MP3397—4-STRING, MAX 350mA/STRING WHITE LED DRIVER

MP3397 Rev. 1.01

www.MonolithicPower.com

6

9/4/2012

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© 2012 MPS. All Rights Reserved.

PIN FUNCTIONS

Pin #

Name

Description

1

COMP

Step-up Converter Compensation Pin. This pin compensates the regulation control loop.

Connect a ceramic capacitor from COMP to GND.

2

EN

Enable Control Input.

let this pin float.

3

DBRT

Brightness Control Input. Apply a PWM signal on this pin for for external PWM dimming

mode. Apply a DC voltage range from 0.2V to 1.2V on this pin to linearly set the internal

dimming duty cycle from 0% to 100% for DC-input PWM dimming mode. The MP3397 has

positive dimming polarity on DBRT.

4

GND

Ground.

5

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.

6

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.

7

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.

8

LED4

LED String 4 Current Input. This pin is the open-drain output of an internal dimming

control switch. Connect the LED String 4 cathode to this pin.

9

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.

10

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.

11

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.

12

OVP

Over-Voltage Protection Input. Connect a resistor divider from output to this pin to

program the OVP threshold. When this pin voltage reaches 1.23V, the MP3397 triggers

Over Voltage Protection mode.

13

ISENSE

Current Sense Input. During normal operation, this pin senses the voltage across the

to limit the inductor current during every switching cycle. If this pin is not used for

cascading applications, tie this pin to GND; do not let this pin float.

14

GATE

Step-up Converter Power Switch Gate Output. This pin drives the external power N-MOS

device.

15

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.

16

VCC

The Internal 6V Linear Regulator Output. VCC provides power supply for the external

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

ceramic capacitor.