Application Circuits

1-Cell to 3.3V SEPIC Power Supply

Figure 4 shows the MAX1896 in a single-ended primary

inductance converter (SEPIC) topology. This topology

is useful when the input voltage can be either higher or

lower than the output voltage, such as when converting

a single lithium-ion (Li+) cell to a 3.3V output. L1 and

L2 are two windings on a single inductor or two sepa-

rate inductors. The coupling capacitor between these

two windings must be a low-ESR type to achieve maxi-

mum efficiency, and must also be able to handle high

ripple currents. Ceramic capacitors are best for this

application.

Layout Procedure

Good PC board layout and routing are required in high-

frequency switching power supplies to achieve good

regulation, and stability. It is strongly recommended

that the evaluation kit PC board layouts be followed as

closely as possible. Refer to the MAX1896 EV kit for a

good layout. Place power components as close togeth-

er as possible, keeping their traces short, direct, and

wide. Avoid interconnecting the ground pins of the

power components using vias through an internal

ground plane. Instead, keep the power components

close together and route them in a star ground configu-

ration using component side copper, then connect the

star ground to internal ground using multiple vias.

1.4MHz SOT23 Current-Mode

Step-Up DC-DC Converter

8

_______________________________________________________________________________________

Figure 1. Typical Application Circuit

LX

IN

2.6V TO 4.5V

GND

5V

SHDN

FB

MAX1896

ON/OFF

SS

33nF

C1

10µF

10V

C2

0.1µF

L

10µH

SUMIDA

CD43-100

0.1µF

22µF

16V

R1

36kΩ

R2

12kΩ

NIHON

EC10QSO2L

Chip Information

TRANSISTOR COUNT: 970