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參數資料
| 型號： | LM494CN |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 穩壓器 |
| 英文描述： | Pulse Width Modulated Control Circuit |
| 中文描述： | 0.25 A SWITCHING CONTROLLER, 300 kHz SWITCHING FREQ-MAX, PDIP16 |
| 封裝： | PLASTIC, DIP-16 |
| 文件頁數： | 4/8頁 |
| 文件大小： | 159K |
| 代理商： | LM494CN |
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
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相關代理商/技術參數 |
參數描述 |
|---|---|
| LM494IN | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:Pulse Width Modulated Control Circuit |
| LM4950 | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:7.5W Mono-BTL or 3.1W Stereo Audio Power Amplifier |
| LM4950TA | 制造商:Texas Instruments 功能描述:AMP 3W STEREO/6W MONO 4950 TO-220 |
| LM4950TA/NOPB | 功能描述:IC AMP AUDIO PWR 7.5W AB TO220-9 RoHS:是 類別:集成電路 (IC) >> 線性 - 音頻放大器 系列:Boomer® 產品培訓模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 標準包裝:2,500 系列:DirectDrive® 類型:H 類 輸出類型:耳機，2-通道（立體聲） 在某負載時最大輸出功率 x 通道數量:35mW x 2 @ 16 歐姆 電源電壓:1.62 V ~ 1.98 V 特點:I²C，麥克風，靜音，短路保護，音量控制 安裝類型:表面貼裝 供應商設備封裝:25-WLP（2.09x2.09） 封裝/外殼:25-WFBGA，WLCSP 包裝:帶卷 (TR) |
| LM4950TS | 功能描述:音頻放大器 RoHS:否 制造商:STMicroelectronics 產品: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 |
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