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參數(shù)資料
| 型號： | LM494 |
| 廠商： | National Semiconductor Corporation |
| 英文描述： | Pulse Width Modulated Control Circuit |
| 中文描述： | 脈寬調(diào)制控制電路 |
| 文件頁數(shù)： | 4/8頁 |
| 文件大小： | 159K |
| 代理商： | LM494 |
Functional Description
The basic oscillator (switching) frequency is controlled by an
external resistor (R
T
) and capacitor (C
T
). The relationship
between the values of R
T
, C
T
and frequency is shown in
Figure 10.
The level of the sawtooth wave form is compared with an
error voltage by the pulse width modulated comparator. The
output of the PWM Comparator directs the pulse steering
flip-flop and the output control logic.
The error voltage is generated by the error amplifier. The
error amplifier boosts the voltage difference between the
output and the 5.0V internal reference. See Figure 7 for
error amp sensing techniques. The second error amp is typi-
cally used to implement current-limiting.
The output control logic selects either push-pull or single-
ended operation of the output transistors (see Figure 6 ).
The dead time control prevents on-state overlap of the out-
put transistors as can be seen inFigure 5. The dead time is
approximately 3.0% or 5.0% of the total period if the dead
time control is grounded. This dead time can be increased
by connecting the dead time control to a voltage up to 5.0V.
The frequency response of the error amps (Figure 11) can
be modified by using external resistors and capacitors.
These components are typically connected between the
compensation terminal and the inverting input of the error
amps.
The switching frequency of two or more LM494 circuits can
be synchronized. The timing capacitor, C
T
, is connected as
shown inFigure 8. Charging current is provided by the mas-
ter circuit. Discharging is through all the circuits slaved to
the master. R
T
is required only for the master circuit.
Test Circuits
TL/H/10056–3
FIGURE 1. Error Amplifier Test Circuit
TL/H/10056–4
FIGURE 2. Current Limit Sense
Amplifier Test Circuit
TL/H/10056–5
TL/H/10056–6
FIGURE 3. Common Emitter Configuration
Test Circuit and Waveform
TL/H/10056–7
TL/H/10056–8
FIGURE 4. Emitter Follower Configuration
Test Circuit and Waveform
TL/H/10056–9
FIGURE 5. Dead Time and Feedback
Control Test Circuit
4
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| LM494CJ | Pulse Width Modulated Control Circuit |
| LM494CN | Pulse Width Modulated Control Circuit |
| LM5026 | Active Clamp Current Mode PWM Controller |
| LM5026MT | Active Clamp Current Mode PWM Controller |
| LM5026MTX | Active Clamp Current Mode PWM Controller |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LM4940 | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:6W Streo Audio Power Amplifier |
| LM4940TS | 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 |
| LM4940TS/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 |
| LM4940TSBD | 功能描述:音頻 IC 開發(fā)工具 LM4940TS 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 |
| LM4940TSBD/NOPB | 功能描述:音頻 IC 開發(fā)工具 LM4940TS EVAL BRD 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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