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参数资料
| 型号： | FAN7602CM |
| 厂商： | Fairchild Semiconductor |
| 文件页数： | 10/18页 |
| 文件大小： | 0K |
| 描述： | IC PWM FLYBACK ISOLATED CM 8SOIC |
| 标准包装： | 95 |
| 输出隔离： | * |
| 频率范围： | * |
| 输入电压： | * |
| 输出电压： | * |
| 功率（瓦特）： | * |
| 工作温度： | * |
| 封装/外壳： | 8-SOIC（0.154"，3.90mm 宽） |
| 供应商设备封装： | * |
| 包装： | 管件 |
Application Information
1. Startup Circuit and Soft-Start Block
The FAN7602C contains a startup switch to reduce the
power loss of the external startup circuit of the
conventional PWM converters. The internal startup
circuit charges the V CC capacitor with 0.9 mA current
I DS
several
μ seconds
t SW =1/f SW
t SW
source if the AC line is connected. The startup switch is
? t
t
turned off 15 ms after IC starts up, as shown in Figure
19. The soft-start function starts when the V CC voltage
f SW
f SW + 1/2 ? f SW
MAX
reaches the start threshold voltage of 12 V and ends
when the internal soft-start voltage reaches 1 V. The
internal startup circuit starts charging the V CC capacitor
several
no repetition
f SW - 1/2 ? f SW
MAX
again if the V CC voltage is lowered to the minimum
operating voltage, 8 V. The UVLO block shuts down the
output drive circuit and some blocks to reduce the IC
operating current and the internal soft-start voltage
drops to zero. If the V CC voltage reaches the start
threshold voltage, the IC starts switching again and the
soft-start block works as well.
During the soft-start, pulse-width modulated (PWM)
comparator compares the CS/FB pin voltage with the
soft-start voltage. The soft-start voltage starts from 0.5 V
and the soft-start ends when it reaches 1 V and the soft-
start time is 10 ms. The startup switch is turned off when
the soft-start voltage reaches 1.3 V.
miliseconds
t
Figure 20. Frequency Fluctuation Waveform
3. Current Sense and Feedback Block
The FAN7602C performs the current sensing for the
current mode PWM and the output voltage feedback
with only one pin, pin 3. To achieve the two functions
with one pin, an internal Leading-Edge Blanking (LEB)
circuit to filter the current sense noise is not included
because the external RC filter is necessary to add the
output voltage feedback information and the current
sense information.
12V
V CC
R S is the current sense resistor to sense the switch
8V
Startup
Current
current. The current sense information is filtered by an
RC filter composed of R F and C F . According to the
output voltage feedback information, I FB charges or
stops charging C F to adjust the offset voltage. If I FB is
1.5V
1V
0.5V
Soft-Start
Voltage
zero, C F is discharged through R F and R S to lower the
offset voltage.
Soft-Start
Time (10ms)
5ms
t
Plimit
V CC
Figure 19. Startup Current and V CC Voltage
PWM
Comparator
PWM+
Offset
Power
R FB
I FB
2. Oscillator Block
Soft-Start
Limit
3
CS/FB
R F
I sw
The oscillator frequency is set internally and FAN7602C
has a random frequency fluctuation function.
Fluctuation of the switching frequency of a switched
power supply can reduce EMI by spreading the energy
over a wider frequency range than the bandwidth
measured by the EMI test equipment. The amount of
EMI reduction is directly related to the range of the
frequency variation. The range of frequency variation is
fixed internally; however, its selection is randomly
chosen by the combination of external feedback voltage
and internal free-running oscillator. This randomly
chosen switching frequency effectively spreads the EMI
noise nearby switching frequency and allows the use of
a cost-effective inductor instead of an AC input line filter
to satisfy the world-wide EMI requirements.
? 2009 Fairchild Semiconductor Corporation
FAN7602C ? Rev. 1.0.1
10
C F
R S
Figure 21. Current Sense and Feedback Circuits
pin. The current sense waveform is added to the offset
voltage, as shown in the Figure 22. The CS/FB pin
voltage is compared with PWM that is 1 V - Plimit offset.
If the CS/FB voltage meets PWM+, the output drive is
shut off. If the feedback offset voltage is LOW, the
switch on-time is increased. If the feedback offset
voltage is HIGH, the switch on-time is decreased. In this
way, the duty cycle is controlled according to the output
load condition. Generally, the maximum output power
increases as input voltage increases because the
current slope during switch on-time increases.
www.fairchildsemi.com
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相关代理商/技术参数 |
参数描述 |
|---|---|
| FAN7602CMX | 功能描述:电流型 PWM 控制器 Greenmode PWM Controller RoHS:否 制造商:Texas Instruments 开关频率:27 KHz 上升时间: 下降时间: 工作电源电压:6 V to 15 V 工作电源电流:1.5 mA 输出端数量:1 最大工作温度:+ 105 C 安装风格:SMD/SMT 封装 / 箱体:TSSOP-14 |
| FAN7602CN | 功能描述:电流型 PWM 控制器 Greenmode PWM Controller RoHS:否 制造商:Texas Instruments 开关频率:27 KHz 上升时间: 下降时间: 工作电源电压:6 V to 15 V 工作电源电流:1.5 mA 输出端数量:1 最大工作温度:+ 105 C 安装风格:SMD/SMT 封装 / 箱体:TSSOP-14 |
| FAN7602M | 功能描述:电流型 PWM 控制器 PWM CONTROL IC GREEN MODE RoHS:否 制造商:Texas Instruments 开关频率:27 KHz 上升时间: 下降时间: 工作电源电压:6 V to 15 V 工作电源电流:1.5 mA 输出端数量:1 最大工作温度:+ 105 C 安装风格:SMD/SMT 封装 / 箱体:TSSOP-14 |
| FAN7602MX | 功能描述:开关变换器、稳压器与控制器 Green Current Mode PWM IC RoHS:否 制造商:Texas Instruments 输出电压:1.2 V to 10 V 输出电流:300 mA 输出功率: 输入电压:3 V to 17 V 开关频率:1 MHz 工作温度范围: 安装风格:SMD/SMT 封装 / 箱体:WSON-8 封装:Reel |
| FAN7602N | 功能描述:电流型 PWM 控制器 POWER_CONVERSION RoHS:否 制造商:Texas Instruments 开关频率:27 KHz 上升时间: 下降时间: 工作电源电压:6 V to 15 V 工作电源电流:1.5 mA 输出端数量:1 最大工作温度:+ 105 C 安装风格:SMD/SMT 封装 / 箱体:TSSOP-14 |
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