www.fairchildsemi.com

Rev.1.2

©2001 Fairchild Semiconductor Corporation

Features

• 85% conversion efficiency at 50mA out

• Start-up voltages as low as 900mV

• ±2.5% accurate outputs

• Complete switch design with only 3 external components

• Automatically senses load variations to select the optimal

duty cycle and extend conversion efficiency over a wide

range

• External transistor configuration to run as switcher

controller

• Shutdown to 0.5µ A

Applications

• Cellular phones, pagers

• Cameras, video recorders

• Palmtops and PDAs

Description

50 mA boost converter using Pulse Frequency Modulation, or

PFM, technique, in 5-lead SOT-89 or a 5-lead SOT-23

package. Only 3 external components are needed to complete

the switcher design.

The ILC6390 automatically senses load variations to choose

between 55% and 75% duty cycles. Normal operation is 55%

duty at 155kHz; when load currents exceed the internal

comparator trip point, a “turbo mode” kicks in to provide

extended

on-time

switching

(75%

duty

at

100kHz

oscillation).

Requiring only 30µA of supply current, the ILC6390

achieves efficiencies as high as 85% at 5V yet shuts down to

0.5µA max.

Standard voltages offered are 2.5, 3.3, and 5.0V and is

available in both a 5 lead SOT-23 and 5 lead SOT-89 package

for small footprint applications.

In addition, the ILC6391 is configured to drive an external

transistor to achieve higher power levels.

2

ILC6390CM

1

3

13

L

V

IN

GND

CE

SD

+

C

L

V

OUT

ILC6390CP

1

2

3

45

CE

V

OUT

C

L

+

L

SD

V

IN

GND

ILC6391CM

1

2

3

45

CE

V

OUT

C

L

+

L

SD

V

IN

GND

R

Tr

ILC6391CP

1

2

3

45

CE

V

OUT

C

L

+

L

SD

V

IN

GND

C

B

R

B

Tr

Figures 1 & 2

L: 100µH (SUMIDA, CD-54)

SD: Diode (Schottky diode;

MATSUSHITA MA 735)

Capacitor; NICHICON, f93)

Figures 3 & 4

L: 47µH (SUMIDA, CD-54)

SD: Diode (Schottky diode;

MATSUSHITA MA735)

Capacitor; NICHICON, F93)

RB: 1k

Ω

CB: 3300pF

Tr: 2SC3279, 2SDI628G

Typical Applications

ILC6390/91

SOT-89 Step-Up PFM Switcher with Auto-Load Sense

©2001 Fairchild Semiconductor Corporation