LM4922
LM4922 Ground-Referenced, Ultra Low Noise, Fixed Gain, 80mW Stereo
Headphone Amplifier
Literature Number: SNAS327D
LM4922 OBSOLETE
October 3, 2011
Ground-Referenced, Ultra Low Noise, Fixed Gain, 80mW
Stereo Headphone Amplifier
General Description
The LM4922 is a ground referenced, fixed-gain audio power
amplifier capable of delivering 80mW of continuous average
power into a 16Ω single-ended load with less than 1% THD
+N from a 3V power supply.
The LM4922 features a new circuit technology that utilizes a
charge pump to generate a negative reference voltage. This
allows the outputs to be biased about ground, thereby elimi-
nating output-coupling capacitors typically used with normal
single-ended loads.
The LM4922 features an Automatic Standby Mode circuitry
(patent pending). In the absence of an input signal, after ap-
proximately 12 seconds, the LM4922 goes into low current
standby mode. The LM4922 recovers into full power operat-
ing mode immediately after a signal is applied to either the left
or right input pins. This feature saves power supply current in
battery operated applications.
Boomer audio power amplifiers were designed specifically to
provide high quality output power with a minimal amount of
external components. The LM4922 does not require output
coupling capacitors or bootstrap capacitors, and therefore is
ideally suited for mobile phone and other low voltage appli-
cations where minimal power consumption is a primary re-
quirement.
The LM4922 features a low-power consumption shutdown
mode selectable for either channel separately. This is accom-
plished by driving either the SD_RC (Shutdown Right Chan-
nel) or SD_LC (Shutdown Left Channel) (or both) pins with
logic low, depending on which channel is desired shutdown.
Additionally, the LM4922 features an internal thermal shut-
down protection mechanism.
The LM4922 contains advanced pop & click circuitry that
eliminates noises which would otherwise occur during turn-on
and turn-off transitions.
The LM4922 has an internal fixed gain of 1.5V/V.
Key Specifications
■ Improved PSRR at 217Hz 70dB (typ)
■ Power Output at VDD = 3V,
RL = 16Ω, THD ≦ 1% 80mW (typ)
■ Shutdown Current 0.01µA (typ)
■ Internal Fixed Gain 1.5V/V (typ)
■ Operating Voltage 1.6V to 4.2V
Features
■Fixed Logic Levels
■Ground referenced outputs
■High PSRR
■Available in space-saving micro SMD package
■Ultra low current shutdown mode
■Improved pop & click circuitry eliminates noises during
turn-on and turn-off transitions
■No output coupling capacitors, snubber networks,
bootstrap capacitors, or gain-setting resistors required
■Shutdown either channel independently
Applications
■Notebook PCs
■Mobile Phone
■PDAs
■Portable electronic devices
■MP3 Players
Boomer® is a registered trademark of National Semiconductor Corporation.
© 2011 National Semiconductor Corporation 201582 www.national.com
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LM4922 Ground-Referenced, Ultra Low Noise, Fixed Gain, 80mW Stereo Headphone Amplifier
Typical Application
201582b8
FIGURE 1. Typical Audio Amplifier Application Circuit
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LM4922
Connection Diagrams
microSMD Package
20158209
Top View
Order Number LM4922TL
See NS Package Number TLE1411A
16 – Bump TL Marking
20158278
Top View
XY – Date Code
TT – Lot Traceability
G – Boomer Family
G1 – LM4922TL
Pin Descriptions
Pin Name Function
A1 R_IN Right Channel Input
A2 SGND Signal Ground
A3 CPVDD Charge Pump Power Supply
A4 CCP+ Positive Terminal - Charge Pump Flying Capacitor
B1 SD_RC Active-Low Shutdown, Right Channel
B2 SD_LC Active-Low Shutdown, Left Channel
B4 PGND Power Ground
C1 L_IN Left Channel Input
C2 R_OUT Right Channel Input
C4 CCP- Negative Terminal - Charge Pump Flying Capacitor
D1 +AVDD Positive Power Supply - Amplifier
D2 L_OUT Left Channel Output
D3 -AVDD Negative Power Supply - Amplifier
D4 VCP_OUT Charge Pump Power Output
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LM4922
Absolute Maximum Ratings (Note 2)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
Supply Voltage 4.5V
Storage Temperature −65°C to +150°C
Input Voltage -0.3V to VDD + 0.3V
Power Dissipation (Note 3) Internally Limited
ESD Susceptibility (Note 4) 2000V
ESD Susceptibility (Note 5) 200V
Junction Temperature 150°C
Thermal Resistance
θJA (typ) TLE1411A (Note 11) 86°C/W
Operating Ratings
Temperature Range
TMIN ≤ TA ≤ TMAX −40°C ≤ TA ≤ 85°C
Supply Voltage (VDD) 1.6V ≤ VDD ≤ 4.2V
Electrical Characteristics VDD = 3V (Note 1)
The following specifications apply for VDD = 3V and 16Ω load unless otherwise specified. Limits apply to TA = 25°C.
