MP2235S –3 A, 16 V, 800 kHz SYNCHRONOUS STEP-DOWN CONVERTER

MP2235S Rev.1.0

www.MonolithicPower.com

9

4/15/2015

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PIN FUNCTIONS

Package

Pin #

Name

Description

1

SS

Soft start. Connect an external capacitor to program the soft-start time for the switch

mode regulator.

2

IN

Supply voltage. IN supplies power for the internal MOSFET and regulator. The MP2235S

operates from a +4.5 V to +16 V input rail. IN requires a low ESR and 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

Switch output. Connect SW to the inductor and bootstrap capacitor. SW is driven up to

SW negative during the off time. The on resistance of the low-side switch and the internal

body diode fixes the negative voltage. Connect SW 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. For best results, connect to GND with copper and vias.

5

BST

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

supply across the high-side switch driver.

6

EN/SYNC

Enable. EN=high to enable the MP2235S. Apply an external clock to change the switching

7

VCC

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

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

8

FB

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

set the output voltage. The frequency foldback comparator lowers the oscillator frequency

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

circuit fault. Place the resistor divider as close to FB as possible. Avoid placing vias on the

FB traces.