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PDF LM48310 Data sheet ( Hoja de datos )
| Número de pieza | LM48310 | |
| Descripción | Class D Audio Power Amplifier | |
| Fabricantes | National Semiconductor | |
| Logotipo |  |
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www.DataSheet4U.com
March 4, 2008
LM48310
Ultra-Low EMI, Filterless, 2.6W, Mono, Class D Audio
Power Amplifier with E2S
General Description
The LM48310 is a single supply, high efficiency, mono, 2.6W,
filterless switching audio amplifier. The LM48310 features
National’s Enhanced Emissions Suppression (E2S) system,
that features a unique patent-pending ultra low EMI, spread
spectrum, PWM architecture, that significantly reduces RF
emissions while preserving audio quality and efficiency. The
E2S system improves battery life, reduces external compo-
nent count, board area consumption, system cost, and sim-
plifying design.
The LM48310 is designed to meet the demands of portable
multimedia devices. Operating from a single 5V supply, the
device is capable of delivering 2.6W of continuous output
power to a 4Ω load with less than 10% THD+N. Flexible power
supply requirements allow operation from 2.4V to 5.5V. The
LM48310 offers two logic selectable modulation schemes,
fixed frequency mode, and an EMI suppressing spread spec-
trum mode. The E2S system includes an advanced, patent-
pending edge rate control (ERC) architecture that further
reduce emissions by minimizing the high frequency compo-
nent of the device output, while maintaining high quality audio
reproduction (THD+N = 0.03%) and high efficiency (η = 88%).
The LM48310 also features a SYNC_IN input and
SYNC_OUT, which allows multiple devices to operate with
the same switching frequency, eliminating beat frequencies
and any other interference caused by clock intermodulation.
The LM48310 features high efficiency compared to conven-
tional Class AB amplifiers, and other low EMI Class D ampli-
fiers. When driving and 8Ω speaker from a 5V supply, the
device operates with 88% efficiency at PO = 1W. The gain of
the LM48310 is internally set to 12dB, further reducing exter-
nal component count. A low power shutdown mode reduces
supply current consumption to 0.01μA.
Advanced output short circuit protection with auto-recovery
prevents the device from being damaged during fault condi-
tions. Superior click and pop suppression eliminates audible
transients on power-up/down and during shutdown.
Key Specifications
■ Efficiency at 3.6V, 400mW into 8Ω
■ Efficiency at 5V, 1W into 8Ω
■ Quiescent Power Supply Current at 5V
■ Power Output at VDD = 5V,
RL = 4Ω, THD+N ≤ 10%
■ Power Output at VDD = 5V,
RL = 8Ω, THD+N ≤ 10%
■ Shutdown current
85% (typ)
88% (typ)
3.2mA
2.6W (typ)
1.6W (typ)
0.01μA (typ)
Features
■ Passes FCC Class B Radiated Emissions with 20 inches
of cable
■ E2S System Reduces EMI while Preserving Audio Quality
and Efficiency
■ Output Short Circuit Protection with Auto-Recovery
■ Stereo Class D operation
■ No output filter required
■ Internally Configured Gain (12dB)
■ Synchronizable Oscillator for Multi-Channel operation
■ Low power shutdown mode
■ Minimum external components
■ "Click and pop" suppression
■ Micro-power shutdown
■ Available in space-saving LLP package
Applications
■ Mobile phones
■ PDAs
■ Laptops
EMI Graph 20in of Speaker Cable
Boomer® is a registered trademark of National Semiconductor Corporation.
© 2008 National Semiconductor Corporation 300374
300374a0
www.national.com
1 page  
wSwywm.DbaotlaSheet4U.com Parameter
Conditions
PO
THD+N
PSRR
CMRR
η
SNR
εOS
Output Power
Total Harmonic Distortion + Noise
Power Supply Rejection Ratio
(Input Referred)
Common Mode Rejection Ratio
Efficiency
Signal to Noise Ratio
Output Noise
RL = 4Ω, THD = 10%
f = 1kHz, 22kHz BW
VDD = 5V
VDD = 3.6V
VDD = 2.5V
RL = 8Ω, THD = 10% (max)
f = 1kHz, 22kHz BW
VDD = 5V
VDD = 3.6V
VDD = 2.5V
RL = 4Ω, THD = 1% (max)
f = 1kHz, 22kHz BW
VDD = 5V
VDD = 3.6V
VDD = 2.5V
RL = 8Ω, THD = 1% (max)
f = 1kHz, 22kHz BW
VDD = 5V
VDD = 3.6V
VDD = 2.5V
PO = 200mW, RL = 8Ω, f = 1kHz
PO = 100mW, RL = 8Ω, f = 1kHz
VRIPPLE = 200mVP-P Sine,
fRIPPLE = 217Hz, Inputs AC GND,
CIN = 1μF, Input referred
VRIPPLE = 200mVP-P Sine,
fRIPPLE = 1kHz, Inputs AC GND,
CIN = 1μF, Input referred
VRIPPLE = 1VP-P
fRIPPLE = 217Hz
VDD = 5V, POUT = 1W
RL = 8Ω, f = 1kHz
VDD = 3.6V, POUT = 400mW
RL = 8Ω, f = 1kHz
VDD = 5V, PO = 1W,
Fixed Frequency Mode
VDD = 5V, PO = 1W,
Spread Spectrum Mode
Input referred,
Fixed Frequency Mode,
A-weighted Filter
Input referred,
Spread Spectrum Mode,
Unweighted
LM48310
Typical
Limit
(Note 6) (Notes 7, 8)
Units
(Limits)
2.6 W
1.3 W
555 mW
1.6 W
800 mW
354 mW
2.1
1
446
1.3
640
286
0.03
0.03
82
W
W
mW
1.1 W (min)
mW
mW
% (max)
%
dB
80 dB
70 dB
88 %
85 %
97 dB
97 dB
14 μV
28 μV
5 www.national.com
5 Page 
wwAwp.DpataliScheaett4iUo.cnomInformation
GENERAL AMPLIFIER FUNCTION
The LM48310 mono Class D audio power amplifier features
a filterless modulation scheme that reduces external compo-
nent count, conserving board space and reducing system
cost. With no signal applied, the outputs (VOUTA and VOUTB)
switch between VDD and GND with a 50% duty cycle, in
phase, causing the two outputs to cancel. This cancellation
results in no net voltage across the speaker, thus there is no
current to the load in the idle state.
