LM4951A
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LM4951A Wide Voltage Range 1.8 Watt Audio Amplifier
With Short Circuit Protection
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1FEATURES DESCRIPTION
The LM4951A is an audio power amplifier designed
23• Pop & Click Circuitry Eliminates Noise During for applications with supply voltages ranging from
Turn-On and Turn-Off Transitions 2.7V up to 9V. The LM4951A is capable of delivering
• Wide Supply Voltage Range: 2.7V to 9V 1.8W continuous average power with less than 1%
• Low Current, Active-Low Shutdown Mode THD+N into a bridge connected 8Ωload when
operating from a 7.5VDC power supply.
• Low Quiescent Current Boomer™ audio power amplifiers were designed
• Thermal Shutdown Protection specifically to provide high quality output power with a
• Short Circuit Protection minimal amount of external components. The
• Unity-Gain Stable LM4951A does not require bootstrap capacitors, or
• External Gain Configuration Capability snubber circuits.
The LM4951A features a low-power consumption
APPLICATIONS active-low shutdown mode. Additionally, the
LM4951A features an internal thermal shutdown
• Portable Devices protection mechanism and short circuit protection.
• Cell Phones The LM4951A contains advanced pop & click circuitry
• Laptop Computers that eliminates noises which would otherwise occur
• Computer Speaker Systems during turn-on and turn-off transitions.
• MP3 Player Speakers The LM4951A is unity-gain stable and can be
configured by external gain-setting resistors.
KEY SPECIFICATIONS
• Wide Voltage Range 2.7V to 9V
• Quiescent Power Supply Current (VDD = 7.5V)
2.5mA (typ)
• Power Output BTL at 7.5V, 1% THD
1.8 W (typ)
• Shutdown Current 0.01µA (typ)
• Fast Turn on Time 25ms (typ)
1Please 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.
2Boomer is a trademark of Texas Instruments.
3All other trademarks are the property of their respective owners.
PRODUCTION DATA information is current as of publication date. Copyright © 2008–2013, Texas Instruments Incorporated
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
1
2
3
4
5
10
9
8
7
6
Bypass
Shutdown
CCHG
NC
VIN
VO+
VDD
NC
GND
VO-
Rf
VDD
0.39 PF
Control
Bias
+
-
-
+
8:
20k
1k
Shutdown
control
1.0 PF
VIH
VIL
1.0 PF
Cs
CiRi
Rc
CBYPASS
VDD
GND
Bypass
Shutdown
VIN
CCHG
AMPA
AMPBVo+
Vo-
20k
20k
LM4951A
SNAS453C –AUGUST 2008–REVISED APRIL 2013
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Typical Application
Figure 1. Typical Bridge-Tied-Load (BTL) Audio Amplifier Application Circuit
Connection Diagram
Top View
Figure 2. WSON Package
See Package Number DPR0010A
Pin Name and Function
Pin Number Name Function Type
½ supply reference voltage bypass output. See sections POWER SUPPLY
1 Bypass BYPASSING and SELECTING EXTERNAL COMPONENTS for more Analog Output
information.
Shutdown control active low signal. A logic low voltage will put the
2 Shutdown Digital Input
LM4951A into Shutdown mode.
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Pin Name and Function (continued)
Pin Number Name Function Type
Input capacitor charge to decrease turn on time. See section Selecting
3 CCHG Analog Output
Value A For RCfor more information.
4 NC No connection to die. Pin can be connected to any potential. No Connect
5 VIN Single-ended signal input pin. Analog Input
6 VO- Inverting output of amplifier. Analog Output
7 GND Ground connection. Ground
8 NC No connection to die. Pin can be connected to any potential. No Connect
9 VDD Power supply. Power
10 VO+ Non-Inverting output of amplifier. Analog Output
No connect. Pin must be electrically isolated (floating) or connected to
Exposed DAP NC No Connect
GND.
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.
Absolute Maximum Ratings(1)(2)
Supply Voltage 9.5V
Storage Temperature −65°C to +150°C
Input Voltage −0.3V to VDD + 0.3V
Power Dissipation(3) Internally limited
ESD Rating(4) 2000V
ESD Rating(5) 200V
Junction Temperature (TJMAX) 150°C
Thermal Resistance θJA (WSON)(3) 73°C/W
Soldering Information AN-1187 (Literature Number SNOA401)
(1) “Absolute Maximum Ratings” indicate limits beyond which damage to the device may occur, including inoperability and degradation of
device reliability and/or performance. Functional operation of the device and/or non-degradation at the sor other conditions beyond
those indicated in the Recommended Operating Conditions is not implied. The Recommended Operating Conditionsindicate conditions
at which the device is functional and the device should not be operated beyond such conditions. All voltages are measured with respect
to the ground pin, unless otherwise specified.
