2014. 01. 04

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Revision No : 0

FTD8201

Typical Application Circuit

OPERATION DESCRIPTION

The FTD8201 uses a constant frequency, peak current mode boost regulator architecture to regulate the series string of

white LEDs. The operation of the FTD8201 can be understood by referring to the simplified block diagram

shown above. At the start of each oscillator cycle, the control logic turns on the power switch M1. The signal at the

non-inverting input of the PWM comparator is proportional to the switch current, summed

together with a portion of the oscillator ramp When this signal reaches the level set by the output of error amplifier, the

PWM comparator resets the latch in the control logic and turns off the power switch. In this manner, error amplifier sets

the correct peak current level to keep the LED current in regulation. If the feedback voltage starts to drop,

the output of the error amplifier increases. This results in more current to flow through M1, hence increasing the power

delivered to the output.

FTD8201