Electronic Components Datasheet Search
  English  ▼
ALLDATASHEET.NET

X  

LM4702B Datasheet(PDF) 10 Page - National Semiconductor (TI)

[Old version datasheet] Texas Instruments acquired National semiconductor.
Part # LM4702B
Description  LM4702 Overture Audio Power Amplifier Series Stereo High Fidelity 200 Volt* Driver with Mute
Download  15 Pages
Scroll/Zoom Zoom In 100%  Zoom Out
Manufacturer  NSC [National Semiconductor (TI)]
Direct Link  http://www.national.com
Logo NSC - National Semiconductor (TI)

LM4702B Datasheet(HTML) 10 Page - National Semiconductor (TI)

Back Button LM4702B Datasheet HTML 6Page - National Semiconductor (TI) LM4702B Datasheet HTML 7Page - National Semiconductor (TI) LM4702B Datasheet HTML 8Page - National Semiconductor (TI) LM4702B Datasheet HTML 9Page - National Semiconductor (TI) LM4702B Datasheet HTML 10Page - National Semiconductor (TI) LM4702B Datasheet HTML 11Page - National Semiconductor (TI) LM4702B Datasheet HTML 12Page - National Semiconductor (TI) LM4702B Datasheet HTML 13Page - National Semiconductor (TI) LM4702B Datasheet HTML 14Page - National Semiconductor (TI) Next Button
Zoom Inzoom in Zoom Outzoom out
 10 / 15 page
background image
Application Information
MUTE FUNCTION
The mute function of the LM4702 is controlled by the amount
of current that flows into the mute pin. If there is less than
1mA of current flowing into the mute pin, the part will be in
mute. This can be achieved by shorting the mute pin to
ground or by floating the mute pin. If there is between 1mA
and 2mA of current flowing into the mute pin, the part will be
in “play” mode. This can be done by connecting a power
supply (Vmute) to the mute pin through a resistor (Rm). The
current into the mute pin can be determined by the equation
Imute = (Vmute – 2.9) / Rm. For example, if a 5V power
supply is connected through a 1.4k resistor to the mute pin,
then the mute current will be 1.5mA, at the center of the
specified range. It is also possible to use Vcc as the power
supply for the mute pin, though Rm will have to be recalcu-
lated accordingly. It is not recommended to flow more than
2mA of current into the mute pin because damage to the
LM4702 may occur.
It is highly recommended to switch between mute and “play”
modes rapidly. This is accomplished most easily through
using a toggle switch that alternatively connects the mute pin
through a resistor to either ground or the mute pin power
supply. Slowly increasing the mute current may result in
undesired voltages on the outputs of the LM4702, which can
damage an attached speaker.
THERMAL PROTECTION
The LM4702 has a sophisticated thermal protection scheme
to prevent long-term thermal stress of the device. When the
temperature on the die exceeds 150˚C, the LM4702 shuts
down. It starts operating again when the die temperature
drops to about 145˚C, but if the temperature again begins to
rise, shutdown will occur again above 150˚C. Therefore, the
device is allowed to heat up to a relatively high temperature
if the fault condition is temporary, but a sustained fault will
cause the device to cycle in a Schmitt Trigger fashion be-
tween the thermal shutdown temperature limits of 150˚C and
145˚C. This greatly reduces the stress imposed on the IC by
thermal cycling, which in turn improves its reliability under
sustained fault conditions.
Since the die temperature is directly dependent upon the
heat sink used, the heat sink should be chosen so that
thermal shutdown is not activated during normal operation.
Using the best heat sink possible within the cost and space
constraints of the system will improve the long-term reliability
of any power semiconductor device, as discussed in the
Determining the Correct Heat Sink section.
POWER DISSIPATION AND HEAT SINKING
When in “play” mode, the LM4702 draws a constant amount
of current, regardless of the input signal amplitude. Conse-
quently, the power dissipation is constant for a given supply
voltage and can be computed with the equation P
DMAX = Icc
* (Vcc – Vee). For a quick calculation of P
DMAX, approximate
the current to be 25mA and multiply it by the total supply
voltage (the current varies slightly from this value over the
operating range).
DETERMINING THE CORRECT HEAT SINK
The choice of a heat sink for a high-power audio amplifier is
made entirely to keep the die temperature at a level such
that the thermal protection circuitry is not activated under
normal circumstances.
The thermal resistance from the die to the outside air,
θ
JA
(junction to ambient), is a combination of three thermal re-
sistances,
θ
JC (junction to case),
θ
CS (case to sink), and
θ
SA
(sink to ambient). The thermal resistance,
θ
JC (junction to
case), of the LM4702T is 0.8˚C/W. Using Thermalloy Ther-
macote thermal compound, the thermal resistance,
θ
CS
(case to sink), is about 0.2˚C/W. Since convection heat flow
(power dissipation) is analogous to current flow, thermal
resistance is analogous to electrical resistance, and tem-
perature drops are analogous to voltage drops, the power
dissipation out of the LM4702 is equal to the following:
P
DMAX =(TJMAX−TAMB)/
θ
JA
(1)
where T
JMAX = 150˚C, TAMB is the system ambient tempera-
ture and
θ
JA =
θ
JC +
θ
CS +
θ
SA.
20158355
Once the maximum package power dissipation has been
calculated using equation 2, the maximum thermal resis-
tance,
θ
SA, (heat sink to ambient) in ˚C/W for a heat sink can
be calculated. This calculation is made using equation 4
which is derived by solving for
θ
SA in equation 3.
θ
SA = [(TJMAX−TAMB)−PDMAX(
θ
JC +
θ
CS)]/PDMAX
(2)
Again it must be noted that the value of
θ
SA is dependent
upon the system designer’s amplifier requirements. If the
ambient temperature that the audio amplifier is to be working
under is higher than 25˚C, then the thermal resistance for the
heat sink, given all other things are equal, will need to be
smaller.
PROPER SELECTION OF EXTERNAL COMPONENTS
Proper selection of external components is required to meet
the design targets of an application. The choice of external
component values that will affect gain and low frequency
response are discussed below.
The gain of each amplifier is set by resistors R
f and Ri for the
non-inverting configuration shown in Figure 1. The gain is
found by Equation (3) below:
A
V =1+Rf /Ri (V/V)
(3)
For best noise performance, lower values of resistors are
used. A value of 1k
Ω is commonly used for R
i and then
setting the value of R
f for the desired gain. For the LM4702
the gain should be set no lower than 26dB. Gain settings
below 26dB may experience instability.
The combination of R
i with Ci (see Figure 1) creates a high
pass filter. The low frequency response is determined by
these two components. The -3dB point can be found from
Equation (4) shown below:
f
i =1/(2
πR
iCi) (Hz)
(4)
If an input coupling capacitor is used to block DC from the
inputs as shown in Figure 5, there will be another high pass
filter created with the combination of C
IN and RIN. When
using a input coupling capacitor R
IN is needed to set the DC
www.national.com
10