(2) The Electrical Characteristics tables list ensured specifications under the listed Recommended Operating Conditions except as
otherwise modified or specified by the Electrical Characteristics Conditions and/or Notes. Typical specifications are estimations only and
are not ensured.
(3) The maximum power dissipation must be derated at elevated temperatures and is dictated by TJMAX,θJA, and the ambient temperature,
TA. The maximum allowable power dissipation is PDMAX = (TJMAX - TA) / θJA or the number given in Absolute Maximum Ratings,
whichever is lower. For the LM4951A typical application (shown in Figure 1) with VDD = 7.5V, RL= 8Ωmono-BTL operation the max
power dissipation is 1.42W. θJA = 73ºC/W.
(4) Human body model, applicable std. JESD22-A114C.
(5) Machine model, applicable std. JESD22-A115-A.
Operating Ratings(1)(2)
Temperature Range TMIN ≤TA≤TMAX −40°C ≤TA≤+85°C
Supply Voltage 2.7V ≤VDD ≤9V
(1) “Absolute Maximum Ratings” indicate limits beyond which damage to the device may occur, including inoperability and degradation of
device reliability and/or performance. Functional operation of the device and/or non-degradation at the sor other conditions beyond
those indicated in the Recommended Operating Conditions is not implied. The Recommended Operating Conditionsindicate conditions
at which the device is functional and the device should not be operated beyond such conditions. All voltages are measured with respect
to the ground pin, unless otherwise specified.
(2) The Electrical Characteristics tables list ensured specifications under the listed Recommended Operating Conditions except as
otherwise modified or specified by the Electrical Characteristics Conditions and/or Notes. Typical specifications are estimations only and
are not ensured.
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Electrical Characteristics VDD = 7.5V(1)(2)
The following specifications apply for VDD = 7.5V, AV-BTL = 6dB, RL= 8Ωunless otherwise specified. Limits apply for TA=
25°C. LM4951A Units
Parameter Test Conditions (Limits)
Typ(3) Limit(4)
IDD Quiescent Power Supply Current VIN = 0V, IO= 0A, RL= 8ΩBTL 2.5 4.5 mA (max)
ISD Shutdown Current VSD = GND(5) 0.01 5 µA (max)
VOS Output Offset Voltage 5 30 mV (max)
VSDIH Shutdown Voltage Input High 1.2 V (min)
VSDIL Shutdown Voltage Input Low 0.4 V (max)
RPULLDOWN Pull-down Resistor on SD pin 75 45 kΩ(min)
TWU Wake-up Time CB= 1.0µF 25 35 ms (max)
TSD Shutdown time CB= 1.0µF 10 ms (max)
150 °C (min)
TSD Thermal Shutdown Temperature 170 190 °C (max)
THD = 1% (max); f = 1kHz
POOutput Power 1.8 1.5 W (min)
RL= 8ΩMono BTL
PO= 600mWRMS; f = 1kHz 0.07 0.5 % (max)
AV-BTL = 6dB
THD+N Total Harmonic Distortion + Noise PO= 600mWRMS; f = 1kHz 0.35 %
AV-BTL = 26dB
A-Weighted Filter, Ri= Rf= 20kΩ
εOS Output Noise 10 µV
Input Referred(6)
VRIPPLE = 200mVp-p, f = 217Hz,
PSRR Power Supply Rejection Ratio 66 56 dB (min)
CB= 1.0μF, Input Referred
(1) “Absolute Maximum Ratings” indicate limits beyond which damage to the device may occur, including inoperability and degradation of
device reliability and/or performance. Functional operation of the device and/or non-degradation at the sor other conditions beyond
those indicated in the Recommended Operating Conditions is not implied. The Recommended Operating Conditionsindicate conditions
at which the device is functional and the device should not be operated beyond such conditions. All voltages are measured with respect
to the ground pin, unless otherwise specified.
(2) The Electrical Characteristics tables list ensured specifications under the listed Recommended Operating Conditions except as
otherwise modified or specified by the Electrical Characteristics Conditions and/or Notes. Typical specifications are estimations only and
are not ensured.
(3) Typical values represent most likely parametric norms at TA= +25ºC, and at the Recommended Operation Conditions at the time of
product characterization and are not specified.
