MP1499 – 16V/5A PEAK SYNCHRONOUS STEP-DOWN CONVERTER

MP1499 Rev. 1.0

www.MonolithicPower.com

8

7/26/2012

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© 2012 MPS. All Rights Reserved.

PIN FUNCTIONS

Package

Pin #

Name

Description

1

FB

Feedback. An external resistor divider from the output to GND, tapped to the FB pin, sets

the output voltage. To prevent current limit run away during a short circuit fault condition

the frequency fold-back comparator lowers the oscillator frequency when the FB voltage is

below 400mV. It is recommended to place the resistor divider as close to FB pin as

possible. Vias should be avoided on the FB traces.

2

VCC

Internal 5V LDO output. The driver and control circuits are powered from this voltage.

Decouple with 0.1μF-0.22μF cap. And the capacitance should be no more than 0.22μF.

3

EN/SY

NC

EN=high to enable the MP1499. External clock can be applied to EN pin for changing

switching frequency. For automatic start-up, connect EN pin to VIN with 100KΩ resistor.

4

BST

Bootstrap. A capacitor connected between SW and BST pins is required to form a floating

supply across the high-side switch driver.

5

NC

No connection internal. This pin can connect to GND.

6, 7

GND

System Ground. This pin is the reference ground of the regulated output voltage.

For this reason care must be taken in PCB layout. Suggested to be connected to GND

with copper and vias.

8

SW

Switch Output. Connect this pin to the inductor and bootstrap capacitor. This pin is driven

up to the VIN voltage by the high-side switch during the on-time of the PWM duty cycle.

The inductor current drives the SW pin negative during the off-time. The on-resistance of

the low-side switch and the internal body diode fixes the negative voltage. Use wide PCB

traces and multiple vias to make the connection.

9

IN

Supply Voltage. The IN pin supplies power for internal MOSFET and regulator. The

MP1499 operates from a +4.5V to +16V input rail. Low ESR, and low inductance capacitor

C1 is needed to decouple the input rail. Place the input capacitor very close to this pin and

connect it with wide PCB traces and multiple vias to make the connection.

10

SS

Soft Start. Connect on external capacitor to program the soft start time for the switch mode

regulator.