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参数资料
| 型号： | IRDC3870 |
| 厂商： | International Rectifier |
| 文件页数： | 14/20页 |
| 文件大小： | 0K |
| 描述： | BOARD EVAL REG SUPIRBUCK DC/DC |
| 产品变化通告： | (EP) Parts Discontinuation 25/May/2012 |
| 标准包装： | 1 |
| 系列： | * |
IR3870MPBF
Output Capacitor Selection
Selection of the output capacitor requires
meeting voltage overshoot requirements during
load removal, and meeting steady state output
ripple voltage requirements. The output
capacitor is the most expensive converter
component and increases the overall system
cost. The output capacitor decoupling in the
converter typically includes the low frequency
capacitor, such as Specialty Polymer Aluminum,
and mid frequency ceramic capacitors.
VESR is usually much greater than VESL. The
IR3870 requires a total ESR such that the ripple
voltage at the FB pin is greater than 7mV.
The second purpose of the output capacitor is to
minimize the overshoot of the output voltage
when the load decreases as shown in Figure 18.
By using the law of energy before and after the
load removal, equation 7 shows the output
capacitance requirement for a load step.
L ? I STEP
The first purpose of output capacitors is to
provide current when the load demand exceeds
the inductor current, as shown in Figure 17.
Equation 6 shows the charge requirement for a
C OUT ?
2
V OS 2 ? V OUT
2
(7)
certain load. The advantage provided by the
IR3870 at a load step is to reduce the delay
compared to a fixed frequency control method (in
microseconds or (1-D)*Ts). If the load increases
right after the PWM signal goes low, the longest
delay will be equal to the minimum lower gate on
as shown in the Electrical Specification table.
The IR3870 also reduces the inductor current
slew time, the time it takes for the inductor
current to reach equality with the output current,
by increasing the switching frequency up to
2.5MHz. The result reduces the recovery time.
Figure 18. Typical Output Voltage Response
Waveform.
Figure 17. Charge Requirement during Load Step
Q ? C ? V ? 0.5 ? Istep ? ? t
(6a)
1 ? 1 L ? Δ Istep 2 ?
V DROP ? ? 2 ? V IN ? V OUT ? ? ?
C OUT ?
? ? ? (6b)
The output voltage drops, VDROP, initially
depending on the characteristic of the output
capacitor. VDROP is the sum of the equivalent
series inductance (ESL) of the output capacitor
times the rate of change of the output current and
the ESR times the change of the output current.
14
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相关代理商/技术参数 |
参数描述 |
|---|---|
| IRDC3871 | 功能描述:电源管理IC开发工具 USER GUIDE FOR IR3871 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 |
| IRDC3876 | 制造商:International Rectifier 功能描述:9999V 999.000A POL IC - Rail/Tube 制造商:International Rectifier 功能描述:BOARD EVAL FOR IR3876 |
| IRDC3894 | 功能描述:电源管理IC开发工具 Design Kit Featuring IR3894M 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 |
| IRDC3895 | 功能描述:电源管理IC开发工具 Design Kit Featuring IR3895M 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 |
| IRDC3897 | 功能描述:电源管理IC开发工具 Design Kit POL IC 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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