MP4600 – WHITE LED DRIVER FOR UP TO 55 INCH TV BACKLIGHTING

MP4600 Rev. 0.91

www.MonolithicPower.com

4

1/6/2012

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PIN FUNCTIONS

Pin #

Name

Description

1

VDD

Positive Voltage Input Pin. A decoupling cap is needed to prevent large voltage spikes from

appearing at the input.

2

VSS

Negative Voltage Output Pin. This pin is the voltage reference for OVP, FB, COMP and

RSET pins. This node should be placed away from switching noise sources. The exposed

pad is connected to this pin.

3

OVP

Over Voltage Protection Pin. Use one external resistor voltage divider across INGND and

VSS to program OVP threshold. Its voltage is referred to VSS. When the OVP pin voltage

reaches the shutdown threshold 1.2V, the switch will be turned off and will recover when OVP

voltage decreases sufficiently. When the OVP pin voltage is lower than 0.4V and FB pin

voltage is lower than 0.1V, the chip frequency will be folded back. Program the OVP pin

voltage from 0.4V to 1.2V for normal operation.

4

FB

LED Current Feedback Input. MP4600 regulates the voltage across the current sensing

resistor between FB and VSS. Connect the current sensing resistor from the bottom of the

LED strings to VSS. The FB pin is connected to the bottom of the LED strings. The regulation

voltage is 0.198V.

5

COMP

Output of error amplifier. Connect a 1nF or larger capacitor on COMP to improve the stability

and to provide a soft on at start up or PWM dimming.

6

RSET

Connect to a resistor to VSS to set the switching frequency.

7

EN/DIM

On/Off Control Input and Dimming Command Input. Its voltage is referred to INGND. A

voltage greater than 0.7V will turn on the chip. When the EN/DIM pin voltage rises from 0.7V

to 1.4V, the LED current will change from 0% to 100% of the maximum LED current. To use

PWM dimming, apply a 100Hz to 20kHz square wave signal with amplitude greater than 1.5V

to this pin.

8

INGND

Input Ground Reference. This pin is the reference for the EN/DIM signal.

9

BST

Bootstrap. A capacitor is connected between SW and BST pins to form a floating supply

across the power switch driver.

10

SW

Switch Output. SW is the source of the internal MOSFET switch. Connect to the power

inductor and cathode of the Schottky rectifier.

Exposed pad should be connected to VSS.