NSC LM4842MH Stereo 2w amplifiers with dc volume control transient free outputs, and cap-less headphone drive Datasheet

LM4842
Stereo 2W Amplifiers with DC Volume Control,
Transient Free Outputs, and Cap-less Headphone Drive
General Description
Key Specifications
The LM4842 is a monolithic integrated circuit that provides
DC volume control, and stereo bridged audio power amplifiers capable of producing 2W into 4Ω (Note 1) or 2.2W into
3Ω (Note 2) with less than 1.0% THD+N.
Boomer ® audio integrated circuits were designed specifically
to provide high quality audio while requiring a minimum
amount of external components. The LM4842 incorporates a
DC volume control, stereo bridged audio power amplifiers,
new cap-less headphone driver circuit (patent pending), selectable gain or bass boost, and an input mux making it
optimally suited for multimedia monitors, portable radios,
desktop, and portable computer applications.
The LM4842 features an externally controlled, low-power
consumption shutdown mode (Shutdown Low), and both a
power amplifier and headphone mute for maximum system
flexibility and performance.
n PO at 1% THD+N
n
into 3Ω (MH and LQ)
n
into 4Ω (MH and LQ)
n
into 8Ω (MT, MH, and LQ)
n Single-ended THD+N at 85mW into 32Ω
n Shutdown current (Shutdown Low)
Note 1: When properly mounted to the circuit board, the LM4842MH will
deliver 2W into 4Ω. The LM4842MT will deliver 1.1W into 8Ω. See the
Application Information section for LM4842MH usage information.
Note 2: An LM4842MH that has been properly mounted to the circuit board
and forced-air cooled will deliver 2.2W into 3Ω.
2.2W(typ)
2.0W(typ)
1.1W(typ)
1.0%(typ)
0.2µA(typ)
Features
n Stereo headphone amplifier mode that eliminates the
Output Coupling Capacitors (patent pending)
n Advanced “click and pop” suppression circuitry
n Acoustically Enhanced DC Volume Control Taper
n 2 Channel Stereo Input MUX
n System Beep Detect
n Stereo switchable bridged/single-ended power amplifiers
n Selectable internal/external gain and bass boost
n Thermal shutdown protection circuitry
Applications
n Portable and Desktop Computers
n Multimedia Monitors
n Portable Radios, PDAs, and Portable TVs
Connection Diagrams
TSSOP Package
20028102
Top View
Order Number LM4842MT
See NS Package Number MTC28 for TSSOP
Order Number LM4842MH
See NS Package Number MXA28A for Exposed-DAP TSSOP
Boomer ® is a registered trademark of NationalSemiconductor Corporation.
© 2002 National Semiconductor Corporation
DS200281
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LM4842 Stereo 2W Amplifiers with DC Volume Control,
Transient Free Outputs, and Cap-less Headphone Drive
September 2002
LM4842
Connection Diagrams
(Continued)
LM4842LQ Pinout
200281A3
Top View
Order Number LM4842LQ
See NS Package Number LQA028AA for Exposed-DAP LLP
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Block Diagram
FIGURE 1. Typical Application Circuit
20028192
LM4842
3
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LM4842
Absolute Maximum Ratings
(Note 10)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
Supply Voltage
6.0V
Storage Temperature
θJC (typ) — LQA028A
3˚C/W
θJA (typ) — LQA028A
42˚C/W
θJC (typ) — MTC28
20˚C/W
θJA (typ) — MTC28
80˚C/W
θJC (typ) — MXA28A
-65˚C to +150˚C
2˚C/W
θJA (typ) — MXA28A (exposed
DAP) (Note 4)
41˚C/W
Internally limited
θJA (typ) — MXA28A (exposed
DAP) (Note 3)
54˚C/W
All pins except Pin 28
2500V
59˚C/W
Pin 28
6500V
θJA (typ) — MXA28A (exposed
DAP) (Note 5)
93˚C/W
−0.3V to VDD +0.3V
Input Voltage
Power Dissipation (Note 11)
ESD Susceptibility (Note 12)
Junction Temperature
150˚C
θJA (typ) — MXA28A (exposed
DAP) (Note 6)
Soldering Information
Vapor Phase (60 sec.)
215˚C
Operating Ratings
Infrared (15 sec.)
220˚C
ESD Susceptibility (Note 13)
200V
See AN-450 “Surface Mounting and their Effects on
Product Reliability” for other methods of soldering surface
mount devices.
Temperature Range
TMIN ≤ TA ≤TMAX
−40˚C ≤TA ≤ 85˚C
Supply Voltage
2.7V≤ VDD ≤ 5.5V
Electrical Characteristics for Entire IC (Notes 7, 10)
The following specifications apply for VDD = 5V and TA = 25˚C unless otherwise noted.
LM4842
Symbol
VDD
Parameter
Conditions
Typical
(Note 14)
Limit
(Note 15)
Supply Voltage
Units
(Limits)
2.7
V (min)
5.5
V (max)
mA (max)
IDD
Quiescent Power Supply Current
VIN = 0V, IO = 0A
15
30
ISD
Shutdown Current
VShutdown = GND
0.7
2.0
VIH
VIN High on all Logic Inputs
0.8 x VDD
V (min)
VIL
VIN Low on all Logic Inputs
0.2 x VDD
V (max)
THum
Un-Mute Threshold Voltage
22
VShutdown = VDD,
Gain 1st Stage = 1
10
40
µA (max)
mVRMS
mVRMS
Electrical Characteristics for Volume Attenuators (Notes 7, 10)
The following specifications apply for VDD = 5V and TA = 25˚C unless otherwise noted.
LM4842
Symbol
Parameter
Conditions
Typical
(Note 14)
Limit
(Note 15)
Units
(Limits)
± 0.75
dB (max)
-75
dB (min)
CRANGE
Attenuator Range
Gain with VDCVol = 5.0V, No Load
CRANGE
Attenuator Range
Attenuation with VDCVol = 0V (BM &
SE)
AM
Mute Attenuation
Vmute = 5V, Bridged Mode (BM)
-78
dB (min)
Vmute = 5V, Single-Ended Mode (SE)
-78
dB (min)
Electrical Characteristics for Single-Ended Mode Operation
(Notes 7, 10)
The following specifications apply for VDD = 5V and TA = 25˚C unless otherwise noted.
LM4842
Symbol
PO
Parameter
Output Power
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Units
(Limits)
Conditions
Typical
(Note 14)
THD+N = 1.0%; f = 1kHz; RL = 32Ω
85
mW
THD+N = 10%; f = 1 kHz; RL = 32Ω
95
mW
4
Limit
(Note 15)
LM4842
Electrical Characteristics for Single-Ended Mode Operation
(Notes 7,
10) (Continued)
The following specifications apply for VDD = 5V and TA = 25˚C unless otherwise noted.
