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参数资料
| 型号： | IRDC3822 |
| 厂商： | International Rectifier |
| 文件页数： | 9/21页 |
| 文件大小： | 0K |
| 描述： | BOARD EVAL SYNC BUCK CONVERTER |
| 产品变化通告： | (EP) Parts Discontinuation 25/May/2012 |
| 标准包装： | 1 |
| 系列： | * |
PD-60333
IR3822MPBF
Soft-Start
The IR3822 has programmable soft-start to
control the output voltage rise and limit the inrush
current during start-up.
20uA
3V
To ensure correct start-up, the soft-start
sequence initiates when Vcc and Vc rise above
their threshold and generate the Power On
Ready (POR) signal. The soft-start function
SS/SD
POR
40uA
operates by sourcing current to charge an
external capacitor to about 3V.
Initially, the soft-start function clamps the output
of error amplifier by injecting a current (40uA)
into the Fb pin and generates a voltage about
Comp
0.6V
Fb
24K
24K
Error Amp
0.96V (40ux24K) across the negative input of
error amplifier (see figure 5).
The magnitude of the injected current is inversely
proportional to the voltage at the soft-start pin. As
the soft-start voltage ramps up, the injected
current decreases linearly and so does the
voltage at negative input of error amplifier.
When the soft-start capacitor is around 1V, the
voltage at the positive input of the error amplifier
is approximately 0.6V.
Fig. 5: Soft-Start circuit for IR3822
Output of UVLO
The output of error amplifier will start increasing
and generating the first PWM signal. As the soft-
start capacitor voltage continues to rise up, the
POR
3V
? 2V
current flowing into the Fb pin will keep
decreasing.
The feedback voltage increases linearly as the
soft start voltage ramps up. When soft-start
voltage is around 2V, the output voltage reaches
Soft-Start
Voltage
Current flowing
into Fb pin
0V
40uA
0uA
? 1V
the steady state and the injected current is zero .
Figure 6 shows the theoretical operating
waveforms during soft-start.
The output voltage start-up time is the time
period when soft-start capacitor voltage
Voltage at negative input ? 0.96V
of Error Amp
0.6V
0.6V
increases from 1V to 2V.
The start-up time will be dependent on the size of
Voltage at Fb pin
0V
the external soft-start capacitor and can be
estimated by:
Fig. 6: Theoretical operation waveforms
20 μ A ?
T start
C ss
= 2 V ? 1 V
during soft-start
For a given start-up time, the soft-start capacitor
can be estimated as:
C SS ? 20 μ A * T start ( ms )
11/04/08
--( 1 )
9
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相关代理商/技术参数 |
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|---|---|
| IRDC3822A | 功能描述:电源管理IC开发工具 IR3822A SYNC CONV 300kHz EVAL BRD RoHS:否 制造商:Maxim Integrated 产品:Evaluation Kits 类型:Battery Management 工具用于评估:MAX17710GB 输入电压: 输出电压:1.8 V |
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| IRDC3831 | 功能描述:电源管理IC开发工具 IR3831 SYNC CONV 600kHz EVAL BRD RoHS:否 制造商:Maxim Integrated 产品:Evaluation Kits 类型:Battery Management 工具用于评估:MAX17710GB 输入电压: 输出电压:1.8 V |
| IRDC3831W | 功能描述:电源管理IC开发工具 User Guide IR3831W Eval Brd RoHS:否 制造商:Maxim Integrated 产品:Evaluation Kits 类型:Battery Management 工具用于评估:MAX17710GB 输入电压: 输出电压:1.8 V |
| IRDC3832W | 功能描述:电源管理IC开发工具 User Guide IR3832W Eval Brd RoHS:否 制造商:Maxim Integrated 产品:Evaluation Kits 类型:Battery Management 工具用于评估:MAX17710GB 输入电压: 输出电压:1.8 V |
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