4/9

MA2009

Major Power Technology Co., Ltd.

Rev 1.0 Sep. 14, 2016



APPLICATION CIRCUIT

R1

20K

C1

22uF

L1

4.7uH

R2

380K

U1

4

5

3

1

VIN

EN

FB

GND

SW

C2

22uF

D1

B340A

2

OUT

R3

100K



FUNCTION DESCRIPTION

The MA2009 uses a fixed frequency, peak current mode boost regulator architecture to

regulate voltage at the feedback pin. The operation of the MA2009 can be understood by

referring to the block diagram of Block Diagram item. At the start of each oscillator cycle the

MOSFET is turned on through the control circuitry. To prevent sub-harmonic oscillations at

duty cycles greater than 50 percent, a stabilizing ramp is added to the output of the current

sense amplifier and the result is fed into the negative input of the PWM comparator. When

this voltage equals the output voltage of the error amplifier the power MOSFET is turned off.

The voltage at the output of the error amplifier is an amplified version of the difference

between the 0.6V band-gap reference voltage and the feedback voltage. In this way the

peak current level keeps the output in regulation. If the feedback voltage starts to drop, the

output of the error amplifier increases. These results in more current to flow through the

power MOSFET, thus increasing the power delivered to the output. The MA2009 has

internal soft start to limit the amount of input current at startup and to also limit the amount

of overshoot on the output.