NCP1251 View Datasheet(PDF) - ON Semiconductor

Part Name

Description

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NCP1251

Current-Mode PWM Controller for Off-line Power Supplies

ON Semiconductor 

OPP

Vlatch

vdd

NCP1251

IpFlag BO

OVP

gone?

600−ns time

constant

Up counter

vdd

RST

4

Vcc logic

management

and fault timer

UVLO

power

on reset

20us time

constant

VOVP

S

Q

Q

Frequency

modulation

R

Power on

reset

1−us

blanking

65 kHz

100 kHz

clock

Rlimit

Iscr

S

Q

Q

Clamp

R

Frequency

foldback

Vfold

Vskip

vdd

RFB

FB

/ 4.2

CS

LEB

Rramp

The soft−start is activated during:

− the startup sequence

− the auto−recovery burst mode

4 ms

SS

IpFlag

250 mV

peak current

freeze

VOPP

VFB < 1.05 V ? setpoint = 250 mV

+ Vlimit + VOPP

Vlimit

Figure 2. Internal Circuit Architecture

Vcc

Drv

GND

http://onsemi.com

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