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| 型号： | MAX15022EVKIT+ |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 23/28页 |
| 文件大小： | 0K |
| 描述： | KIT EVAL FOR MAX15022 |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 1 |
| 主要目的： | DC/DC，LDO 步降 |
| 输出及类型： | 4，非隔离 |
| 输出电压： | 3.3V，1.5V，1.2V，2.5V |
| 电流 - 输出： | 4A，2A，500mA，500mA |
| 输入电压： | 4.5 ~ 5.5 V |
| 稳压器拓扑结构： | 降压 |
| 频率 - 开关： | 2MHz |
| 板类型： | 完全填充 |
| 已供物品： | 板 |
| 已用 IC / 零件： | MAX15022 |
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Dual, 4A/2A, 4MHz, Step-Down DC-DC
Regulator with Dual LDO Controllers
The input capacitance to the base of the pass transistor
(C QIN ), any external base-to-emitter capacitance (C BE ,
see the Base-Drive Noise Reduction section), the tran-
sistor’s input resistance (R IN ), and the base-to-emitter
pullup resistor (R P_ ) set a second pole:
If the output capacitor is a high-ESR capacitor, then
cancel the ESR zero with a pole at FB3/4. This is
accomplished by adding a capacitor (C FB3/4 ) from
FB3/4 to ground, such that:
f POLE2 [kHz] =
1
2 π ( C BE + C QIN ) [ μ F ] × R TOTAL [ k ? ]
C FB3/4 [ μ F ] =
1
2 π × (R 1FB3/4 R 2FB3/4 ) [ k ? ] × f ESR [kHz]
For a sufficiently low output capacitance, choose a fast
R P1/2 >> R IN ≈
where R TOTAL = R IN R P1/2 .
To maintain the stability, at a minimum the following
condition must be satisfied:
A V × f POLE1 < f POLE2
i.e., the second pole must occur above the unity-gain
crossover. At heavy output load, we can simplify as fol-
lows:
R OUT3/4 << R 1FB3/4 + R 2FB3/4
C BE << C QIN ≈ g m ? PNP × τ F
β
g m ? PNP
And hence, the output capacitance (C OUT3/4 ) must sat-
isfy the following equation:
C OUT3/4 > α × g C_ × τ F × β 2
where:
PNP transistor without an excessively high ?. Note,
selecting a transistor with a ? that is too low can
adversely impact load regulation.
Output 3 and Output 4 Capacitors
Connect C OUT (as determined above) between the lin-
ear regulator’s output and ground, as close as possible
to the MAX15022 and the external pass transistors.
Depending on the selected pass transistor, larger
capacitor values may be required for stability (see the
Stability Requirement section).
Once the minimum capacitor value for stability is deter-
mined, verify that the linear regulator’s output does not
contain excessive noise. Although adequate for stabili-
ty, small capacitor values can provide too much band-
width, making the linear regulator sensitive to noise.
Larger capacitor values reduce the bandwidth, thereby
reducing the regulator’s noise sensitivity.
Base-Drive Noise Reduction
The high-impedance base driver is susceptible to sys-
tem noise, especially when the linear regulator is lightly
loaded. Capacitively coupled switching noise or induc-
α=
R 2FB3/4
R 1FB3/4 + R 2FB3/4
tively coupled EMI on the base drive may cause fluctu-
ations in the base current, which appear as noise on
the linear regulator’s output. To avoid this, keep the
base-driver traces away from the step-down converter
? is the current gain of the PNP transistor, g C_ is the
transconductance of the internal amplifier (1.2mA/mV
typical), and τ F is the forward transit time of the PNP
transistor. For example, using a PNP transistor with a ?
of 120, τ F of 400ps, g C_ = 1.2mA/mV, and α = 0.5 for a
1.2V output voltage, C OUT must be at least 3.9μF.
If the second pole occurs well after unity-gain crossover,
the linear regulator remains stable. If not, then increase
the output capacitance, C OUT3/4 , such that:
f POLE2 > 2 × f COUT_
and as short as possible to minimize noise coupling.
A bypass capacitor (C BE ) can be placed across the
base-to-emitter resistor. This bypass capacitor, in addi-
tion to the transistor’s input capacitance, reduces the
frequency of the second pole (f POLE2 ) that could desta-
bilize the linear regulator. Therefore, the stability
requirements determine the maximum base-to-emitter
capacitance (C BE ) that can be added. A capacitance
in the range of 470pF to 2200pF is recommended.
______________________________________________________________________________________
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相关代理商/技术参数 |
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| MAX15022EVKIT+ | 功能描述:电源管理IC开发工具 MAX15022 Eval Kit 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 |
| MAX15023ETG/V+ | 功能描述:DC/DC 开关控制器 4.5-28V Input Dual Out Synch Buck RoHS:否 制造商:Texas Instruments 输入电压:6 V to 100 V 开关频率: 输出电压:1.215 V to 80 V 输出电流:3.5 A 输出端数量:1 最大工作温度:+ 125 C 安装风格: 封装 / 箱体:CPAK |
| MAX15023ETG/V+T | 功能描述:DC/DC 开关控制器 4.5-28V Input Dual Out Synch Buck RoHS:否 制造商:Texas Instruments 输入电压:6 V to 100 V 开关频率: 输出电压:1.215 V to 80 V 输出电流:3.5 A 输出端数量:1 最大工作温度:+ 125 C 安装风格: 封装 / 箱体:CPAK |
| MAX15023ETG+ | 功能描述:DC/DC 开关控制器 4.5-28V Input Dual Out Synch Buck RoHS:否 制造商:Texas Instruments 输入电压:6 V to 100 V 开关频率: 输出电压:1.215 V to 80 V 输出电流:3.5 A 输出端数量:1 最大工作温度:+ 125 C 安装风格: 封装 / 箱体:CPAK |
| MAX15023ETG+ | 制造商:Maxim Integrated Products 功能描述:BUCK CONTROLL SYNC 4.5~28V 24QFN 制造商:Maxim Integrated Products 功能描述:BUCK CONTROLL, SYNC, 4.5~28V, 24QFN |
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