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參數(shù)資料
| 型號： | LME49830TB |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 音頻／視頻放大 |
| 英文描述： | LME49830 Mono High Fidelity 200 Volt MOSFET Power Amplifier Input Stage with Mute; Package: TO-247 SINGLE GAUGE; No of Pins: 15 |
| 中文描述： | 1 CHANNEL, AUDIO AMPLIFIER, PZFM15 |
| 封裝： | PLASTIC, TO-247, 15 PIN |
| 文件頁數(shù)： | 4/20頁 |
| 文件大?。?/td> | 516K |
| 代理商： | LME49830TB |
Application Information
MUTE FUNCTION
The mute function of the LME49830 is controlled by the
amount of current that flows into the MUTE pin. If there is less
than 100
μA of current flowing into the MUTE pin, the part will
be in mute mode. This can be achieved by shorting the MUTE
pin to ground. It is recommended to connect a capacitor C
M
(its value not less than 47
μF) between the MUTE pin and
ground for reducing voltage fluctuation when switching be-
tween ‘play’ and ‘mute’ mode. If there is between 130
μA 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,
V
MUTE, to the MUTE pin through a resister, RM. The current
into the MUTE pin can be determined by the equation I
MUTE
= (V
MUTE – VBE) / (1k +RM) (A), where VBE 0.7V. For ex-
ample, if a 5V power supply is connected through a 27k
resistor to the MUTE pin, then the mute current will be
154
μA, at the center of the specified range. It is also possible
to use V
CC as the power supply for the MUTE pin, though RM
will have to be recalculated accordingly. It is not recommend-
ed to flow more than 2mA of current into the MUTE pin
because damage to the LME49830 may occur.
THERMAL PROTECTION
When the temperature on the die exceeds 150°C, the
LME49830 shuts down. It starts operating again when the die
temperature drops to about 145°C. When in thermal shut-
down, the current supply internal to the LME49830 will be cut-
off. There will be no signal generated to the output while in
thermal shutdown. After the die temperature decreases, the
LME49830 will power up again and resume normal operation.
If the fault conditions continue, thermal protection will be ac-
tivated and repeat the cycle preventing the LME49830 from
over heating.
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 pow-
er semiconductor device, as discussed in the Determining the
Correct Heat Sink section. It is recommended to use a sepa-
rate heat sink from the output stage heat sink for the
LME49830. A heat sink may not be needed if the supply volt-
ages are low.
POWER DISSIPATION AND HEAT SINKING
When in “play” mode, the LME49830 draws a constant
amount of current, regardless of the input signal amplitude.
Consequently, the power dissipation is constant for a given
supply voltage and can be computed with the equation
P
DMAX = ICC * (VCC – VEE) (W). For a quick calculation of
P
DMAX, approximate the current to be 20mA 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 any power IC is made entirely to
keep the die temperature at a level such that the thermal pro-
tection 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 resis-
tances,
θ
JC (junction to case), θCS (case to sink), and θSA (sink
to ambient). The thermal resistance,
θ
JC (junction to case), of
the LME49830TB is 4°C/W. Using Thermalloy Thermacote
thermal compound, the thermal resistance,
θ
CS (case to sink),
is about 0.2°C/W. Since convection heat flow (power dissi-
pation) is analogous to current flow, thermal resistance is
analogous to electrical resistance, and temperature drops are
analogous to voltage drops, the power dissipation out of the
LME49830 is equal to the following:
P
DMAX = (TJMAXTAMB) / θJA (W)
(1)
where T
JMAX = 150°C, TAMB is the system ambient tempera-
ture and
θ
JA = θJC + θCS + θSA.
30005055
Once the maximum package power dissipation has been cal-
culated, the maximum thermal resistance,
θ
SA, (heat sink to
ambient) in °C/W for a heat sink can be calculated. This cal-
culation is made using equation 2 which is derived by solving
for
θ
SA in equation 1.
θ
SA = [(TJMAXTAMB)PDMAX(θJC +θCS)] / PDMAX (°C/W)
(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, then the thermal resistance for the heat sink, given all
other things are equal, will need to be smaller (better heat
sink).
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 re-
sponse are discussed below.
The gain is set by resistors R
f and Ri for the non-inverting
tion 3 below:
A
V = 1 + Rf / Ri (V/V)
(3)
For best noise performance, lower values of resistors are
used. For the LME49830 the gain should be set no lower than
26dB. Gain settings below 26dB may experience instability.
The combination of R
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 / (2πRiCi) (Hz)
(4)
If an input coupling capacitor is used to block DC from the
inputs as shown in Figure 1, 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 bias
point on the amplifier's input terminal. The resulting -3dB fre-
quency response due to the combination of C
IN and RIN can
be found from Equation 5 shown below:
f
IN = 1 / (2πRINCIN) (Hz)
(5)
With large values of R
IN oscillations may be observed on the
outputs when the inputs are left floating. Decreasing the value
of R
IN or not letting the inputs float will remove the oscillations.
www.national.com
12
LME49830
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| LME49830TB/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(fēng)格:SMD/SMT 封裝 / 箱體:TQFP-64 封裝:Reel |
| LME49830TBBD | 功能描述:音頻 IC 開發(fā)工具 LME49830TB 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 |
| LME49860 | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:44V Dual High Performance, High Fidelity Audio Operational Amplifier |
| LME49860MA | 制造商:Texas Instruments 功能描述:OP Amp Dual GP 制造商:Texas Instruments 功能描述:OP AMP, HIFI AUDIO, DUAL, 44V, SMD |
| LME49860MA/NOPB | 功能描述:音頻放大器 44V Hi Fidelity Aud Op amp 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(fēng)格:SMD/SMT 封裝 / 箱體:TQFP-64 封裝:Reel |
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