Symbol Parameter Conditions
LM4922
Units
(Limits)
Typ
(Note 6)
Limit
(Note 7)
(Note 8)
IDD
Quiescent Power Supply Current
Auto Standby Mode
VIN = 0V, inputs terminated
both channels enabled 2.3 mA
Quiescent Power Supply Current
Full Power Mode
VIN = 0V, inputs terminated
both channels enabled 7 10 mA (max)
VIN = 0V, inputs terminated
one channel enabled 5 mA
ISD Shutdown Current VSD_LC = VSD_RC = GND 0.1 1.8 µA (max)
VOS Output Offset Voltage RL = 32Ω, VIN = 0V 0.7 5 mV (max)
AVVoltage Gain –1.5 V/V
ΔAVGain Match 1 %
RIN Input Resistance 20 15
25
kΩ (min)
kΩ (max)
POOutput Power
THD+N = 1% (max); f = 1kHz,
RL = 16Ω, one channel 80 mW
THD+N = 1% (max); f = 1kHz,
RL = 32Ω, one channel 65 mW
THD+N = 1% (max); f = 1kHz,
RL = 16Ω, (two channels in phase) 43 38 mW (min)
THD+N = 1% (max); f = 1kHz,
RL = 32Ω, (two channels in phase) 50 45 mW (min)
THD+N Total Harmonic Distortion +
Noise
PO = 60mW, f = 1kHz, RL = 16Ω
single channel
0.04
%
PO = 50mW, f = 1kHz, RL = 32Ω
single channel
0.03
PSRR Power Supply Rejection Ratio
Full Power Mode
VRIPPLE = 200mVp-p, Input Referred
f = 217Hz 70
dB f = 1kHz 65
f = 20kHz 50
SNR Signal-to-Noise Ratio
RL = 32Ω, POUT = 20mW,
(A-weighted)
f = 1kHz, BW = 20Hz to 22kHz
100 dB
VIH Shutdown Input Voltage High VDD = 1.8V to 4.2V 1.2 V (min)
VIL Shutdown Input Voltage Low VDD = 1.8V to 4.2V 0.45 V (max)
TWU Wake Up Time From Auto-
Standby
5 µs
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LM4922
Symbol Parameter Conditions
LM4922
Units
(Limits)
Typ
(Note 6)
Limit
(Note 7)
(Note 8)
XTALK Crosstalk RL = 16Ω, PO = 1.6mW,
f = 1kHz 60 dB
ZOUT Output Impedance
VSD-LC = VSD-RC = GND
Input Terminated
Input not terminated
50
∞
30 kΩ
ZOUT Output Impedance
VSD-LC = VSD-RC = GND
–500mV ≤ VOUT ≤ +500mV
(Note 12)
8 2 kΩ (min)
ILInput Leakage ±0.1 nA
VIN THRESH Input Voltage Threshold 2.8 mVp
Note 1: All voltages are measured with respect to the GND pin unless otherwise specified.
Note 2: 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
that 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 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 LM4922, see power de-
rating currents for more information.
Note 4: Human body model, 100pF discharged through a 1.5kΩ resistor.
Note 5: Machine Model, 220pF - 240pF discharged through all pins.
Note 6: Typicals are measured at 25°C and represent the parametric norm.
Note 7: Limits are guaranteed to National's AOQL (Average Outgoing Quality Level).
