LM3445MSLASHNOPB datasheet(3/42 Pages) TI1

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N/C

ASNS

DIM

GND

FLTR1

COFF

FLTR2

N/C

BLDR

N/C

ISNS

9 VCC

8 GATE

ISNS

FLTR1

GATE

BLDR

COFF

VCC

ASNS

DIM

FLTR2

GND

LM3445

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SNVS570M – JANUARY 2009 – REVISED NOVEMBER 2015

5 Pin Configuration and Functions

DGS Package

D Package

10-Pin VSSOP

14-Pin SOIC

Top View

Pin Functions

I/O

DESCRIPTION

NAME

SOIC

VSSOP

PWM output of the TRIAC dim decoder circuit. Outputs a 0 to 4-V PWM signal

ASNS

with a duty cycle proportional to the TRIAC dimmer on-time.

Bleeder pin. Provides the input signal to the angle detect circuitry as well as a

BLDR

current path through a switched 230-

Ω resistor to ensure proper firing of the

TRIAC dimmer.

OFF time setting pin. A user set current and capacitor connected from the

COFF

output to this pin sets the constant OFF time of the switching controller.

Input/output dual function dim pin. This pin can be driven with an external PWM

signal to dim the LEDs. It may also be used as an output signal and connected

DIM

I/O

to the DIM pin of other LM3445s or other LED drivers to dim multiple LED

circuits simultaneously.

First filter input. The 120-Hz PWM signal from ASNS is filtered to a DC signal

and compared to a 1 to 3 V, 5.85-kHz ramp to generate a higher frequency

FLTR1

PWM signal with a duty cycle proportional to the TRIAC dimmer firing angle.

Pull above 4.9-V (typical) to tri-state DIM.

Second filter input. A capacitor tied to this pin filters the PWM dimming signal

FLTR2

to supply a DC voltage to control the LED current. Could also be used as an

analog dimming input.

Power MOSFET driver pin. This output provides the gate drive for the power

GATE

switching MOSFET of the buck controller.

GND

—

Circuit ground connection

LED current sense pin. Connect a resistor from main switching MOSFET

ISNS

source, ISNS to GND to set the maximum LED current.

N/C

2, 5, 6, 11

—

No Connect

Input voltage pin. This pin provides the power for the internal control circuitry

VCC

and gate driver.

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