Motor de Búsqueda de Datasheet de Componentes Electrónicos
  Spanish  ▼
ALLDATASHEET.ES

X  

LM4895IBP Datasheet(PDF) 11 Page - National Semiconductor (TI)

[Old version datasheet] Texas Instruments acquired National semiconductor.
No. de pieza LM4895IBP
Descripción Electrónicos  1 Watt Fully Differential Audio Power Amplifier With Shutdown Select and Fixed 6dB Gain
Download  15 Pages
Scroll/Zoom Zoom In 100%  Zoom Out
Fabricante Electrónico  NSC [National Semiconductor (TI)]
Página de inicio  http://www.national.com
Logo NSC - National Semiconductor (TI)

LM4895IBP Datasheet(HTML) 11 Page - National Semiconductor (TI)

Back Button LM4895IBP Datasheet HTML 7Page - National Semiconductor (TI) LM4895IBP Datasheet HTML 8Page - National Semiconductor (TI) LM4895IBP Datasheet HTML 9Page - National Semiconductor (TI) LM4895IBP Datasheet HTML 10Page - National Semiconductor (TI) LM4895IBP Datasheet HTML 11Page - National Semiconductor (TI) LM4895IBP Datasheet HTML 12Page - National Semiconductor (TI) LM4895IBP Datasheet HTML 13Page - National Semiconductor (TI) LM4895IBP Datasheet HTML 14Page - National Semiconductor (TI) LM4895IBP Datasheet HTML 15Page - National Semiconductor (TI)  
Zoom Inzoom in Zoom Outzoom out
 11 / 15 page
background image
Application Information
DIFFERENTIAL AMPLIFIER EXPLANATION
The LM4895 is a fully differential audio amplifier that fea-
tures differential input and output stages. Internally this is
accomplished by two circuits: a differential amplifier and a
common mode feedback amplifier that adjusts the output
voltages so that the average value remains V
DD/2. The
LM4895 features precisely matched internal gain-setting re-
sistors, thus eliminating the need for external resistors and
fixing the differential gain at A
VD = 6dB.
A differential amplifier works in a manner where the differ-
ence between the two input signals is amplified. In most
applications, this would require input signals that are 180˚
out of phase with each other.
The LM4895 provides what is known as a ’bridged mode’
output (bridge-tied-load, BTL). This results in output signals
at V
o1 and Vo2 that are 180˚ out of phase with respect to
each other. Bridged mode operation is different from the
single-ended amplifier configuration that connects the load
between the amplifier output and ground. A bridged amplifier
design has distinct advantages over the single-ended con-
figuration: it provides differential drive to the load, thus dou-
bling maximum possible output swing for a specific supply
voltage. Four times the output power is possible compared
with a single-ended amplifier under the same conditions.
This increase in attainable output power assumes that the
amplifier is not current limited or clipped.
A bridged configuration, such as the one used in the
LM4895, also creates a second advantage over single-
ended amplifiers. Since the differential outputs, V
o1 and Vo2,
are biased at half-supply, no net DC voltage exists across
the load. BTL configuration eliminates the output coupling
capacitor required in single-supply, single-ended amplifier
configurations. If an output coupling capacitor is not used in
a single-ended output configuration, the half-supply bias
across the load would result in both increased internal IC
power dissipation as well as permanent loudspeaker dam-
age. Further advantages of bridged mode operation specific
to fully differential amplifiers like the LM4895 include in-
creased power supply rejection ratio, common-mode noise
reduction, and click and pop reduction.
EXPOSED-DAP PACKAGE PCB MOUNTING
CONSIDERATIONS
The LM4895’s exposed-DAP (die attach paddle) package
(LD) provide 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 1.4W at
≤ 1% THD with a 4Ω load. This high power
is achieved through careful consideration of necessary ther-
mal design. Failing to optimize thermal design may compro-
mise the LM4895’s high power performance and activate
unwanted, though necessary, thermal shutdown protection.
The LD package must have its DAP soldered to a copper
pad on the PCB. The DAP’s PCB copper pad is connected to
a large plane of continuous unbroken copper. This plane
forms a thermal mass and 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 4 (2x2) vias.
The via diameter should be 0.012in - 0.013in with a 0.050in
pitch. Ensure efficient thermal conductivity by plating-
through and solder-filling the vias.
Best thermal performance is achieved with the largest prac-
tical copper heat sink area. If the heatsink and amplifier
share the same PCB layer, a nominal 2.5in
2 (min) area is
necessary for 5V operation with a 4
Ω load. Heatsink areas
not placed on the same PCB layer as the LM4895 should be
5in
2 (min) for the same supply voltage and load resistance.
The last two area recommendations apply for 25˚C ambient
temperature. In all circumstances and conditions, the junc-
tion temperature must be held below 150˚C to prevent acti-
vating the LM4895’s thermal shutdown protection. The
LM4895’s power de-rating curve in the Typical Performance
Characteristics shows the maximum power dissipation ver-
sus temperature. Example PCB layouts for the exposed-
DAP TSSOP and LLP packages are shown in the Demon-
stration Board Layout section. Further detailed and specific
information concerning PCB layout, fabrication, and mount-
ing an LLP package is available from National Semiconduc-
tor’s package Engineering Group under application note
AN-1187.
PCB LAYOUT AND SUPPLY REGULATION
CONSIDERATIONS FOR DRIVING 3
Ω 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 imped-
ance decreases, load dissipation becomes increasingly de-
pendent on the interconnect (PCB trace and wire) resistance
between the amplifier output pins and the load’s connec-
tions. Residual trace resistance causes a voltage drop,
which results in power dissipated in the trace and not in the
load as desired. For example, 0.1
Ω trace resistance reduces
the output power dissipated by a 4
Ω load from 1.4W to
1.37W. This problem of decreased load dissipation is exac-
erbated as load impedance decreases. Therefore, to main-
tain 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 sup-
plies, trace resistance creates the same effects as poor
sup-ply 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 designing a
successful amplifer, whether the amplifier is bridged or
single-ended. Equation 2 states the maximum power dissi-
pation point for a single-ended amplifier operating at a given
supply voltage and driving a specified output load.
P
DMAX=(VDD)
2/(2
π2R
L) Single-Ended
(1)
www.national.com
11


