LM5020 datasheet(3/13 Pages) NSC

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Pin Descriptions

Name

Description

Application Information

VIN

Source Input Voltage

Input to the start-up regulator. Input range is 13V to

100V.

Feedback Signal

Inverting input of the internal error amplifier. The

non-inverting input is internally connected to a 1.25V

reference.

COMP

The output of the error amplifier and input to

the Pulse Width Modulator

COMP pull-up is provided by an internal 5K resistor

which may be used to bias an opto-coupler transistor.

VCC

Output of the internal high voltage series pass

regulator. Regulated output voltage is 7.7V

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.

OUT

Output of the PWM controller

Gate driver output with a 1A peak current capability.

GND

Ground return

UVLO

Line Under-Voltage Shutdown

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

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.

RT / SYNC

Oscillator timing resistor pin and

synchronization input

An external resistor connected from RT to GND sets the

oscillator frequency. This pin also accepts

synchronization pulses from an external clock.

Softstart Input

An external capacitor and an internal 10µA current

source set the soft-start ramp rate.

LM5020 Datasheet(PDF) 3 Page - National Semiconductor (TI)

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