PL384XBQ8 Datasheet, PDF (1/15 Pages) Cystech Electonics Corp. – High Performance Current Mode PWM Controllers

Spec. No. : C510Q8
CYStech Electronics Corp.
Issued Date : 2003.04.24
Revised Date :
Page No. : 1/15
High Performance Current Mode PWM Controllers
PL384XBQ8
Description
The PL384XBQ8 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
GROUND
UVLO
2.50V
5V
S/R
REF
VREF GOOD
LOGIC
INTERNAL
BIAS
4
RT/CT
VFB
2
1
COMP
3
CURRENT
SENSE
PL384XBQ8
OSC
ERROR AMP.
2R
R
T
S
1V
R
PWM
LATCH
CURRENT
SENSE
COMPARATOR
8
VREF
5V50mA
6
OUTPUT
PL3842B
CYStek Product Specification