LM4842
Symbol
Parameter
Units
(Limits)
Conditions
Typical
(Note 14)
0.065
%
Limit
(Note 15)
THD+N
Total Harmonic Distortion+Noise
VOUT = 1VRMS, f=1kHz, RL = 10kΩ,
AVD = 1
PSRR
Power Supply Rejection Ratio
CB = 1.0 µF, f =120 Hz,
VRIPPLE = 200 mVrms
58
dB
SNR
Signal to Noise Ratio
POUT =75 mW, R
Filter
102
dB
Xtalk
Channel Separation
f=1kHz, CB = 1.0 µF
65
dB
L
= 32Ω, A-Wtd
Electrical Characteristics for Bridged Mode Operation
(Notes 7, 10)
The following specifications apply for VDD = 5V and TA = 25˚C unless otherwise noted.
LM4842
Symbol
Parameter
Conditions
Typical
(Note 14)
Limit
(Note 15)
5
± 50
Units
(Limits)
VOS
Output Offset Voltage
VIN = 0V, No Load
PO
Output Power
THD + N = 1.0%; f=1kHz; RL = 3Ω
(Note 8)
2.2
W
THD + N = 1.0%; f=1kHz; RL = 4Ω
(Note 9)
2
W
THD = 1.0% (max);f = 1 kHz;
RL = 8Ω
1.1
1.0
mV (max)
W (min)
THD+N = 10%;f = 1 kHz; RL = 8Ω
1.5
W
THD+N
Total Harmonic Distortion+Noise
PO = 1W, 20 Hz < f < 20 kHz,
RL = 8Ω, AVD = 2
0.3
%
PO = 340 mW, RL = 32Ω
1.0
%
PSRR
Power Supply Rejection Ratio
CB = 1.0 µF, f = 120 Hz,
VRIPPLE = 200 mVrms; RL = 8Ω
74
dB
SNR
Signal to Noise Ratio
VDD = 5V, POUT = 1.1W, RL = 8Ω,
A-Wtd Filter
93
dB
Xtalk
Channel Separation
f=1kHz, CB = 1.0 µF
70
dB
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LM4842
Electrical Characteristics for Bridged Mode Operation
(Notes 7, 10) (Continued)
Note 3: The θJA given is for an MXA28A package whose exposed-DAP is soldered to an exposed 2in 2 piece of 1 ounce printed circuit board copper.
Note 4: The θJA given is for an MXA28A package whose exposed-DAP is soldered to a 2in2 piece of 1 ounce printed circuit board copper on a bottom side layer
through 21 8mil vias.
Note 5: The θJA given is for an MXA28A package whose exposed-DAP is soldered to an exposed 1in 2 piece of 1 ounce printed circuit board copper.
Note 6: The θJA given is for an MXA28A package whose exposed-DAP is not soldered to any copper.
Note 7: All voltages are measured with respect to the ground pins, unless otherwise specified. All specifications are tested using the typical application as shown
in Figure 2.
Note 8: When driving 3Ω loads from a 5V supply the LM4842MH and LM4842LQ exposed DAP must be soldered to the circuit board and forced-air cooled.
Note 9: When driving 4Ω loads from a 5V supply the LM4842MH and LM4842LQ exposed DAP must be soldered to the circuit board.
Note 10: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is
functional, but do not guarantee specific performance limits. Electrical Characteristics state DC and AC electrical specifications under particular test conditions which
guarantee specific performance limits. This assumes that the device is within the Operating Ratings. Specifications are not guaranteed for parameters where no limit
is given, however, the typical value is a good indication of device performance.
Note 11: The maximum power dissipation must be derated at elevated temperatures and is dictated by TJMAX, θ JA, and the ambient temperature TA. The maximum
allowable power dissipation is PDMAX = (TJMAX − TA )/θJA. For the LM4842MT and LM4842LQ, TJMAX = 150˚C. See Power Dissipation for further information.
Note 12: Human body model, 100 pF discharged through a 1.5 kΩ resistor.
Note 13: Machine Model, 220 pF–240 pF discharged through all pins.
Note 14: Typicals are measured at 25˚C and represent the parametric norm.
Note 15: Limits are guaranteed to National’s AOQL (Average Outgoing Quality Level.) Datasheet min/max specification limits are guaranteed by design, test, or
statistical analysis.
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Typical Application
FIGURE 2. Typical Application Circuit ( MT & MH pinout )
20028191
LM4842
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LM4842
Truth Table for Logic Inputs
(Note 16)
Mute
Mode
Mux
Control
HP Sense
Bass
Boost
Inputs Selected
Bridged Output
Single-Ended
Output
0
0
0
0
on
A0 & B0
Vol. Adjustable
-
0
0
0
1
off
A0 & B0
Muted
Vol. Adjustable
0
0
1
0
on
A1 & B1
Vol. Adjustable
-
0
0
1
1
off
A1 & B1
Muted
Vol. Adjustable
0
1
X
0
on
A0 & B0
Vol. Adjustable
-
0
1
X
1
off
A1 & B1
Muted
Vol. Adjustable
1
X
X
X
muted
X
Muted
Muted
Note 16: If system beep is detected on the Beep In and the beep signal is fed to the inputs, the system beep will be passed through the bridged amplifier regardless
of the logic of the Mute, HP sense, or DC Volume Control pins.
Typical Performance Characteristics
MH/LQ Specific Characteristics
LM4842MH/LQ
THD+N vs Output Power
LM4842MH/LQ
THD+N vs Frequency
20028171
20028170
LM4842MH/LQ
THD+N vs Output Power
LM4842MH/LQ
THD+N vs Frequency
20028172
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20028173
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LM4842
Typical Performance Characteristics
MH/LQ Specific Characteristics (Continued)
LM4842MH/LQ
Power Dissipation vs Output Power
LM4842MH/LQ (Note 17)
Power Derating Curve
20028164
20028165
Note 17: These curves show the thermal dissipation ability of the LM4842MH/LQ at different ambient temperatures given these conditions:
500LFPM + 2in2: The part is soldered to a 2in2, 1 oz. copper plane with 500 linear feet per minute of forced-air flow across it.
2in2on bottom: The part is soldered to a 2in2, 1oz. copper plane that is on the bottom side of the PC board through 21 8 mil vias.
2in2: The part is soldered to a 2in2, 1oz. copper plane.
1in2: The part is soldered to a 1in2, 1oz. copper plane.
