KA3511BS Datasheet, PDF (1/20 Pages) Fairchild Semiconductor – Intelligent Voltage Mode PWM IC

KA3511BS
Intelligent Voltage Mode PWM IC
www.fairchildsemi.com
Features
• Complete PWM control and house keeping circuitry
• Few external components
• Precision voltage reference trimmed to 2%
• Dual output for push-pull operation
• Each output TR for 200mA sink current
• Variable duty cycle by dead time control
• Soft start capability by using dead time control
• Double pulse suppression logic
• Over voltage protection for 3.3V / 5V / 12V
• Under voltage protection for 3.3V / 5V / 12V
• One more external input for various protection (PT)
• Remote on/off control function (PS-ON)
• Latch function controlled by remote and protection input
• Power good signal generator with hysteresis
Precision reference section
The reference voltage trimmed to ± 2%
(4.9V≤Vref≤5.1V)
PG (Power good signal generator) section
Power good signal generator is to monitor the volt-
age level of power supply for safe operation of a
microprocessor.
KA3511BS requires few external components to
accomplish a complete housekeeping circuits for
SMPS.
Description
The KA3511BS is a fixed-frequency improved-
performance pulse-width modulation control cir-
cuit with complete housekeeping circuitry for use
in the secondary side of SMPS (Switched mode
power supply). It contains various functions, which
are precision voltage reference, over voltage pro-
tection, under voltage protection, remote on/off
control, power good signal generator and etc.
OVP (Over voltage protection) section
It has OVP functions for +3.3V,+5V,+12V and PT
outputs. The circuit is made up of a comparator
with four detecting inputs and without hysteresis
voltage. Especially, PT (Pin18) is prepared for an
extra OVP input or another protection signal.
UVP (Under voltage protection) section
It also has UVP functions for +3.3V, +5V, +12V out-
puts. The block is made up of a comparator with three
detecting inputs and without hysteresis voltage.
Remote on/off section
Remote on/off section is used to control SMPS ex-
ternally. If a high signal is supplied to the remote
on/off input, PWM signal becomes a high state and
all secondary outputs are grounded. The remote on/
off signal is transferred with some on-delay and
off-delay time of 8ms, 24ms respectively.
24-SDIP
©2000 Fairchild Semiconductor Interaltional
1
Rev. 5.0