CYStech Electronics Corp.
High Performance Current Mode PWM Controllers
Spec. No. : C510P8
Issued Date : 2003.04.24
Revised Date :
Page No. : 1/15
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
Block Diagram
( toggle flip flop used only in PL3844B and PL3845B)
VI
7
34V
5
UVLO
S/R
5V
REF
8
GROUND
VREF
5V50mA
2.50V
INTERNAL
BIAS
VREF GOOD
LOGIC
6
OUTPUT
4
RT/CT
OSC
ERROR AMP.
VFB
2
T
2R
R
1V
S
R
CURRENT
SENSE
COMPARATOR
PWM
LATCH
COMP
1
CURRENT
SENSE
3
PL3842B
CYStek Product Specification
PL384XBP8
CYSTEKEC [ CYSTECH ELECTONICS CORP. ]