Not Attached: The part is not soldered down and is not forced-air cooled.
Non-MH/LQ Specific Characteristics
THD+N vs Frequency
THD+N vs Frequency
20028157
20028158
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LM4842
Non-MH/LQ Specific Characteristics
(Continued)
THD+N vs Frequency
THD+N vs Frequency
20028114
20028115
THD+N vs Frequency
THD+N vs Frequency
20028116
20028117
THD+N vs Frequency
THD+N vs Frequency
20028118
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20028119
10
LM4842
Non-MH/LQ Specific Characteristics
(Continued)
THD+N vs Frequency
THD+N vs Frequency
20028120
20028121
THD+N vs Frequency
THD+N vs Output Power
20028124
20028122
THD+N vs Output Power
THD+N vs Output Power
20028125
20028126
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LM4842
Non-MH/LQ Specific Characteristics
(Continued)
THD+N vs Output Power
THD+N vs Output Power
20028127
20028128
THD+N vs Output Power
THD+N vs Output Power
20028130
20028129
THD+N vs Output Power
THD+N vs Output Power
20028131
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20028132
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LM4842
Non-MH/LQ Specific Characteristics
(Continued)
THD+N vs Output Power
THD+N vs Output Power
20028134
20028133
THD+N vs Output Voltage
Docking Station Pins
THD+N vs Output Voltage
Docking Station Pins
20028160
20028159
Output Power vs
Load Resistance
Output Power vs
Load Resistance
20028162
20028106
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LM4842
Non-MH/LQ Specific Characteristics
(Continued)
Output Power vs
Load Resistance
Output Power vs
Load Resistance
20028107
20028108
Power Dissipation vs
Output Power
Dropout Voltage
20028151
20028153
Power Supply
Rejection Ratio
Volume Control
Characteristics
20028135
20028136
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LM4842
Non-MH/LQ Specific Characteristics
(Continued)
Power Dissipation vs
Output Power
External Gain/Bass Boost
Characteristics
20028161
20028152
Power Derating Curve
Crosstalk
20028163
20028149
Output Power
vs Supply voltage
Output Power
vs Supply Voltage
20028154
20028156
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LM4842
Non-MH/LQ Specific Characteristics
(Continued)
Supply Current
vs Supply Voltage
20028109
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LM4842
Application Information
ELIMINATING OUTPUT COUPLING CAPACITORS
Typical single-supply audio amplifiers that can switch between driving bridge-tied-load (BTL) speakers and
single-ended (SE) headphones use a coupling capacitor on
each SE output. This capacitor blocks the half-supply voltage to which the output amplifiers are typically biased and
couples the audio signal to the headphones. The signal
return to circuit ground is through the headphone jack’s
sleeve.
The LM4842 eliminates these coupling capacitors. AmplifierA+ (pin 28 on MT/MH) is internally configured to apply
VDD/2 to a stereo headphone jack’s sleeve. This voltage
matches the quiescent voltage present on the AmpAout- and
AmpBout- outputs that drive the headphones. The headphones operate in a manner very similar to a
bridge-tied-load (BTL). The same DC voltage is applied to
both headphone speaker terminals. This results in no net DC
current flow through the speaker. AC current flows through a
headphone speaker as an audio signal’s output amplitude
increases on the speaker’s terminal.
When operating as a headphone amplifier, the headphone
jack sleeve is not connected to circuit ground. Using the
headphone output jack as a line-level output will place the
LM4842’s one-half supply voltage on a plug’s sleeve connection. Driving a portable notebook computer or
audio-visual display equipment is possible. This presents no
difficulty when the external equipment uses capacitively
coupled inputs. For the very small minority of equipment that
is DC-coupled, the LM4842 monitors the current supplied by
the amplifier that drives the headphone jack’s sleeve. If this
current exceeds 500mAPK, the amplifier is shutdown, protecting the LM4842 and the external equipment. For more
information, see the section titled ’Single-Ended Output
Power Performance and Measurement Considerations’.
20028198
FIGURE 3. Differential output signal (Trace B) is devoid
of transients. The SHUTDOWN pin is driven by a
shutdown signal (Trace A). The inverting output (Trace
C) and the non-inverting output (Trace D) are applied
across an 8Ω BTL load.
Figure 3 shows the LM4842’s lack of transients in the differential signal (Trace B) across a BTL 8Ω load. The LM4842’s
active-high SHUTDOWN pin is driven by the logic signal
shown in Trace A. Trace C is the VOUT- output signal and
trace D is the VOUT+ output signal. The shutdown signal
frequency is 1Hz with a 50% duty cycle. Figure 4 is generated with the same conditions except that the output drives a
32Ω single-ended (SE) load. Again, no trace of output transients on Trace B can be observed.
OUTPUT TRANSIENT (’POPS AND CLICKS’)
ELIMINATED
The LM4842 contains advanced circuitry that eliminates output transients (’pop and click’). This circuitry prevents all
traces of transients when the supply voltage is first applied,
when the part resumes operation after shutdown, or when
switching between BTL speakers and SE headphones. Two
circuits combine to eliminate pop and click. One circuit
mutes the output when switching between speaker loads.
Another circuit monitors the input signal. It maintains the
muted condition until there is sufficient input signal magnitude ( > 22mVRMS, typ) to mask any remaining transient that
may occur. (See Turn On Characteristics).
20028199
FIGURE 4. Single-ended output signal (Trace B) is
devoid of transients. The SHUTDOWN pin is driven by
a shutdown signal (Trace A). The inverting output
(Trace C) and the VBYPASS output (Trace D) are applied
across a 32Ω BTL load.
EXPOSED-DAP PACKAGE PCB MOUNTING
CONSIDERATIONS
The LM4842’s exposed-DAP (die attach paddle) package
(MH,LQ) provides a low thermal resistance between the die
and the PCB to which the part is mounted and soldered. This
allows rapid heat transfer from the die to the surrounding
PCB copper traces, ground plane and, finally, surrounding
air. The result is a low voltage audio power amplifier that
produces 2.1W at ≤ 1% THD with a 4Ω load. This high power
is achieved through careful consideration of necessary ther-
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LM4842
Application Information
BRIDGE CONFIGURATION EXPLANATION
As shown in Figure 1, the LM4842 output stage consists of
two pairs of operational amplifiers, forming a two-channel
(channel A and channel B) stereo amplifier. (Though the
following discusses channel A, it applies equally to channel
B.)
Figure 1 shows that the first amplifier’s negative (-) output
serves as the second amplifier’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 −OUTA and +OUTA and driven differentially (commonly referred to as “bridge mode”). This
results in a differential gain of
(Continued)
mal design. Failing to optimize thermal design may compromise the LM4842’s high power performance and activate
unwanted, though necessary, thermal shutdown protection.
