also change by over 6 times. If an additional resistor is connected from the input pin
of the amplifier to ground, as shown in the figure below, the variation of the cut-off frequency will be much
reduced.
C
I
R
IN
Z
I
Z
F
Input
Signal
The –3 dB frequency can be calculated using equation 4:
(4)
f
–3 dB
+
1
2pC
I
ǒ
RøZ
I
Ǔ
If the filter must be more accurate, the value of the capacitor should be increased while value of the resistor to
ground should be decreased. In addition, the order of the filter could be increased.
input capacitor, C
I
In the typical application an input capacitor, CI, is required to allow the amplifier to bias the input signal to the
proper dc level for optimum operation. In this case, CI and the input impedance of the amplifier, ZI, form a
high-pass filter with the corner frequency determined in equation 5.
f
c(highpass)
+
1
2pZ
I
C
I
–3 dB
f
c
(5)
TPA2000D2
2-W FILTERLESS STEREO CLASS-D AUDIO POWER AMPLIFIER
SLOS291B – MARCH 2000 – REVISED APRIL 2000
13
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
APPLICATION INFORMATION
The value of CI is important as it directly affects the bass (low frequency) performance of the circuit. Consider
the example where ZI is 20 kΩ and the specification calls for a flat bass response down to 80 Hz. Equation 5
is reconfigured as equation 6.
CI+
1
2pZIf
c
(6)
In this example, C
I
is 0.1 µF so one would likely choose a value in the range of 0.1 µF to 1 µF . If the gain is known
and will be constant, use ZI from T able 1 to calculate CI. A further consideration for this capacitor is the leakage
path from the input source through the input network (C
I
) and the feedback network to the load. This leakage
current creates a dc offset voltage at the input to the amplifier that reduces useful headroom, especially in high
gain applications. For this reason a low-leakage tantalum or ceramic capacitor is the best choice. When
polarized capacitors are used, the positive side of the capacitor should face the amplifier input in most
applications as the dc level there is held at VDD/2, which is likely higher than the source dc level. Note that it
is important to confirm the capacitor polarity in the application.
CI must be 10 times smaller than the bypass capacitor to reduce clicking and popping noise from power on/off
and entering and leaving shutdown. After sizing CI for a given cut-off frequency, size the bypass capacitor to
10 times that of the input capacitor.
(7)CI ≤ C
BYP
/ 10
power supply decoupling, C
S
The TP A2000D2 is a high-performance CMOS audio amplifier that requires adequate power supply decoupling
to ensure the output total harmonic distortion (THD) is as low as possible. Power supply decoupling also
prevents oscillations for long lead lengths between the amplifier and the speaker. The optimum decoupling is
achieved by using two capacitors of different types that target different types of noise on the power supply leads.
For higher frequency transients, spikes, or digital hash on the line, a good low equivalent-series-resistance
(ESR) ceramic capacitor, typically 0.1 µF placed as close as possible to the device V
DD
lead works best. For
filtering lower-frequency noise signals, a larger aluminum electrolytic capacitor of 10 µF or greater placed near
the audio power amplifier is recommended.
midrail bypass capacitor, C
BYP
The midrail bypass capacitor, C
BYP
, is the most critical capacitor and serves several important functions. During
start-up or recovery from shutdown mode, C
BYP
determines the rate at which the amplifier starts up. The second
function is to reduce noise produced by the power supply caused by coupling into the output drive signal. This
noise is from the midrail generation circuit internal to the amplifier, which appears as degraded PSRR and
THD+N.
Bypass capacitor, C
BYP
, values of 0.47 µF to 1 µF ceramic or tantalum low-ESR capacitors are recommended
for the best THD and noise performance.
Increasing the bypass capacitor reduces clicking and popping noise from power on/off and entering and leaving
shutdown. To have minimal pop, C
BYP
should be 10 times larger than CI.
(8)C
BYP
≥ 10 × C
I
TPA2000D2
2-W FILTERLESS STEREO CLASS-D AUDIO POWER AMPLIFIER
SLOS291B – MARCH 2000 – REVISED APRIL 2000
14
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
APPLICATION INFORMATION
differential input
The differential input stage of the amplifier cancels any noise that appears on both input lines of a channel. To
use the TP A2000D2 EVM with a differential source, connect the positive lead of the audio source to the RINP
(LINP) input and the negative lead from the audio source to the RINN (LINN) input. T o use the TP A2000D2 with
a single-ended source, ac ground the RINN and LINN inputs through a capacitor and apply the audio single to
the RINP and LINP inputs. In a single-ended input application, the RINN and LINN inputs should be ac grounded
at the audio source instead of at the device inputs for best noise performance.
shutdown modes
The TP A2000D2 employs a shutdown mode of operation designed to reduce supply current, IDD, to the absolute
minimum level during periods of nonuse for battery-power conservation. The SHUTDOWN input terminal
should be held high during normal operation when the amplifier is in use. Pulling SHUTDOWN low causes the
outputs to mute and the amplifier to enter a low-current state, I
DD(SD)
= 1 µA. SHUTDOWN should never be left
unconnected because amplifier operation would be unpredictable.
