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参数资料
| 型号： | IRDC3811 |
| 厂商： | International Rectifier |
| 文件页数： | 10/21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-60334
IR3811MPbF
Over-Current Protection
The over current protection is performed by
sensing current through the R DS(on) of the low-
side MOSFET. This method enhances the
converter’s efficiency and reduces cost by
eliminating a current sense resistor. As shown in
figure 7, an external resistor (R SET ) is connected
between OCSet pin and the inductor point which
sets the current limit set point.
The internal current source develops a voltage
across R SET . When the low side MOSFET is
turned on, the inductor current flows through the
Q2 and results a voltage which is given by:
Fig. 8: 3uA current source for discharging
soft-start capacitor during hiccup
The OCP circuit starts sampling current when the
V OCSet = (I OCSet ? R OCSet ) ? (R DS(on) ? I L )
--( 2 )
low gate drive is about 3V. The OCSet pin is
internally clamped about 1.5V during on time of
high side gate to prevent false trigging, figure 9
shows the OCSet pin during one switching cycle.
As shown, there is about 150ns delay to mask
the dead time. Since this node contains switching
noises, this delay also functions as a filter.
Deadtime
Fig. 7: Connection of over current sensing resistor
The critical inductor current can be calculated by
setting:
I OCSet *R OCSet
Blanking time
Clamp voltage
V OCSet = (I OCSet ? R OCSet ) ? (R DS(on) ? I L ) = 0
Fig. 9: OCset pin during normal condition
I SET = I L ( critical )
=
R OCSet ? I OCSet
R DS ( on )
--( 3 )
Ch1: Inductor point, Ch3:OCSet
An over current is detected if the OCSet pin goes
below ground. This trips the OCP comparator
and cycles the soft start function in hiccup mode.
The hiccup is performed by charging and
discharging the soft-start capacitor in a certain
slope rate. As shown in figure 8 a 3uA current
source is used to discharge the soft-start
capacitor.
The OCP comparator resets after every soft start
cycle. The converter stays in this mode until the
overload or short circuit is removed. The
converter will automatically recover.
10/04/08
The value of R SET should be checked in an actual
circuit to ensure that the over current protection
circuit activates as expected. The IR3811 current
limit is designed primarily as disaster preventing,
and doesn't operate as a precision current
regulator.
10
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相关代理商/技术参数 |
参数描述 |
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| IRDC3812 | 功能描述:电源管理IC开发工具 IR3812 Eval Board 600kHz Controller 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 |
| IRDC3820 | 功能描述:电源管理IC开发工具 IR3820 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 |
| IRDC3820A | 功能描述:电源管理IC开发工具 IR3820A 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 |
| IRDC3821 | 功能描述:电源管理IC开发工具 IR3821 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 |
| IRDC3821A | 功能描述:电源管理IC开发工具 IR3821A 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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