The MH and LQ packages must have their exposed DAPs
soldered to a grounded copper pad on the PCB. The DAP’s
PCB copper pad is connected to a large grounded plane of
continuous unbroken copper. This plane forms a thermal
mass heat sink and radiation area. Place the heat sink area
on either outside plane in the case of a two-sided PCB, or on
an inner layer of a board with more than two layers. Connect
the DAP copper pad to the inner layer or backside copper
heat sink area with 32(4x8) MH or 6(3x2) LQ vias. The via
diameter should be 0.012in–0.013in with a 1.27mm pitch.
Ensure efficient thermal conductivity by plating-through and
solder-filling the vias.
AVD = 2 * (Rf/R i)
(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 a distinct advantage over the single-ended configuration: its differential output doubles the voltage
swing across the load. 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 or that the
output signal is not clipped. To ensure minimum output signal clipping when choosing an amplifier’s closed-loop gain,
refer to the Audio Power Amplifier Design section.
Another advantage of the differential bridge output is no net
DC voltage across the load. This is accomplished by biasing
channel A’s and channel B’s outputs at half-supply. This
eliminates the coupling capacitor that single supply, singleended amplifiers require. Eliminating an output coupling capacitor in a 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.
Best thermal performance is achieved with the largest practical copper heat sink area. If the heatsink and amplifier
share the same PCB layer, a nominal 2.5in2 (min) area is
necessary for 5V operation with a 4Ω load. Heatsink areas
not placed on the same PCB layer as the LM4842MH and
LQ packages should be 5in2 (min) for the same supply
voltage and load resistance. The last two area recommendations apply for 25˚C ambient temperature. Increase the
area to compensate for ambient temperatures above 25˚C.
The junction temperature must be held below 150˚C to prevent activating the LM4842’s thermal shutdown protection.
The LM4842’s power de-rating curve in the Typical Performance Characteristics shows the maximum power dissipation versus temperature. Example PCB layouts for the
exposed-DAP TSSOP and LQ packages are shown in the
Demonstration Board Layout section. Further detailed and
specific information concerning PCB layout and fabrication is
available in National Semiconductor’s AN1187.
PCB LAYOUT AND SUPPLY REGULATION
CONSIDERATIONS FOR DRIVING 3Ω AND 4Ω LOADS
Power dissipated by a load is a function of the voltage swing
across the load and the load’s impedance. As load impedance decreases, load dissipation becomes increasingly dependent on the interconnect (PCB trace and wire) resistance
between the amplifier output pins and the load’s connections. Residual trace resistance causes a voltage drop,
which results in power dissipated in the trace and not in the
load as desired. For example, 0.1Ω trace resistance reduces
the output power dissipated by a 4Ω load from 2.1W to 2.0W.
This problem of decreased load dissipation is exacerbated
as load impedance decreases. Therefore, to maintain the
highest load dissipation and widest output voltage swing,
PCB traces that connect the output pins to a load must be as
wide as possible.
Poor power supply regulation adversely affects maximum
output power. A poorly regulated supply’s output voltage
decreases with increasing load current. Reduced supply
voltage causes decreased headroom, output signal clipping,
and reduced output power. Even with tightly regulated supplies, trace resistance creates the same effects as poor
supply regulation. Therefore, making the power supply
traces as wide as possible helps maintain full output voltage
swing.
POWER DISSIPATION
Power dissipation is a major concern when
successful single-ended or bridged amplifier.
states the maximum power dissipation point
ended amplifier operating at a given supply
driving a specified output load.
PDMAX = (VDD)2/(2π2RL)
designing a
Equation (2)
for a singlevoltage and
Single-Ended
(2)
However, a direct consequence of the increased power delivered to the load by a bridge amplifier is higher internal
power dissipation for the same conditions.
The LM4842 has two operational amplifiers per channel. The
maximum internal power dissipation per channel operating in
the bridge mode is four times that of a single-ended amplifier. From Equation (3), assuming a 5V power supply and a
4Ω load, the maximum single channel power dissipation is
1.27W or 2.54W for stereo operation.
PDMAX = 4 * (VDD)2/(2π2RL)
Bridge Mode
(3)
The LM4842’s power dissipation is twice (2 channels) that
given by Equation (2) or Equation (3) when operating in the
single-ended mode or bridge mode, respectively. Twice the
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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
LM4842’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 LM4842’s power supply pin and
ground as short as possible. Connecting a 1µF 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 a capacitor,
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 (as
explained in the section, Proper Selection of External
Components), system cost, and size constraints.
(Continued)
maximum power dissipation point given by Equation (3)
must not exceed the power dissipation given by Equation
(4):
PDMAX' = (TJMAX − TA)/θJA
(4)
The LM4842’s TJMAX = 150˚C. In the LQ package soldered
to a DAP pad that expands to a copper area of 5in2 on a
PCB, the LM4842’s θJA = 20˚C/W. In the MH and LQ packages soldered to a DAP pad that expands to a copper area
of 2in2 on a PCB, the LM4842MH’s and LQ’s θJA is 41˚C/W.
For the LM4842MT package, θJA = 80˚C/W. At any given
ambient temperature TA, use Equation (4) to find the maximum internal power dissipation supported by the IC packaging. Rearranging Equation (4) and substituting PDMAX for
PDMAX' results in Equation (5). This equation gives the maximum ambient temperature that still allows maximum stereo
power dissipation without violating the LM4842’s maximum
junction temperature.
TA = TJMAX – 2*PDMAX θJA
PROPER SELECTION OF EXTERNAL COMPONENTS
Optimizing the LM4842’s performance requires properly selecting external components. Though the LM4842 operates
well when using external components with wide tolerances,
best performance is achieved by optimizing component values.
The LM4842 is unity-gain stable, giving a designer maximum
design flexibility. The gain should be set to no more than a
given application requires. This allows the amplifier to
achieve minimum THD+N and maximum signal-to-noise ratio. These parameters are compromised as the closed-loop
gain increases. However, low gain circuits demand input
signals with greater voltage swings to achieve maximum
output power. Fortunately, many signal sources such as
audio CODECs have outputs of 1VRMS (2.83VP-P). Please
refer to the Audio Power Amplifier Design section for more
information on selecting the proper gain.
(5)
For a typical application with a 5V power supply and an 4Ω
load, the maximum ambient temperature that allows maximum stereo power dissipation without exceeding the maximum junction temperature is approximately 45˚C for the MH
package.
