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| 型号： | LMZ14201EVAL/NOPB |
| 厂商： | National Semiconductor |
| 文件页数： | 13/27页 |
| 文件大小： | 0K |
| 描述： | EVAL BOARD FOR LMZ14201 |
| 产品培训模块： | SIMPLE SWITCHER Power Modules |
| 标准包装： | 1 |
| 系列： | SIMPLE SWITCHER® |
| 主要目的： | DC/DC，步降 |
| 输出及类型： | 1，非隔离 |
| 输出电压： | 3.3V |
| 电流 - 输出： | 1A |
| 输入电压： | 6 ~ 24 V |
| 稳压器拓扑结构： | 降压 |
| 频率 - 开关： | 最高 1MHz |
| 板类型： | 完全填充 |
| 已供物品： | 板 |
| 已用 IC / 零件： | LMZ14201 |
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LMZ14201
www.ti.com
SNVS649F – JANUARY 2010 – REVISED OCTOBER 2013
For V O = 0.8V the FB pin can be connected to the output directly so long as an output preload resistor remains
that draws more than 20uA. Converter operation requires this minimum load to create a small inductor ripple
current and maintain proper regulation when no load is present.
A feed-forward capacitor is placed in parallel with R FBT to improve load step transient response. Its value is
usually determined experimentally by load stepping between DCM and CCM conduction modes and adjusting for
best transient response and minimum output ripple.
A table of values for R FBT , R FBB , C FF and R ON is included in the applications schematic.
SOFT-START CAPACITOR SELECTION
Programmable soft-start permits the regulator to slowly ramp to its steady state operating point after being
enabled, thereby reducing current inrush from the input supply and slowing the output voltage rise-time to
prevent overshoot.
Upon turn-on, after all UVLO conditions have been passed, an internal 8uA current source begins charging the
external soft-start capacitor. The soft-start time duration to reach steady state operation is given by the formula:
t SS = V REF * C SS / Iss = 0.8V * C SS / 8uA
This equation can be rearranged as follows:
C SS = t SS * 8 μ A / 0.8V
(4)
(5)
Use of a 0.022 μ F results in 2.2 msec soft-start interval which is recommended as a minimum value.
As the soft-start input exceeds 0.8V the output of the power stage will be in regulation. The soft-start capacitor
continues charging until it reaches approximately 3.8V on the SS pin. Voltage levels between 0.8V and 3.8V
have no effect on other circuit operation. Note that the following conditions will reset the soft-start capacitor by
discharging the SS input to ground with an internal 200 μ A current sink.
?
?
?
?
The enable input being “pulled low”
Thermal shutdown condition
Over-current fault
Internal Vcc UVLO (Approximately 4V input to V IN )
C O SELECTION
None of the required C O output capacitance is contained within the module. At a minimum, the output capacitor
must meet the worst case minimum ripple current rating of 0.5 * I LR P-P , as calculated in Equation 19 below.
Beyond that, additional capacitance will reduce output ripple so long as the ESR is low enough to permit it. A
minimum value of 10 μ F is generally required. Experimentation will be required if attempting to operate with a
minimum value. Ceramic capacitors or other low ESR types are recommended. See AN-2024 for more detail.
Equation 6 provides a good first pass approximation of C O for load transient requirements:
C O ≥ I STEP *V FB *L*V IN / (4*V O *(V IN —V O )*V OUT-TRAN )
Solving:
C O ≥ 1A*0.8V*10 μ H*24V / (4*3.3V*( 24V — 3.3V)*33mV) ≥ 21.3 μ F
(6)
(7)
The LMZ14201 demonstration and evaluation boards are populated with a 100 uF 6.3V X5R output capacitor.
Locations for other output capacitors are provided.
C IN SELECTION
The LMZ14201 module contains an internal 0.47 μF input ceramic capacitor. Additional input capacitance is
required external to the module to handle the input ripple current of the application. This input capacitance should
be located in very close proximity to the module. Input capacitor selection is generally directed to satisfy the input
ripple current requirements rather than by capacitance value. Worst case input ripple current rating is dictated by
Equation 8 :
I(C IN(RMS) ) ? 1 /2 * I O * √ (D / 1-D)
(8)
where D ? V O / V IN
(As a point of reference, the worst case ripple current will occur when the module is presented with full load
current and when V IN = 2 * V O ).
Copyright ? 2010–2013, Texas Instruments Incorporated
Product Folder Links: LMZ14201
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LMZ14201EXT | 制造商:NSC 制造商全称:National Semiconductor 功能描述:1A SIMPLE SWITCHER? Power Module with 42V Maximum Input Voltage for Military and Rugged Applications |
| LMZ14201EXTEVAL/NOPB | 功能描述:电源管理IC开发工具 LMZ14201EXT EVAL BOARD 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 |
| LMZ14201EXTTZ | 制造商:NSC 制造商全称:National Semiconductor 功能描述:1A SIMPLE SWITCHER? Power Module with 42V Maximum Input Voltage for Military and Rugged Applications |
| LMZ14201EXTTZ/NOPB | 功能描述:直流/直流开关转换器 1A SIMPLE SWITCHER POWER MOD, 42V MAX RoHS:否 制造商:STMicroelectronics 最大输入电压:4.5 V 开关频率:1.5 MHz 输出电压:4.6 V 输出电流:250 mA 输出端数量:2 最大工作温度:+ 85 C 安装风格:SMD/SMT |
| LMZ14201EXTTZE | 制造商:NSC 制造商全称:National Semiconductor 功能描述:1A SIMPLE SWITCHER? Power Module with 42V Maximum Input Voltage for Military and Rugged Applications |
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