参数资料
| 型号： | NCP5211BDR2G |
| 厂商： | ON Semiconductor |
| 文件页数： | 8/13页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM 14-SOIC |
| 产品变化通告： | Product Obsolescence 19/Dec/2008 |
| 标准包装： | 1 |
| PWM 型： | 电流/电压模式，V²? |
| 输出数： | 1 |
| 频率 - 最大： | 900kHz |
| 占空比： | 100% |
| 电源电压： | 4.5 V ~ 14 V |
| 降压： | 是 |
| 升压： | 无 |
| 回扫： | 无 |
| 反相： | 无 |
| 倍增器： | 无 |
| 除法器： | 无 |
| Cuk： | 无 |
| 隔离： | 无 |
| 工作温度： | -40°C ~ 85°C |
| 封装/外壳： | 14-SOIC（0.154"，3.90mm 宽） |
| 包装： | 剪切带 (CT) |
| 其它名称： | NCP5211BDR2GOSCT |
NCP5211
APPLICATIONS INFORMATION
DF + O
APPLICATIONS AND COMPONENT SELECTION
Inductor Component Selection
The output inductor may be the most critical component
in the converter because it will directly effect the choice of
other components and dictate both the steady?state and
transient performance of the converter. When selecting an
inductor the designer must consider factors such as DC
current, peak current, output voltage ripple, core material,
magnetic saturation, temperature, physical size, and cost
(usually the primary concern).
In general, the output inductance value should be as low
and physically small as possible to provide the best transient
response and minimum cost. If a large inductance value is
used, the converter will not respond quickly to rapid changes
in the load current. On the other hand, too low an inductance
value will result in very large ripple currents in the power
components (MOSFETs, capacitors, etc) resulting in
increased dissipation and lower converter efficiency. Also,
increased ripple currents will force the designer to use
higher rated MOSFETs, oversize the thermal solution, and
use more, higher rated input and output capacitors ? the
converter cost will be adversely effected.
One method of calculating an output inductor value is to
size the inductor to produce a specified maximum ripple
current in the inductor. Lower ripple currents will result in
less core and MOSFET losses and higher converter
efficiency. The following equation may be used to calculate
the minimum inductor value to produce a given maximum
ripple current ( α ? I O,MAX ). The inductor value calculated by
this equation is a minimum because values less than this will
produce more ripple current than desired. Conversely,
higher inductor values will result in less than the maximum
ripple current.
LoMIN + (Vin * Vout) @ Vout ( a @ IO,MAX @ Vin @ fSW)
α is the ripple current as a percentage of the maximum
output current ( α = 0.15 for ± 15%, α = 0.25 for ± 25%, etc)
and f sw is the switching frequency. If the minimum inductor
value is used, the inductor current will swing ±α /2% about
Iout. Therefore, the inductor must be designed or selected
such that it will not saturate with a peak current of (1 + α /2)
? I O,MAX .
Power dissipation in the inductor can now be calculated
from the RMS current level. The RMS of the AC component
of the inductor is given by the following relationship:
Input Capacitor Selection and Considerations
The input capacitor is used to reduce the current surges
caused by conduction of current of the top pass transistor
charging the PWM inductor.
The input current is pulsing at the switching frequency
going from 0 to peak current in the inductor. The duty factor
will be a function of the ratio of the input to output voltage
and of the efficiency.
V 1
VI Eff
The RMS value of the ripple into the input capacitors can
now be calculated:
IIN(RMS) + IOUT DF * DF2
The input RMS is maximum at 50% DF, so selection of the
possible duty factor closest to 50% will give the worst case
dissipation in the capacitors. The power dissipation of the
input capacitors can be calculated by multiplying the square
of the RMS current by the ESR of the capacitor.
Output Capacitor
The output capacitor filters output inductor ripple current
and provides low impedance for load current changes. The
effect of the capacitance for handling the power supply
induced ripple will be discussed here. Effects of load
transient behavior can be considered separately.
The principle consideration for the output capacitor is the
ripple current induced by the switches through the inductor.
This ripple current was calculated as I AC in the above
discussion of the inductor. This ripple component will
induce heating in the capacitor by a factor of the RMS
current squared multiplied by the ESR of the output
capacitor section. It will also create output ripple voltage.
The ripple voltage will be a vector summation of the ripple
current times the ESR of the capacitor, plus the ripple current
integrating in the capacitor, and the rate of change in current
times the total series inductance of the capacitor and
connections.
The inductor ripple current acting against the ESR of the
output capacitor is the major contributor to the output ripple
voltage. This fact can be used as a criterion to select the
output capacitor.
VPP + IPP CESR
The power dissipation in the output capacitor can be
calculated from:
IAC + PP
I
12
where:
P + IAC2
CESR
where IPP = α ? I O,MAX .
The total I RMS of the current will be calculated from:
I AC = AC RMS of the inductor
C ESR = Effective series resistance of the output capacitor
IRMS +
IOUT2 ) IAC2
network.
The power dissipation for the inductor can be determined
from:
MOSFET & Heatsink Selection
Power dissipation, package size, and thermal solution
P + IRMS2
RL
drive MOSFET selection. To adequately size the heat sink,
http://onsemi.com
8
相关PDF资料 |
PDF描述 |
|---|---|
| NCP5212AMNTXG | IC REG CTRLR BUCK PWM 16-QFN |
| NCP5214AMNR2G | IC CTLR NOTEBOOK DDR PWR 22-DFN |
| NCP5214MNR2G | IC CTLR NOTEBOOK DDR PWR 22-DFN |
| NCP5215MNR2G | IC CTLR SYNC BUCK DUAL 40-QFN |
| NCP5217AMNTXG | IC REG CTRLR BUCK PWM 14-QFN |
相关代理商/技术参数 |
参数描述 |
|---|---|
| NCP5211DR2G | 功能描述:DC/DC 开关控制器 ANA SYNC BUCK CNTRL 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 |
| NCP5212A | 制造商:ONSEMI 制造商全称:ON Semiconductor 功能描述:Single Synchronous Step-Down Controller |
| NCP5212A_09 | 制造商:ONSEMI 制造商全称:ON Semiconductor 功能描述:Single Synchronous Step-Down Controller |
| NCP5212AGEVB | 功能描述:BOARD EVAL NCP5212A RoHS:是 类别:编程器，开发系统 >> 评估演示板和套件 系列:* 标准包装:1 系列:PCI Express® (PCIe) 主要目的:接口，收发器，PCI Express 嵌入式:- 已用 IC / 零件:DS80PCI800 主要属性:- 次要属性:- 已供物品:板 |
| NCP5212AMNTXG | 功能描述:DC/DC 开关控制器 SYNC STEP DOWN CTRL 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 |
发布紧急采购，3分钟左右您将得到回复。