MP3385A – 4-STRING WLED CONTROLLER WITH I

MP3385A Rev. 1.01

www.MonolithicPower.com

11

8/29/2017

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PIN FUNCTIONS

Package

Pin #

Name

Description

1

DRV

Step-up converter power switch gate output.

DRV drives the external power N-

channel MOSFET device. Connect a resistor (e.g.: 10Ω) to DRV.

2

VCC

Internal 6V linear regulator output.

VCC provides a power supply for the external

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

ceramic capacitor.

3

EN

Enable control input.

A voltage greater than 1.5V turns the part on. A voltage less than

0.6V turns the part off. Do not float EN.

4

VIN

Supply input.

VIN must be bypassed locally.

5

PWM

PWM input signal for brightness control.

Ensure that the PWM amplitude voltage

PWM signal frequency determines the LED current dimming ratio when the MP3385A

works in direct PWM dimming mode. For external analog and mixed dimming modes,

the PWM pulse is filtered to a DC signal by an LPF capacitor, and the LED current is

proportional to the input PWM duty. If PWM is floated, weakly pull PWM to GND

internally.

6

SCL

I

7

SDA

I

8

FT

Fault indication output

. FT is an open drain during normal operation. FT is pulled low

during a fault condition.

9

LPF

Low-pass filter output for analog dimming with PWM input.

A capacitor is

connected between LPF and GND when the part operates in external PWM input analog

dimming or mixed dimming mode. Remove the LPF capacitor when the part operates in

direct PWM dimming mode.

10

OSC

Switching frequency set.

Connect a resistor

step-up converter switching frequency. The clock frequency is proportional to the current

sourced from OSC. There is a 100~900kHz switching frequency selected by the I

interface when connected to a 100kΩ resistor at OSC.

11

COMP

Step-up converter compensation.

COMP compensates for the regulation control loop.

Connect a ceramic capacitor and resistor from COMP to GND.

12

ISET

LED current set.

Tie a current-setting resistor from ISET to ground to program the

current in each LED string.

13

LED4

LED string 4 current input.

LED4 is the open-drain output of an internal dimming

control switch. Connect the LED string 4 cathode to LED4.

14

LED3

LED string 3 current input.

LED3 is the open-drain output of an internal dimming

control switch. Connect the LED string 3 cathode to LED3.

15

PGND

Power ground.

16

LED2

LED string 2 current input.

LED2 is the open-drain output of an internal dimming

control switch. Connect the LED string 2 cathode to LED2.

17

LED1

LED string 1 current input.

LED1 is the open-drain output of an internal dimming

control switch. Connect the LED string 1 cathode to LED1.

18

OVP

Output over-voltage protection.

19

IS

Current sense input.

During normal operation, IS senses the voltage across the

limits the inductor current during every switching cycle. If the MP3385A is used for

cascading applications, tie IS of the slave chip to GND. Do not float IS.

20

AGND

Signal ground.