Note 8: Datasheet min/max specification limits are guaranteed by design, test, or statistical analysis.
Note 9: If the product is in shutdown mode and VDD exceeds 4.2V (to a max of 4.5V VDD), then most of the excess current will flow through the ESD protection
circuits. If the source impedance limits the current to a max of 10mA, then the part will be protected. If the part is enabled when VDD is above 4.5V, circuit
performance will be curtailed or the part may be permanently damaged.
Note 10: Human body model, 100pF discharged through a 1.5kΩ resistor.
Note 11: θJA value is measured with the device mounted on a PCB with a 3” x 1.5”, 1oz copper heatsink.
Note 12: VOUT refers to signal applied to the LM4922 outputs.
External Components Description
(Figure 1)
Components Functional Description
1. CiInput coupling capacitor which blocks the DC voltage at the amplifier's input terminals. Also creates a high-pass
filter with Ri at fC = 1/(2πRiCi). Refer to the section Proper Selection of External Components, for an explanation
of how to determine the value of Ci.
2. C1Flying capacitor. Low ESR ceramic capacitor (≤100mΩ)
3. C2Output capacitor. Low ESR ceramic capacitor (≤100mΩ)
4. C3Tantalum capacitor. Supply bypass capacitor which provides power supply filtering. Refer to the Power Supply
Bypassing section for information concerning proper placement and selection of the supply bypass capacitor.
5. C4Ceramic capacitor. Supply bypass capacitor which provides power supply filtering. Refer to the Power Supply
Bypassing section for information concerning proper placement and selection of the supply bypass capacitor.
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LM4922
Typical Performance Characteristics
THD+N vs Frequency
VDD = 1.6V, RL = 16Ω, PO = 1mW
20158228
THD+N vs Frequency
VDD = 1.6V, RL = 32Ω, PO = 1mW
20158229
THD+N vs Frequency
VDD = 1.8V, RL = 16Ω, PO = 5mW
20158230
THD+N vs Frequency
VDD = 1.8V, RL = 32Ω, PO = 5mW
20158231
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LM4922
THD+N vs Frequency
VDD = 3V, RL = 16Ω, PO = 50mW
20158232
THD+N vs Frequency
VDD = 3V, RL = 32Ω, PO = 50mW
20158233
THD+N vs Frequency
VDD = 3.6V, RL = 16Ω, PO = 100mW
20158234
THD+N vs Frequency
VDD = 3.6V, RL = 32Ω, PO = 100mW
20158235
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LM4922
THD+N vs Frequency
VDD = 4.2V, RL = 16Ω, PO = 150mW
20158236
THD+N vs Frequency
VDD = 4.2V, RL = 32Ω, PO = 150mW
20158237
THD+N vs Output Power
VDD = 1.6V, RL = 16Ω, f = 1kH
One channel enabled
20158247
THD+N vs Output Power
VDD = 1.6V, RL = 32Ω, f = 1kHz
One channel enabled
20158249
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LM4922
THD+N vs Output Power
VDD = 1.6V, RL = 16Ω, f = 1kHz
Two channels in phase
20158251
THD+N vs Output Power
VDD = 1.6V, RL = 32Ω, f = 1kHz
Two channels in phase
20158253
THD+N vs Output Power
VDD = 1.8V, RL = 16Ω, f = 1kHz
One channel enabled
20158259
THD+N vs Output Power
VDD = 1.8V, RL = 32Ω, f = 1kHz
One channel enabled
20158261
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LM4922
THD+N vs Output Power
VDD = 1.8V, RL = 16Ω, f = 1kHz
Two channels in phase
20158263
THD+N vs Output Power
VDD = 1.8V, RL = 32Ω, f = 1kHz
Two channels in phase
20158265
THD+N vs Output Power
VDD = 3.0V, RL = 16Ω, f = 1kHz
One channel enabled
201582g2
THD+N vs Output Power
VDD = 3.0V, RL = 32Ω, f = 1kHz
One channel enabled
201582e1
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LM4922
THD+N vs Output Power
VDD = 3.0V, RL = 16Ω, f = 1kHz
Two channels in phase
201582g4
THD+N vs Output Power
VDD = 3.0V, RL = 32Ω, f = 1kHz
Two channels in phase
201582e5
THD+N vs Output Power
VDD = 3.6V, RL = 16Ω, f = 1kHz