Número de pieza similar - LM4895IBP

Fabricante ElectrónicoNo. de piezaDatasheetDescripción Electrónicos
logo
National Semiconductor ...
LM4890 NSC-LM4890 Datasheet
1Mb / 31P
   1 Watt Audio Power Amplifier
logo
Texas Instruments
LM4890 TI-LM4890 Datasheet
1Mb / 36P
[Old version datasheet]   1 Watt Audio Power Amplifier
LM48901 TI-LM48901 Datasheet
821Kb / 51P
[Old version datasheet]   Audio Power Amplifier Series
LM48901RL TI-LM48901RL Datasheet
821Kb / 51P
[Old version datasheet]   Audio Power Amplifier Series
LM48901RLX TI-LM48901RLX Datasheet
821Kb / 51P
[Old version datasheet]   Audio Power Amplifier Series
More results

Descripción similar - LM4895IBP

Fabricante ElectrónicoNo. de piezaDatasheetDescripción Electrónicos
logo
National Semiconductor ...
LM4899 NSC-LM4899 Datasheet
593Kb / 16P
   1 Watt Fully Differential Audio Power Amplifier With Shutdown Select and Fixed 6dB Gain
logo
Texas Instruments
LM4898 TI1-LM4898_14 Datasheet
1Mb / 23P
[Old version datasheet]   1 Watt Fully Differential Audio Power Amplifier With Shutdown Select
logo
National Semiconductor ...
LM4894 NSC-LM4894 Datasheet
770Kb / 19P
   1 Watt Fully Differential Audio Power Amplifier With Shutdown Select
LM4898 NSC-LM4898 Datasheet
596Kb / 17P
   1 Watt Fully Differential Audio Power Amplifier With Shutdown Select
LM4923 NSC-LM4923_07 Datasheet
390Kb / 14P
   1.1 Watt Fully Differential Audio Power Amplifier With Shutdown Select
LM4923 NSC-LM4923 Datasheet
433Kb / 12P
   1.1 Watt Fully Differential Audio Power Amplifier With Shutdown Select
logo
Texas Instruments
LM4923 TI1-LM4923_14 Datasheet
947Kb / 23P
[Old version datasheet]   1.1 Watt Fully Differential Audio Power Amplifier With Shutdown Select
LM4923 TI1-LM4923 Datasheet
980Kb / 23P
[Old version datasheet]   1.1 Watt Fully Differential Audio Power Amplifier With Shutdown Select
logo
National Semiconductor ...
LM4927 NSC-LM4927 Datasheet
827Kb / 14P
   2.5 Watt Fully Differential Audio Power Amplifier With Shutdown
logo
Texas Instruments
LM4927 TI1-LM4927_14 Datasheet
939Kb / 20P
[Old version datasheet]   Audio Power Amplifier Series 2.5 Watt Fully Differential Audio Power Amplifier With Shutdown
More results


Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15


Datasheet Descarga

Go To PDF Page


Enlace URL




Política de Privacidad
ALLDATASHEET.ES
¿ALLDATASHEET es útil para Ud.?  [ DONATE ] 

Todo acerca de Alldatasheet   |   Publicidad   |   Contáctenos   |   Política de Privacidad   |   Intercambio de Enlaces   |   Lista de Fabricantes
All Rights Reserved©Alldatasheet.com


Mirror Sites
English : Alldatasheet.com  |   English : Alldatasheet.net  |   Chinese : Alldatasheetcn.com  |   German : Alldatasheetde.com  |   Japanese : Alldatasheet.jp
Russian : Alldatasheetru.com  |   Korean : Alldatasheet.co.kr  |   Spanish : Alldatasheet.es  |   French : Alldatasheet.fr  |   Italian : Alldatasheetit.com
Portuguese : Alldatasheetpt.com  |   Polish : Alldatasheet.pl  |   Vietnamese : Alldatasheet.vn
Indian : Alldatasheet.in  |   Mexican : Alldatasheet.com.mx  |   British : Alldatasheet.co.uk  |   New Zealand : Alldatasheet.co.nz
Family Site : ic2ic.com  |   icmetro.com