using low-ESR capacitors
Low-ESR capacitors are recommended throughout this application section. A real (as opposed to ideal)
capacitor can be modeled simply as a resistor in series with an ideal capacitor. The voltage drop across this
resistor minimizes the beneficial effects of the capacitor in the circuit. The lower the equivalent value of this
resistance the more the real capacitor behaves like an ideal capacitor.
evaluation circuit
RIN–
RIN+
S1
SHUTDOWN
LIN–
TPA2000D2
U1
C7
220 pF
GND
120 k
R1
R3
120 k
C18
C2
C3
C4
LIN+
GND
C17
C1
C6
C5
LOUT–
LOUT+
GND
C8
10 uF
VDD
VDD
GND
ROUT+
GND
ROUT–
GND
R2
120k
R4
120 k
C19
C20
C21
GAIN1
GAIN0
0.1 µF
0.1 µF
0.1 µF
0.1 µF
0.1 µF
0.1 µF
1 µF
10 µF
0.1 µF
0.1 µF
0.1 µF
SHUTDOWN
PGND
LOUTN
GAIN0
LPVDD
LINN
AGND
COSC
RINN
RPVDD
ROUTN
PGND
PGND
LOUTP
BYPASS
LPVDD
LINP
VDD
ROSC
RINP
RPVDD
GAIN1
ROUTP
PGND
NOTE: R1, R3, and R4 are used in the EVM but are not required for normal applications.
TPA2000D2
2-W FILTERLESS STEREO CLASS-D AUDIO POWER AMPLIFIER
SLOS291B – MARCH 2000 – REVISED APRIL 2000
15
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
APPLICATION INFORMATION
Table 3. TPA2000D2 Evaluation Bill of Materials
REFERENCE DESCRIPTION SIZE QUANTITY MANUFACTURER PART NUMBER
C1–4,
C17–21
Capacitor, ceramic chip, 0.1 µF, ±10%, X7R, 50 V 0805 9 Kemet C0805C104K5RAC
C5 Capacitor, ceramic, 1.0 µF, +80%/–20%, Y5V , 16 V 0805 1 Murata GRM40-Y5V105Z16
C6, C8 Capacitor, ceramic, 10 µF, +80%/–20%, Y5V , 16 V 1210 2 Murata GRM235-Y5V106Z16
C7 Capacitor, ceramic, 220 pF, ±10%, XICON, 50 V 0805 2 Mouser 140–CC501B221K
R2, R1†,
R3†, R4
†
Resistor, chip, 120 kΩ, 1/10 W, 5%, XICON 0805 2 Mouser 260–120K
U1 IC, TPA2000D2, audio power amplifier, 2-W,
2-channel, class-D
24 pin
TSSOP
1 TI TPA2000D2PWP
†
These components are used in the EVM, but they are not required for normal applications.
TPA2000D2
2-W FILTERLESS STEREO CLASS-D AUDIO POWER AMPLIFIER
SLOS291B – MARCH 2000 – REVISED APRIL 2000
16
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
MECHANICAL DATA
PWP (R-PDSO-G**) PowerPAD PLASTIC SMALL-OUTLINE
4073225/F 10/98
0,50
0,75
0,25
0,15 NOM
Thermal Pad
(See Note D)
Gage Plane
2824
7,70
7,90
20
6,40
6,60
9,60
9,80
6,60
6,20
11
0,19
4,50
4,30
10
0,15
20
A
1
0,30
1,20 MAX
1614
5,10
4,90
PINS **
4,90
5,10
DIM
A MIN
A MAX
0,05
Seating Plane
0,65
0,10
M
0,10
0°–8°
20 PINS SHOWN
NOTES: A. All linear dimensions are in millimeters.
B. This drawing is subject to change without notice.
C. Body dimensions do not include mold flash or protrusions.
D. The package thermal performance may be enhanced by bonding the thermal pad to an external thermal plane.
This pad is electrically and thermally connected to the backside of the die and possibly selected leads.
E. Falls within JEDEC MO-153
PowerPAD is a trademark of Texas Instruments Incorporated.
IMPORTANT NOTICE
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any product or service without notice, and advise customers to obtain the latest version of relevant information
to verify, before placing orders, that information being relied on is current and complete. All products are sold
subject to the terms and conditions of sale supplied at the time of order acknowledgment, including those
pertaining to warranty, patent infringement, and limitation of liability.
TI warrants performance of its semiconductor products to the specifications applicable at the time of sale in
accordance with TI’s standard warranty. Testing and other quality control techniques are utilized to the extent
TI deems necessary to support this warranty. Specific testing of all parameters of each device is not necessarily
performed, except those mandated by government requirements.
Customers are responsible for their applications using TI components.
In order to minimize risks associated with the customer’s applications, adequate design and operating
safeguards must be provided by the customer to minimize inherent or procedural hazards.
TI assumes no liability for applications assistance or customer product design. TI does not warrant or represent
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Copyright 2000, Texas Instruments Incorporated
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