LM3433 datasheet(2/15 Pages) TI1

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TON

ADJ

DIM

VIN

CGND

VCC

BST

LM3433

SNVS535B – OCTOBER 2007 – REVISED MARCH 2008

www.ti.com

Connection Diagram

Top View

Figure 1. 24-Lead LLP

NS Package Number SQA24A

Pin Functions

Pin Descriptions

Name

Function

On-time programming pin. Tie an external resistor (RON) from TON to CSN, and a capacitor (CON)

TON

from TON to VEE. This sets the nominal operating frequency when the LED is fully illuminated.

Analog LED current adjust. Tie to VIN for fixed 60mV average current sense resistor voltage. Tie to

an external reference to adjust the average current sense resistor voltage (programmed output

ADJ

current). Refer to the "VSENSE vs. ADJ Voltage" graphs in the Typical Performance Characteristics

section and the Design Procedure section of the datasheet.

Enable pin. Connect this pin to logic level HI or VIN for normal operation. Connect this pin to CGND

for low current shutdown. EN is internally tied to VIN through a 100k resistor.

DIM

Logic level input for LED PWM dimming. DIM is internally tied to CGND through a 100k resistor.

VIN

Logic power input: Connect to positive voltage between +3.0V and +5.8V w.r.t. CGND.

CGND

Chassis ground connection.

VEE

Negative voltage power input: Connect to voltage between –14V to –9V w.r.t. CGND.

COMP

Compensation pin. Connect a capacitor between this pin and VEE.

No internal connection. Tie to VEE or leave open.

Soft Start pin. Tie a capacitor from SS to VEE to reduce input current ramp rate. Leave pin open if

function is not used. The SS pin is pulled to VEE when the device is not enabled.

No internal connection. Tie to VEE or leave open.

Low side FET gate drive return pin.

Low side FET gate drive output. Low in shutdown.

Low side FET gate drive power bypass connection and boost diode anode connection. Tie a 2.2µF

VCC

capacitor between VCC and VEE.

BST

High side "synchronous" FET drive bootstrap rail.

High side "synchronous" FET gate drive output. Pulled to HS in shutdown.

Switching node and high side "synchronous" FET gate drive return.

DIMR

LED dimming FET gate drive return. Tie to LED cathode.

DIMO

LED dimming FET gate drive output. DIMO is a driver that switches between DIMR and BST2.

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