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, Inc.
AME5138
n
Function Block Diagram
L
V
IN
C
IN
V
IN
SW
D
Micropower Step-Up
DC/DC Converter
V
OUT
C
OUT
V
OUT
Vref=1.23
Enable
Comp
R1
FB
+
-
R2
400ns one
Shot
+
CL
Comp
-
Current sensing
CL Adjust
Driver
Under Voltage
Lockout
Logic
control
EN
GND
Figure 3
：
AME5138 Block Diagram
2
AME, Inc.
AME5138
n
Pin Configuration
SOT-25
Top View
5
4
Micropower Step-Up
DC/DC Converter
AME5138
1. SW
2. GND
AME5138
3. FB
4. EN
5. V
IN
1
2
3
* Die Attach:
Conductive Epoxy
n
Pin Description
Pin Number
1
Pin Name
SW
Pin Description
Power Switch input.
This is the drain of the internal NMOS power switch. Minimize the metal
trace area connected to this pin to minimize EMI.
Ground.
Tie directly to ground plane.
Output voltage feedback input.
Set the output voltage by selecting values for R1 and R2 using:
2
GND
3
FB
V
R
1
=
R
2
out
−
1
1 . 23
V
Connect the ground of the feedback network to an AGND(Analog Ground)
plane which should be tied directly to the GND pin.
4
EN
Shutdown control input, active low.
The shutdown pin is an active low control. Tie this pin above 1V to enable
the device. Tie this pin below 0.4V to turn off the device.
Analog and Power input.
Input Supply Pin. Bypassed this pin with a capacitor as close to the device
as possible.
5
V
IN
3
AME, Inc.
AME5138
n
Ordering Information
AME5138 x x x x xxx x
Special Feature
Output Voltage
Number of Pins
Package Type
Operating Ambient Temperature Range
Pin Configuration
Micropower Step-Up
DC/DC Converter
Pin
Configuration
A
(SOT-25)
Operating Ambient
Package Type
Temperature Range
E: -40
O
C to +85
O
C
E: SOT-2X
Number
of
Pins
V: 5
Output Voltage
Special Feature
1. SW
2. GND
3. FB
4. EN
5. V
IN
ADJ: Adjustable
Y: Lead free
& Low profile
Z: Lead free
n
Ordering Information
Part Number
AME5138AEEVADJY
AME5138AEEVADJZ
Marking*
BDYww
BDYww
Output Voltage
ADJ
ADJ
Package
TSOT-25
SOT-25
Operating Ambient
Temperature Range
-40
O
C to +85
O
C
-40
O
C to +85
O
C
Note: ww represents the date code and pls refer to Date Code Rule before Package Dimension.
* A line on top of the first letter represents lead free plating such as BDYww.
Please consult AME sales office or authorized Rep./Distributor for the availability of package type.
4
AME, Inc.
AME5138
n
Absolute Maximum Ratings
Parameter
Input Supply Voltage
EN, V
FB
Voltages
SW Voltage
N-Channel Switch Sink Current
ESD Classification
Micropower Step-Up
DC/DC Converter
Symbol
V
IN
V
EN
,V
FB
V
SW
I
SW
Maximum
6
V
IN
V
OUT
+0.3
800
B*
Unit
V
V
V
mA
Caution: Stress above the listed absolute maximum rating may cause permanent damage to the device
* HBM B:2000V~3999V
n
Recommended Operating Conditions
Parameter
Input Supply Voltage
Ambient Temperature Range
Junction Temperature Range
Symbol
V
IN
T
A
T
J
Rating
2 to 5.5
-40 to +85
Unit
V
o
C
-40 to +125
n
Thermal Information
Parameter
Thermal Resistance*
(Junction to Case)
Thermal Resistance
(Junction to Ambient)
Internal Power Dissipation
Maximum Junction Temperature
Solder Iron (10 Sec)**
* Measure
θ
JC
on backside center of molding compund if IC has no tab.
** MIL-STD-202G210F
5
Package
Die Attach
Symbol
θ
J
C
Maximum
81
Unit
o
C/W
SOT-25
Conductive Epoxy
θ
JA
P
D
260
400
150
350
mW
o
C
C
o
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