MP4600 – WHITE LED DRIVER FOR UP TO 55 INCH TV BACKLIGHTING

MP4600 Rev. 0.91

www.MonolithicPower.com

5

1/6/2012

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OPERATION

The MP4600 is a current mode controlled Buck-

Boost regulator. The sensing resistor senses the

LED current and feeds it back to an error

amplifier, which regulates it to 198mV with an

inside compensation network. The COMP pin is

the output of the error amplifier. The inductor

peak current is proportional to the COMP pin

voltage. An increase of the COMP voltage

increases the current delivered to the output.

Open LED Protection

If the LED is open, there is no voltage on the FB

shutdown threshold set by the external resistor.

Dimming Control

The MP4600 allows both DC and PWM dimming.

When the voltage on EN is <0.6V, the chip is

turned off. For analog dimming, when the voltage

on EN is from 0.7V to 1.4V, the LED current will

change from 0% to 100% of the maximum LED

current. If the voltage on EN pin is higher than

1.4, maximum LED current will be generated. For

exceed 1.5V. The PWM waveform is internally

clamped to 0.198V.

COMP

Figure 1—Functional Block Diagram