MP3391—8-CHANNEL, 120mA/CH STEP-UP WLED DRIVER CONTROLLER

MP3391 Rev. 1.11

www.MonolithicPower.com

6

3/14/2013

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PIN FUNCTIONS

Pin #

Name

Description

1

VDD

The Internal 10V Linear Regulator Output. VDD provides power supply for the internal

MOSFET switch gate driver circuitry. Bypass VDD to GND with a ceramic capacitor.

2

VIN

Supply Input. VIN supplies the power to the chip, Drive VIN with 9V to 35V power source.

Must be locally bypassed with a ceramic capacitor..

3

VCC

Option NC. The Internal 5V Linear Regulator Output. VCC provides power supply for 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 MP3391 has positive dimming polarity on DBRT.

7

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.

8

GND

Analog Ground.

9

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 resistor from this pin to GND, and

apply the PWM signal on DBRT pin.

10

TSET

Short LED Protection Timer Set. Connect a ceramic capacitor on this pin to set the

protection timer. The protection is triggered when internal 50uA current source charges

the capacitor voltage to 1.24V. Tset(ms)=0.0248×C(nF), Tset is about 11.7ms for 470nF

capacitor.

11

ISET

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

current in each LED string. This pin voltage is regulated to 1.23V. the LED current is

proportional to the current through the ISET resistor.

12

SSET

Short LED Protection Voltage Threshold Set. Connect this pin to VCC through external

divide resistors to set the short LED protection threshold. When LEDX pin voltage reaches

4.5 times of SSET pin voltage, the TSET pin capacitor is charged up for a protection timer.

Vshort= 4.5×Vsset.

13

LED1

LED String 1 Current Input. This pin is the open-drain output of an internal dimming

control switch. Connect the LED String 1 cathode to this pin.

14

LED2

LED String 2 Current Input. This pin is the open-drain output of an internal dimming

control switch. Connect the LED String 2 cathode to this pin.

15

LED3

LED String 3 Current Input. This pin is the open-drain output of an internal dimming

control switch. Connect the LED String 3 cathode to this pin.