MP2481 –36V, 1.2A, 1.4MHz WHITE LED DRIVER

MP2481 Rev. 1.42

www.MonolithicPower.com

4

4/28/2012

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© 2012 MPS. All Rights Reserved.

PIN FUNCTIONS

Pin #

Name

Description

1

VDD

Supply Voltage. The MP2481 operates from a +4.5V to +36V unregulated input (with respect

to VSS). C1 is needed to prevent large voltage spikes from appearing at the input.

2

VSS

Power Return Pin. Connect to the lowest potential in the circuit, which is typically the anode

of the Schottky rectifier. This pin is the voltage reference for the regulated output voltage.

For this reason care must be taken in its layout. This node should be placed outside of the

D1 to C1 ground path to prevent switching current spikes from inducing voltage noise into

the part. The exposed pad is also connected to this pin.

3

OVP

Over Voltage Protection Pin. Use one external resistor voltage divider to program OVP

threshold. When the OVP pin voltage (with respect to VSS) is lower than 0.4V, the chip

frequency will be folded back. Program the OVP pin voltage from 0.4V to 1.23V for normal

operation. When the OVP pin voltage reaches the shutdown threshold 1.23V, the switch will

be turned off

4

FB

LED Current Feedback Input. MP2481 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 0.2V.

5

EN/DIM

On/Off Control Input and Dimming Command Input. A voltage greater than 0.7V will turn on

the chip. When the EN/DIM pin voltage (with respect to INGND) 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 1kHz square wave signal with amplitude greater than 1.4V to this

pin.

6

INGND

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

7

BST

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

across the power switch driver. This capacitor is needed to drive the power switch’s gate

above the supply voltage.

8

SW

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

inductor and cathode of the Schottky rectifier.