(4) Datasheet min/max specification limits are ensured by test or statistical analysis.
(5) Shutdown current is measured in a normal room environment. The Shutdown pin should be driven as close as possible to GND for
minimum shutdown current.
(6) Noise measurements are dependent on the absolute values of the closed loop gain setting resistors (input and feedback resistors).
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Electrical Characteristics VDD = 3.3V(1)(2)
The following specifications apply for VDD = 3.3V, AV-BTL = 6dB, RL= 8Ωunless otherwise specified. Limits apply for TA=
25°C. LM4951A Units
Parameter Test Conditions (Limits)
Typ(3) Limit(4)
IDD Quiescent Power Supply Current VIN = 0V, IO= 0A, RL= 8ΩBTL 2.5 4.5 mA (max)
ISD Shutdown Current VSHUTDOWN = GND(5) 0.01 2 µA (max)
VOS Output Offset Voltage 3 30 mV (max)
VSDIH Shutdown Voltage Input High 1.2 V (min)
VSDIL Shutdown Voltage Input Low 0.4 V (max)
TWU Wake-up Time CB= 1.0µF 25 ms
TSD Shutdown time CB= 1.0µF 10 ms (max)
THD = 1% (max); f = 1kHz
POOutput Power 280 230 mW (min)
RL= 8ΩMono BTL
PO= 100mWRMS = 1kHz 0.07 0.5 % (max)
AV-BTL = 6dB
THD+N Total Harmonic Distortion + Noise PO= 100mWRMS; f = 1kHz 0.35 %
AV-BTL = 26dB
A-Weighted Filter, Ri= Rf= 20kΩ
εOS Output Noise 10 µV
Input Referred,(6)
VRIPPLE = 200mVp-p, f = 217Hz,
PSRR Power Supply Rejection Ratio 71 61 dB (min)
CB= 1μF, Input Referred
(1) “Absolute Maximum Ratings” indicate limits beyond which damage to the device may occur, including inoperability and degradation of
device reliability and/or performance. Functional operation of the device and/or non-degradation at the sor other conditions beyond
those indicated in the Recommended Operating Conditions is not implied. The Recommended Operating Conditionsindicate conditions
at which the device is functional and the device should not be operated beyond such conditions. All voltages are measured with respect
to the ground pin, unless otherwise specified.
(2) The Electrical Characteristics tables list ensured specifications under the listed Recommended Operating Conditions except as
otherwise modified or specified by the Electrical Characteristics Conditions and/or Notes. Typical specifications are estimations only and
are not ensured.
(3) Typical values represent most likely parametric norms at TA= +25ºC, and at the Recommended Operation Conditions at the time of
product characterization and are not specified.
(4) Datasheet min/max specification limits are ensured by test or statistical analysis.
(5) Shutdown current is measured in a normal room environment. The Shutdown pin should be driven as close as possible to GND for
minimum shutdown current.
(6) Noise measurements are dependent on the absolute values of the closed loop gain setting resistors (input and feedback resistors).
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20 100 1k 20k
FREQUENCY (Hz)
0.01
0.02
0.05
0.1
0.2
0.5
1
2
5
10
THD+N (%)
10k
200 2k500 5k
50
20 200 2k 20k
FREQUENCY (Hz)
0.1
0.5
1
10
THD+N (%)
2
0.2
5
20 100 1k 20k
FREQUENCY (Hz)
0.01
0.02
0.05
0.1
0.2
0.5
1
2
5
10
THD+N (%)
10k
200 2k500 5k
50
20 100 1k 20k
FREQUENCY (Hz)
0.01
0.02
0.05
0.1
0.2
0.5
1
2
5
10
THD+N (%)
10k
200 2k500 5k
50
20 200 2k 20k
FREQUENCY (Hz)
0.01
0.1
1
10
THD+N (%)
20 100 1k 20k
FREQUENCY (Hz)
0.01
0.02
0.05
0.1
0.2
0.5
1
2
5
10
THD+N (%)
10k
200 2k500 5k
50
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Typical Performance Characteristics
THD+N vs Frequency THD+N vs Frequency
VDD = 3.3V, PO= 100mW, AV= 6dB VDD = 3.3V, PO= 100mW, AV= 26dB
Figure 3. Figure 4.
THD+N vs Frequency THD+N vs Frequency
VDD = 5V, PO= 400mW, AV= 6dB VDD = 5V, PO= 400mW, AV= 26dB
Figure 5. Figure 6.
