ACT6311

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www.active-semi.com

Copyright © 2011 Active-Semi, Inc.

Rev 3, 22-Feb-11

FUNCTIONAL DESCRIPTION

The ACT6311 is a high efficiency step-up DC/DC

converter that employs a current-mode, fixed

frequency

pulse-width

modulation

(PWM)

architecture with excellent line and load regulation.

Figure 3 shows the functional block diagram of the

IC. The flip-flop is set at the start of each oscillator

cycle, and turns on the power switch. During this on

time, the switch current level is sensed and added

to a ramp signal, and the resulting sum is compared

with the output of the error amplifier. If the error

comparator output is high, the flip-flop is reset and

the power switch turns off. Thus, the peak inductor

current level is controlled by the error amplifier

output, which is integrated from the difference

between FB input and the 1.24V reference point.

The ACT6311 operates at a constant switching

frequency for output current higher than 4mA. If the

output current decreases further, the IC will enter

frequency modulation mode, resulting in some low

frequency ripple.

Figure 3. Functional Block Diagram

ERROR

AMPLIFIER