MP3216 –36V, 1.3MHz STEP-UP CONVERTER WITH A 0.75A SWITCH

MP3216 Rev. 0.92

www.MonolithicPower.com

7

12/25/2013

MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.

© 2013 MPS. All Rights Reserved.

OPERATION

The MP3216 uses a constant frequency, peak

current mode boost regulator architecture to

regulate the output voltage. The operation of

the MP3216 can be understood by referring to

the block diagram of Figure 1.

At the start of each oscillator cycle the FET 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 positive

input of the PWM comparator. When this

voltage equals the output voltage of the error

amplifier the power FET is turned off.

The voltage at the output of the error amplifier

is an amplified version of the difference

between the 1.24V 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. This results in

more current flowing through the power FET,

thus increasing the power delivered to the

output.

Over voltage protection shuts off the MP3216 if

the output voltage goes too high. In some cases,

loose high side resistor or improper divided

resistor; this results in the feedback voltage is

always below reference. The part runs at

maximum duty cycle boosting the output

voltage higher and higher. If the output ever

exceeds 42V, the part shuts down. And It does

not switch again until the power is recycled.

The MP3216 also has output short protection

function.

When

short

condition

occurs,

switching stops and internal disconnecting N-

MOSFET limits the inductor current to 210mA,

which prevents the freewheel diode and IC from

damaging. Once short condition is released, the

system returns to normal operation.

INTERNAL

REGULATOR

CP

IN

L

M2

ENABLE&

REFERENCE

CONTROL

Figure 1—Functional Block Diagram