MP1475 – SYNCHRONOUS STEP-DOWN CONVERTER

MP1475 Rev. 1.01

www.MonolithicPower.com

7

4/3/2014

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

© 2014 MPS. All Rights Reserved.

PIN FUNCTIONS

Package

Pin #

Name

Description

1

PG

Power Good Output. The output of this pin is an open drain that goes high if the output

voltage exceeds 90% of the normal voltage. There is a 0.4ms delay between when

FB≥90% to when the PG pin goes high.

2

IN

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

MP1475 operates from a +4.5V to +16V input rail. Requires a low-ESR, and low-

inductance capacitor (C1) 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.

3

SW

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

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. Connect using wide PCB traces

and multiple vias.

4

GND

System Ground. Reference ground of the regulated output voltage. PCB layout requires

extra care. For best results connect to GND with copper and vias.

5

BST

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

a floating supply across the high-side switch driver.

6

EN/SYNC

Enable. EN=high to enable the MP1475. Apply an external clock to change the switching

7

VCC

Internal 5V LDO output. Powers the driver and control circuits are powered from this

voltage. Decouple with a 0.1μF-0.22μF capacitor. Do not use a capacitor ≥0.22μF.

8

FB

Feedback. Connect to the tap of an external resistor divider from the output to GND to set

the output voltage. The frequency fold-back comparator lowers the oscillator frequency

when the FB voltage is below 400mV to prevent current limit runaway during a short-circuit

fault condition. Place the resistor divider as close to the FB pin as possible. Avoid placing

vias on the FB traces.