SD4842P67K65 Ver la hoja de datos (PDF) - Unspecified

Número de pieza

componentes Descripción

Fabricante

SD4842P67K65

CURRENT MODE PWM CONTROLLER WITH BUILT-IN HIGH VOLTAGE MOSFET

Unspecified 

SD4840/4841/4842/4843/4844

3. Frequency Jitter

The oscillation frequency is kept changed for low EMI and decreasing radiation on one frequency. The oscillation

frequency changes within a very small range to simplify EMI design. The rule of frequency changing: change

from 65KHz to 69KHz.

4. Light Load Mode

Working in this mode to reduce power dissipation. It works normally when FB is 500mV above and during

350mV<FB <500mV, there are two different conditions: when FB changes from low to high, there is no action for

switch and it is the same with condition of FB lower than 350mV; the other is that FB changes form high to low,

comparison value is increased for increasing turning on time to decrease switch loss.

For this mode, during FB changes form high to low, the output voltage increases (increasing speed is decided

by load) because of the high comparison value to decrease FB until it is 350mV below; when FB <350mV, there

is no action for switch and output voltage decrease (decreasing speed is also decided by load) to increase FB.

This is repeated to decrease action of switch for lower power dissipation.

5. Leading Edge Blanking

For this current-controlled circuit, there is pulse peak current during the transient of switch turning on and there is

an error operation if the current is sampled during this time. And leading edge blanking is adopted to eliminate

this error operation. The output of PWM comparator is used for controlling shutdown after the leading edge

blanking if there is any output drive.

HANGZHOU SILAN MICROELECTRONICS CO.,LTD

Http: //www.silan.com.cn

REV:1.2 2008.12.17

Page 7 of 11

Share Link: