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參數資料
| 型號： | FA5305APS |
| 廠商： | FUJI ELECTRIC HOLDINGS CO., LTD. |
| 元件分類： | 基準電壓源/電流源 |
| 英文描述： | Bipolar IC For Switching Power Supply Control |
| 中文描述： | 雙極集成電路開關電源控制 |
| 文件頁數： | 6/17頁 |
| 文件大小： | 280K |
| 代理商： | FA5305APS |
6
FA5304AP(S)/FA5305AP(S)
4. CS pin circuit
As shown in Figure 5, capacitor C
S
is connected to the CS pin.
When power is turned on, the constant current source (10
μ
A)
begins to charge capacitor C
S
. Accordingly, the CS pin voltage
rises as shown in Figure 6. The CS pin is connected to an
input of the PWM comparator. The device is in soft-start mode
while the CS pin voltage is between 1.0V and 1.9V common to
FA5304A and FA5305A. During normal operation, the CS pin
is clamped at 3.6V by internal zener diode Zn. If the output
voltage drops due to an overload, etc., the clamp voltage shifts
from 3.6V to 8.0V. As a result, the CS pin voltage rises to 8.0V.
The CS pin is also connected to latch comparator C2. If the pin
voltage rises above 7.0V, the output of comparator C2 goes
high to turn off the bias circuit , thereby shutting the output
down. Comparator C2 can be used not only for shutdown in
response to an overload, but also for shutdown in response to
an overvoltage. Comparator C1 is also connected to the CS
pin, and the bias circuit is turned off and the output is shut
down if the CS pin voltage drops below 0.42V. In this way,
comparator C1 can also be used for output on/off control.
As explained above, the CS pin can be used for soft-start
operation, overload and overvoltage output shutdown and
output on/off control.
Further details on the four functions of the CS pin are given
below.
4.1 Soft start function
Figure 7 shows the soft start circuit. Figure 8 is the soft-start
operation timing chart. The CS pin is connected to capacitor
C
S
. When power is turned on, a 10
μ
A constant-current source
begins to charge the capacitor. As shown in the timing chart,
the CS pin voltage rises slowly in response to the charging
current. The CS pin is connected internally to the PWM
comparator. The comparator output pulse slowly widens as
shown in the timing chart.
The soft start period can be approximately evaluated by the
period ts from the time the IC is activated to the time the output
pulse width widens to 30%. Period ts is given by the following
equation:
t
S
(m
S
) = 160C
S
(
μ
F).................................(2)
Fig. 5 CS pin circuit
Fig. 6 CS pin waveform
Fig. 7 Soft-start circuit
Fig. 8 Soft-start timing chart
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相關代理商/技術參數 |
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| FA5305AS | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:(367.00 k) |
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| FA5310 | 制造商:FUJI 制造商全稱:Fuji Electric 功能描述:Bipolar IC For Switching Power Supply Control |
| FA5310BP | 制造商:FUJI 制造商全稱:Fuji Electric 功能描述:Bipolar IC For Switching Power Supply Control |
| FA5310BP(S) | 制造商:未知廠家 制造商全稱:未知廠家 功能描述: |
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