MP3213 – 700KHZ/1.3MHZ BOOST CONVERTER WITH A 3.5A SWITCH
MP3213 Rev. 1.3 www.MonolithicPower.com 6
9/23/2009 MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2009 MPS. All Rights Reserved.
OPERATION
The MP3213 uses a constant frequency, peak
current mode boost regulation architecture to
regulate the feedback voltage. The operation of
the MP3213 can be understood by referring to
the block diagram of Figure 1.
At the beginning of each cycle, the N-Channel
MOSFET switch is turned on, forcing the
inductor current to rise. The current at the
source of the switch is internally measured and
converted to a voltage by the current sense
amplifier. That voltage is compared to the error
voltage at COMP. The voltage at the output of
the error amplifier is an amplified version of the
difference between the 1.25V reference voltage
and the feedback voltage.
When these two voltages are equal, the PWM
comparator turns off the switch forcing the
inductor current to the output capacitor through
the external rectifier. This causes the inductor
current to decrease. The peak inductor current
is controlled by the voltage at COMP, which in
turn is controlled by the output voltage. Thus
the output voltage is regulated by the inductor
current to satisfy the load. The use of current
mode regulation improves transient response
and control loop stability.
PWM
CONTROL
LOGIC
CURRENT
SENSE
AMP
OSCILLATOR
INTERNAL REGULATOR
AND ENABLE CIRCUITRY
--
+
GM
+
--
GND
FB
COMP
SS
1.25V
SW
IN
--
+
FSEL
EN
Figure 1—Functional Block Diagram
