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参数资料
| 型号： | NCV5171EDR2G |
| 厂商： | ON Semiconductor |
| 文件页数： | 14/19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
R3
fSW
D I + V 1 * e R3C3fSW
Subharmonic Oscillation
Subharmonic oscillation (SHM) is a problem found in
current ? mode control systems, where instability results
when duty cycle exceeds 50%. SHM only occurs in
switching regulators with a continuous inductor current.
This instability is not harmful to the converter and usually
does not affect the output voltage regulation. SHM will
increase the radiated EM noise from the converter and can
cause, under certain circumstances, the inductor to emit
high ? frequency audible noise.
SHM is an easily remedied problem. The rising slope of
the inductor current is supplemented with internal “slope
compensation” to prevent any duty cycle instability from
carrying through to the next switching cycle. In
NCV5171/73, the slope compensation is added during the
entire switch on ? time, typically in the amount of 180 mA/ m s.
In some cases, SHM can rear its ugly head despite the
presence of the onboard slope compensation. The simple
cure to this problem is more slope compensation to avoid the
unwanted oscillation. In that case, an external circuit, shown
in Figure 33, can be added to increase the amount of slope
compensation used. This circuit requires only a few
components and is “tacked on” to the compensation
network.
pin. In normal operation, V SW looks similar to a square
wave, and is dependent on the converter topology. Formulas
for calculating V SW in the boost and flyback topologies are
given in the section “V SW Voltage Limit.” The voltage on
V SW charges capacitor C3 when the switch is off, causing
the voltage at the V C pin to shift upwards. When the switch
turns on, C3 discharges through R3, producing a negative
slope at the V C pin. This negative slope provides the slope
compensation.
The amount of slope compensation added by this circuit
is:
* (1 * D)
D T SW R 2 ) R 3 (1 * D)REAV
where:
D I/ D T = the amount of slope compensation added (A/s);
V SW = the voltage at the switch node when the transistor
is turned off (V);
f SW = the switching frequency, typically 280 kHz
(NCV5171) or 560 kHz (NCV5173)
D = the duty cycle;
R E = 0.063 W , the value of the internal emitter resistor;
A V = 5 V/V, the gain of the current sense amplifier.
In selecting appropriate values for the slope compensation
V C
V SW
V SW
network, the designer is advised to choose a convenient
capacitor, then select values for R2 and R3 such that the
amount of slope compensation added is 100 mA/ m s. Then
R2 may be increased or decreased as necessary. Of course,
the series combination of R2 and R3 should be large enough
to avoid drawing excessive current from V SW . Additionally,
to ensure that the control loop stability is improved , the time
R3C3 t 1 * D
C1
R1
C2
R2
constant formed by the additional components should be
chosen such that
fSW
Finally, it is worth mentioning that the added slope
compensation is a tradeoff between duty cycle stability and
transient response. The more slope compensation a designer
C3
R3
adds, the slower the transient response will be, due to the
external circuitry interfering with the proper operation of the
error amplifier.
Figure 33. Technique for Increasing Slope
Compensation
The dashed box contains the normal compensation
circuitry to limit the bandwidth of the error amplifier.
Resistors R2 and R3 form a voltage divider off of the V SW
Soft ? Start
Through the addition of an external circuit, a Soft ? Start
function can be added to the NCV5171/73 family of
components. Soft ? Start circuitry prevents the V C pin from
slamming high during startup, thereby inhibiting the
inductor current from rising at a high slope.
http://onsemi.com
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相关代理商/技术参数 |
参数描述 |
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| 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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