THD+N vs Frequency THD+N vs Frequency
VDD = 7.5V, PO= 600mW, AV= 6dB VDD = 7.5V, PO= 600mW, AV= 26dB
Figure 7. Figure 8.
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10m 100m
OUTPUT POWER (W)
0.01
0.1
1
10
THD+N (%)
120m 200m 250m 500m 3
0.02
0.2
2
0.05
0.5
5
10m 100m
OUTPUT POWER (W)
0.1
10
THD+N (%)
120m 200m 250m 500m 3
1
0.2
2
0.5
5
100m 1
OUTPUT POWER (W)
0.1
1
10
THD+N (%)
10m 200m20m 500m50m
0.2
2
0.5
5
10m 100m 1
OUTPUT POWER (W)
0.01
0.02
0.05
0.1
0.2
0.5
1
2
5
10
THD+N (%)
20m 200m
50m 500m
10m 500m
OUTPUT POWER (W)
0.1
10
THD+N (%)
20m30m
40m
50m
60m
70m
80m 400m
300m
200m
100m
1
0.2
2
0.5
5
10m 30m 100m 500m
OUTPUT POWER (W)
0.01
0.1
10
THD+N (%)
1
LM4951A
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Typical Performance Characteristics (continued)
THD+N vs Output Power THD+N vs Output Power
VDD = 3.3V, f = 1kHz, AV= 6dB VDD = 3.3V, f = 1kHz, AV= 26dB
Figure 9. Figure 10.
THD+N vs Output Power THD+N vs Output Power
VDD = 5V, f = 1kHz, AV= 6dB VDD = 5V, f = 1kHz, AV= 26dB
Figure 11. Figure 12.
THD+N vs Output Power THD+N vs Output Power
VDD = 7.5V, f = 1kHz, AV= 6dB VDD = 7.5V, f = 1kHz, AV= 26dB
Figure 13. Figure 14.
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20 20k
FREQUENCY (Hz)
-100
+0
PSRR (dB)
10k1k 2k 5k50 100 200 500
-90
-80
-70
-60
-50
-40
-30
-20
-10
20 100 1k 20k
FREQUENCY (Hz)
-60
-45
-40
-35
-30
-25
-20
-15
-10
-5
+0
PSRR (dB)
-55
-50
10k
-47.5
-42.5
-37.5
-32.5
-27.5
-22.5
-17.5
-12.5
-7.5
-2.5
-57.5
-52.5
200 2k500 5k
50
20 20k
FREQUENCY (Hz)
-100
+0
PSRR (dB)
10k1k 2k 5k50 100 200 500
-90
-80
-70
-60
-50
-40
-30
-20
-10
20 100 1k 20k
FREQUENCY (Hz)
-60
-45
-40
-35
-30
-25
-20
-15
-10
-5
+0
PSRR (dB)
-55
-50
10k
-47.5
-42.5
-37.5
-32.5
-27.5
-22.5
-17.5
-12.5
-7.5
-2.5
-57.5
-52.5
200 2k500 5k
50
20 20k
FREQUENCY (Hz)
-100
+0
PSRR (dB)
10k1k 2k 5k50 100 200 500
-90
-80
-70
-60
-50
-40
-30
-20
-10
20 100 1k 20k
FREQUENCY (Hz)
-60
-45
-40
-35
-30
-25
-20
-15
-10
-5
+0
PSRR (dB)
-55
-50
10k
-47.5
-42.5
-37.5
-32.5
-27.5
-22.5
-17.5
-12.5
-7.5
-2.5
-57.5
-52.5
200 2k500 5k
50
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Typical Performance Characteristics (continued)
Power Supply Rejection vs Frequency Power Supply Rejection vs Frequency
VDD = 3.3V, AV= 6dB, VRIPPLE = 200mVP-P VDD = 3.3V, AV= 26dB, VRIPPLE = 200mVP-P
Input Terminated into 10ΩInput Terminated into 10Ω
Figure 15. Figure 16.
Power Supply Rejection vs Frequency Power Supply Rejection vs Frequency
VDD = 5V, AV= 6dB, VRIPPLE = 200mVP-P VDD = 5V, AV= 26dB, VRIPPLE = 200mVP-P
Input Terminated into 10ΩInput Terminated into 10Ω
Figure 17. Figure 18.
Power Supply Rejection vs Frequency Power Supply Rejection vs Frequency
VDD = 7.5V, AV= 6dB, VRIPPLE = 200mVP-P VDD = 7.5V, AV= 26dB, VRIPPLE = 200mVP-P
Input Terminated into 10ΩInput Terminated into 10Ω
Figure 19. Figure 20.
