MP4690 – SMART BYPASS FOR LED OPEN PROTECTION

MP4690 Rev. 1.0

www.MonolithicPower.com

6

7/7/2011

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BLOCK DIAGRAM

Functional Block Diagram

OPERATION

The MP4690 monitors the drain to source

higher than the threshold voltage of 6V, the

MOSFET is turned on to provide a current path

to replace the opened LED.

After the MOSFET is turned on, the MP4690

checks the LED status every 40us~100us. If the

LED is healed, the MP4690 exits the protection

and gives the current path back to the LED. If

the

LED is still open, the MP4690 continues its

protection. The current goes through the

internal MOSFET of the MP4690.

The status-check duration can be as short as

120ns. During the 120ns, the LED current of

string is maintained through the zener diode

inside the MP4690. The voltage across the

MP4690 is clamped to 7V.