SD4840 查看數據表（PDF） - Silan Microelectronics

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产品描述 (功能)

比赛名单

SD4840

CURRENT MODE PWM CONTROLLER WITH BUILT-IN HIGH VOLTAGE MOSFET

Silan Microelectronics 

SD4840/4841/4842/4843/4844

6. Over Voltage Protection

The output is shutdown if voltage at Vcc exceeds the threshold and this state is kept until the circuit is powered

on reset.

7. Overload Protection

FB voltage increase if there is overload and the output is shutdown when FB voltage is up to the feedback

shutdown voltage. This state is kept until the circuit is powered on reset.

8. Peak Current Limit Cycle By Cycle

During each cycle, the peak current value is decided by the comparison value of the comparator, which will not

exceed the peak current limited value to guarantee the current on MOSFET will not be more than the rating

current. The output power will not increase if the current reaches the peak value to limit the max. output power.

The output voltage decreases and FB voltage increases if there is overload and corresponding protection occurs.

9. Abnormal Over Current Protection

That secondary diode is short, or the transformer is short will cause this event. At this time, once it is over current

in spite of the leading edge blanking (L.E.B) time, protection will begin after 350nS, and is active for every cycle.

When the voltage on the current sense resistor is 1.6V, this protection will occur and the output is shut down.

This state is kept until the under voltage occurs, and the circuit will start.

10. Thermal Shutdown

If the circuit is over temperature, the over temperature protection will shut down the output to prevent the circuit

from damage. This state is kept until the under voltage occurs, and the circuit will start.

HANGZHOU SILAN MICROELECTRONICS CO.,LTD

Http: //www.silan.com.cn

REV:1.2 2008.12.17

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