TJMAX = PDMAX θJA + TA
(6)
Equation (6) gives the maximum junction temperature
TJMAX. If the result violates the LM4842’s 150˚C TJMAX,
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 a surface
mount part 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.
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. 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 pin(s), supply pin and amplifier output pins. External,
solder attached SMT heatsinks such as the Thermalloy
7106D can also improve power dissipation. When adding a
heat sink, the θJA is the sum of θJC, θCS, and θSA. (θJC is the
junction-to-case thermal impedance, θCS is the case-to-sink
thermal impedance, and θSA is the sink-to-ambient thermal
impedance.) Refer to the Typical Performance Characteristics curves for power dissipation information at lower output power levels.
Input Capacitor Value Selection
Amplifying the lowest audio frequencies requires a high
value input coupling capacitor (0.33µF in Figure 2). A high
value capacitor can be expensive and may compromise
space efficiency in portable designs. In many cases, however, the speakers used in portable systems, whether internal or external, have little ability to reproduce signals below
150Hz. Applications using speakers with this limited frequency response reap little improvement by using a large
input capacitor.
Besides effecting system cost and size, the input coupling
capacitor has an affect on the LM4842’s click and pop performance. When the supply voltage is first applied, a transient (pop) is created as the charge on the input capacitor
changes from zero to a quiescent state. The magnitude of
the pop is directly proportional to the input capacitor’s size.
Higher value capacitors need more time to reach a quiescent
DC voltage (usually VDD/2) when charged with a fixed current. The amplifier’s output charges the input capacitor
through the feedback resistor, Rf. Thus, pops can be minimized by selecting an input capacitor value that is no higher
than necessary to meet the desired −3dB frequency.
As shown in Figure 1, the input resistors (RIN = 20K) and the
input capacitosr (CIN = 0.33µF) produce a −6dB high pass
filter cutoff frequency that is found using Equation (7).
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 5V regulator typically
use a 10µF in parallel with a 0.1µF filter capacitor to stabilize
19
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LM4842
Application Information
LM4842
Application Information
using these outputs. Typical values for the output coupling
capacitors are 0.33µF to 1.0µF. If polarized coupling capacitors are used, connect their ’+’ terminals to the respective
output pin.
Since the Dock outputs precede the internal volume control,
the signal amplitude will be equal to the input signal’s magnitude and cannot be adjusted. However, the input amplifier’s closed-loop gain can be adjusted using external resistors. These 20k resistors (RFA and RFB) are shown in Figure
2 and they set each input amplifier’s gain to -1. Use Equation
7 to determine the input and feedback resistor values for a
desired gain.
(Continued)
(7)
As an example when using a speaker with a low frequency
limit of 150Hz, the input coupling capacitor using Equation
(7), is 0.053µF. The 0.33µF input coupling capacitor shown
in Figure 1 allows the LM4842 to drive high efficiency, full
range speaker whose response extends below 30Hz.
TURN ON Characteristics
- Av = RF / RIN
The LM4842 contains advanced circuitry that minimizes
turn-on and shutdown transients or “clicks and pops”. For
this discussion, turn-on refers to either applying the power
supply voltage or when the shutdown mode is deactivated.
While the power supply is ramping to its final value, the
LM4842’s internal amplifiers are configured as unity gain
buffers. An internal current source changes the voltage of
the BYPASS pin in a controlled, linear manner. Ideally, the
input and outputs track the voltage applied to the BYPASS
pin. The gain of the internal amplifiers remains unity until the
voltage on the BYPASS pin reaches 1/2 VDD. As soon as the
voltage on the BYPASS pin is stable, the LM4842 is ready to
be fully turned on. To turn the device on, the input signal
must exceed 22mVrms. This is accomplished through a
threshold detect circuit that enables all appropriate output
amplifiers after the 22mVrms limit is reached. Until this
threshold is reached, some of the amplifiers remain in a
tri-state mode. This insures that there is no current flowing
through to the speakers or headphones during power up.
Without current flow, the speakers or headphones remain
silent. During headphone mode, A+, B-, and B+ are in tristate mode during power up. During speaker mode, A+ and
B+ are in tri-state mode during power up.
Adjusting the input amplifier’s gain sets the minimum gain for
that channel. Although the single ended output of the Bridge
Output Amplifiers can be used to drive line level outputs, it is
recommended that the A & B Dock Outputs simpler signal
path be used for better performance.
MUX CONTROL AND MODE PINS
The LM4842 has two pairs of stereo inputs. The MUX CONTROL pin determines which of these stereo pairs of inputs
are active. Applying 0V to the MUX CONTROL pin (with the
Mode pin tied low) selects inputs A0 and B0. Applying VDD to
the MUX CONTROL (with the Mode pin tied low) pin selects
inputs A1 and B1 (See Truth Table for Logic Inputs).
When the Mode pin is pulled high the MUX Control is disabled and the Headphone Sense Pin controls the A and B
input pairs as follows:
Headphone Sense enabled (Headphone plugged in) selects inputs A1 and B1.
Headphone Sense disabled (Headphone not plugged in)
selects inputs A0 and B0.
When the MODE pin is high the HP SENSE controls the
MUX inputs. This configuration can be very useful, for example, when the headphone acoustic output needs to be
much lower than the BTL Speaker Output. Two different
gains can be hardwired into the two pairs of MUX input
circuits. This allows the user to have the HP SENSE automatically change the output level for either of the MUX input
pairs by switching between the two pairs of MUX inputs, if
the same input signal is connected to both MUX inputs.
When the MODE pin is low the MUX pin switches the MUX
input pairs directly.
Although the BYPASS pin current cannot be modified,
changing the size of CBYPASS alters the device’s turn-on
time. As the size of CBYPASS increases, the turn-on time
increases. There is a linear relationship between the size of
CBYPASS and the turn-on time. Here are some typical turn-on
times for various values of CBYPASS:
CBYPASS
TON
0.01µF
2ms
0.1µF
20ms
0.22µF
44ms
0.47µF
94ms
1.0µF
200ms
BEEP DETECT FUNCTION
Computers and notebooks produce a system ’beep’ signal
that drives a small speaker. The speaker’s auditory output
signifies that the system requires user attention or input. To
accommodate this system alert signal, the LM4842’s beep
input pin is a mono input that accepts the beep signal.
Internal level detection circuitry at this input monitors the
beep signal’s magnitude. When a signal level greater than
VDD/2 is detected on the BEEP IN pin, the bridge output
amplifiers are enabled. The beep signal is amplified and
applied to the load connected to the output amplifiers. A valid
beep signal will be applied to the load even when MUTE is
active. Use the input resistors connected between the BEEP
IN pin and the stereo input pins to accommodate different
beep signal amplitudes. These resistors are shown as
200kΩ devices in Figure 1. Use higher value resistors to
reduce the gain applied to the beep signal. The resistors
must be used to pass the beep signal to the stereo inputs.