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20 20k
FREQUENCY (Hz)
1P
50P
OUTPUT NOISE VOLTAGE (V)
10k1k 2k 5k
2P
3P
4P
5P
6P
7P
8P
9P
40P
30P
20P
10P
50 100 200 500
20 20k
FREQUENCY (Hz)
50P
100P
150P
OUTPUT NOISE VOLTAGE (V)
10k1k 2k 5k50 100 200 500
62P
75P
85P
90P
120P
52P
55P
65P
72P
95P
82P
20 20k
FREQUENCY (Hz)
1P
50P
OUTPUT NOISE VOLTAGE (V)
10k1k 2k 5k
2P
3P
4P
5P
6P
7P
8P
9P
40P
30P
20P
10P
50 100 200 500
20 20k
FREQUENCY (Hz)
50P
100P
150P
OUTPUT NOISE VOLTAGE (V)
10k1k 2k 5k50 100 200 500
62P
75P
85P
90P
120P
52P
55P
65P
72P
95P
82P
20 20k
FREQUENCY (Hz)
1P
50P
OUTPUT NOISE VOLTAGE (V)
10k1k 2k 5k
2P
3P
4P
5P
6P
7P
8P
9P
40P
30P
20P
10P
50 100 200 500
20 20k
FREQUENCY (Hz)
50P
100P
150P
OUTPUT NOISE VOLTAGE (V)
10k1k 2k 5k50 100 200 500
62P
75P
85P
90P
120P
52P
55P
65P
72P
95P
82P
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Typical Performance Characteristics (continued)
Noise Floor Noise Floor
VDD = 3.3V, AV= 6dB, Ri= Rf= 20kΩVDD = 3V, AV= 26dB, Ri= 20kΩ, Rf= 200kΩ
BW < 80kHz, A-weighted BW < 80kHz, A-weighted
Figure 21. Figure 22.
Noise Floor Noise Floor
VDD = 5V, AV= 6dB, Ri= Rf= 20kΩVDD = 5V, AV= 26dB, Ri= 20kΩ, Rf= 200kΩ
BW < 80kHz, A-weighted BW < 80kHz, A-weighted
Figure 23. Figure 24.
Noise Floor Noise Floor
VDD = 7.5V, AV= 6dB, Ri= Rf= 20kΩVDD = 7.5V, AV= 26dB, Ri= 20kΩ, Rf= 200kΩ
BW < 80kHz, A-weighted BW < 80kHz, A-weighted
Figure 25. Figure 26.
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2.7
SUPPLY VOLTAGE (V)
0
0.5
1
1.5
2
2.5
3
3.5
4
OUTPUT POWER (mW)
3 3.5 4 4.5 5 5.5 6 6.5 7 7.5 8 8.5 9
0 20 100
LOAD RESISTANCE (W)
0
50
100
150
200
250
300
350
400
450
OUTPUT POWER (mW)
40 60 80
0 2 4 6 8 10
SUPPLY VOLTAGE (V)
0
0.2
0.4
0.6
0.8
1
1.2
1.4
DROPOUT VOPLTAGE (V)
2 3 4 5 6 7 8 9
SUPPLY VOLTAGE (V)
0
0.5
1
1.5
2
2.5
SUPPLY CURRENT (mA)
10
0 50 100 150 200 250 300
OUTPUT POWER (mW)
0
50
100
150
200
250
300
POWER DISSIPATION (mW)
0
OUTPUT POWER (mW)
POWER DISSIPATION (mW)
200 400 600 800 1000 1200 1400
0
200
400
600
800
1000
1200
1400
1600
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Typical Performance Characteristics (continued)
Power Dissipation Power Dissipation
vs Output Power vs Output Power
VDD = 3.3V, RL= 8Ω, f = 1kHz VDD = 7.5V, RL= 8Ω, f = 1kHz
Figure 27. Figure 28.
Clipping Voltage vs Supply Voltage
Supply Current RL= 8Ω,
vs Supply Voltage from top to bottom: Negative Voltage Swing; Positive
RL= 8Ω, VIN = 0V, Rsource = 50ΩVoltage Swing
Figure 29. Figure 30.
Output Power vs Supply Voltage Output Power vs Load Resistance
RL= 8Ω, VDD = 3.3V, f = 1kHz
from top to bottom: THD+N = 10%, THD+N = 1% from top to bottom: THD+N = 10%, THD+N = 1%
Figure 31. Figure 32.
