LM3450 Datasheet, PDF (2/40 Pages) National Semiconductor (TI) – LED Driver with Active Power Factor Correction and Phase Dimming Decoder

LM3450
SNVS681D – NOVEMBER 2010 – REVISED MAY 2013
Connection Diagram
Top View
1 _VREF
2 _VADJ
3 _FLT2
4 _FLT1
5 _DIM
6 _VAC
7 _COMP
8 _FB
BIAS ¹⁶
HOLD ¹⁵
ZCD ¹⁴
VCC ¹³
GATE ¹²
CS ¹¹
GND ¹⁰
ISEN ⁹
Figure 1. 16-Lead TSSOP
Package Number PW
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PIN DESCRIPTIONS
Pin
Name
Description
Application Information
1
V_REF
3V Reference
Reference Output: Connect directly to V_ADJ or to resistor divider feeding V_ADJ
and to necessary external circuits.
2
V_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.
3
FLT2
Filter 2
Ramp Comparator Input: Connect a series resistor from FLT1 capacitor and a
capacitor to GND to establish second filter pole.
4
FLT1
Filter 1
Angle Decoder Output: Connect a series resistor to a capacitor to GND to
establish first filter pole.
5
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.
6
V_AC
Sampled Rectified Line
Multiplier and Angle Decoder Input: Connect to resistor divider from rectified AC
line.
7
COMP
Compensation
Error Amplifier Output and PWM Comparator Input: Connect a capacitor to GND
to set the compensation.
8
FB
Feedback
Error Amplifier Inverting Input: Connect to output voltage via resistor divider to
control PFC voltage loop for non-isolated designs. Connect a 5.11kΩ resistor to
GND for isolated designs (bypasses error amplifier). Also includes over-voltage
protection and shutdown modes.
Input Current Sense Non-Inverting Input: Connect to diode bridge return and
9
I_SEN
Input Current Sense 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.
10
GND
Power Ground
System Ground
11
CS
Current Sense
MosFET Current Sense Input: Connect to positive terminal of sense resistor in
PFC MosFET source.
12
GATE
Gate Drive
Gate Drive Output: Connect to gate of main power MosFET for PFC.
13
V_CC
Input Supply
Power Supply Input: Connect to primary bias supply. Connect a 0.1µF bypass
capacitor to ground.
14
ZCD
Zero Crossing Detector
Demagnetization Sense Input: Connect a 100kΩ resistor to transformer/inductor
winding to detect when all energy has been transferred.
15
HOLD
Dynamic Hold
Open Drain Dynamic Hold Input: Connect to holding resistor which is connected
to source of passFET.
16
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.
2
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