FA5304AP 데이터 시트보기 (PDF) - Fuji Electric

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FA5304AP

Bipolar IC For Switching Power Supply Control

Fuji Electric 

FA5304AP(S)/FA5305AP(S)

2. Disabling overload shutdown function

As shown in Figure 24, connect a 330kΩ to 470kΩ resistor

between the CS pin and ground. Then, the CS pin voltage

does not rise high enough to reach the reference voltage

(7.0V) of the latch comparator, and the IC does not enter the

OFF latch mode. With this connection, the overvoltage

shutdown function is not available.

3. Setting soft start period and OFF latch delay

independently

Figure 25 shows a circuit for setting the soft start period and

OFF latch delay independently. In this circuit, capacitance CS

determines the soft start period, and capacitance CL

determines the OFF latch delay. If the overload shutdown and

overvoltage shutdown functions raise the CS pin voltage to

around 5V, zener diode Zn becomes conductive to charge CL.

The OFF latch delay can be thus prolonged by CL.

4. Laying out Vcc and ground lines

Figure 26 and Figure 27 show the recommended layouts of

VCC and ground lines. The bold lines represent paths carrying

large currents. The lines must have an adequate thickness.

5. Sink current setting for CS terminal

A sink current to CS terminal must be satisfied the following

condition to prevent from the malfunction which uncontrolled

pulse output generates at OUT terminal when latch-mode

protection should be operated for overvoltage.

150µA < Ics(sink) < 500µA at Vcs= 6.5(V)

Ics(sink): Sink current to CS terminal

Example (for the circuit shown in Fig. 28 )

Ics(sink) = (28(V)–18(V)– 6.5(V))/7.5(kΩ)

Լ 467 (µA) < 500 (µA)

Fig. 25 Independent setting of soft-start period and OFF latch

delay

Fig. 26 Vcc line and ground line for FA5304A

Fig. 24 Disabling overload shutdown function

12

Fig. 27 Vcc line and ground line for FA5305A

CS

VCC

7.5kΩ 18V Zener diode

Under 500µA

Fig. 28 Setting sink current for CS terminal

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