lm5020sdx-2 National Semiconductor Corporation, lm5020sdx-2 Datasheet - Page 3

• Manufacturer Part Number: lm5020sdx-2
• Description: 100v Current Mode Pwm Controller
• Manufacturer: National Semiconductor Corporation

Pin Descriptions
Pin
10
1
2
3
4
5
6
7
8
9
RT / SYNC
COMP
Name
UVLO
VCC
OUT
GND
VIN
FB
CS
SS
Source Input Voltage
Feedback Signal
The output of the error amplifier and input to
the Pulse Width Modulator
Output of the internal high voltage series pass
regulator. Regulated output voltage is 7.7V
Output of the PWM controller
Ground return
Line Under-Voltage Shutdown
Current Sense input
Oscillator timing resistor pin and
synchronization input
Softstart Input
Description
3
Input to the start-up regulator. Input range is 13V to
100V.
Inverting input of the internal error amplifier. The
non-inverting input is internally connected to a 1.25V
reference.
COMP pull-up is provided by an internal 5K resistor
which may be used to bias an opto-coupler transistor.
If an auxiliary winding raises the voltage on this pin
above the regulation set point, the internal series pass
regulator will shut down, reducing the internal power
dissipation.
Gate driver output with a 1A peak current capability.
An external resistor divider from the power converter
source voltage sets the shutdown levels. The threshold
at this pin is 1.25V. Hysteresis is set by a switched
internal 20µA current source.
Current sense input for current mode control and
over-current protection. Current limiting is accomplished
using a dedicated current sense comparator. If the CS
pin voltage exceeds 0.5V the OUT pin switches low for
cycle-by-cycle current limiting. CS is held low for 50ns
after OUT switches high to blank leading edge current
spikes.
An external resistor connected from RT to GND sets the
oscillator frequency. This pin also accepts
synchronization pulses from an external clock.
An external capacitor and an internal 10µA current
source set the soft-start ramp rate.
Application Information
www.national.com