AME, Inc.
1
AME5138
Micropower Step-Up
DC/DC Converter
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.
n General Description
n Features
n Applications
n Typical Application
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
l White LED Back-Lighting
l Hand-held Devices
l Digital Cameras
l Portable Applications
l LCD Bias Power
Figure 1 Four White LEDs Application in Li-lon：
Battery
Figure 2 Typical 20V Application：
* ILED=VFB/R2
CIN
4.7mF
Ceramic
2
5 1
L
15mH
4
VIN
2.5V-4.2V
3
R2
13K
D
AME5138
SWVIN
FB
GND
EN
COUT
1mF
Ceramic
R1
200K
20V
10mA
CIN
4.7mF
Ceramic
AME5138
VIN SW
FBEN GND
2
5 1
L
10mH
4
0V
>1.1V
VIN
2.5V-4.2V
3
R2
80W
COUT
1mF
Ceramic
D Option for
4LEDs
ILED