With the input signal applied, the duty cycle (pulse width) of
the LM48310 outputs changes. For increasing output voltage,
the duty cycle of VOUTAincreases, while the duty cycle of
VOUTB decreases. For decreasing output voltages, the con-
verse occurs. The difference between the two pulse widths
yields the differential output voltage.
ENHANCED EMISSIONS SUPPRESSION SYSTEM (E2S)
The LM48310 features National’s patent-pending E2S system
that reduces EMI, while maintaining high quality audio repro-
duction and efficiency. The E2S system features a synchro-
nizable oscillator with selectable spread spectrum, and
advanced edge rate control (ERC). The LM48310 ERC great-
ly reduces the high frequency components of the output
square waves by controlling the output rise and fall times,
slowing the transitions to reduce RF emissions, while maxi-
mizing THD+N and efficiency performance. The overall result
of the E2S system is a filterless Class D amplifier that passes
FCC Class B radiated emissions standards with 20in of twist-
ed pair cable, with excellent 0.03% THD+N and high 88%
efficiency.
FIXED FREQUENCY MODE (SYNC_IN = GND)
The LM48310 features two modulations schemes, a fixed fre-
quency mode and a spread spectrum mode. Select the fixed
frequency mode by setting SYNC_IN = GND. In fixed fre-
quency mode, the amplifier output switch at a constant
300kHz. In fixed frequency mode, the output spectrum con-
sists of the fundamental and its associated harmonics (see
Typical Performance Characteristics).
SPREAD SPECTRUM MODE (SYNC_IN = VDD)
The logic selectable spread spectrum mode eliminates the
need for output filters, ferrite beads or chokes. In spread
spectrum mode, the switching frequency varies randomly by
30% about a 300kHz center frequency, reducing the wide-
band spectral contend, improving EMI emissions radiated by
the speaker and associated cables and traces. Where a fixed
frequency class D exhibits large amounts of spectral energy
at multiples of the switching frequency, the spread spectrum
architecture of the LM48310 spreads that energy over a larger
bandwidth (See Typical Performance Characteristics). The
cycle-to-cycle variation of the switching period does not affect
the audio reproduction, efficiency, or PSRR. Set SYNC_IN =
VDD for spread spectrum mode.
EXTERNAL CLOCK MODE (SYNC_IN = CLOCK)
Connecting a clock signal to SYNC_IN synchronizes the
LM48310 oscillator to an external clock, moving the output
spectral components out of a sensitive frequency band, and
minimizing audible beat frequencies when multiple LM48310s
are used in a single system. The LM48310 accepts an exter-
nal clock frequency between 200kHz and 1MHz. The
LM48310 can be synchronized to a spread spectrum clock,
allowing multiple LM48310s to be synchronized in spread
spectrum mode (see SYNC_OUT section).
SYNC_OUT
SYNC_OUT is a clock output for synchronizing external de-
vices. The SYNC_OUT signal is identical in frequency and
duty cycle of the amplifier’s switching frequency. When the
LM48310 is in fixed frequency mode, SYNC_OUT is a fixed,
300kHz clock. When the LM48310 is in spread spectrum
mode, SYNC_OUT is an identical spread spectrum clock.
When the LM48310 is driven by an external clock,
SYNC_OUT is identical to the external clock. If unused, leave
SYNC_OUT floating.
Multiple LM48310s can be synchronized to a single clock. In
Figure 2, device U1 is the master, providing a spread spec-
trum clock to the slave device (U2). This configuration syn-
chronizes the switching frequencies of the two devices,
eliminating any audible beat frequencies. Because
SYNC_OUT has no audio content, there is minimal THD+N
degredation or crosstalk between the devices, Figure 3-5.
11 www.national.com
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| PDF Descargar | [ Datasheet LM48310.PDF ] | |
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