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20 100 1k 20k
FREQUENCY (Hz)
-28
-24
-20
-16
-12
-8
-4
0
4
8
12
16
20
OUTPUT LEVEL (dB)
2k 5k 10k500200
50
8 16 4832
LOAD RESISTANCE (W)
0
500
1000
1500
2000
2500
3000
OUTPUT POWER (mW)
64 80 96 112
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Typical Performance Characteristics (continued)
Output Power vs Load Resistance Frequency Response vs Input Capacitor Size
VDD = 7.5V, f = 1kHz RL= 8Ω
from top to bottom: THD+N = 10%, THD+N = 1% from top to bottom: Ci= 1.0µF, Ci= 0.39µF, Ci= 0.039µF
Figure 33. Figure 34.
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APPLICATION INFORMATION
BRIDGE CONFIGURATION EXPLANATION
As shown in Figure 1, the LM4951A consists of two operational amplifiers that drive a speaker connected
between their outputs. The value of input and feedback resistors determine the gain of each amplifier. External
resistors Riand Rfset the closed-loop gain of AMPA, whereas two 20kΩinternal resistors set AMPB's gain to -1.
Figure 1 shows that AMPA's output serves as AMPB's input. This results in both amplifiers producing signals
identical in magnitude, but 180° out of phase. Taking advantage of this phase difference, a load is placed
between AMPAand AMPBand driven differentially (commonly referred to as "bridge-tied load"). This results in a
differential, or BTL, gain of:
AVD = 2(Rf/Ri) (V/V) (1)
Bridge mode amplifiers are different from single-ended amplifiers that drive loads connected between a single
amplifier's output and ground. For a given supply voltage, bridge mode has an advantage over the single-ended
configuration: its differential output doubles the voltage swing across the load. Theoretically, this produces four
times the output power when compared to a single-ended amplifier under the same conditions. This increase in
attainable output power assumes that the amplifier is not current limited and that the output signal is not clipped.
Under rare conditions, with unique combinations of high power supply voltage and high closed loop gain settings,
the LM4951A may exhibit low frequency oscillations.
Another advantage of the differential bridge output is no net DC voltage across the load. This is accomplished by
biasing AMP1's and AMP2's outputs at half-supply. This eliminates the coupling capacitor that single supply,
single-ended amplifiers require. Eliminating an output coupling capacitor in a typical single-ended configuration
forces a single-supply amplifier's half-supply bias voltage across the load. This increases internal IC power
dissipation and may permanently damage loads such as speakers.
POWER DISSIPATION
The LM4951A's dissipation when driving a BTL load is given by Equation 2. For a 7.5V supply and a single 8Ω
BTL load, the dissipation is 1.42W.
PDMAX-MONOBTL = 4(VDD)2/2π2RL(W) (2)
The maximum power dissipation point given by Equation 2 must not exceed the power dissipation given by
Equation 3:
PDMAX = (TJMAX - TA)/θJA (3)
The LM4951A's TJMAX = 150°C. In the SD package, the LM4951A's θJA is 73°C/W when the metal tab is soldered
to a copper plane of at least 1in2. This plane can be split between the top and bottom layers of a two-sided PCB.
Connect the two layers together under the tab with an array of vias. At any given ambient temperature TA, use
Equation 3 to find the maximum internal power dissipation supported by the IC packaging. Rearranging
Equation 3 and substituting PDMAX for PDMAX' results in Equation 4. This equation gives the maximum ambient
temperature that still allows maximum stereo power dissipation without violating the LM4951A's maximum
junction temperature.
TA= TJMAX - PDMAX-MONOBTLθJA (°C) (4)
For a typical application with a 7.5V power supply and a BTL 8Ωload, the maximum ambient temperature that
allows maximum stereo power dissipation without exceeding the maximum junction temperature is 46°C for the
SD package.
TJMAX = PDMAX-MONOBTLθJA + TA(°C) (5)
Equation 5 gives the maximum junction temperature TJMAX. If the result violates the LM4951A's maximum
junction temperature of 150°C, reduce the maximum junction temperature by reducing the power supply voltage
or increasing the load resistance. Further allowance should be made for increased ambient temperatures.
The above examples assume that a device is operating around the maximum power dissipation point. Since
internal power dissipation is a function of output power, higher ambient temperatures are allowed as output
power or duty cycle decreases.
