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参数资料
| 型号： | IRDC3856 |
| 厂商： | International Rectifier |
| 文件页数： | 21/35页 |
| 文件大小： | 0K |
| 描述： | BOARD EVAL FOR IR3856 |
| 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： | 1.8V |
| 电流 - 输出： | 0 ~ 6A |
| 输入电压： | 12V |
| 稳压器拓扑结构： | 降压 |
| 频率 - 开关： | 600kHz |
| 板类型： | 完全填充 |
| 已供物品： | 板 |
| 已用 IC / 零件： | IR3856 |
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PD-97528
IR3856MPbF
Output Capacitor Selection
The voltage ripple and transient requirements
determine the output capacitors type and values.
The criteria is normally based on the value of the
Effective Series Resistance (ESR). However the
actual capacitance value and the Equivalent
The output LC filter introduces a double pole,
–40dB/decade gain slope above its corner
resonant frequency, and a total phase lag of 180 o
(see figure 13). The resonant frequency of the LC
filter is expressed as follows:
Series Inductance (ESL) are other contributing
components. These components can be
described as
F LC =
1
2 ? π L o ? C o
.......... .......... .......... .. (17)
Δ V o ( ESL ) = ? in
? V ? V o ?
Δ V o = Δ V o ( ESR ) + Δ V o ( ESL ) + Δ V o ( C )
Δ V o ( ESR ) = Δ I L * ESR
? * ESL
? L ?
Figure 14 shows gain and phase of the LC filter.
Since we already have 180 o phase shift from the
output filter alone, the system runs the risk of
being unstable.
Δ V o ( C ) =
Δ V o = Output
Δ I L
8 * C o * F s
voltage ripple
.......... ..... (16)
Δ I L = Inductor
ripple
current
Since the output capacitor has a major role in the
overall performance of the converter and
determines the result of transient response,
selection of the capacitor is critical. The IR3856
can perform well with all types of capacitors.
As a rule, the capacitor must have low enough
ESR to meet output ripple and load transient
requirements.
The goal for this design is to meet the voltage
ripple requirement in the smallest possible
capacitor size. Therefore it is advisable to select
ceramic capacitors due to their low ESR and ESL
and small size. Four of the TDK
C2102X5R0J226M (22uF, 6.3V, 3mOhm)
capacitors is a good choice.
Feedback Compensation
The IR3856 is a voltage mode controller. The
control loop is a single voltage feedback path
including error amplifier and error comparator. To
achieve fast transient response and accurate
output regulation, a compensation circuit is
Fig. 14. Gain and Phase of LC filter
The IR3856 uses a voltage-type error amplifier
with high-gain (110dB) and wide-bandwidth. The
output of the amplifier is available for DC gain
control and AC phase compensation.
The error amplifier can be compensated either in
Type-II or Type-III compensation.
Local feedback with Type-II compensation is
shown in figure 14.
This method requires that the output capacitor
should have enough ESR to satisfy stability
requirements. In general, for Type-II
compensation the output capacitor’s ESR
generates a zero typically at 5kHz to 50kHz
which is essential for an acceptable phase
margin.
The ESR zero of the output capacitor is
expressed as follows:
necessary. The goal of the compensation
network is to provide a closed-loop transfer
function with the highest 0 dB crossing frequency
F ESR =
1
2 ? π *ESR*C o
.......... .......... ....... (18)
and adequate phase margin (greater than 45 o ).
Rev 4.0
21
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相关代理商/技术参数 |
参数描述 |
|---|---|
| IRDC3856 - SUPIRBUCK | 制造商:International Rectifier 功能描述:INTERNATIONAL RECIFIER - GEN 2.1 SUPIRBUCK FAMILY - Bulk |
| IRDC3856 | 制造商:International Rectifier 功能描述:; MCU Supported Families:IR3856; Feature |
| IRDC3856W | 功能描述:电源管理IC开发工具 User Guide IR3856W 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 |
| IRDC3859 | 功能描述:电源管理IC开发工具 User Guide IR3859 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 |
| IRDC3859 - SUPIRBUCK | 制造商:International Rectifier 功能描述:INTERNATIONAL RECIFIER - GEN 2.1 SUPIRBUCK FAMILY - Bulk |
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