DOCKING STATION INTERFACE
Applications such as notebook computers can take advantage of a docking station to connect to external devices such
as monitors or audio/visual equipment that sends or receives
line level signals. The LM4842 has two outputs, Dock A and
Dock B, which connect to outputs of the internal input amplifiers that drive the volume control inputs. These input
amplifiers can drive loads of > 1kΩ (such as powered speakers) with a rail-to-rail signal. Since the output signal present
on the Dock A and Dock B pins are biased to VDD/2, coupling
capacitors should be connected in series with the load when
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(8)
20
ers. The LM4842’s shutdown mode must be deactivated
before a system alert signal is applied to the BEEP IN pin.
(Continued)
The BEEP IN pin is used only to detect the beep signal’s
magnitude: it does not pass the signal to the output amplifi-
20028196
FIGURE 5. Headphone Sensing Circuit
contact will accomplish this because there is an internal
pull-up resistor), the bridge−connected speakers are muted
and Amp A -OUT and Amp B -OUT drive the stereo headphones. When a switch shorts the HP−IN pin to GND (pulling
down the internal pull-up resistor), the LM4842 operates in
bridge mode. If headphone drive is not needed, short the
HP−IN pin to the −OUTB pin.
Figure 6 shows an optional resistor connected between the
amplifier output that drives the headphone jack sleeve and
ground. This resistor provides a ground path that supresses
power supply hum. This hum may occur in applications such
as notebook computers in a shutdown condition and connected to an external powered speaker. The resistor’s 100Ω
value is a suggested starting point. Its final value must be
determined based on the tradeoff between the amount of
noise suppression that may be needed and minimizing the
additional current drawn by the resistor (25mA for a 100Ω
resistor and a 5V supply).
CAP-LESS HEADPHONE (SINGLE-ENDED) AMPLIFIER
OPERATION
An internal pull−up circuit is connected to the HP Sense (Pin
21 HP-IN on the MT/MH packages) headphone amplifier
control pin. When this pin is left unconnected, VDD is applied
to the HP−IN. This turns off Amp B +OUT (not seen in Fig 5,
see Fig 2 Pin 15) and switches Amp A +OUT’s input signal
from an audio signal to the VDD/2 voltage present on pin 28
(Amp A + OUT). The result is muted bridge-connected loads.
Quiescent current consumption is reduced when the IC is in
this single−ended mode.
Figure 5 above shows the implementation of the LM4842’s
headphone control function. An internal comparator with a
nominal 400mV offset monitors the signal present at the
−OUT B output. It compares this signal against the signal
applied to the HP−IN pin (Notice in Figure 5, Pin 21 is
shorted to Pin 17 without a headphone plugged in). When
these signals are equal, as in the case when a BTL is
connected to the amplifier, an internal comparator forces the
LM4842 to maintain bridged−amplifier operation. When the
HP−IN pin is externally floated, such as when headphones
are connected to the jack shown in Figure 5, an internal
pull−up forces VDD on the internal comparator’s HP−IN inputs. This changes the comparator’s output state and enables the headphone function: it turns off Amp B +OUT (not
seen in Fig 5, see Fig 2 Pin 15), switches the Amp A +OUT
input signal from an audio signal to the VDD/2 DC voltage
present on pin 28, and mutes the bridge-connected loads.
Amp A -OUT and Amp B -OUT drive the headphones.
Figures 2 and 6 also show suggested headphone jack electrical connections. The jack is designed to mate with a
three−wire plug. The plug’s tip and ring should each carry
one of the two stereo output signals, whereas the sleeve
provides the return to Amp A +OUT. A headphone jack with
one control pin contact is sufficient to drive the HP−IN pin
when connecting headphones.
A switch can replace the headphone jack contact pin. When
a switch shorts the HP−IN pin to VDD (An open switch
MUTE FUNCTION
The LM4842 mutes the amplifier and DOCK outputs when
VDD is applied to the MUTE pin. Even while muted, the
LM4842 will amplify a system alert (beep) signal whose
magnitude satisfies the BEEP DETECT circuitry. Applying
0V to the MUTE pin returns the LM4842 to normal, unmuted
operation. Prevent unanticipated mute behavior by connecting the MUTE pin to VDD or ground. Do not let the mute pin
float.
MICRO-POWER SHUTDOWN
The voltage applied to the SHUTDOWN pin controls the
LM4842’s shutdown function. Activate micro-power shutdown by applying ground (logic low) to the SHUTDOWN pin.
When activated, the LM4842’s micro-power shutdown feature turns off the amplifier’s bias circuitry, reducing the supply current. On the demo board, the micro-power shutdown
feature is controlled by a single pole switch that connects the
shutdown pin to either VDD, for normal operation, or directly
21
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LM4842
Application Information
LM4842
Application Information
cies, CBA and CBB will be virtual open circuits and have no
effect on the overall gain of the circuit. However at higher
frequencies, the capacitors will be virtual short circuits and
this will cause the gain of the bridge amplifiers to be reduced
from a gain of 4 to a gain of 2. An example of actual values
for this circuit are as follows: a first order pole is formed with
a corner frequency at: fc = 1/(2π10kΩ CBA) (9) With CBA =
0.1µF, which results in a corner frequency of 160Hz. This
bass boost feature can be useful in systems where speakers
are housed in small enclosures and require a little more
acoustic output at lower frequencies to make the sound
more natural and balanced.
(Continued)
to ground to enable shutdown. In a system with a microprocessor or a microcontroller, use a digital output to apply the
control voltage to the SHUTDOWN pin.
BASS BOOST
The ’Bass Boost Mode’ is enabled whenever the LM4842 is
NOT in headphone mode (please refer to the ’Cap-Less
Headphone’ description in the previous section for headphone on/off conditions). In BTL output mode, the Bass
Boost feature is enabled and the low frequency gain of the A
and B Channel amplifiers can be set by installing the external bass boost capacitors, CBA across pins 25 and 26 and
CBB across pins 17 and 18, as shown in Figure 2 (MT/MH
package pin numbers). If the Bass Boost feature is not
desired, then the capacitors can be left out of the circuit.
When the capacitors are installed and the bass boost is
enabled, the output amplifiers will be internally set at a gain
of 4 in bridged mode, as shown in Figure 2. At low frequen-
ESD Protection
As stated in the Absolute Maximum Ratings, pin 28 on the
MT and MH packages have a maximum ESD susceptibility
rating of 6500V. For higher ESD voltages, the addition of an
PCDN042 dual transil (from California Micro Devices), as
shown in Figure 6, will provide additional protection.
