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參數(shù)資料
| 型號： | SG5841SZ |
| 廠商： | FAIRCHILD SEMICONDUCTOR CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | Highly Integrated Green-Mode PWM Controller |
| 中文描述： | 0.23 A SWITCHING CONTROLLER, 68 kHz SWITCHING FREQ-MAX, PDSO8 |
| 封裝： | LEAD FREE, MS-012AA, SOP-8 |
| 文件頁數(shù)： | 9/14頁 |
| 文件大小： | 506K |
| 代理商： | SG5841SZ |
Product Specification
Highly Integrated Green-Mode PWM Controller
OPERATION DESCRIPTION
Start-up Current
SG5841/J
System General Corp.
Version 1.3.1 (IAO33.0017.B6)
- 9 -
www.sg.com.tw www.fairchildsemi.com
September 20, 2007
Typical start-up current is only 14μA,
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 1.5M
, 0.25W start-up resistor
and a 10μF/25V V
DD
hold-up capacitor are enough for
this application.
Operating Current
Operating current is around 4mA. The low operating
current enables better efficiency and reduces the
requirement of V
DD
hold-up capacitance.
Green-Mode Operation
The proprietary green-mode function provides off-time
modulation to continuously decrease the PWM frequency
under light-load conditions. To avoid acoustic noise
problems, the minimum PWM frequency is set above
22kHz. This green-mode function dramatically reduces
power consumption under light-load and zero-load
conditions. Power supplies using a SG5841/J controller
can meet even the most restrictive international
regulations regarding standby power consumption.
Oscillator Operation
A resistor connected from the RI pin to the GND pin
generates a constant current source for the SG5841/J
controller. This current is used to determine the center
PWM frequency. Increasing the resistance reduces PWM
frequency. Using a 26K
Ω
resistor, R
I
, results in a
corresponding 65KHz PWM frequency. The relationship
between R
I
and the switching frequency is:
(KHz)
1690
)
(K
R
Ω
=
PWM
f
----------------------------
(1)
The range of the PWM oscillation frequency is designed
as 47KHz ~ 109KHz.
SG5841J also integrates frequency hopping function
internally. The frequency variation ranges from around
62KHz to 68KHz for a center frequency of 65KHz. The
frequency hopping function helps reduce EMI emission of
a power supply with minimum line filters.
Current Sensing / PWM Current Limiting
Peak-current-mode control is utilized in SG5841/J to
regulate output voltage and provide pulse-by-pulse
current limiting. The switch current is detected by a sense
resistor into the SENSE pin. The PWM duty cycle is
determined by this current sense signal and the feedback
voltage. When the voltage on the SENSE pin reaches
around V
COMP
= (V
FB
–1.0)/3.2, a switch cycle is
terminated immediately. V
COMP
is internally clamped to a
variable voltage around 0.85V for output power limit.
Leading-Edge Blanking
Each time the power MOSFET is switched on, a turn-on
spike occurs at the sense-resistor. To avoid premature
termination of the switching pulse, a leading-edge
blanking time is built in. During this blanking period, the
current-limit comparator is disabled and cannot switch off
the gate drive.
Under-Voltage Lockout (UVLO)
The turn-on and turn-off thresholds of SG5841/J are fixed
internally at 16V/10V. During start-up, the hold-up
capacitor must be charged to 16V through the start-up
resistor for the IC to be enabled. The hold-up capacitor
continues 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 ensures that hold-up
capacitor is adequate to supply V
DD
during start-up.
Gate Output / Soft Driving
The SG5841/J BiCMOS output stage is a fast totem pole
gate driver. Cross conduction has been avoided to
minimize heat dissipation, increase efficiency, and
enhance reliability. The output driver is clamped by an
internal 18V Zener diode to protect power MOSFET
transistors against undesirable gate over-voltage. A soft
driving waveform is implemented to minimize EMI.
Built-in Slope Compensation
The sensed voltage across the current-sense resistor is
used for peak-current-mode control and pulse-by-pulse
current limiting. Built-in slope compensation improves
stability or prevents sub-harmonic oscillation. SG5841/J
inserts a synchronized, positive-going ramp at every
switching cycle.
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| SG5842ASZ | Highly Integrated Green-Mode PWM Controller |
| SG5842A | Highly Integrated Green-Mode PWM Controller |
| SG5842ADZ | Highly Integrated Green-Mode PWM Controller |
| SG5842JA | Highly Integrated Green-Mode PWM Controller |
| SG5842JADZ | Highly Integrated Green-Mode PWM Controller |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| SG5841SZ_SB82167 | 功能描述:電流型 PWM 控制器 HI-INTEGRD GRN-MODE PWM CONTROLLER RoHS:否 制造商:Texas Instruments 開關(guān)頻率:27 KHz 上升時間: 下降時間: 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 |
| SG5842A | 制造商:FAIRCHILD 制造商全稱:Fairchild Semiconductor 功能描述:Highly Integrated Green-Mode PWM Controller |
| SG5842A_09 | 制造商:FAIRCHILD 制造商全稱:Fairchild Semiconductor 功能描述:Highly Integrated Green-Mode PWM Controller |
| SG5842ADZ | 制造商:FAIRCHILD 制造商全稱:Fairchild Semiconductor 功能描述:Highly Integrated Green-Mode PWM Controller |
| SG5842ASY | 制造商:FAIRCHILD 制造商全稱:Fairchild Semiconductor 功能描述:Highly Integrated Green-Mode PWM Controller |
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