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參數(shù)資料
| 型號： | LM3478MM |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | High Efficiency Low-Side N-Channel Controller for Switching Regulator |
| 中文描述： | 1 A SWITCHING CONTROLLER, 1000 kHz SWITCHING FREQ-MAX, PDSO8 |
| 封裝： | MSOP-8 |
| 文件頁數(shù)： | 10/21頁 |
| 文件大?。?/td> | 624K |
| 代理商： | LM3478MM |
Functional Description
(Continued)
SLOPE COMPENSATION RAMP
The LM3478 uses a current mode control scheme. The main
advantages of current mode control are inherent cycle-by-
cycle current limit for the switch, and simpler control loop
characteristics. It is also easy to parallel power stages using
current mode control since current sharing is automatic.
Current mode control has an inherent instability for duty
cycles greater than 50%, as shown in
Figure 2
. In
Figure 2
,
a small increase in the load current causes the switch cur-
rent to increase by
I
O
. The effect of this load change,
I
1
, is
:
From the above equation, when D
>
0.5,
I
will be greater
than
I
. In other words, the disturbance is divergent. So a
very small perturbation in the load will cause the disturbance
to increase.
To prevent the sub-harmonic oscillations, a compensation
ramp is added to the control signal, as shown in
Figure 3
.
With the compensation ramp,
10135507
FIGURE 1. Basic Operation of the PWM comparator
10135509
FIGURE 2. Sub-Harmonic Oscillation for D
>
0.5
L
www.national.com
10
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相關代理商/技術參數(shù) |
參數(shù)描述 |
|---|---|
| LM3478MM/E7001794 | 制造商:Texas Instruments 功能描述: |
| LM3478MM/NOPB | 功能描述:DC/DC 開關控制器 HI EFF LOW-SIDE N CH CONTROLLER RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開關頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數(shù)量:1 最大工作溫度:+ 125 C 安裝風格: 封裝 / 箱體:CPAK |
| LM3478MM/NOPB | 制造商:Texas Instruments 功能描述:Pulse Width Modulation (PWM) Controller |
| LM3478MMX | 功能描述:DC/DC 開關控制器 RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開關頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數(shù)量:1 最大工作溫度:+ 125 C 安裝風格: 封裝 / 箱體:CPAK |
| LM3478MMX/HALF | 制造商:Texas Instruments 功能描述: |
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