200281A4
FIGURE 6. The PCDN042 provides additional ESD protection beyond the 6500V shown in the
Absolute Maximum Ratings for the AMP2A output
DC VOLUME CONTROL
The LM4842 has an internal stereo volume control whose
setting is a function of the DC voltage applied to the DC VOL
CONTROL pin.
The LM4842 volume control consists of 31 steps that are
individually selected by a variable DC voltage level on the
volume control pin. The range of the steps, controlled by the
DC voltage, are from 0dB - 78dB. Each gain step corresponds to a specific input voltage range, as shown in table 2.
To minimize the effect of noise on the volume control pin,
which can affect the selected gain level, hysteresis has been
implemented. The amount of hysteresis corresponds to half
of the step width, as shown in Volume Control Characterization Graph (DS200133-40).
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For highest accuracy, the voltage shown in the ’recommended voltage’ column of the table is used to select a
desired gain. This recommended voltage is exactly halfway
between the two nearest transitions to the next highest or
next lowest gain levels.
The gain levels are 1dB/step from 0dB to -6dB, 2dB/step
from -6dB to -36dB, 3dB/step from -36dB to -47dB, 4dB/step
from -47db to -51dB, 5dB/step from -51dB to -66dB, and
12dB to the last step at -78dB.
22
Gain
(dB)
Voltage Range (% of Vdd)
Voltage Range (Vdd = 5)
Voltage Range (Vdd = 3)
Low
High
Recommended Low
High
Recommended Low
High
Recommended
0
77.5%
100.00%
100.000%
5.000
5.000
3.000
3.000
-1
75.0%
78.5%
76.875%
3.750
3.938
3.844
2.250
2.363
2.306
-2
72.5%
76.25%
74.375%
3.625
3.813
3.719
2.175
2.288
2.231
-3
70.0%
73.75%
71.875%
3.500
3.688
3.594
2.100
2.213
2.156
-4
67.5%
71.25%
69.375%
3.375
3.563
3.469
2.025
2.138
2.081
-5
65.0%
68.75%
66.875%
3.250
3.438
3.344
1.950
2.063
2.006
-6
62.5%
66.25%
64.375%
3.125
3.313
3.219
1.875
1.988
1.931
-8
60.0%
63.75%
61.875%
3.000
3.188
3.094
1.800
1.913
1.856
-10
57.5%
61.25%
59.375%
2.875
3.063
2.969
1.725
1.838
1.781
-12
55.0%
58.75%
56.875%
2.750
2.938
2.844
1.650
1.763
1.706
-14
52.5%
56.25%
54.375%
2.625
2.813
2.719
1.575
1.688
1.631
-16
50.0%
53.75%
51.875%
2.500
2.688
2.594
1.500
1.613
1.556
-18
47.5%
51.25%
49.375%
2.375
2.563
2.469
1.425
1.538
1.481
-20
45.0%
48.75%
46.875%
2.250
2.438
2.344
1.350
1.463
1.406
-22
42.5%
46.25%
44.375%
2.125
2.313
2.219
1.275
1.388
1.331
-24
40.0%
43.75%
41.875%
2.000
2.188
2.094
1.200
1.313
1.256
-26
37.5%
41.25%
39.375%
1.875
2.063
1.969
1.125
1.238
1.181
-28
35.0%
38.75%
36.875%
1.750
1.938
1.844
1.050
1.163
1.106
-30
32.5%
36.25%
34.375%
1.625
1.813
1.719
0.975
1.088
1.031
-32
30.0%
33.75%
31.875%
1.500
1.688
1.594
0.900
1.013
0.956
-34
27.5%
31.25%
29.375%
1.375
1.563
1.469
0.825
0.937
0.881
-36
25.0%
28.75%
26.875%
1.250
1.438
1.344
0.750
0.862
0.806
-39
22.5%
26.25%
24.375%
1.125
1.313
1.219
0.675
0.787
0.731
-42
20.0%
23.75%
21.875%
1.000
1.188
1.094
0.600
0.712
0.656
-45
17.5%
21.25%
19.375%
0.875
1.063
0.969
0.525
0.637
0.581
-47
15.0%
18.75%
16.875%
0.750
0.937
0.844
0.450
0.562
0.506
-51
12.5%
16.25%
14.375%
0.625
0.812
0.719
0.375
0.487
0.431
-56
10.0%
13.75%
11.875%
0.500
0.687
0.594
0.300
0.412
0.356
-61
7.5%
11.25%
9.375%
0.375
0.562
0.469
0.225
0.337
0.281
-66
5.0%
8.75%
6.875%
0.250
0.437
0.344
0.150
0.262
0.206
-78
0.0%
6.25%
0.000%
0.000
0.312
0.000
0.000
0.187
0.000
3.875
23
2.325
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LM4842
Volume Control Table ( Table 2 )
LM4842
The last step in this design example is setting the amplifier’s
−3dB frequency bandwidth. To achieve the desired ± 0.25dB
pass band magnitude variation limit, the low frequency response must extend to at least one-fifth the lower bandwidth
limit and the high frequency response must extend to at least
five times the upper bandwidth limit. The gain variation for
both response limits is 0.17dB, well within the ± 0.25dB
desired limit. The results are an
Audio Power Amplifier Design
AUDIO AMPLIFIER DESIGN: DRIVING 1W INTO AN 8Ω
LOAD
The following are the desired operational parameters:
Power Output:
1 WRMS
Load Impedance:
8Ω
Input Level:
1 VRMS
Input Impedance:
Bandwidth:
fL = 100Hz/5 = 20Hz
(12)
fH = 20kHz x 5 = 100kHz
(13)
20 kΩ
100 Hz−20 kHz ± 0.25 dB
and an
The design begins by specifying the minimum supply voltage
necessary to obtain the specified output power. One way to
find the minimum supply voltage is to use the Output Power
vs Supply Voltage curve in the Typical Performance Characteristics section. Another way, using Equation (9), is to
calculate the peak output voltage necessary to achieve the
desired output power for a given load impedance. To account for the amplifier’s dropout voltage, two additional voltages, based on the Dropout Voltage vs Supply Voltage in the
Typical Performance Characteristics curves, must be
added to the result obtained by Equation (9). The result is
Equation (10).
As mentioned in the Selecting Proper External Components section, Ri (Right & Left) and Ci (Right & Left) create
a highpass filter that sets the amplifier’s lower bandpass
frequency limit. Find the coupling capacitor’s value using
Equation (14).
