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參數(shù)資料
| 型號(hào)： | SG6841S |
| 廠商： | Electronic Theatre Controls, Inc. |
| 英文描述： | High-integrated Green-mode PWM Controller |
| 中文描述： | 高集成度綠色模式PWM控制器 |
| 文件頁(yè)數(shù)： | 9/14頁(yè) |
| 文件大?。?/td> | 357K |
| 代理商： | SG6841S |
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Product Specification
High-integrated Green-mode PWM Controller
SG6841
OPERATION DESCRIPTION
Start-up current
System General Corp. - 9 - www.sg.com.tw
Version 1.7 (IRO33.0001.B1) JUL.25,2003
Typical start-up current is only 30uA so that a high
resistance, and low-wattage, start-up resistor can be used
to minimize power loss. For an AC/DC adapter with
universal input range, a 1.5 M
, 0.25W, start-up resistor
and a 10uF/25V VDD hold-up capacitor are enough for
this application.
Operating current
Operating current has been reduced to 3mA. The low
operating current enables a better efficiency and reduces
the requirement of VDD hold-up capacitance.
Green Mode Operation
The patented green-mode function provides an
off-time modulation to reduce the switching frequency in
the light load and no load conditions. The on time is
limited for better abnormal or brownout protection. V
FB
,
which is derived from the voltage feedback loop, is taken
as the reference. Once V
FB
is lower than the threshold
voltage, switching frequency will be linearly decreased to
the minimum green mode frequency around 10kHz (R
i
=26k
).
Oscillator Operation
A resistor from RI pin to ground will generate a
constant current source for SG6841. This current is used
to charge an internal capacitor and hence the internal
clock and switching frequency are determined. Increase
the resistance will decrease the current source and reduce
the switching frequency. A 26k
resistor R
i
creates a
50uA constant current I
i
and generates 65kHz switching
frequency. The relation between Ri and switching
freauency is:
)
(
kHz
)
(k
R
1690
PWM
f
=
---------------------------- (1)
The range of the PWM oscillation frequency is
designed as 50kHz ~ 90kHz.
Current sensing and PWM current
limiting
Peak current mode control is utilized in SG6841 to
regulate output voltage and provide pulse by pulse current
limiting. The switch current is detected by a sense resistor
into the sense pin of SG6841. The PWM duty cycle is
determined by this current sense signal and V
FB
, the
feedback voltage. When the voltage on sense pin reaches
V
COMP
= (V
FB
–1.0)/3, a switch cycle will be terminated
immediately. V
COMP
is internally clamped to a variable
voltage around 0.85v for output power limit.
Leading Edge Blanking
Each time when the power MOSFET is switched on,
a turn-on spike will inevitably occur on the sense-resistor.
To avoid premature termination of the switching pulse, a
270 nsec leading-edge blanking time is built in.
Conventional RC filtering can therefore be omitted.
During this blanking period, the current-limit comparator
is disabled and it cannot switch off the gate driver.
Under-voltage lockout (UVLO)
The turn-on and turn-off threshold of SG6841 are
fixed internally at 16V/10V. During start-up, the hold-up
capacitor must be charged to 16V through the start-up
resistor so that SG6841 will be enabled. The hold-up
capacitor will continue to supply V
DD
before the energy
can be delivered from auxiliary winding of the main
transformer. V
DD
must not drop below 10V during this
start-up process. This UVLO hysteresis window insures
that hold-up capacitor is adequate to supply V
DD
during
start-up.
Gate Output / Soft Driving
The SG6841 BiCMOS output stage is a fast totem
pole gate driver. Cross conduction has been avoided to
minimize heat dissipation, increases efficiency and
enhances reliability. The output driver is clamped by an
internal 18V Zener diode in order to protect power
MOSFET transistors against undesirable gate over
voltage. A soft driving waveform is implemented to
minimize EMI.
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| SG6846LD | Highly-Integrated Green-Mode PWM Controller |
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| SG6846CS | Highly-Integrated Green-Mode PWM Controller |
| SG6846CSZ | Highly-Integrated Green-Mode PWM Controller |
| SG6846LS | Highly-Integrated Green-Mode PWM Controller |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| SG6841SZ | 功能描述:電壓模式 PWM 控制器 HI-INTEGRD GRN-MODE PWM CONTROLLER RoHS:否 制造商:Texas Instruments 輸出端數(shù)量:1 拓?fù)浣Y(jié)構(gòu):Buck 輸出電壓:34 V 輸出電流: 開(kāi)關(guān)頻率: 工作電源電壓:4.5 V to 5.5 V 電源電流:600 uA 最大工作溫度:+ 125 C 最小工作溫度:- 40 C 封裝 / 箱體:WSON-8 封裝:Reel |
| SG6841SZ3 | 功能描述:電壓模式 PWM 控制器 HI-INTEGRD GRN-MODE PWM CONTROLLER RoHS:否 制造商:Texas Instruments 輸出端數(shù)量:1 拓?fù)浣Y(jié)構(gòu):Buck 輸出電壓:34 V 輸出電流: 開(kāi)關(guān)頻率: 工作電源電壓:4.5 V to 5.5 V 電源電流:600 uA 最大工作溫度:+ 125 C 最小工作溫度:- 40 C 封裝 / 箱體:WSON-8 封裝:Reel |
| SG6842BLVDZ | 制造商:Fairchild Semiconductor Corporation 功能描述: |
| SG6842BLVSY | 功能描述:電流型 PWM 控制器 Current Mode PWM Controller RoHS:否 制造商:Texas Instruments 開(kāi)關(guān)頻率:27 KHz 上升時(shí)間: 下降時(shí)間: 工作電源電壓:6 V to 15 V 工作電源電流:1.5 mA 輸出端數(shù)量:1 最大工作溫度:+ 105 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:TSSOP-14 |
| SG6842BLVSZ | 制造商:Rochester Electronics LLC 功能描述: 制造商:Fairchild Semiconductor Corporation 功能描述: |
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