One channel enabled
201582f1
THD+N vs Output Power
VDD = 3.6V, RL = 32Ω, f = 1kHz
One channel enabled
201582f3
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LM4922
THD+N vs Output Power
VDD = 3.6V, RL = 16Ω, f = 1kHz
Two channels in phase
201582f5
THD+N vs Output Power
VDD = 3.6V, RL = 32Ω, f = 1kHz
two channels in phase
201582f7
THD+N vs Output Power
VDD = 4.2V, RL = 16Ω, f = 1kHz
One channel enabled
20158273
THD+N vs Output Power
VDD = 4.2V, RL = 32Ω, f = 1kHz
One channel enabled
20158280
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LM4922
THD+N vs Output Power
VDD = 4.2V, RL = 16Ω, f = 1kHz
Two channels in phase
20158282
THD+N vs Output Power
VDD = 4.2V, RL = 32Ω, f = 1kHz
Two channels in phase
20158284
PSRR vs Frequency
VDD = 1.6V, RL = 16Ω
20158240
PSRR vs Frequency
VDD = 1.6V, RL = 32Ω
20158241
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LM4922
PSRR vs Frequency
VDD = 3V, RL = 16Ω
20158242
PSRR vs Frequency
VDD = 3V, RL = 32Ω
20158243
PSRR vs Frequency
VDD = 4.2V, RL = 16Ω
20158244
PSRR vs Frequency
VDD = 4.2V, RL = 32Ω
20158245
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LM4922
Output Power vs Supply Voltage
RL = 16Ω, one channel
20158238
Output Power vs Supply Voltage
RL = 32Ω, one channel
20158239
Output Power vs Supply Voltage
RL = 16Ω, 2 channels in phase
201582g8
Output Power vs Supply Voltage
RL = 32Ω, 2 channels in phase
201582g9
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LM4922
Supply Current vs Supply Voltage
RL = 16Ω
20158289
Representation of Automatic Standby Mode Behavior
VDD = 3V
20158219
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LM4922
Application Information
SUPPLY VOLTAGE SEQUENCING
It is a good general practice to first apply the supply voltage
to a CMOS device before any other signal or supply on other
pins. This is also true for the LM4922 audio amplifier which is
a CMOS device.
Before applying any signal to the inputs or shutdown pins of
the LM4922, it is important to apply a supply voltage to the
VDD pins. After the device has been powered, signals may be
applied to the shutdown pins (see MICRO POWER SHUT-
DOWN) and input pins.
ELIMINATING THE OUTPUT COUPLING CAPACITOR
The LM4922 features a low noise inverting charge pump that
generates an internal negative supply voltage. This allows the
outputs of the LM4922 to be biased about GND instead of a
nominal DC voltage, like traditional headphone amplifiers.
Because there is no DC component, the large DC blocking
capacitors (typically 220µF) are not necessary. The coupling
capacitors are replaced by two, small ceramic charge pump
capacitors, saving board space and cost.
Eliminating the output coupling capacitors also improves low
frequency response. In traditional headphone amplifiers, the
headphone impedance and the output capacitor form a high
pass filter that not only blocks the DC component of the out-
put, but also attenuates low frequencies, impacting the bass
response. Because the LM4922 does not require the output
coupling capacitors, the low frequency response of the device
is not degraded by external components.
In addition to eliminating the output coupling capacitors, the
ground referenced output nearly doubles the available dy-
namic range of the LM4922 when compared to a traditional
headphone amplifier operating from the same supply voltage.
OUTPUT TRANSIENT ('CLICK AND POPS') ELIMINATED
The LM4922 contains advanced circuitry that virtually elimi-
nates output transients ('clicks and pops'). This circuitry pre-
vents all traces of transients when the supply voltage is first
applied or when the part resumes operation after coming out
of shutdown mode.