Ci≥ 1/(2πR ifL)
The result is
1/(2π*20kΩ*20Hz) = 0.397µF
The product of the desired high frequency cutoff (100kHz in
this example) and the differential gain AVD, determines the
upper passband response limit. With AVD = 3 and fH =
100kHz, the closed-loop gain bandwidth product (GBWP) is
300kHz. This is less than the LM4842’s 3.5MHz GBWP. With
this margin, the amplifier can be used in designs that require
more differential gain while avoiding performance,restricting
bandwidth limitations.
(10)
The Output Power vs Supply Voltage graph for an 8Ω load
indicates a minimum supply voltage of 4.6V. This is easily
met by the commonly used 5V supply voltage. The additional
voltage creates the benefit of headroom, allowing the
LM4842 to produce peak output power in excess of 1W
without clipping or other audible distortion. The choice of
supply voltage must also not create a situation that violates
of maximum power dissipation as explained above in the
Power Dissipation section.
After satisfying the LM4842’s power dissipation requirements, the minimum differential gain needed to achieve 1W
dissipation in an 8Ω load is found using Equation (11).
Recommended Printed Circuit
Board Layout
Figures 7 through 9 show the recommended 2 later PC
board layout that is optimized for the MT/MH packaged
LM4842 and associated external components. Figures 10
through 12 show the recommended 2 layer PC board layout
that is optimized for the LQ packaged LM4842 and associated external components. These circuits are designed for
use with an external 5V supply and 4Ω or 8Ω speakers.
These circuit boards are easy to use. Apply 5V and ground to
the board’s VDD and GND pads, respectively. Connect 4Ω or
8Ω speakers between the board’s −OUTA and +OUTA and
OUTB and +OUTB pads.
(11)
Thus, a minimum overall gain of 2.83 allows the LM4842’s to
reach full output swing and maintain low noise and THD+N
performance.
www.national.com
(15)
Use a 0.39µF capacitor, the closest standard value.
(9)
VDD ≥ (VOUTPEAK+ (VODTOP + VODBOT))
(14)
24
LM4842
Recommended Printed Circuit Board Layout - MH/MT Packages
20028193
FIGURE 7. Top Layer SilkScreen - ( Not to Scale )
20028195
FIGURE 8. Top Layer - ( Not to Scale )
25
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LM4842
Recommended Printed Circuit Board Layout - MH/MT Packages
20028194
FIGURE 9. Bottom Layer - ( Not to Scale )
200281A2
FIGURE 10. Top Layer SilkScreen - ( Not to Scale )
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26
(Continued)
LM4842
Recommended Printed Circuit Board Layout - LQ Package
200281A1
FIGURE 11. Top Layer - ( Not to Scale )
200281A0
FIGURE 12. Bottom Layer - ( Not to Scale )
27
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LM4842
Analog Audio LM4842 TSSOP and LQ Eval Boards
Assembly Part Number: 980011373-100
Revision: A
Bill of Material
Item Part Number
Part Description
1
551011373-001
LM4842 Eval Board PCB 1
etch 001
10
482911373-001
LM4842 TSSOP or LQ
1
20
151911368-001
Cer Cap 0.068µF 50V
10% 1206
2
25
152911368-001
Tant Cap 0.1µF 10V 10% 3
Size = A 3216
C2, C3, C4
26
152911368-002
Tant Cap 0.33µF 10V
10% Size = A 3216
5
CinA0, CinA1, CinB0, CinB1,
Cinbeep
27
152911368-003
Tant Cap 1µF 16V 10%
Size = A 3216
1
CBYPASS
28
152911368-004
Tant Cap 10µF 10V 10% 1
Size = C 6032
C1
31
472911368-002
Res 20K Ohm 1/8W 1%
1206
8
RinA0, RinA1, RinB0, RinB1
RFA0, RFA1, RFB0, RFB1
33
472911368-004
Res 200K Ohm 1/16W
1% 0603
4
RBEEPA0, RBEEPA1,
RBEEPB0, RBEEPB1
40
131911368-001
Stereo Headphone Jack 1
W/ Switch
41
131911368-002
Slide Switch
4
Mute, MUX, SD, Mode
Mouser # 10SP003
42
131911368-003
Potentiometer
1
Volume Control
Mouser # 317-2090-100K
43
131911368-004
RCA Jack
5
A0, A1, B0, B1, BeepIn
Mouser # 16PJ097
44
131911368-005
Banana Jack, Black
3
AOUT-, BOUT-, GND
Mouser # ME164-6219
45
131911368-006
Banana Jack, Red
3
AOUT+, BOUT+, VDD
Mouser # ME164-6218
www.national.com
Qty Ref Designator (on PCB)
Remark
CBA, CBB
Switchcraft
#35RAPC4BH3
28
LM4842
Physical Dimensions
inches (millimeters) unless otherwise noted
TSSOP Package
Order Number LM4842MT
NS Package Number MTC28 for TSSOP
29
www.national.com
LM4842
Physical Dimensions
inches (millimeters) unless otherwise noted (Continued)
Exposed-DAP TSSOP Package
Order Number LM4842MH
NS Package Number MXA28A for Exposed-DAP TSSOP
www.national.com
30
LM4842 Stereo 2W Amplifiers with DC Volume Control,
Transient Free Outputs, and Cap-less Headphone Drive
Physical Dimensions
inches (millimeters) unless otherwise noted (Continued)
LLP Package
Order Number LM4842LQ
NS Package Number LQA28A for Exposed-DAP LLP
LIFE SUPPORT POLICY
NATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT
DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT AND GENERAL
COUNSEL OF NATIONAL SEMICONDUCTOR CORPORATION. As used herein:
1. Life support devices or systems are devices or
systems which, (a) are intended for surgical implant
into the body, or (b) support or sustain life, and
whose failure to perform when properly used in
accordance with instructions for use provided in the
labeling, can be reasonably expected to result in a
significant injury to the user.
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Email: [email protected]
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Email: [email protected]
Deutsch Tel: +49 (0) 69 9508 6208
English Tel: +44 (0) 870 24 0 2171
Français Tel: +33 (0) 1 41 91 8790
2. A critical component is any component of a life
support device or system whose failure to perform
can be reasonably expected to cause the failure of
the life support device or system, or to affect its
safety or effectiveness.
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Asia Pacific Customer
Response Group
Tel: 65-2544466
Fax: 65-2504466
Email: [email protected]
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Tel: 81-3-5639-7560
Fax: 81-3-5639-7507
National does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and National reserves the right at any time without notice to change said circuitry and specifications.
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