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參數(shù)資料
| 型號： | FSDM0465RB |
| 廠商： | Fairchild Semiconductor Corporation |
| 英文描述： | Green Mode Fairchild Power Switch (FPS) |
| 中文描述： | 綠色模式飛兆半導(dǎo)體功率開關(guān)（FPS） |
| 文件頁數(shù)： | 10/18頁 |
| 文件大小： | 250K |
| 代理商： | FSDM0465RB |
FSDM0465RB
10
Functional Description
1.
Startup:
In previous generations of Fairchild Power
Switches (FPS
TM
) the Vcc pin had an external start-up
resistor to the DC input voltage line. In this generation the
startup resistor is replaced by an internal high voltage current
source. At startup, an internal high voltage current source
supplies the internal bias and charges the external capacitor
(C
a
) that is connected to the Vcc pin as illustrated in Figure
4. When Vcc reaches 12V, the FSDM0465RB begins
switching and the internal high voltage current source is
disabled. Then, the FSDM0465RB continues its normal
switching operation and the power is supplied from the
auxiliary transformer winding unless Vcc goes below the
stop voltage of 8V.
Figure 4. Internal Startup Circuit
2. Feedback Control:
FSDM0465RB employs current
mode control, as shown in Figure 5. An opto-coupler (such
as the H11A817A) and shunt regulator (such as the KA431)
are typically used to implement the feedback network.
Comparing the feedback voltage with the voltage across the
Rsense resistor plus an offset voltage makes it possible to
control the switching duty cycle. When the reference pin
voltage of the KA431 exceeds the internal reference voltage
of 2.5V, the H11A817A LED current increases, thus
decreasing the feedback voltage and reducing the duty cycle.
This event typically happens when the input voltage is
increased or the output load is decreased.
2.1 Pulse-by-Pulse Current Limit:
Because current mode
control is employed, the peak current through the SenseFET
is limited by the inverting input of the PWM comparator
(Vfb*) as shown in Figure 5. Assuming that the 0.9mA
current source flows only through the internal resistor (2.5R
+R= 2.8 k
), the cathode voltage of diode D2 is about 2.5V.
Since D1 is blocked when the feedback voltage (Vfb)
exceeds 2.5V, the maximum voltage of the cathode of D2 is
clamped at this voltage, thus clamping Vfb*. Therefore, the
peak value of the current through the SenseFET is limited.
2.2 Leading Edge Blanking (LEB):
At the instant the
internal SenseFET is turned on, there usually exists a high
current spike through the SenseFET, caused by primary-side
capacitance and secondary-side rectifier reverse recovery.
Excessive voltage across the Rsense resistor would lead to
incorrect feedback operation in the current mode PWM
control. To counter this effect, the FSDM0465RB employs
an LEB circuit. This circuit inhibits the PWM comparator for
a short time (T
LEB
) after the, SenseFET is turned on.
Figure 5. Pulse Width Modulation (PWM) Circuit
3. Protection Circuit:
The FSDM0465RB has several self
protective functions such as over load protection (OLP), over
voltage protection (OVP), and thermal shutdown (TSD).
Because these protection circuits are fully integrated into the
IC without external components, the reliability can be
improved without increasing cost. Once the fault condition
occurs, switching is terminated and the SenseFET remains
off. This causes Vcc to fall. When Vcc reaches the UVLO
stop voltage, 8V, the protection is reset and the internal high
voltage current source charges the Vcc capacitor via the Vstr
pin. When Vcc reaches the UVLO start voltage,12V, the
FSDM0465RB resumes its normal operation. In this manner,
the auto-restart can alternately enable and disable the
switching of the power Sense FET until the fault condition is
eliminated (see Figure 6).
8V/12V
3
Vref
Internal
Bias
Vcc
6
Vstr
I
CH
Vcc Good
V
DC
C
a
4
OSC
Vcc
Vref
I
delay
I
FB
V
SD
R
2.5R
driver
Driver
OLP
D1
D2
+
V
fb
*
-
Vfb
KA431
C
B
Vo
H11A817A
R
sense
SenseFET
Gate
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| FSDM07652RBWDTU | Green Mode Fairchild Power Switch (FPS) |
| FSDM0565RBI | Green Mode Fairchild Power Switch (FPS) |
| FSDM0565RB | Green Mode Fairchild Power Switch (FPS) |
| FSDM07652RB | Green Mode Fairchild Power Switch (FPS) |
| FSDM07652R | Green Mode Fairchild Power Switch (FPS) |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| FSDM0465RBWDTU | 功能描述:電源開關(guān) IC - 配電 TF220 GREEN MODE POWER SWITCH RoHS:否 制造商:Exar 輸出端數(shù)量:1 開啟電阻（最大值）:85 mOhms 開啟時間（最大值）:400 us 關(guān)閉時間（最大值）:20 us 工作電源電壓:3.2 V to 6.5 V 電源電流（最大值）: 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:SOT-23-5 |
| FSDM0465RE | 制造商:FAIRCHILD 制造商全稱:Fairchild Semiconductor 功能描述:Green-Mode Fairchild Power Switch |
| FSDM0465RE_07 | 制造商:FAIRCHILD 制造商全稱:Fairchild Semiconductor 功能描述:Green Mode Fairchild Power Switch (FPS⑩) |
| FSDM0465REWDTU | 功能描述:電流型 PWM 控制器 SMPS POWER SWITCH BUILT-IN SOFT START 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 |
| FSDM0465RS | 制造商:FAIRCHILD 制造商全稱:Fairchild Semiconductor 功能描述:Green Mode Fairchild Power Switch |
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