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If the result of Equation 2 is greater than that of Equation 3, then decrease the supply voltage, increase the load
impedance, or reduce the ambient temperature. Further, ensure that speakers rated at a nominal 8Ωdo not fall
below 6Ω. If these measures are insufficient, a heat sink can be added to reduce θJA. The heat sink can be
created using additional copper area around the package, with connections to the ground pins, supply pin and
amplifier output pins. Refer to the Typical Performance Characteristics curves for power dissipation information at
lower output power levels.
POWER SUPPLY BYPASSING
As with any power amplifier, proper supply bypassing is critical for low noise performance and high power supply
rejection. Applications that employ a voltage regulator typically use a 10µF in parallel with a 0.1µF filter
capacitors to stabilize the regulator's output, reduce noise on the supply line, and improve the supply's transient
response. However, their presence does not eliminate the need for a local 1.0µF tantalum bypass capacitance
connected between the LM4951A's supply pins and ground. Do not substitute a ceramic capacitor for the
tantalum. Doing so may cause oscillation. Keep the length of leads and traces that connect capacitors between
the LM4951A's power supply pin and ground as short as possible. Connecting a larger capacitor, CBYPASS,
between the BYPASS pin and ground improves the internal bias voltage's stability and improves the amplifier's
PSRR. The PSRR improvements increase as the bypass pin capacitor value increases. Too large, however,
increases turn-on time and can compromise the amplifier's click and pop performance. The selection of bypass
capacitor values, especially CBYPASS, depends on desired PSRR requirements, click and pop performance,
system cost, and size constraints.
MICRO-POWER SHUTDOWN
The LM4951A features an active-low micro-power shutdown mode. When active, the LM4951A's micro-power
shutdown feature turns off the amplifier's bias circuitry, reducing the supply current. The low 0.01µA typical
shutdown current is achieved by applying a voltage to the SHUTDOWN pin that is as near to GND as possible. A
voltage that is greater than GND may increase the shutdown current.
SELECTING EXTERNAL COMPONENTS
Input Capacitor Value Selection
Two quantities determine the value of the input coupling capacitor: the lowest audio frequency that requires
amplification and desired output transient suppression.
As shown in Figure 1, the input resistor (Ri) and the input capacitor (Ci) create a high-pass filter. The cutoff
frequency can be found using Equation 6.
fc= 1/2πRiCi(Hz) (6)
As an example when using a speaker with a low frequency limit of 50Hz, Ci, using Equation 6 is 0.159µF with Ri
set to 20kΩ. The values for Ciand Rishown in Figure 1 allow the LM4951A to drive a high efficiency, full range
speaker whose response extends down to 20Hz.
Selecting Value A For RC
The LM4951A is designed for very fast turn on time. The CCHG pin allows the input capacitor to charge quickly to
improve click/pop performance. RCprotects the CCHG pin from any over/under voltage conditions caused by
excessive input signal or an active input signal when the device is in shutdown. The recommended value for RC
is 1kΩ. If the input signal is less than VDD+0.3V and greater than -0.3V, and if the input signal is disabled when in
shutdown mode, RCmay be shorted out.
OPTIMIZING CLICK AND POP REDUCTION PERFORMANCE
The LM4951A contains circuitry that eliminates turn-on and shutdown transients ("clicks and pops"). For this
discussion, turn-on refers to either applying the power supply voltage or when the micro-power shutdown mode
is deactivated.
As the VDD/2 voltage present at the BYPASS pin ramps to its final value, the LM4951A's internal amplifiers are
configured as unity gain buffers. An internal current source charges the capacitor connected between the
BYPASS pin and GND in a controlled manner. Ideally, the input and outputs track the voltage applied to the
BYPASS pin.
Copyright © 2008–2013, Texas Instruments Incorporated Submit Documentation Feedback 13
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The gain of the internal amplifiers remains unity until the voltage on the bypass pin reaches VDD/2. As soon as
the voltage on the bypass pin is stable, there is a delay to prevent undesirable output transients (“click and
pops”). After this delay, the device becomes fully functional.
THERMAL SHUTDOWN AND SHORT CIRCUIT PROTECTION
The LM4951A has thermal shutdown and short circuit protection to fully protect the device. The thermal
shutdown circuit is activated when the die temperature exceeds a safe temperature. The short circuit protection
circuitry senses the output current. When the output current exceeds the threshold under a short condition, a
short will be detected and the output deactivated until the short condition is removed. If the output current is
lower than the threshold then a short will not be detected and the outputs will not be deactivated. Under such
conditions the die temperature will increase and, if the condition persist to raise the die temperature to the
thermal shutdown threshold, initiate a thermal shutdown response. Once the die cools the outputs will become
active.
