1

4

3

2

16

13

14

15

ASNS

DIM

GND

FLTR1

COFF

FLTR2

5

12

BLDR

ISNS

11

NC

NC

VCC

GND

10

8

9

SW

SW

6

7

SW

SW

LM3448

SNOSB51B – SEPTEMBER 2011 – REVISED NOVEMBER 2011

www.ti.com

These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam

during storage or handling to prevent electrostatic damage to the MOS gates.

Connection Diagram

Top View

Figure 2. 16-Lead Narrow SOIC Package

PIN DESCRIPTIONS

Pin(s)

Name

Description

1, 2, 15,

SW

Drain connection of internal 600V MOSFET.

16

3, 14

NC

No connect. Provides clearance between high voltage and low voltage pins. Do not tie to GND.

4

BLDR

Bleeder pin. Provides the input signal to the angle detect circuitry. A 230

Ω internal resistor ensures BLDR is pulled

down for proper angle sense detection.

5, 12

GND

Circuit ground connection.

6

VCC

Input voltage pin. This pin provides the power for the internal control circuitry and gate driver. Connect a 22uF

(minimum) bypass capacitor to ground.

7

ASNS

PWM output of the TRIAC dim decoder circuit. Outputs a 0 to 4V PWM signal with a duty cycle proportional to the

TRIAC dimmer on-time.

8

FLTR1

First filter input. The 120Hz PWM signal from ASNS is filtered to a DC signal and compared to a 1 to 3V, 5.85 kHz

ramp to generate a higher frequency PWM signal with a duty cycle proportional to the TRIAC dimmer firing angle.

Pull above 4.9V (typical) to TRI-STATE™ DIM.

9

DIM

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 to the DIM pin of other LM3448/LM3445 devices or LED drivers

to dim multiple LED circuits simultaneously.

10

COFF

OFF time setting pin. A user set current and capacitor connected from the output to this pin sets the constant OFF

time of the switching controller.

11

FLTR2

Second filter input. A capacitor tied to this pin filters the PWM dimming signal to supply a DC voltage to control the

LED current. Could also be used as an analog dimming input.

13

ISNS

LED current sense pin (internally connected to MOSFET source). Connect a resistor from ISNS to GND to set the

maximum LED current.

2

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