1FEATURES

2• Critical Conduction Mode PFC

• Over-Voltage Protection

• Feedback Short Circuit Protection

• 70:1 PWM Decoded From Phase Dimmer

• Analog Dimming

• Programmable Dimming Range

• Digital Angle and Dimmer Detection

• Dynamic Holding Current

• Smooth Dimming Transitions

• Low Power Operation

• Start-Up Pre-Regulator Bias

• Precision Voltage Reference

APPLICATIONS

• Dimmable Downlights, Troffers, and Lowbays

• Large Form Factor Bulbs

• Indoor and Outdoor Area SSL

• Power Supply PFC

DESCRIPTION

The LM3450/50A is a power factor controller (PFC)

with separate phase dimming decoder. The PFC

regulates the output voltage while maintaining

excellent power factor. The phase dimming decoder

interprets the phase angle and remaps it to a 500Hz

PWM output. This device is ideal for implementing a dimmable off-line LED driver for 10-100W loads.

The phase dimming decoder has several unique

features. The input-output mapping is programmable

for design flexibility, while a dynamic filter and

variable sampling rate provide smooth uniform

dimming. A dynamic hold circuit ensures that the phase dimmer angle is decoded properly while

minimizing extra power loss.

The LM3450A is identical to the LM3450 with the

exception of one circuit operation. The dynamic hold

current is sampled in the LM3450 while it

continuously operates in the LM3450A. This

difference between the two devices defines the suitable applications for each. The following is a

general guideline for choosing the correct device:

• Any 120V designs with POUT > 15W - LM3450A

• Any 230V designs with POUT > 25W - LM3450A

• 120V 2-Stage designs with POUT < 15W - LM3450

• 230V 2-Stage designs with POUT