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參數(shù)資料
| 型號(hào)： | LM3224MMX-ADJ |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | 615kHz/1.25MHz Step-up PWM DC/DC Converter |
| 中文描述： | 2.8 A SWITCHING REGULATOR, 1500 kHz SWITCHING FREQ-MAX, PDSO8 |
| 封裝： | PLASTIC, MSOP-8 |
| 文件頁數(shù)： | 9/18頁 |
| 文件大?。?/td> | 920K |
| 代理商： | LM3224MMX-ADJ |
Operation
CONTINUOUS CONDUCTION MODE
The LM3224 is a current-mode, PWM boost regulator. A
boost regulator steps the input voltage up to a higher output
voltage. In continuous conduction mode (when the inductor
current never reaches zero at steady state), the boost regu-
lator operates in two cycles.
In the first cycle of operation, shown in
Figure 1
(a), the
transistor is closed and the diode is reverse biased. Energy
is collected in the inductor and the load current is supplied by
C
OUT
.
The second cycle is shown in
Figure 1
(b). During this cycle,
the transistor is open and the diode is forward biased. The
energy stored in the inductor is transferred to the load and
output capacitor.
The ratio of these two cycles determines the output voltage.
The output voltage is defined approximately as:
where D is the duty cycle of the switch, D and D' will be
required for design calculations.
SETTING THE OUTPUT VOLTAGE
The output voltage is set using the feedback pin and a
resistor divider connected to the output as shown in the
typical operating circuit. The feedback pin voltage is 1.26V,
so the ratio of the feedback resistors sets the output voltage
according to the following equation:
SOFT-START CAPACITOR
The LM3224 has a soft-start pin that can be used to limit the
inductor inrush current on start-up. The external SS pin is
used to tailor the soft-start for a specific application but is not
required for all applications and can be left open when not
needed. When used, a current source charges the external
soft-start capacitor, Css. The soft-start time can be estimated
as:
Tss = Css*1.24V/Iss
THERMAL SHUTDOWN
The LM3224 includes thermal shutdown protection. If the die
temperature exceeds 140C the regulator will shut off the
power switch, significantly reducing power dissipation in the
device. The switch will remain off until the die temperature is
reduced to approximately 120C. If the cause of the excess
heating is not removed (excessive ambient temperature,
excessive power dissipation, or both) the device will con-
tinue to cycle on and off in this manner to protect from
damage.
20097602
FIGURE 1. Simplified Boost Converter Diagram
(a) First Cycle of Operation (b) Second Cycle Of Operation
L
www.national.com
9
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LM3224MMX-ADJ/NOPB | 功能描述:DC/DC 開關(guān)控制器 RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開關(guān)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(fēng)格: 封裝 / 箱體:CPAK |
| LM322H | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:Precision Timers |
| LM322N | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:Precision Timers |
| LM322N/B+ | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Analog Timer Circuit |
| LM323 | 制造商:STMICROELECTRONICS 制造商全稱:STMicroelectronics 功能描述:Three-terminal 3 A adjustable voltage regulators |
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