MP3389—12-STRING WHITE LED DRIVER WITH STEP-UP CONTROLLER

MP3389 Rev. 1.04

www.MonolithicPower.com

5

3/27/2013

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PIN FUNCTIONS

Pin #

Name Description

1

NC

No Connect.

2

VIN

Supply Input. VIN supplies the power to the chip, as well as the step-up converter switch. Drive

VIN with a 5V to 28V power source. Must be locally bypassed.

3

VCC

The Internal 5V Linear Regulator Output. VCC provides power supply for the internal MOSFET

switch gate driver and the internal control circuitry. Bypass VCC to GND with a ceramic

capacitor.

4

COMP

Step-up Converter Compensation Pin. This pin is used to compensate the regulation control

loop. Connect a capacitor or a series RC network from COMP to GND.

5

EN

Enable Control Input. Do not let this pin floating.

6

DBRT

Brightness Control Input. To use external PWM dimming mode, apply a PWM signal on this pin

for brightness control. To use DC input PWM dimming mode, apply a DC voltage range from

0.2V to 1.2V on this pin linearly to set the internal dimming duty cycle from 0% to 100%. The

MP3389 has positive dimming polarity on DBRT.

7

GND

Analog Ground.

8

OSC

Switching Frequency Set. Connect a resistor between OSC and GND to set the step-up

converter switching frequency. The voltage at this pin is regulated to 1.23V. The clock frequency

is proportional to the current sourced from this pin.

9

ISET

LED Current Set. Tie a current setting resistor from this pin to ground to program the current in

each LED string. The MP3389 regulates the voltage across the current setting resistor. The

regulation voltage is 1.22V. The proportion of the current through the ISET resistor and the LED

current is 1:1000.

10

BOSC

Dimming Repetition Set. This is the timing pin for the oscillator to set the dimming frequency. To

use DC input PWM dimming mode, connect a capacitor from this pin to GND to set the internal

dimming frequency. A saw-tooth waveform is generated on this pin. To use external PWM

dimming mode, connect a 100kΩ resistor from this pin to GND, and apply the PWM signal on

DBRT pin.

11

LED12

LED String 12 Current Input. This pin is the open-drain output of an internal dimming control

switch. Connect the LED String 12 cathode to this pin. If this string is not used, connect Vin to

this pin.

12

LED11

LED String 11 Current Input. This pin is the open-drain output of an internal dimming control

switch. Connect the LED String 11 cathode to this pin. If this string is not used, connect Vin to

this pin.

13

LED10

LED String 10 Current Input. This pin is the open-drain output of an internal dimming control

switch. Connect the LED String 10 cathode to this pin. If this string is not used, connect Vin to

this pin.

14

LED9

LED String 9 Current Input. This pin is the open-drain output of an internal dimming control

switch. Connect the LED String 9 cathode to this pin. If this string is not used, connect Vin to this

pin.