CYStech Electronics Corp.

Spec. No. : C510P8

Issued Date : 2003.04.24

Revised Date :

Page No. : 1/15

PL384XBP8

CYStek Product Specification

High Performance Current Mode PWM Controllers

PL384XBP8

Description

The PL384XBP8 family of control ICs provides the necessary features to implement off-line or DC to DC fixed

frequency current mode control schemes with a minimal external parts count. Internally implemented circuits

include a trimmed oscillator for precise duty cycle control, under voltage lockout featuring start-up current less than

0.5mA, a precision reference trimmed for accuracy at the error amp input, logic to insure latched operation, a PWM

comparator which also provides current limit control, and a totem pole output stage designed to source or sink high

peak current. The output stage, suitable for driving N-channel MOSFETs, is low in the off-state.

Differences between members of this family are the under-voltage lockout thresholds and maximum duty cycle

ranges. The PL3842B and PL3844B have UVLO thresholds of 16V (on) and 10V (off), ideally suited off-line

applications. The corresponding thresholds for the PL3843B and PL3845B are 8.5V and 7.9V. The PL3842B and

PL3843B can operate to duty cycles approaching 100%. A range of the zero to <50% is obtained by the PL3844B

and PL3845B by the addition of an internal toggle flip flop which blanks the output off every other clock cycle.

Features

• Trimmed oscillator for precise frequency control

• Oscillator frequency guaranteed at 250 kHz

• Current mode operation to 500kHz

• Automatic feed forward compensation

• Latching PWM for cycle-by-cycle current limiting

• Internally trimmed reference with undervoltage lockout

• High current totem pole output

• Undervoltage lockout with hysteresis

• Low start-up and operating current

S/R

5V

REF

2.50V

VREF GOOD

LOGIC

INTERNAL

BIAS

OSC

ERROR AMP.

2R

R

1V

R

S

T

CURRENT

SENSE

COMPARATOR

PWM

LATCH

VREF

5V50mA

OUTPUT

8

6

VI

GROUND

RT/CT

VFB

COMP

CURRENT

SENSE

7

5

34V

UVLO

4

2

1

3

PL3842B