www.fairchildsemi.com
KA3511DS
Intelligent Voltage Mode PWM IC
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
Description
The KA3511DS is a fixed frequency improved performance
pulse width modulation control circuit 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 protection, 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
Precision reference section
The reference voltage trimmed to
±
2%
(4.9V
≤
Vref
≤
5.1V)
It also has UVP functions for +3.3V, +5V, +12V outputs. The
block is made up of a comparator with three detecting inputs
and without hysteresis voltage.
PG (Power good signal generator) section
Power good signal generator is to monitor the voltage level
of power supply for safe operation of a microprocessor.
KA3511DS requires few external components to accomplish
a complete housekeeping circuits for SMPS.
Remote on/off section
Remote on/off section is used to control SMPS externally. 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
1
Rev. 1.0.0
©2001 Fairchild Semiconductor Corporation
KA3511DS
Pin Number Pin Name
1
2
3
4
5
V
CC
COMP
E/A(-)
E/A(+)
TREM
Pin Function Descrition
Supply voltage. Operating range is 10V~30V. V
CC
=20V, Ta=25°C at test.
Error amplifier output. It is connected to non-inverting input of pulse width modulator
comparator.
Error amplifier inverting input. Its reference voltage is always 1.25V.
Error amplifier non-inverting input feedback voltage.This pin may be used to sense
power supply output voltage.
Remote on/off delay. Ton/Toff=8ms/24ms (Typ.) with C=0.1uF. Its high/low threshold
voltage is 1.8V/0.6V.
Remote on/off input. It is TTL operation and its threshold voltage is 1.4V. Voltage at
this pin can reach normal 4.6V, with aDSolutely maximum voltage, 5.25V.
If REM =
“Low”,
PWM =
“Low”.
That means the main SMPS is operational.
When REM =
“High”,
then PWM =
“High”
and the main SMPS is turned-off.
Oscillation frequency setting R. (Test Condition R
T
=10kΩ)
Oscillation frequency setting C. (Test Condition C
T
=0.01uF)
Under voltage detection pin. Its threshold voltage is 1.25V Typ.
PG delay. Td=250ms (Typ) with C
PG
=2.2uF. The high/low threshold voltage are 1.8V/
0.6V and the voltage of Pin10 is clamped at 2.9V for noise margin.
Power good output signal. PG =
“High”
means that the power is
“Good”
for operation
and PG =
“Low”
means
“Power
fail”.
Precision voltage reference trimmed to 2%. (Typical Value = 5.03V)
OVP, UVP input for output 3.3V. (Typical Value = 4.1V/2.3V)
OVP, UVP input for output 5V. (Typical Value = 6.4V/4.0V)
OVP, UVP input for output 12V. (Typical Value = 14.2V/10V)
This is prepared for an extra OVP input or another protection signal.
(Typical Value = 1.25V)
Timing pin for under voltage protection blank-out time. Its threshold voltage is 1.8V
and clamped at 2.9V after full charging. Target of delay time is 250ms and it is
realized through external (C=2.2uF).
Signal ground.
Deadtime control input. The dead-time control comparator has an effective 120mV
input offset which limits the minimum output dead time. Dead time may be imposed
on the output by setting the dead time control input to a fixed voltage, ranging
between 0V to 3.3V.
Output drive pin for push-pull operation.
Power ground.
Output drive pin for push-pull operation.
6
REM
7
8
9
10
11
14
15
16
17
18
RT
CT
DET
T
PG
PG
Vref
V3.3
V5
V12
PT
19
20
T
UVP
GND
21
DTC
22
23
24
C2
E
C1
4
Talking
京公网安备 11010802033920号
EEWORLD
