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PDF LM4926 Data sheet ( Hoja de datos )
| Número de pieza | LM4926 | |
| Descripción | Ground-Referenced and Ultra Low Noise - Fixed Gain - 80mW Stereo Headphone Amplifier | |
| Fabricantes | National Semiconductor | |
| Logotipo |  |
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June 2005
www.DataSheet4U.com
LM4926
Ground-Referenced, Ultra Low Noise, Fixed Gain, 80mW
Stereo Headphone Amplifier
General Description
The LM4926 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 LM4926 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 LM4926 features an Automatic Standby Mode circuitry
(patent pending). In the absence of an input signal, after
approximately 12 seconds, the LM4926 goes into low cur-
rent standby mode. The LM4926 recovers into full power
operating 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 LM4926 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 LM4926 features a low-power consumption shutdown
mode selectable for either channel separately. This is ac-
complished by driving either the SD_RC (Shutdown Right
Channel) or SD_LC (Shutdown Left Channel) (or both) pins
with logic low, depending on which channel is desired shut-
down. Additionally, the LM4926 features an internal thermal
shutdown protection mechanism.
The LM4926 contains advanced pop & click circuitry that
eliminates noises which would otherwise occur during
turn-on and turn-off transitions.
The LM4926 has an internal fixed gain of 1.5V/V.
Key Specifications
j Improved PSRR at 217Hz
j Power Output at VDD = 3V,
RL = 16Ω, THD % 1%
j Shutdown Current
j Internal Fixed Gain
j Operating Voltage
70dB (typ)
80mW (typ)
0.01µA (typ)
1.5V/V (typ)
1.6V to 4.2V
Features
n Ground referenced outputs
n High PSRR
n Available in space-saving micro SMD package
n Ultra low current shutdown mode
n Improved pop & click circuitry eliminates noises during
turn-on and turn-off transitions
n No output coupling capacitors, snubber networks,
bootstrap capacitors, or gain-setting resistors required
n Shutdown either channel independently
Applications
n Notebook PCs
n Mobile Phone
n PDAs
n Portable electronic devices
n MP3 Players
Boomer® is a registered trademark of National Semiconductor Corporation.
© 2005 National Semiconductor Corporation DS201161
www.national.com
1 page  
Electrical Characteristics VDD = 3V (Note 1) (Continued)
The following specifications apply for VDD = 3V and 16Ω load unless otherwise specified. Limits apply to TA =w2w5˚wC..DataSheet4U.com
Symbol
Parameter
Conditions
LM4926
Units
Typ
Limit
(Limits)
(Note 6) (Notes 7, 8)
XTALK
Crosstalk
RL = 16Ω, PO = 1.6mW,
f = 1kHz
60
dB
Input Terminated
∞
ZOUT
Output Impedance
Input not terminated
60
kΩ
IL
VIN THRESH
Input Leakage
Input Voltage Threshold
±0.1
2.8
nA
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 LM4926, 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.
External Components Description (Figure 1)
Components
1. Ci
2. C1
3. C2
4. C3
5. C4
Functional Description
Input 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.
Flying capacitor. Low ESR ceramic capacitor (≤100mΩ)
Output capacitor. Low ESR ceramic capacitor (≤100mΩ)
Tantalum 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.
Ceramic 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 www.national.com
5 Page 
Typical Performance Characteristics (Continued)
THD+N vs Output Power
VDD = 3.0V, RL = 16Ω, f = 1kHz
Two channels in phase
www.DataSheet4U.com
THD+N vs Output Power
VDD = 3.0V, RL = 32Ω, f = 1kHz
Two channels in phase
THD+N vs Output Power
VDD = 3.6V, RL = 16Ω, f = 1kHz
One channel enabled
201161G4
THD+N vs Output Power
VDD = 3.6V, RL = 32Ω, f = 1kHz
One channel enabled
201161E5
201161F1
11
201161F3
www.national.com
11 Page | ||
| Páginas | Total 22 Páginas | |
| PDF Descargar | [ Datasheet LM4926.PDF ] | |
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