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參數(shù)資料
| 型號(hào)： | FSCM0465R |
| 廠(chǎng)商： | Fairchild Semiconductor Corporation |
| 英文描述： | Green Mode Fairchild Power Switch |
| 中文描述： | 綠色模式飛兆半導(dǎo)體功率開(kāi)關(guān) |
| 文件頁(yè)數(shù)： | 10/20頁(yè) |
| 文件大?。?/td> | 457K |
| 代理商： | FSCM0465R |
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F
2006 Fairchild Semiconductor Corporation
FSCM0465R Rev. 1.0.1
www.fairchildsemi.com
10
Functional Description
1. Startup
: Figure 16 shows the typical startup circuit
and transformer auxiliary winding for the FSCM0465R
application. Before the FSCM0465R begins switching, it
consumes only startup current (typically 20μA) and the
current supplied from the DC link supply current
consumed by the FPS (I
CC
) and charges the external
capacitor (C
a
) connected to the V
CC
pin. When V
CC
reaches start voltage of 12V (V
START
), the FSCM0465R
begins switching and the current consumed by the
FSCM0465R increases to 2.5mA. Then the
FSCM0465R
continues its normal switching operation and the power
required for this device is supplied from the transformer
auxiliary winding, unless V
CC
drops below the stop
voltage of 8V (V
STOP
). To guarantee the stable operation
of the control IC, V
CC
has under-voltage lockout (UVLO)
with 4V hysteresis. Figure 17 shows the relationship
between the current consumed by the FPS (I
CC
) and the
supply voltage (V
CC
).
Figure 16. Startup Circuit
Figure 17. Relation Between Operating Supply
Current and V
CC
Voltage
The minimum current supplied through the startup
resistor is given by:
where
V
linemin
is the minimum input voltage,
V
start
is the
start voltage (12V) and
R
str
is the startup resistor. The
startup resistor should be chosen so that
I
supmin
is larger
than the maximum startup current (40μA). If not, V
CC
can
not be charged to the start voltage and FPS fails to start.
2. Feedback Control
: The FSCM0465R employs
current mode control, as shown in Figure 18. An opto-
coupler (such as the H11A817A) and a 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 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,
pulling down 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 determined by the inverting input of the
PWM comparator (Vfb*) as shown in Figure 18. When
the current through the opto-transistor is zero and the
current limit pin (#5) is left floating, the feedback current
source (I
FB
) of 0.9mA flows only through the internal
resistor (R+2.5R=2.8k). In this case, the cathode voltage
of diode D2 and the peak drain current have maximum
values of 2.5V and 2.5A, respectively. The pulse-by-
pulse current limit can be adjusted using a resistor to
GND on the
current limit pin (#5). The current limit level
using an external resistor (R
LIM
) is given by:
Figure 18. Pulse Width Modulation (PWM) Circuit
FSCM0465R
Rstr
V
CC
Ca
Da
I
SUP
AC line
min
- V
line
(V
line
max
)
C
DC
I
CC
FSCM0465R Rev. 00
I
CC
V
CC
Vstop=8V
3mA
Vstart=12V
Vz
Power Up
Power Down
25
μ
A
FSCM0465R Rev. 00
(
)
min
min
sup
line
start
V
str
1
I
V
R
2
=
(1)
LIM
K
LIM
LIM
R
A
I
R
2.5
2.8
=
Ω +
(2)
4
OSC
Vcc
Vref
I
delay
I
FB
V
SD
R
2.5R
Gate
driver
OLP
D1
D2
+
V
fb
*
-
Vfb
KA431
C
B
Vo
H11A817A
R
sense
SenseFET
6
R
LI M
0.9mA
0.3k
FSCM0465R Rev. 00
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| FSCM0465RG | Green Mode Fairchild Power Switch |
| FSCM0465RGWDTU | Green Mode Fairchild Power Switch |
| FSCM0465RI | Green Mode Fairchild Power Switch |
| FSCM0465RIWDTU | Green Mode Fairchild Power Switch |
| FSCM0465RJ | Green Mode Fairchild Power Switch |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| FSCM0465RG | 制造商:FAIRCHILD 制造商全稱(chēng):Fairchild Semiconductor 功能描述:Green Mode Fairchild Power Switch |
| FSCM0465RGWDTU | 功能描述:電源開(kāi)關(guān) IC - 配電 SMPS Power Switch for Set Top Box RoHS:否 制造商:Exar 輸出端數(shù)量:1 開(kāi)啟電阻（最大值）:85 mOhms 開(kāi)啟時(shí)間（最大值）:400 us 關(guān)閉時(shí)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 |
| FSCM0465RI | 制造商:FAIRCHILD 制造商全稱(chēng):Fairchild Semiconductor 功能描述:Green Mode Fairchild Power Switch |
| FSCM0465RIWDTU | 功能描述:電源開(kāi)關(guān) IC - 配電 FPS FOR LCD RoHS:否 制造商:Exar 輸出端數(shù)量:1 開(kāi)啟電阻（最大值）:85 mOhms 開(kāi)啟時(shí)間（最大值）:400 us 關(guān)閉時(shí)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 |
| FSCM0465RJ | 功能描述:電源開(kāi)關(guān) IC - 配電 FPS FOR LCD RoHS:否 制造商:Exar 輸出端數(shù)量:1 開(kāi)啟電阻（最大值）:85 mOhms 開(kāi)啟時(shí)間（最大值）:400 us 關(guān)閉時(shí)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 |
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