LM3450 datasheet(3/28 Pages) NSC

3 / 28 page

Pin Descriptions

Name

Description

Application Information

REF

3V Reference

Reference Output: Connect directly to V

ADJ or to resistor divider feeding VADJ and

to necessary external circuits.

ADJ

Analog Adjust

Analog Dim and Phase Dimming Range Input: Connect directly to V

REF to force

standard 70% phase dimming range. Connect to resistor divider from V

REF to

extend usable range of some phase dimmers or for analog dimming. Connect to

GND for low power mode.

FLT2

Filter 2

Ramp Comparator Input: Connect a series resistor from FLT1 capacitor and a

capacitor to GND to establish second filter pole.

FLT1

Filter 1

Angle Decoder Output: Connect a series resistor to a capacitor to GND to

establish first filter pole.

DIM

500 Hz

PWM Output

Open Drain PWM Dim Output: Connect to dimming input of output stage LED

driver (directly or with isolation) to provide decoded dimming command.

Sampled

Rectified Line

Multiplier and Angle Decoder Input: Connect to resistor divider from rectified AC

line.

COMP

Compensation

Error Amplifier Output and PWM Comparator Input: Connect a capacitor to GND

to set the compensation.

Feedback

Error Amplifier Inverting Input: Connect to output voltage via resistor divider to

control PFC voltage loop for non-isolated designs. Connect a 5.11k

Ω resistor to

GND for isolated designs (bypasses error amplifier). Also includes over-voltage

protection and shutdown modes.

SEN

Input Current

Sense

Input Current Sense Non-Inverting Input: Connect to diode bridge return and

resistor to GND to sense input current for dynamic hold. Connect a 0.1µF

capacitor and Schottky diode to GND, and a 0.22µF capacitor to HOLD.

GND

Power Ground

System Ground

Current Sense

MosFET Current Sense Input: Connect to positive terminal of sense resistor in

PFC MosFET source.

GATE

Gate Drive

Gate Drive Output: Connect to gate of main power MosFET for PFC.

Input Supply

Power Supply Input: Connect to primary bias supply. Connect a 0.1µF bypass

capacitor to ground.

ZCD

Zero Crossing

Detector

Demagnetization Sense Input: Connect a 100k

Ω resistor to transformer/inductor

winding to detect when all energy has been transferred.

HOLD

Dynamic Hold

Open Drain Dynamic Hold Input: Connect to holding resistor which is connected

to source of passFET.

BIAS

Pre-regulator

Gate Bias

Pre-regulator Gate Bias Output: Connect to gate of passFET and through resistor

to rectified AC (drain of passFET) to aid with startup.

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