MP4651—OFF LINE LED DRIVER

MP4651 Rev.1.0

www.MonolithicPower.com

6

1/13/2011

MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.

© 2011 MPS. All Rights Reserved.

PIN FUNCTIONS

Pin #

Name

Description

1

OVP

Over Voltage Protection. The output voltage is sensed by this pin through a voltage divider

from the anode of the LED to ground. If the voltage at OVP exceeds 2.38V for 7us, the Fault

Mode is triggered.

2

SYNC

Synchronization for the burst dimming frequency. Applying a synchronizing signal with a

narrow pulse on this pin will synchronize the burst frequency on BFS pin. The frequency of

the synchronizing signal should be higher than the frequency set by BFS pin.

3

SSD

Short String Detection. A comparator is integrated in this pin for short string protection. If the

voltage on this pin gets lower than 2.36V for 7us, the Fault Mode is triggered.

4

FB

LED Current Feedback Input. Connect this pin to the cathode of the LED and shunt a sense

resistor to ground. The internal error amplifier sinks a current from the COMP pin proportional

to the absolute value of the voltage at this pin. The average voltage at this pin is regulated to

0.6V reference voltage.

The voltage on this pin is also used for short string detection. When the voltage on this pin

gets higher than 1.2V for 7us, the IC recognizes this as short string condition and triggers the

Fault Mode.

5

COMP

Feedback Compensation Node. Connect a compensation capacitor or a R-C network from

this pin to GND.

6

FT

Fault Timer. Connect a timing capacitor from this pin to GND to set the fault timer to recover

the system. When the voltage on this pin gets higher than the 2.38V threshold, the IC

recovers.

7

PWMOUT

This pin outputs the PWM dimming signal to LED for fast dimming. At Fault Mode, the

PWMOUT is pulled down.

8

FSET

Frequency Set. Connect a resistor from this pin to GND. This resistor sets the operating

frequency of the MP4651. A 25kOhm resistor sets the operating frequency at typical 50kHz.

9

BFS

Burst Frequency Set. Connect a resistor in parallel with a capacitor from BFS to GND. The

resistor and capacitor programs the burst dimming frequency. If the burst dimming is to be

controlled by an external PWM signal, pull up BFS to VCC through a 20kΩ resistor and apply

the PWM signal to the PWMIN pin.

10

PWMIN

Burst-Mode (Digital) Brightness Control Input. For DC input burst dimming, the voltage range

from 0 V to 1.2V at PWMIN linearly sets the burst-mode duty cycle from 0 to 100%. For

external PWM input dimming, directly apply the logic signal on this pin. The MP4651 has

positive dimming polarity.

11

EN

Enable Input. Pull EN high to turn on the chip, and pull EN low to turn it off.

12

VIN

Supply voltage input.

13

VCC

Linear Regulator Output and Bias Supply of the Gate Driver. It provides the supply for the

gate driver and also the external control circuit, the typical value is 9.7V. Bypass VCC with a

1µF or larger ceramic capacitor.

14

GL

Driving signal output, 180 degree phase shifted of GR

15

GND

Ground.

16

GR

Driving signal output, 180 degree phase shifted of GL