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| 型号： | FAN1577AMX |
| 厂商： | Fairchild Semiconductor |
| 文件页数： | 12/15页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BST PWM VM 20-SOIC |
| 标准包装： | 1 |
| PWM 型： | 电压模式 |
| 输出数： | 2 |
| 频率 - 最大： | 372kHz |
| 占空比： | 95% |
| 电源电压： | 10 V ~ 15 V |
| 降压： | 是 |
| 升压： | 是 |
| 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： | 20-SOIC（0.295"，7.50mm 宽） |
| 包装： | 标准包装 |
| 其它名称： | FAN1577AMXDKR |
Type II Compensation Design (for Output Capacitors with High ESR)
FAN1577A is a voltage-mode controller. The control
loop is a single-voltage feedback path, including an
error amplifier and PWM comparator, as shown in
Figure 30. To achieve fast transient response and
accurate output regulation, an adequate compensator
design is necessary. A stable control loop has a 0dB
gain crossing with -20dB/decade slope and a phase
margin greater than 45°.
2. Compensation Frequency Equations
The compensation network consists of the error
amplifier and the impedance networks Z C and Z f as
Figure 31 shows.
Figure 31.
Compensation Loop
Figure 30.
Closed Loop
f P 1 = 0
f Z 1 =
f P 2 =
1. Modulator Frequency Equations
The modulator transfer function is the small-signal
transfer function of V OUT /V E/A . This transfer function is
dominated by a DC gain and the output filter (L O and
C O ) with a double-pole frequency at f LC and a zero at
f ESR . The DC gain of the modulator is the input voltage
(V IN ) divided by the peak-to-peak oscillator voltage
Δ V RAMP (=1.6V). The first step is to calculate the complex
conjugate poles contributed by the LC output filter. The
output LC filter introduces a double pole, -40dB /
decade gain slope above its corner resonant frequency
and a total phase lag of 180 degrees. The resonant
frequency of the LC filter expressed as:
1
2 π × R 2 × C 2 (7)
1
2 π × R 2 × ( C 1 // C 2 )
Compensation gain uses external impedance networks
Z C and Z f to provide a stable high-bandwidth loop.
High crossover frequency is desirable for fast transient
response, but often jeopardizes system stability. To
cancel one of the LC filter poles, place the zero before
the LC filter resonant frequency. Place the zero at 75%
of the LC filter resonant frequency. Crossover frequency
should be higher than the ESR zero, but less than 1/5
of the switching frequency. The second pole should be
f P(LC) =
1
2 π × L O × C O
(5)
placed at half the switching frequency.
The next step of compensation design is to calculate
the ESR zero contributed by the ESR associated with
the output capacitance. Note that this requires that the
output capacitor have enough ESR to satisfy stability
requirements. The ESR zero of the output capacitor is
expressed as:
f Z ( ESR ) =
1
2 π × C O × ESR
(6)
? 2010 Fairchild Semiconductor Corporation
FAN1577A ? Rev. 1.0.0
12
www.fairchildsemi.com
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相关代理商/技术参数 |
参数描述 |
|---|---|
| FAN1581 | 制造商:FAIRCHILD 制造商全称:Fairchild Semiconductor 功能描述:5A Adjustable/Fixed Ultra Low Dropout Linear Regulator |
| FAN1581D15X | 功能描述:低压差稳压器 - LDO 5A Adjustable Low Dropout Voltage Regulator (LDO) 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 |
| FAN1581D25X | 功能描述:低压差稳压器 - LDO 5A Adjustable Low Dropout Voltage Regulator (LDO) 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 |
| FAN1581DX | 功能描述:低压差稳压器 - LDO 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 |
| FAN1581M | 制造商:未知厂家 制造商全称:未知厂家 功能描述:Positive Adjustable Voltage Regulator |
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