MP3378E

– 4-CHANNEL WLED CONTROLLER WITH BUCK CONVERTER

MP3378E Rev. 1.02

www.MonolithicPower.com

10

5/26/2017

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PIN FUNCTIONS

Pin #

Name

Description

1

GND1

Ground for WLED controller.

2

OSC

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

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

frequency is proportional to the current sourced from OSC.

3

ISET

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

current in each LED string. The ISET voltage is regulated to 1.225V. The LED current is

proportional to the current through the ISET resistor.

4

ADIM

Input for analog brightness control. The LED current amplitude is determined by

ADIM, and the input signal can be either a PWM signal or a DC voltage signal. An

internal RC filter (10M

Ω resistor and 100pF capacitor) is integrated into ADIM. If a PWM

signal is applied to ADIM, a >20kHz frequency is recommended for better PWM signal

filtering performance to ensure that the amplitude voltage is higher than 1.5V, and the

low-level voltage is less than 0.4V. For a DC signal input, apply a DC input signal

ranging from 0.41V to 1.49V to set the LED current linearly from minimum to full scale.

Internally pull to GND if ADIM is floated.

5

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.

6

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.

7

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.

8

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.

9

OVP

Over-voltage protection input. Connect a resistor divider from the output to OVP to

program the OVP threshold.

10, 11

NC

Not connected.

12

FB

Buck converter feedback. An external resistor divider from the output to AGND tapped

to FB sets the output voltage. To prevent current-limit runaway during a short-circuit fault

condition, the frequency foldback comparator lowers the oscillator frequency when the

FB voltage is below 400mV.

13

EN2

Buck converter enable. Pull EN2 high to enable the buck converter.

14

VCC2

Bias supply for buck converter. Decouple with a 0.1

μF-0.22μF capacitor. The

capacitance should be no more than 0.22

μF.

15

VIN2

Supply voltage input for buck converter. A ceramic capacitor is needed to decouple

the input rail. Use a wide PCB trace to make the connection.

16

SW

Switch output for buck converter. Use a wide PCB trace to make the connection.

17, 18

GND2

Ground for buck converter.

19

AGND

Analog ground for buck converter.