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| 型号： | CS5171ED8 |
| 厂商： | ON Semiconductor |
| 文件页数： | 16/21页 |
| 文件大小： | 0K |
| 描述： | IC REG MULTI CONFIG 1.5A 8SOIC |
| 产品变化通告： | Product Discontinuation 27/Jun/2007 |
| 标准包装： | 98 |
| 类型： | 升压（升压），回扫，正向转换器，Sepic |
| 输出数： | 1 |
| 输入电压： | 2.7 V ~ 30 V |
| PWM 型： | 电流模式 |
| 频率 - 开关： | 280kHz |
| 电流 - 输出： | 1.5A |
| 同步整流器： | 无 |
| 工作温度： | -40°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 8-SOIC（0.154"，3.90mm 宽） |
| 包装： | 管件 |
| 供应商设备封装： | 8-SOICN |
CS5171, CS5172, CS5173, CS5174
This circuit, shown in Figure 40, requires a minimum
number of components and allows the Soft ? Start circuitry to
activate any time the SS pin is used to restart the converter.
when the switch is turned off. The specifications section of
this datasheet reveals that the typical operating current, I Q ,
due to this circuitry is 5.5 mA. Additional guidance can be
found in the graph of operating current vs. temperature. This
V IN
V CC
graph shows that IQ is strongly dependent on input voltage,
V IN , and temperature. Then
PBIAS + VINIQ
SS
D1
SS
D2
V C
R1
Since the onboard switch is an NPN transistor, the base
drive current must be factored in as well. This current is
drawn from the V IN pin, in addition to the control circuitry
current. The base drive current is listed in the specifications
as D I CC / D I SW , or switch transconductance. As before, the
designer will find additional guidance in the graphs. With
that information, the designer can calculate
C3
C1
C2
PDRIVER + VINISW
where:
ICC
D ISW
D
I SW = the current through the switch;
D = the duty cycle or percentage of switch on ? time.
ISW(AVG) ^ IL(AVG)
D
D ^ OUT
ISW(AVG) ^ OUT LOAD
VOUT
VOUT ) N S P VIN
Figure 40. Soft Start
Resistor R1 and capacitors C1 and C2 form the
compensation network. At turn on, the voltage at the V C pin
starts to come up, charging capacitor C3 through Schottky
diode D2, clamping the voltage at the V C pin such that
switching begins when V C reaches the V C threshold,
typically 1.05 V (refer to graphs for detail over temperature).
VC + VF(D2) ) VC3
Therefore, C3 slows the startup of the circuit by limiting
the voltage on the V C pin. The Soft ? Start time increases with
the size of C3.
Diode D1 discharges C3 when SS is low. If the shutdown
function is not used with this part, the cathode of D1 should
be connected to V IN .
Calculating Junction Temperature
To ensure safe operation of the CS5171/2/3/4, the
designer must calculate the on ? chip power dissipation and
determine its expected junction temperature. Internal
thermal protection circuitry will turn the part off once the
junction temperature exceeds 180 ° C ± 30 ° . However,
repeated operation at such high temperatures will ensure a
reduced operating life.
Calculation of the junction temperature is an imprecise
but simple task. First, the power losses must be quantified.
There are three major sources of power loss on the CS517x:
? biasing of internal control circuitry, P BIAS
? switch driver, P DRIVER
? switch saturation, P SAT
The internal control circuitry, including the oscillator and
linear regulator, requires a small amount of power even
I SW and D are dependent on the type of converter. In a
boost converter,
1
Efficiency
V * VIN
VOUT
In a flyback converter,
V I 1 1
VIN Efficiency D
D ^ N
The switch saturation voltage, V (CE)SAT , is the last major
source of on ? chip power loss. V (CE)SAT is the
collector ? emitter voltage of the internal NPN transistor
when it is driven into saturation by its base drive current. The
value for V (CE)SAT can be obtained from the specifications
or from the graphs, as “Switch Saturation Voltage.” Thus,
PSAT ^ V(CE)SATISW D
Finally, the total on ? chip power losses are
PD + PBIAS ) PDRIVER ) PSAT
Power dissipation in a semiconductor device results in the
generation of heat in the junctions at the surface of the chip.
This heat is transferred to the surface of the IC package, but
a thermal gradient exists due to the resistive properties of the
package molding compound. The magnitude of the thermal
gradient is expressed in manufacturers’ data sheets as q JA ,
or junction ? to ? ambient thermal resistance. The on ? chip
junction temperature can be calculated if q JA , the air
temperature near the surface of the IC, and the on ? chip
power dissipation are known.
http://onsemi.com
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相关代理商/技术参数 |
参数描述 |
|---|---|
| CS5171ED8G | 功能描述:直流/直流开关调节器 1.5A High Efficiency Boost 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 |
| CS5171EDR8 | 功能描述:直流/直流开关调节器 1.5A High Efficiency 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 |
| CS5171EDR8G | 功能描述:直流/直流开关调节器 1.5A High Efficiency Boost 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 |
| CS5171GD8 | 功能描述:直流/直流开关调节器 1.5A High Efficiency 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 |
| CS5171GD8G | 功能描述:直流/直流开关调节器 1.5A High Efficiency Boost 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 |
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