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参数资料
| 型号： | SG6841SZ |
| 厂商： | Fairchild Semiconductor |
| 文件页数： | 10/14页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR FLYBACK PWM 8-SOIC |
| 产品变化通告： | Mold Compound Change 12/Dec/2007 |
| 标准包装： | 2,500 |
| PWM 型： | 控制器 |
| 输出数： | 1 |
| 频率 - 最大： | 70kHz |
| 占空比： | 90% |
| 电源电压： | 10 V ~ 20 V |
| 降压： | 无 |
| 升压： | 无 |
| 回扫： | 是 |
| 反相： | 无 |
| 倍增器： | 无 |
| 除法器： | 无 |
| Cuk： | 无 |
| 隔离： | 无 |
| 工作温度： | -20°C ~ 85°C |
| 封装/外壳： | 8-SOIC（0.154"，3.90mm 宽） |
| 包装： | 带卷 (TR) |
Product Specification
High-integrated Green-mode PWM Controller
Built-in Slope Compensation
The sensed voltage across the current sense resistor
is used for current mode control and pulse-by-pulse
current limiting. Built-in slope compensation will
improve stability or prevent sub-harmonic oscillation of
peak current mode control. SG6841 inserts a
synchronized positive-going ramp at every switching
cycle. Vs-comp = 0.33V.
Constant Output Power Limit
When the SENSE voltage, across the sense resistor
Rs, reaches the threshold voltage, around 1.0V, the output
GATE drive will be turned off after a small propagation
delay t D . This propagation delay will introduce an
additional current proportional to t D *Vin/Lp. Since the
propagation delay is nearly constant regardless of the
input line voltage V IN. Higher input line voltage will result
in a larger additional current and hence the output power
limit is also higher than that under low input line voltage.
To compensate this variation for wide AC input range, the
threshold voltage is adjusted by the V IN current. Since
VIN pin is connected to the rectified input line voltage
through the start-up resistor, a higher line voltage will
generate higher V IN current into the VIN pin. The
threshold voltage is decreased if the V IN current is
increased. Smaller threshold voltage, forces the output
GATE drive to terminate earlier, thus reduce the total
PWM turn-on time and make the output power equal to
that of low line input. This proprietary internal
compensation ensures a constant output power limit for
wide AC input voltage from 90VAC to 264VAC.
Thermal Protection
An NTC thermistor Rntc in series with a resistor Ra
can be connected from pin RT to ground. A constant
current I RT is output from pin RT. The voltage on RT pin
can be expressed as V RT = I RT × (Rntc + Ra) in which I RT =
2 x (1.3V / Ri).
SG6841
At high ambient temperature, Rntc will be smaller
such that V RT will decrease. When V RT is less than 0.65V
(V OTP,START ), the PWM duty cycle will be decreased to
lower the internal temperature of power supply. If the
over heating situation still exists such that V RT decreases
further to 0.62V (V OTP,STOP ), the PWM will be completely
turned off.
Limited Power Control
Every time when the output of power supply is
shorted or over loaded, the FB voltage will increase. If the
FB voltage is higher than a designed threshold, 4.2V, for
longer than 31msec, the PWM output will then be turned
off eternally. V DD , the supply voltage for SG6841, will
decrease due to the supply current for SG6841. When V DD
is lower than the turn-off threshold such as 10V, SG6841
will be totally shut down. Due to the start up resistor, V DD
will be charged up to the turn-on threshold voltage 16V
until SG6841 is enabled again. If the over loading
condition still exists, above protection will take place
repeatedly. This will prevent the power supply from being
overheated under over loading condition.
Noise immunity
Noise on the current sense or control signal may
cause significant pulse width jitter, particularly in the
continuous conduction mode. Slope compensation helps
alleviate this problem. Good placement and layout
practices should be followed. Avoiding long PCB traces
and component leads, locating compensation and filter
components near to the SG6841, and increasing the power
MOS gate resistance will always help.
?System General Corp.
Version 2.1 (IRO33.0001.B5)
- 10 -
www.sg.com.tw
Jun.15,2006
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相关代理商/技术参数 |
参数描述 |
|---|---|
| SG6841SZ3 | 功能描述:电压模式 PWM 控制器 HI-INTEGRD GRN-MODE PWM CONTROLLER RoHS:否 制造商:Texas Instruments 输出端数量:1 拓扑结构:Buck 输出电压:34 V 输出电流: 开关频率: 工作电源电压:4.5 V to 5.5 V 电源电流:600 uA 最大工作温度:+ 125 C 最小工作温度:- 40 C 封装 / 箱体:WSON-8 封装:Reel |
| SG6842BLVDZ | 制造商:Fairchild Semiconductor Corporation 功能描述: |
| SG6842BLVSY | 功能描述:电流型 PWM 控制器 Current Mode 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 |
| SG6842BLVSZ | 制造商:Rochester Electronics LLC 功能描述: 制造商:Fairchild Semiconductor Corporation 功能描述: |
| SG6842JLDZ | 制造商:Fairchild Semiconductor Corporation 功能描述: |
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