AMPLIFIER CONFIGURATION EXPLANATION
As shown in Figure 2, the LM4922 has two internal opera-
tional amplifiers. The two amplifiers have internally configured
gain, the closed loop gain is set by selecting the ratio of Rf to
Ri. Consequently, the gain for each channel of the IC is
AV = -(Rf / Ri) = 1.5 V/V
where RF = 30kΩ and Ri = 20kΩ.
Since this is an output ground-referenced amplifier, by driving
the headphone through ROUT (Pin C2) and LOUT (Pin D2), the
LM4922 does not require output coupling capacitors. The typ-
ical single-ended amplifier configuration requires large, ex-
pensive output capacitors.
POWER DISSIPATION
Power dissipation is a major concern when using any power
amplifier and must be thoroughly understood to ensure a suc-
cessful design. Equation 1 states the maximum power dissi-
pation point for a single-ended amplifier operating at a given
supply voltage and driving a specified output load.
PDMAX = (VDD) 2 / (2π2RL) (1)
Since the LM4922 has two operational amplifiers in one pack-
age, the maximum internal power dissipation point is twice
that of the number which results from Equation 1. Even with
large internal power dissipation, the LM4922 does not require
heat sinking over a large range of ambient temperatures.
From Equation 1, assuming a 3V power supply and a 16Ω
load, the maximum power dissipation point is 28mW per am-
plifier. Thus the maximum package dissipation point is 56mW.
The maximum power dissipation point obtained must not be
greater than the power dissipation that results from Equation
2:
PDMAX = (TJMAX - TA) / (θJA) (2)
For the micro SMD package, θJA = 105°C/W. TJMAX = 150°C
for the LM4922. Depending on the ambient temperature, TA,
of the system surroundings, Equation 2 can be used to find
the maximum internal power dissipation supported by the IC
packaging. If the result of Equation 1 is greater than that of
Equation 2, then either the supply voltage must be decreased,
the load impedance increased or TA reduced. For the typical
application of a 3V power supply, with a 16Ω load, the maxi-
mum ambient temperature possible without violating the max-
imum junction temperature is approximately 144°C provided
that device operation is around the maximum power dissipa-
tion point. Power dissipation is a function of output power and
thus, if typical operation is not around the maximum power
dissipation point, the ambient temperature may be increased
accordingly.
POWER SUPPLY BYPASSING
As with any power amplifier, proper supply bypassing is crit-
ical for low noise performance and high power supply rejec-
tion. Applications that employ a 3V power supply typically use
a 4.7µF capacitor in parallel with a 0.1µF ceramic filter ca-
pacitor to stabilize the power supply's output, reduce noise on
the supply line, and improve the supply's transient response.
Keep the length of leads and traces that connect capacitors
between the LM4922's power supply pin and ground as short
as possible.
AUTOMATIC STANDBY MODE
The LM4922 features Automatic Standby Mode circuitry
(patent pending). In the absence of an input signal, after ap-
proximately 12 seconds, the LM4922 goes into low current
standby mode. The LM4922 recovers into full power operat-
ing mode immediately after a signal, which is greater than the
input threshold voltage, is applied to either the left or right
input pins. The input threshold voltage is not a static value, as
the supply voltage increases, the input threshold voltage de-
creases. This feature reduces power supply current con-
sumption in battery operated applications. Please see also
the graph entitled Representation of Automatic Standby
Mode Behavior in the Typical Performance Characteristics
section.
To ensure correct operation of Automatic Standby Mode,
proper layout techniques should be implemented. Separating
PGND and SGND can help reduce noise entering the LM4922
in noisy environments. Auto Standby mode works best when
output impedance of the audio source driving LM4922 is
equal or less than 50 Ohms. While Automatic Standby Mode
reduces power consumption very effectively during silent pe-
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LM4922
riods, maximum power saving is achieved by putting the
device into shutdown when it is not in use.
MICRO POWER SHUTDOWN
The voltage applied to the SD_LC (shutdown left channel) pin
and the SD_RC (shutdown right channel) pin controls the
LM4922’s shutdown function. When active, the LM4922’s mi-
cropower shutdown feature turns off the amplifiers’ bias cir-
cuitry, reducing the supply current. The trigger point is 0.45V
for a logic-low level, and 1.2V for logic-high level. The low
0.01µA (typ) shutdown current is achieved by applying a volt-
age that is as near as ground a possible to the SD_LC/
SD_RC pins. A voltage that is higher than ground may in-
crease the shutdown current.
