MP28373 – 3A, 28V, 1.4MHz STEP-DOWN CONVERTER

MP28373 Rev. 1.0

www.MonolithicPower.com

3

12/12/2007

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© 2007 MPS. All Rights Reserved.

PIN FUNCTIONS

Pin #

Name Description

1

BS

High-Side Gate Drive Boost Input. BS supplies the drive for the high-side N-Channel MOSFET

switch. Connect a 10nF or greater capacitor from SW to BS to power the high side switch.

2

IN

Power Input. IN supplies the power to the IC, as well as the step-down converter switches.

Drive IN with a 4.75V to 28V power source. Bypass IN to GND with a suitably large capacitor

to eliminate noise on the input to the IC. See Input Capacitor

3

SW

Power Switching Output. SW is the switching node that supplies power to the output. Connect

the output LC filter from SW to the output load. Note that a capacitor is required from SW to BS

to power the high-side switch.

4

GND

Ground. Connect the exposed pad on backside to Pin 4.

5

FB

Feedback Input. FB senses the output voltage to regulate said voltage. Drive FB with a

resistive voltage divider from the output voltage. The feedback threshold is 0.92V. See Setting

the Output Voltage

6

COMP

Compensation Node. COMP is used to compensate the regulation control loop. Connect a

series RC network from COMP to GND to compensate the regulation control loop. In some

cases, an additional capacitor from COMP to GND is required. See Compensation

7

EN

Enable Input. EN is a digital input that turns the regulator on or off. Drive EN higher than 2.9V

to turn on the regulator, lower than 0.9V to turn it off. For automatic startup, leave EN

unconnected.

8

SS

Soft-Start Control Input. SS controls the soft start period. Connect a capacitor from SS to GND

to set the soft-start period. A 0.1μF capacitor sets the soft-start period to 10ms.

ELECTRICAL CHARACTERISTICS

8.0

7.5

7.0

6.5

6.0

5.5

5.0

0

20406080

DUTY CYCLE (%)

Peak Current vs

Duty Cycle

0.95

0.94

0.93

0.92

0.91

0.90

0.89

-40

0

-20

40

20

80

60

120

100

Feedback Voltage vs

Die Temperature

90

80

70

60

50

40

30

0

0.5 1.0

2.0

3.0

1.5

2.5

3.5

LOAD CURRENT (A)

Efficiency vs

Load Current