Similar Part No. - LM4702B

ManufacturerPart #DatasheetDescription
logo
Texas Instruments
LM4702BTA/NOPB TI1-LM4702BTA/NOPB Datasheet
511Kb / 20P
[Old version datasheet]   LM4702 Audio Power Amplifier Series Stereo High Fidelity 200 Volt Driver with Mute
More results

Similar Description - LM4702B

ManufacturerPart #DatasheetDescription
logo
Texas Instruments
LM4702CTA TI1-LM4702CTA Datasheet
511Kb / 20P
[Old version datasheet]   LM4702 Audio Power Amplifier Series Stereo High Fidelity 200 Volt Driver with Mute
90074 TI-90074 Datasheet
856Kb / 16P
[Old version datasheet]   Audio Power Amplifier Series Stereo High Fidelity 200 Volt Driver with Mute
logo
National Semiconductor ...
LME49830 NSC-LME49830 Datasheet
515Kb / 22P
   Mono High Fidelity 200 Volt MOSFET Power Amplifier Input Stage with Mute
logo
Texas Instruments
LME49830 TI1-LME49830 Datasheet
811Kb / 23P
[Old version datasheet]   LME49830 Mono High Fidelity 200 Volt MOSFET Power Amplifier Input Stage with Mute
LM4766 TI-LM4766_15 Datasheet
955Kb / 23P
[Old version datasheet]    Overture Audio Power Amplifier Series Dual 40W Audio Power Amplifier with Mute
logo
National Semiconductor ...
LM2876 NSC-LM2876_00 Datasheet
658Kb / 22P
   Overture Audio Power Amplifier Series High-Performance 40W Audio Power Amplifier w/Mute
logo
Texas Instruments
LME49811 TI1-LME49811 Datasheet
416Kb / 19P
[Old version datasheet]   Audio Power Amplifier Series High Fidelity 200 Volt Power Amplifier Input Stage with Shutdown
logo
National Semiconductor ...
LM4781 NSC-LM4781 Datasheet
1Mb / 25P
   Overture??Audio Power Amplifier Series 3 Channel 35W Audio Power Amplifier with Mute
LM2876 NSC-LM2876 Datasheet
565Kb / 19P
   Overture??Audio Power Amplifier Series High-Performance 40W Audio Power Amplifier w/Mute
LM4701 NSC-LM4701 Datasheet
541Kb / 15P
   LM4701 Overture??Audio Power Amplifier Series 30W Audio Power Amplifier with Mute and Standby Modes
More results


Html Pages

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


Datasheet Download

Go To PDF Page


Link URL




Privacy Policy
ALLDATASHEET.NET
Does ALLDATASHEET help your business so far?  [ DONATE ] 

About Alldatasheet   |   Advertisement   |   Contact us   |   Privacy Policy   |   Link Exchange   |   Manufacturer List
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