AME, Inc.
AME5138
n
General Description
The AME5138 is a fixed off-time step-up DC/DC con-
verter in a small 5-lead SOT-25 package.The AME5138
is ideal for LCD panels requiring low current and high effi-
ciency as well as LED applications for cellular phone back-
lighting, PDAs,and other hand-held devices. The low 400ns
off-time allows the use of tiny external components.
AME5138 is designed to drive up to four white LEDs
in series with a constant current from a single Li-lon bat-
tery. To control LED brightness, the LED current can be
adjusted by applying a PWM (pulse width modulated)
signal with a frequency range of 100Hz to 50KHz to the
EN pin.
Micropower Step-Up
DC/DC Converter
n
Typical Application
V
IN
2.5V-4.2V
5
V
IN
L
10µH
1
SW
I
LED
C
OUT
1µF
Ceramic
D
Option for
4LEDs
C
IN
4.7µF
Ceramic
AME5138
>1.1V 4
EN
0V
GND
2
FB
3
R2
80Ω
* I
LED
=V
FB
/R2
n
Features
l
0.7Ω internal switch
l
Uses small surface mount components
l
Adjustable output voltage up to 20V
l
2V to 5.5V input range
l
Input undervoltage lockout
l
0.01µA shutdown current
l
Small 5-Lead SOT-25 package
l
All AME's lead free Product Meet RoHS
Standard
Figure 1
：
Four White LEDs Application in Li-lon
Battery
V
IN
2.5V-4.2V
L
15µH
D
20V
10mA
5
C
IN
4.7µF
Ceramic
4
V
IN
1
SW
R1
200K
AME5138
FB
3
EN
GND
2
R2
13K
C
OUT
1µF
Ceramic
n
Applications
l
l
l
l
l
White LED Back-Lighting
Hand-held Devices
Digital Cameras
Portable Applications
LCD Bias Power
Figure 2
：
Typical 20V Application
1
AME [ ANALOG MICROELECTRONICS ]
