MP1475S – HIGH-EFFICIENCY, 3A, 16V, 500kHz SYNCHRONOUS STEP-DOWN CONVERTER

MP1475S Rev. 1.0

www.MonolithicPower.com

9

1/8/2015

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PIN FUNCTIONS

Package

Pin #

Name

Description

1

PG

Power Good Indicator. PG is the open drain of the internal MOSFET and should be

connected to VCC (or another voltage source) through a resistor (e.g. 100k). When the FB

voltage reaches 90% of the REF voltage, PG is pulled high (after a 0.6ms delay). After the

FB voltage drops to 85% of the REF voltage, PG is pulled low.

2

IN

Supply Voltage. IN supplies power for the internal MOSFET and regulator. The MP1475S

operates from a +4.5V to +16V input rail; it requires a low ESR and a low-inductance

capacitor (C1) to decouple the input rail. Place the input capacitor very close to IN and

connect it with wide PCB traces and multiple vias.

3

SW

by the high-side switch during the PWM duty cycle on-time. The inductor current drives

SW 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. GND is the reference ground of the regulated output voltage. PCB layout

requires extra care (see recommended “PCB Layout Guidelines” on page 16). For best

results, connect to GND with copper and vias.

5

BST

Bootstrap. BST requires a capacitor connected between SW and BST to form a floating

supply across the high-side switch driver.

6

EN/SYNC

Enable/Synchronize. EN/SYNC=high to enable the MP1475S. Apply an external clock to

100kΩ resistor.

7

VCC

Internal 5V LDO Output. VCC powers the driver and control circuits. Decouple with a

0.1μF to 0.22μF capacitor. Do NOT use a capacitor ≥0.22μF.

8

FB

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

set the output voltage. To prevent current-limit runaway during a short-circuit fault, the

frequency foldback comparator lowers the oscillator frequency when the FB voltage is

below 400mV. Place the resistor divider as close to FB as possible. Avoid placing vias on

the FB traces.