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參數資料
| 型號： | FA3641N |
| 廠商： | FUJI ELECTRIC CO LTD |
| 元件分類： | 穩壓器 |
| 英文描述： | PWM control IC with light load power saving function For Switching Power Supply Control |
| 中文描述： | 1 A SWITCHING CONTROLLER, 500 kHz SWITCHING FREQ-MAX, PDSO8 |
| 封裝： | SOP-8 |
| 文件頁數： | 11/21頁 |
| 文件大小： | 406K |
| 代理商： | FA3641N |
FA3641P(N), FA3647P(N)
68
Fig. 14 Overcurrent limiting circuit
Fig. 15 Overcurrent timing chart
Fig. 17 Overvoltage shutdown timing chart
Fig. 16 Overvoltage shutdown circuit
5. Overcurrent limiting circuit
The overcurrent limiting circuit detects the peak value of every
drain current pulse (pulse by pulse method) of the main
switching MOSFET to limit the overcurrent. The detection
threshold voltage is +0.235V for FA3641 or
–
0.168V for FA3647
with respect to the ground as shown in Figure 14.
The drain current of the MOSFET is converted to voltage by
resistor Rs and fed to the IS pin of the IC. If the voltage
exceeds the reference voltage +0.235V (FA3641) or
–
0.168V
(FA3647) of comparator C4, comparator C4 works to set flip-
flop output Q to high. The output is immediately turned off to
shut off the current. Flip-flop output Q is reset on the next cycle
to turn on the output again. This operation is repeated to limit
the overcurrent.
If the overcurrent limiting circuit malfunctions due to noise,
place an RC filter between the IS pin and MOSFET as shown in
Figure 14. (See item 14 in
“
Design advice.
”
)
Figure 15 is a timing chart that illustrates overcurrent-limiting
operations.
6. Vcc overvoltage protection circuit
The IC contains a Vcc overvoltage protection circuit to protect
the IC from damage by overvoltage. Figure 16 shows the
overvoltage protection circuit. Figure 17 is a timing chart that
illustrates overvoltage protection operations.
Overvoltage is detected if the supply voltage Vcc rises to 32V
(Icc = 13mA) or more and current flows in the built-in zener
diode. The output of comparator C5 then goes high and the
constant current source (0.9mA) raises the CS pin voltage.
When the CS pin voltage exceeds 8.5V, the output of
comparator C2 goes high to turn off the 5V REF circuit. The IC
then enters the latched mode and the IC output is put in the off
(low voltage) state. When latched mode, the IC current
consumption is 45
μ
A (typ) (Vcc = 10V). This current must be
supplied through the startup resistor.
The overvoltage shutdown operation can be reset by lowering
the supply voltage to below 9.0V or forcing the CS pin voltage
below 7.9V.
(When you want to enable Vcc overvoltage shutdown at a
desired voltage, see item 7 in
“
Design advice.
”
相關PDF資料 |
PDF描述 |
|---|---|
| FA3641P | PWM control IC with light load power saving function For Switching Power Supply Control |
| FA3647 | PWM control IC with light load power saving function For Switching Power Supply Control |
| FA3647N | PWM control IC with light load power saving function For Switching Power Supply Control |
| FA3647P | PWM control IC with light load power saving function For Switching Power Supply Control |
| FA365 | THIN SMD HIGH-FREQUENCY CRYSTAL UNIT |
相關代理商/技術參數 |
參數描述 |
|---|---|
| FA3641N-H1 | 制造商:Fuji Electric 功能描述: |
| FA3641P | 制造商:FUJI 制造商全稱:Fuji Electric 功能描述:PUJI Power Supply Controllc |
| FA3641P_00 | 制造商:FUJI 制造商全稱:Fuji Electric 功能描述:PUJI Power Supply Controllc |
| FA3641P-D1 | 制造商:Fuji Electric 功能描述: |
| FA3647 | 制造商:FUJI 制造商全稱:Fuji Electric 功能描述:PWM control IC with light load power saving function For Switching Power Supply Control |
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