RECOMMENDED PRINTED CIRCUIT BOARD LAYOUT
Figures 2–4 show the recommended two-layer PC board layout that is optimized for the SD10A. This circuit is
designed for use with an external 7.5V supply 8Ω(min) speakers.
Demonstration Board Circuit
Figure 35. Demo Board Circuit
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Figure 38. Bottom Layer
Bill Of Materials
Table 1. Bill Of Materials
Designator Value Tolerance Part Description Comments
RIN1 20kΩ1% 1/8W, 0805 Resistor
R1200kΩ1% 1/8W, 0805 Resistor
RPULLUP 100kΩ1% 1/8W, 0805 Resistor
R21kΩ1% 1/8W, 0805 Resistor
R4, R50Ω1% 1/8W, 0805 Resistor
CIN1 0.39μF 10% Ceramic Capacitor, 25V, Size 1206
CSUPPLY 4.7μF 10% 16V Tantalum Capacitor, Size A
CBYPASS 1μF 10% 16V Tantalum Capacitor, Size A
C1Not Used
0.100” 1x2 header, vertical mount Input, Output, Vdd/GND Shutdown
U1LM4951A, Mono, 1.8W, Audio Amplifier DPR0010A package
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SNAS453C –AUGUST 2008–REVISED APRIL 2013
REVISION HISTORY
Rev Date Description
1.0 08/13/08 Initial release.
1.01 09/05/08 Text edits.
Changes from Revision B (April 2013) to Revision C Page
• Changed layout of National Data Sheet to TI format .......................................................................................................... 16
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PACKAGE OPTION ADDENDUM
www.ti.com 14-Feb-2014
Addendum-Page 1
PACKAGING INFORMATION
Orderable Device Status
(1)
Package Type Package
Drawing Pins Package
Qty Eco Plan
(2)
Lead/Ball Finish
(6)
MSL Peak Temp
(3)
Op Temp (°C) Device Marking
(4/5)
Samples
LM4951ASD/NOPB ACTIVE WSON DPR 10 1000 Green (RoHS
& no Sb/Br) CU SN Level-1-260C-UNLIM -40 to 85 4951ASD
LM4951ASDX/NOPB ACTIVE WSON DPR 10 4500 Green (RoHS
& no Sb/Br) CU SN Level-1-260C-UNLIM -40 to 85 4951ASD
(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.
(4) There may be additional marking, which relates to the logo, the lot trace code information, or the environmental category on the device.
(5) Multiple Device Markings will be inside parentheses. Only one Device Marking contained in parentheses and separated by a "~" will appear on a device. If a line is indented then it is a continuation
of the previous line and the two combined represent the entire Device Marking for that device.
(6) Lead/Ball Finish - Orderable Devices may have multiple material finish options. Finish options are separated by a vertical ruled line. Lead/Ball Finish values may wrap to two lines if the finish
value exceeds the maximum column width.
Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on information
provided by third parties, and makes no representation or warranty as to the accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and
continues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals.
TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited information may not be available for release.
PACKAGE OPTION ADDENDUM
www.ti.com 14-Feb-2014
Addendum-Page 2
In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI to Customer on an annual basis.
TAPE AND REEL INFORMATION
*All dimensions are nominal
Device Package
Type Package
Drawing Pins SPQ Reel
Diameter
(mm)
Reel
Width
W1 (mm)
A0
(mm) B0
(mm) K0
(mm) P1
(mm) W
(mm) Pin1
Quadrant
LM4951ASD/NOPB WSON DPR 10 1000 178.0 12.4 4.3 4.3 1.3 8.0 12.0 Q1
LM4951ASDX/NOPB WSON DPR 10 4500 330.0 12.4 4.3 4.3 1.3 8.0 12.0 Q1
PACKAGE MATERIALS INFORMATION
www.ti.com 11-Oct-2013
Pack Materials-Page 1
*All dimensions are nominal
Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm)
LM4951ASD/NOPB WSON DPR 10 1000 210.0 185.0 35.0
LM4951ASDX/NOPB WSON DPR 10 4500 367.0 367.0 35.0
PACKAGE MATERIALS INFORMATION
www.ti.com 11-Oct-2013
Pack Materials-Page 2
MECHANICAL DATA
DPR0010A
www.ti.com
SDC10A (Rev A)
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