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参数资料
| 型号： | IRDC3871 |
| 厂商： | International Rectifier |
| 文件页数： | 15/21页 |
| 文件大小： | 0K |
| 描述： | BOARD EVAL FOR IRDC3871 |
| 标准包装： | 1 |
| 系列： | SupIRBuck™ |
| 主要目的： | DC/DC，步降 |
| 输出及类型： | 1，非隔离 |
| 输出电压： | 1.05V |
| 电流 - 输出： | 8A |
| 输入电压： | 12V |
| 稳压器拓扑结构： | 降压 |
| 频率 - 开关： | 300kHz |
| 板类型： | 完全填充 |
| 已供物品： | 板 |
| 已用 IC / 零件： | IR3871 |
IR3871MPBF
COMPONENT SELECTION
OUTPUT CAPACITOR SELECTION
Selection of the output capacitor requires meeting
The second purpose of the output capacitor is to
minimize the overshoot of the output voltage
voltage
overshoot
requirements
during
load
when the load decreases as shown in Figure
removal, and meeting steady state output ripple
voltage requirements. The output capacitor is the
23. By using the law of energy before and after
the load removal, equation 8 shows the output
most
expensive
converter
component
and
capacitance requirement for a load step.
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.
The first purpose of output capacitors is to provide
current when the load demand exceeds the
inductor current, as shown in Figure 22. Equation
7 shows the charge requirement for a certain load.
The advantage provided by the IR3871 at a load
C OUT ?
V OUT
V L
V DROP
V ESR
L ? I STEP 2
V OS 2 ? V OUT 2
V OS
(8)
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
I OUT
I STEP
Electrical Specification table. The IR3871 also
reduces the inductor current slew time, the time it
takes for the inductor current to reach equality
Figure 23. Typical Output Voltage Response
Waveform.
with the output current, by increasing
the
BOOT CAPACITOR SELECTION
switching frequency up to 2.5MHz. The result
The boot capacitor starts the cycle fully charged
reduces the recovery time.
to a voltage of VB(0).
Cg equals 0.65nF in
Load
Current
Output
I STEP
IR3871. Choose a sufficiently small ΔV such
that VB(0)- ΔV exceeds the maximum gate
threshold voltage to turn on the high side
C BOOT ? C g ? ? B
? 1 ? (9)
Charge
Inductor
Slew
Rate
MOSFET.
? V (0)
? ΔV
?
?
Δ t
t
Choose a boot capacitor value larger than the
calculated C BOOT in equation 9. Equation 9 is
Figure 22. Charge Requirement during Load Step
based on charge balance at CCM operation.
Q ? C ? V ? 0.5 ? Istep ? ? t
(7a)
Usually the boot capacitor will be discharged to
a much lower voltage when the circuit is
1 ? 1 L ? Istep 2 ?
V DROP ?? 2 ? V IN ? V OUT ? ??
C OUT ?
?
(7b)
operating in DCM mode at light load, due to
much longer Q2 off time and the bias current
drawn by the IC. Boot capacitance needs to be
increased if insufficient turn-on of Q1 is
The output voltage drop, VDROP, initially depends
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. VESR is
usually much greater than VESL. The IR3871
requires a total ESR such that the ripple voltage at
observed at light load, typically larger than
0.1μF is needed. The voltage rating of this part
needs to be larger than VB(0) plus the desired
derating voltage. Its ESR and ESL needs to be
low in order to allow it to deliver the large
current and di/dt’s which drive MOSFETs most
efficiently. In support of these requirements a
ceramic capacitor should be chosen.
the FB pin is greater than 7mV.
15
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相关代理商/技术参数 |
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| 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 |
| IRDC3897-P1V2 | 制造商:IRF 制造商全称:International Rectifier 功能描述:USER GUIDE FOR IR3897 EVALUATION BOARD |
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