There are a few ways to control the micro-power shutdown.
These include using a single-pole, single-throw switch, a mi-
croprocessor, or a microcontroller. When using a switch,
connect an external 100kΩ pull-up resistor between the
SD_LC/SD_RC pins and VDD. Connect the switch between
the SD_LC/SD_RC pins and ground. Select normal amplifier
operation by opening the switch. Closing the switch connects
the SD_LC/SD_RC pins to ground, activating micro-power
shutdown. The switch and resistor guarantee that the
SD_LC/SD_RC pins will not float. This prevents unwanted
state changes. In a system with a microprocessor or micro-
controller, use a digital output to apply the control voltage to
the SD_LC/SD_RC pins. Driving the SD_LC/SD_RC pins
with active circuitry eliminates the pull-up resistor.
SELECTING PROPER EXTERNAL COMPONENTS
Optimizing the LM4922's performance requires properly se-
lecting external components. Though the LM4922 operates
well when using external components with wide tolerances,
best performance is achieved by optimizing component val-
ues.
Charge Pump Capacitor Selection
Use low ESR (equivalent series resistance) (<100mΩ) ce-
ramic capacitors with an X7R dielectric for best performance.
Low ESR capacitors keep the charge pump output
impedance to a minimum, extending the headroom on the
negative supply. Higher ESR capacitors result in reduced
output power from the audio amplifiers.
Charge pump load regulation and output impedance are af-
fected by the value of the flying capacitor (C1). A larger valued
C1 (up to 3.3uF) improves load regulation and minimizes
charge pump output resistance. Beyond 3.3uF, the switch-on
resistance dominates the output impedance for capacitor val-
ues above 2.2uF.
The output ripple is affected by the value and ESR of the out-
put capacitor (C2). Larger capacitors reduce output ripple on
the negative power supply. Lower ESR capacitors minimize
the output ripple and reduce the output impedance of the
charge pump.
The LM4922 charge pump design is optimized for 2.2uF, low
ESR, ceramic, flying, and output capacitors.
Input Capacitor Value Selection
Amplifying the lowest audio frequencies requires high value
input coupling capacitors (Ci in Figure 1). A high value ca-
pacitor can be expensive and may compromise space effi-
ciency in portable designs. In many cases, however, the
speakers used in portable systems, whether internal or ex-
ternal, have little ability to reproduce signals below 150Hz.
Applications using speakers with this limited frequency re-
sponse reap little improvement by using high value input and
output capacitors.
Besides affecting system cost and size, Ci has an effect on
the LM4922's click and pop performance. The magnitude of
the pop is directly proportional to the input capacitor's size.
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 internal input resistor, Ri and the
input capacitor, Ci, produce a -3dB high pass filter cutoff fre-
quency that is found using Equation (3). Conventional head-
phone amplifiers require output capacitors; Equation (3) can
be used, along with the value of RL, to determine towards the
value of output capacitor needed to produce a –3dB high pass
filter cutoff frequency.
fi-3dB = 1 / 2πRiCi(3)
Also, careful consideration must be taken in selecting a cer-
tain type of capacitor to be used in the system. Different types
of capacitors (tantalum, electrolytic, ceramic) have unique
performance characteristics and may affect overall system
performance. (See the section entitled Charge Pump Capac-
itor Selection.)
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LM4922
LM4922 micro SMD DEMO BOARD ARTWORK
Top Layer
20158205
Mid Layer 1
20158206
Mid Layer 2
20158207
Bottom Layer
20158208
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LM4922
Revision History
Rev Date Description
1.0 11/16/05 Initial release.
1.1 11/18/06 Text edits.
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LM4922
Physical Dimensions inches (millimeters) unless otherwise noted
14 – Bump micro SMD
Order Number LM4922TL
NS Package Number TLE1411A
X1 = 1.970±0.03mm, X2 = 1.970±0.03mm, X3 = 0.600±0.075mm,
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LM4922
Notes
LM4922 Ground-Referenced, Ultra Low Noise, Fixed Gain, 80mW Stereo Headphone Amplifier
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