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參數(shù)資料
| 型號： | LM4781TA |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 音頻／視頻放大 |
| 英文描述： | Overture⑩ Audio Power Amplifier Series 3 Channel 35W Audio Power Amplifier with Mute |
| 中文描述： | 35 W, 3 CHANNEL, AUDIO AMPLIFIER, PZFM27 |
| 封裝： | PLASTIC, TO-220, 27 PIN |
| 文件頁數(shù)： | 15/25頁 |
| 文件大小： | 1125K |
| 代理商： | LM4781TA |
Typical Performance Characteristics
(Continued)
Frequency Response of Demo Board
P
OUT
= 10W/Channel = 0dB, R
IN
= 47k
R
L
= 8
, No Filters
200673C9
Note 17:
Bridge mode graphs were taken using the demo board and inverting the signal to the channel B input.
Note 18:
Parallel mode graphs were taken using the demo board connecting each output through a 0.1
/3W resistor to the load.
Application Information
MUTE MODE
The muting function allows the user to mute the amplifier.
This can be accomplished as shown in the Typical Applica-
tion Circuit. The resistor R
is chosen with reference to the
negative supply voltage and is used in conjunction with a
switch. The switch, when opened or switched to GND, cuts
off the current flow from the MUTE pins to V
, thus placing
the LM4781 into mute mode. Refer to the Mute Attenuation
vs Mute Current curves in the
Typical Performance Char-
acteristics
section for values of attenuation per current out
of each MUTE pin. The resistance R
M
is calculated by the
following equation:
R
M
≤
(|V
EE
| 2.6V) / I
MUTE
Where I
MUTE
≥
0.5mA for each MUTE pin.
The MUTE pins can be tied together so that only one resistor
is required for the mute function. The mute resistor value
must be chosen so that a minimum of 1.5mA is pulled
through the resistor R
M
. This ensures that each amplifier is
fully operational. Taking into account supply line fluctuations,
it is a good idea to pull out 1mA per MUTE pin or 3mA total
if all pins are tied together.
A turn-on MUTE or soft start circuit may also be used during
power up. A simple circuit like the one shown below may be
used.
200673B7
The RC combination of C
and R
may cause the voltage
at point A to change more slowly than the -V
supply
voltage. Until the voltage at point A is low enough to have
0.5mA of current per MUTE pin flow through R
M2
, the IC will
be in mute mode. The series combination of R
and R
needs to satisfy the mute equation above for all operating
voltages or mute mode may be activated during normal
operation. For a longer turn-on mute time, a larger time
constant,
τ
= RC = R
C
(sec), is needed. For the values
show above and with the MUTE pins tied together, the
LM4781 will enter play mode when the voltage at point A is
-25.1V. The voltage at point A is found with Equation (1)
below.
V
A
(t) = (V
f
- V
O
)e
-t/
τ
(Volts)
where:
t = time (sec)
τ
= RC (sec)
V
o
= Voltage on C at t = 0 (Volts)
V
f
= Final voltage, -V
EE
in this circuit (Volts)
(1)
UNDER-VOLTAGE PROTECTION
Upon system power-up, the under-voltage protection cir-
cuitry allows the power supplies and their corresponding
capacitors to come up close to their full values before turning
on the LM4781. Since the supplies have essentially settled
to their final value, no DC output spikes occur. At power
down, the outputs of the LM4781 are forced to ground before
the power supply voltages fully decay preventing transients
on the output.
OVER-VOLTAGE PROTECTION
The LM4781 contains over-voltage protection circuitry that
limits the output current while also providing voltage clamp-
ing. The clamp does not, however, use internal clamping
diodes. The clamping effect is quite the same because the
output transistors are designed to work alternately by sinking
large current spikes.
SPiKe PROTECTION
The
LM4781
temperature stressing of the power transistor array. The Safe
Operating graph in the
Typical Performance Characteris-
is
protected
from
instantaneous
peak-
L
www.national.com
15
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| LM4781TA/NOPB | 功能描述:音頻放大器 RoHS:否 制造商:STMicroelectronics 產(chǎn)品:General Purpose Audio Amplifiers 輸出類型:Digital 輸出功率: THD + 噪聲: 工作電源電壓:3.3 V 電源電流: 最大功率耗散: 最大工作溫度: 安裝風格:SMD/SMT 封裝 / 箱體:TQFP-64 封裝:Reel |
| LM4781TABD | 功能描述:音頻 IC 開發(fā)工具 LM4871 EVAL BOARD RoHS:否 制造商:Texas Instruments 產(chǎn)品:Evaluation Kits 類型:Audio Amplifiers 工具用于評估:TAS5614L 工作電源電壓:12 V to 38 V |
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| LM4782 | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:Overture Audio Power Amplifier Series 3 Channel 25W Audio Power Amplifier with Mute and Standby |
| LM4782_06 | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:Overture Audio Power Amplifier Series 3 Channel 25W Audio Power Amplifier with Mute and Standby |
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