MP8352 – 3V to 6V INPUT, 6A, 600KHz STEP-DOWN WITH SYNCHRONOUS GATE DRIVER

MP8352 Rev. 1.0

www.MonolithicPower.com

7

1/25/2010

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OPERATION

IN

EN/SYNC

FB

SW

VCC

BG

GND

PG

BST

OSCILLATOR

600KHz

DRIVER

CURRENT SENSE

AMPLIFIER

x40

ERROR

AMPLIFIER

CURRENT

LIMIT

COMPARATOR

PWM

COMPARATOR

DRIVER

RSEN

5m

Ω

REFERENCE

--

+

--

+

--

+

S

R

R

Q

Q

C1

50pF

C1

1pF

R1

300k

Ω

POWER

GOOD

Figure 1—Functional Block Diagram

The MP8352 is a fixed frequency, synchronous,

step-down switching regulator with an integrated

high-side power MOSFET and a gate driver for a

low-side external MOSFET. It achieves 6A

continuous output current over a wide input

supply range with excellent load and line

regulation. It provides a single highly efficient

solution with current mode control for fast loop

response and easy compensation.

The MP8352 operates in a fixed frequency, peak

current control mode to regulate the output

voltage. A PWM cycle is initiated by the internal

clock. The integrated high-side power MOSFET is

turned on and remains on until its current reaches

the value set by the COMP voltage. When the

power switch is off, it remains off until the next

clock cycle starts. If, in 90% of one PWM period,

the current in the power MOSFET does not reach

the COMP set current value, the power MOSFET

will be forced to turn off.

Error Amplifier

The error amplifier compares the FB pin voltage

with the internal 0.8V reference (REF) and

outputs a current proportional to the difference

between the two. This output current is then used

to charge or discharge the internal compensation

network to form the COMP voltage, which is used

to control the power MOSFET current. The

optimized

internal

compensation

network

minimizes the external component counts and

simplifies the control loop design.