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Date: 5/25/04

SP6231 500mA, 3.3V Linear Regulator

© Copyright 2004 Sipex Corporation

SP6231

GND

C5

2.2µF

C4

10µF

GND

C3

2.2µF

GND

1

2

3

4

+5V

USB Connector

GND

LX

SHDN

J1

10µH

SHDN

C2

100µF

Schottky

Diode

D1

1

2

3

C1

100µF

5

4

1

2

3

SP6641B

J3

1

2

3

6

5

4

SP6231 500mA, 3.3V CMOS LDO

with Auxiliary Backup

SP6641B Two Cell Boost

To prevent the device from entering thermal

shutdown, maximum power dissipation can not

be exceeded. Using the output voltage 3.3V and

an output current of 500mA, the maximum input

voltage can be determined. Ground pin current

can be taken from the electrical characteristics

maximum input voltage is determined as fol-

lows:

After calculations, we find that the maximum

input voltage of a 500mA application in a 3x3

MLP package, with a minimum footprint lay-

out, is 6.8V.

APPLICATION INFORMATION: continued

This application circuit is available as the evaluation board SP6231EB and is described in detail in the

SP6231 Evaluation Board Manual.

Portable Application Circuit: SP6231 and SP6641B

SP6231 with SP6641 in a Portable

Application

In a portable application, the power sources are

often switched between batteries and USB 5V

supplies. Utilizing USB power eliminates the

loading on the batteries when the device is

connected to computers, and thus can signifi-

cantly increase battery life. When the device is

powered by single or dual alkaline batteries, a

boost regulator, such as SP6641A/B, converts

the battery voltages to a regulated 3.3V.

SP6641A/B is packaged in a tiny SOT-23 pack-

age and requires less than 10

µA quiescent cur-

rent. When the output of SP6641A/B is con-

nected to SP6231 as an auxiliary supply, SP6231

will automatically disconnect its load when the

presence of USB power is detected. However,

when the portable device is disconnected from

USB, SP6231 seamlessly reconnects SP6641A/

B output to the load.