收藏本站
NCP3125
LP _DC + I RMS 2 @ DCR 3
281 mW + 4.01 2 @ 17.5 m W
(eq. 11)
The ESL of capacitors depends on the technology chosen,
but tends to range from 1 nH to 20 nH, where ceramic
capacitors have the lowest inductance and electrolytic
V ESLON + 3
D
10 nH * 1.2 A * 350 kHz
15.27 mV +
I RMS = Inductor RMS current
DCR = Inductor DC resistance
LP CU_DC = Inductor DC power dissipation
The core losses and AC copper losses will depend on the
geometry of the selected core, core material, and wire used.
Most vendors will provide the appropriate information to
make accurate calculations of the power dissipation at which
point the total inductor losses can be captured by the
capacitors have the highest. The calculated contributing
voltage ripple from ESL is shown for the switch on and
switch off below:
ESL * Ipp * F SW
(eq. 15)
27.5%
V ESLOFF + 3
equation below:
LP tot + LP CU_DC ) LP CU_AC ) LP Core 3
303 mW + 281 mW ) 1 mW ) 21 mW
LP CU_DC = Inductor DC power dissipation
LP CU_AC = Inductor AC power dissipation
LP Core = Inductor core power dissipation
(eq. 12)
ESL * Ipp * F SW
(1 * D )
10 nH * 1.2 A * 350 kHz
5.79 mV +
1 * 27.5%
D = Duty ratio
ESL = Capacitor inductance
(eq. 16)
Co RMS + I OUT @
3 0.346 A + 4 A
V ESR_C + I OUT * ra * Co ESR )
3
60.91 mV + 4 * 30% * 50 m W )
(eq. 18)
2.3 A
5.6 m H
Output Capacitor Selection
The important factors to consider when selecting an
output capacitor are DC voltage rating, ripple current rating,
output ripple voltage requirements, and transient response
requirements.
The output capacitor must be rated to handle the ripple
current at full load with proper derating. The RMS ratings
given in datasheets are generally for lower switching
frequency than used in switch mode power supplies, but a
multiplier is usually given for higher frequency operation.
The RMS current for the output capacitor can be calculated
below:
ra 30%
(eq. 13)
12 12
Co RMS = Output capacitor RMS current
I OUT = Output current
ra = Ripple current ratio
The maximum allowable output voltage ripple is a
combination of the ripple current selected, the output
capacitance selected, the Equivalent Series Inductance
(ESL), and Equivalent Series Resistance (ESR).
The main component of the ripple voltage is usually due
to the ESR of the output capacitor and the capacitance
selected, which can be calculated as shown in Equation 14:
1
8 * F SW * C OUT
(eq. 14)
1
8 * 350 kHz * 470 m F
Co ESR = Output capacitor ESR
C OUT = Output capacitance
F SW = Switching frequency
I OUT = Output current
ra = Ripple current ratio
F SW = Switching frequency
Ipp = Peak ? to ? peak current
The output capacitor is a basic component for the fast
response of the power supply. For the first few microseconds
of a load transient, the output capacitor supplies current to
the load. Once the regulator recognizes a load transient, it
adjusts the duty ratio, but the current slope is limited by the
inductor value.
During a load step transient, the output voltage initially
drops due to the current variation inside the capacitor and the
ESR (neglecting the effect of the ESL).
D V OUT * ESR + I TRAN Co ESR 3 115 mV + 2.3 50 m W
(eq. 17)
Co ESR = Output capacitor Equivalent Series
Resistance
I TRAN = Output transient current
D V OUT_ESR = Voltage deviation of V OUT due to the
effects of ESR
A minimum capacitor value is required to sustain the
current during the load transient without discharging it. The
voltage drop due to output capacitor discharge is given by
the following equation:
2
I TRAN L OUT
D V OUT * DIS + 3
2 D MAX C OUT V IN * V OUT
2
4.9 mV +
2 75% 470 m F 12 V * 3.3 V
C OUT = Output capacitance
D MAX = Maximum duty ratio
I TRAN = Output transient current
L OUT = Output inductor value
V IN = Input voltage
V OUT = Output voltage
D V OUT_DIS = Voltage deviation of V OUT due to the effects
of capacitor discharge
http://onsemi.com
11
发布紧急采购，3分钟左右您将得到回复。

采购需求

(若只采购一条型号，填写一行即可)

发布成功！您可以继续发布采购。也可以进入我的后台，查看报价

发布成功！您可以继续发布采购。也可以进入我的后台，查看报价

*型号 *数量 厂商 批号 封装
添加更多采购

我的联系方式

*
*
*
相关PDF资料
A9AAT-1304F FLEX CABLE - AFE13T/AF13/AFE13T
MAX6006BESA+ IC VREF SHUNT PREC 1.25V 8-SOIC
A9CAA-0802E FLEX CABLE - AFK08A/AE08/AFH08T
A9AAT-2203E FLEX CABLE - AFH22T/AE22/AFH22T
RE-1512S/H CONV DC/DC 1W 15VIN 12VOUT
NCP3127AGEVB BOARD EVALUATION NCP3127
A9CAG-0603F FLEX CABLE - AFG06G/AF06/AFE06T
A9BBG-0204F FLEX CABLE - AFF02G/AF02/AFF02G
相关代理商/技术参数
NCP3125CRAGEVB 功能描述:电源管理IC开发工具 NCP3125 Ceramic 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
NCP3126ADR2G 功能描述:直流/直流开关转换器 3A PWM Switching Buck Regulator 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
NCP3126AGEVB 功能描述:电源管理IC开发工具 NCP3126 EVB 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
NCP3126CRAGEVB 功能描述:电源管理IC开发工具 NCP3126 CERAMIC EVB 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
NCP3127ADR2G 功能描述:直流/直流开关转换器 2A PWM Switching Buck Regulator 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
NCP3127AGEVB 功能描述:电源管理IC开发工具 NCP3127 EVALUATION 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
NCP3127CRAGEVB 功能描述:电源管理IC开发工具 NCP3127 CERAMIC EVB 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
NCP3155ADR2G 功能描述:直流/直流开关调节器 BUCK CONTROLLER RoHS:否 制造商:International Rectifier 最大输入电压:21 V 开关频率:1.5 MHz 输出电压:0.5 V to 0.86 V 输出电流:4 A 输出端数量: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:PQFN 4 x 5