MP3378

– 4-CHANNEL WLED CONTROLLER PLUS BUCK CONVERTER

MP3378 Rev. 1.01

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 1.23 V. 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. ISET voltage is regulated to 1.225 V. 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

ADMIN. The input signal can be either a PWM signal or a DC voltage signal. An internal

RC filter (10 M

Ω resistor and 100 pF capacitor) is integrated to ADMIN. If a PWM signal

is applied to ADMIN, a >20 kHz frequency is recommended. This obtains a better PWM

signal filtering performance and ensures the amplitude voltage is higher than 1.5 V and

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

signal range from 0.41 V to 1.49 V to set linearly

the LED current from minimum to full

scale. If ADMIN is floated, pull internally to GND.

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

No connection.

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 400 mV.

13

AAM

AAM mode setting for buck converter. Connect a resistor from AAM to ground to set

the AAM voltage and force the buck converter into non-synchronous mode when the

load is small. Driving AAM high (=VCC2) forces the buck converter into CCM.