- 您现在的位置：买卖IC网 > PDF目录17233 > NCP5424EVB (ON Semiconductor)EVAL BOARD FOR NCP5424 PDF资料下载
参数资料
| 型号： | NCP5424EVB |
| 厂商： | ON Semiconductor |
| 文件页数： | 16/18页 |
| 文件大小： | 0K |
| 描述： | EVAL BOARD FOR NCP5424 |
| 产品变化通告： | Product Obsolescence 24/Jan/2011 |
| 设计资源： | NCP5424 Demo Board BOM NCP5424EVB Gerber Files NCP5424EVB Schematic |
| 标准包装： | 1 |
| 主要目的： | DC/DC，步降 |
| 输出及类型： | 1，非隔离 |
| 输出电压： | 1.5V |
| 电流 - 输出： | 17A |
| 输入电压： | 3.3V，5V，12V |
| 稳压器拓扑结构： | 降压 |
| 频率 - 开关： | 300kHz |
| 板类型： | 完全填充 |
| 已供物品： | 板 |
| 已用 IC / 零件： | NCP5424 |
| 其它名称： | NCP5424EVBOS |
NCP5424
RSENSE + 0.070 V
+ RS1C
(1 * e t )
VSLOPECOMP + VGATE(L)
RS1 +
ILIM + 0.070 V
ILIMIT
In a high current supply, the sense resistor will be a very
low value, typically less than 10 m W . Such a resistor can be
either a discrete component or a PCB trace. The resistance
value of a discrete component can be more precise than a
PCB trace, but the cost is also greater.
Setting the current limit using an external sense resistor is
very precise because all the values can be designed to
specific tolerances. However, the disadvantage of using a
sense resistor is its additional constant power loss and heat
generation.
Inductor ESR. Another means of sensing current is to use
the intrinsic resistance of the inductor. A model of an
inductor reveals that the windings of an inductor have an
effective series resistance (ESR).
The voltage drop across the inductor ESR can be
measured with a simple parallel circuit: an RC integrator. If
the value of R S1 and C are chosen such that:
L
ESR
then the voltage measured across the capacitor C will be:
VC + ESR ILIM
Selecting Components. Select the capacitor C first. A
value of 0.1 m F is recommended. The value of R S1 can be
selected according to:
1
ESR C
Typical values for inductor ESR range in the low m;
consult manufacturer ’s datasheet for specific details.
Selection of components at these values will result in a
current limit of:
ESR
current limit. Finally, one or two more components are
required for this approach than with resistor sensing.
Adding External Slope Compensation
Today’s voltage regulators are expected to meet very
stringent load transient requirements. One of the key factors
in achieving tight dynamic voltage regulation is low ESR.
Low ESR at the regulator output results in low output
voltage ripple. The consequence is, however, that very little
voltage ramp exists at the control IC feedback pin (V FB ),
resulting in increased regulator sensitivity to noise and the
potential for loop instability. In applications where the
internal slope compensation is insufficient, the performance
of the NCP5424?based regulator can be improved through
the addition of a fixed amount of external slope
compensation at the output of the PWM Error Amplifier (the
COMP pin) during the regulator off?time. Referring to
Figure 8, the amount of voltage ramp at the COMP pin is
dependent on the gate voltage of the lower (synchronous)
FET and the value of resistor divider formed by R1and R2.
?t
R2
R1 ) R2
where:
V SLOPECOMP = amount of slope added;
V GATE(L) = lower MOSFET gate voltage;
R1, R2 = voltage divider resistors;
t = t ON or t OFF (switch off?time);
τ = RC constant determined by C1 and the parallel
combination of R1, R2 neglecting the low driver
output impedance.
COMP
C COMP
V CC
L
ESR
NCP5424
R2
C1
R1
GATE(H)
RS1
C
Co
GATE(L)
To Synchronous
GATE(L)
IS+
IS?
Figure 9. Inductor ESR Current Sensing
Given an ESR value of 3.5 m W , the current limit becomes
20 A. If an increased current limit is required, a resistor
divider can be added.
The advantages of setting the current limit by using the
winding resistance of the inductor are that efficiency is
maximized and heat generation is minimized. The tolerance
of the inductor ESR must be factored into the design of the
FET
Figure 10. Small RC Filter Provides the
Proper Voltage Ramp at the Beginning of
Each On?Time Cycle
The artificial voltage ramp created by the slope
compensation scheme results in improved control loop
stability provided that the RC filter time constant is smaller
than the off?time cycle duration (time during which the
lower MOSFET is conducting). It is important that the series
combination of R1 and R2 is high enough in resistance to
avoid loading the GATE(L) pin. Also, C1 should be very
small (less than a few nF) to avoid heating the part.
http://onsemi.com
16
相关PDF资料 |
PDF描述 |
|---|---|
| BRL3225T6R8M | INDUCTOR 6.8UH 20% 1210 SMD |
| GBC13DRTI | CONN EDGECARD 26POS DIP .100 SLD |
| RCM06DCCT | CONN EDGECARD 12POS R/A .156 SLD |
| BRL3225T330K | INDUCTOR 33UH 10% 1210 SMD |
| GBC06DRTF | CONN EDGECARD 12POS DIP .100 SLD |
相关代理商/技术参数 |
参数描述 |
|---|---|
| NCP5425 | 制造商:ONSEMI 制造商全称:ON Semiconductor 功能描述:Dual Synchronous Buck Controller |
| NCP5425/D | 制造商:未知厂家 制造商全称:未知厂家 功能描述:Dual Synchronous Buck Controller |
| NCP5425_06 | 制造商:ONSEMI 制造商全称:ON Semiconductor 功能描述:Dual Synchronous Buck Controller |
| NCP5425DB | 功能描述:DC/DC 开关控制器 Dual Synchronous 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 |
| NCP5425DBG | 功能描述:DC/DC 开关控制器 Dual Synchronous 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 |
发布紧急采购，3分钟左右您将得到回复。