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参数资料
| 型号： | NCV5171EDR2G |
| 厂商： | ON Semiconductor |
| 文件页数： | 15/19页 |
| 文件大小： | 0K |
| 描述： | IC REG MULTI CONFIG 1.5A 8SOIC |
| 标准包装： | 2,500 |
| 类型： | 升压（升压），反相，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 ~ 125°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 8-SOIC（0.154"，3.90mm 宽） |
| 包装： | 带卷 (TR) |
| 供应商设备封装： | 8-SOICN |
NCV5171, NCV5173
This circuit, shown in Figure 34, 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.
V IN
V CC
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
graph shows that IQ is strongly dependent on input voltage,
V IN , and temperature. Then
PBIAS + VINIQ
Since the onboard switch is an NPN transistor, the base
SS
SS
V C
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
D1
D2
that information, the designer can calculate
C1
R1
PDRIVER + VINISW
ICC
D ISW
D
C3
C2
where:
I SW = the current through the switch;
D = the duty cycle or percentage of switch on ? time.
I SW and D are dependent on the type of converter. In a
boost converter,
Figure 34. Soft Start
ISW(AVG) ^ IL(AVG)
D
1
Efficiency
D ^ OUT
ISW(AVG) ^ OUT LOAD
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).
V * VIN
In a flyback converter,
V I 1
VIN Efficiency
VOUT
1
D
VOUT
VOUT ) N S P VIN
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 NCV5171/73, 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
NCV5171/73:
? biasing of internal control circuitry, P BIAS
? switch driver, P DRIVER
? switch saturation, P SAT
The internal control circuitry, including the oscillator and
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.
linear regulator, requires a small amount of power even
when the switch is turned off. The specifications section of
http://onsemi.com
15
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相关代理商/技术参数 |
参数描述 |
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| NCV5173EDR2G | 功能描述:直流/直流开关转换器 1.5A 560KHZ BOOST RG 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 |
| NCV5230DR2G | 功能描述:运算放大器 - 运放 LOW VOLTAGE OP-AMP RoHS:否 制造商:STMicroelectronics 通道数量:4 共模抑制比（最小值）:63 dB 输入补偿电压:1 mV 输入偏流（最大值）:10 pA 工作电源电压:2.7 V to 5.5 V 安装风格:SMD/SMT 封装 / 箱体:QFN-16 转换速度:0.89 V/us 关闭:No 输出电流:55 mA 最大工作温度:+ 125 C 封装:Reel |
| NCV5500 | 制造商:ONSEMI 制造商全称:ON Semiconductor 功能描述:500 mA Linear Regulator |
| NCV5500DADJR2G | 功能描述:低压差稳压器 - LDO LDO REG 500mA ADJ RoHS:否 制造商:Texas Instruments 最大输入电压:36 V 输出电压:1.4 V to 20.5 V 回动电压（最大值）:307 mV 输出电流:1 A 负载调节:0.3 % 输出端数量: 输出类型:Fixed 最大工作温度:+ 125 C 安装风格:SMD/SMT 封装 / 箱体:VQFN-20 |
| NCV5500DT15RKG | 功能描述:低压差稳压器 - LDO ANA LDO REG RoHS:否 制造商:Texas Instruments 最大输入电压:36 V 输出电压:1.4 V to 20.5 V 回动电压（最大值）:307 mV 输出电流:1 A 负载调节:0.3 % 输出端数量: 输出类型:Fixed 最大工作温度:+ 125 C 安装风格:SMD/SMT 封装 / 箱体:VQFN-20 |
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