Page 1
AX2012
1.9A Fixed Frequency White LED Driver
GENERAL DESCRIPTION
The AX2012 is a step-up converter designed for driving up to 8 series white LEDs for
backlighting application. The AX2012 uses current mode, 1.2MHZ fixed frequency
architecture to regulate the LED current, which is set through an external current sense
resistor. Its low 300mV feedback voltage reduces power loss and improves efficiency. The
OV pin monitors the output voltage and turns off the converter if an over-voltage condition is
present due to an open circuit condition. The AX2012 includes under-voltage lockout, current
limiting and thermal shutdown protection preventing damage in the event of an output
overload. The driver is available in small 6-pin TSOT-23 and 8-pin TDFN (2mm x 2mm)
packages.
FEATURES
- 2.5V to 5.5 V operating input voltage range
- Drives up to 8 series White LEDs
- 1.2MHz Fixed Switching Frequency
- Wide range for PWM dimming (200Hz to 200KHz)
- Internal 1.9A switching current limit
- Over Voltage Protection (OVP)
- Internal Soft-start Function
- Current limit and Thermal shutdown protection
- Under voltage Lockout
- Available in the 6-pin TSOT-23 and 8-pin TDFN Packages
Axelite Confidential Materials, do not copy or distribute without written consent.
1/11
Rev.1.1 Nov.05, 2010
Page 2
AX2012
VCC
LX
Control and
Driver Logic
EN
Reference
1.238V
Soft Start
Current
Sense
Slope
Compensation
Oscillator
1.2MHz
FB
Error
Amplifier
Summing
Comparator
Thermal
Shutdown
Enable
Logic
GND
N-MOS
10ms
300mV
Shutdown
OVP
OV
UVLO
TDFN-8L (2*2)
1
2
3
4 5
6
7
8
GND
SW
(GND)
NC
FB
GND
VCC
OV
EN
Name
Description
GND
Ground Pin
VCC
Power Input Pin
OV
OVP Sense Pin
EN
Enable with Dimming Pin; Internal
Pull-Low; Logic High Active
FB
Feedback Pin; Put a Resistor to GND
to Setting the Current
NC
No Connect Pin
SW
Switch Output Pin
(Top View)
TSOT-23-6L
3
2
6
4
1
GND
VCCSW
OV
5
FB EN
BLOCK DIAGRAM
PIN ASSIGNMENT
The packages of AX2012 are TSOT23-6L and TDFN-8L; the pin assignment is given by:
Axelite Confidential Materials, do not copy or distribute without written consent.
2/11
Rev.1.1 Nov.05, 2010
Page 3
AX2012
Order Information
AX2012
XX X
Package Type
Packing
Blank : Bag
A : Taping
CT: TSOT-23-6L
Z8: TDFN-8L (2*2)
Top Marking (TSOT-23-6L)
Top Marking (TDFN-8L)
J
AX2012
Week: 01~26(A~Z)
27~52(a~z)
Year : A = 2010
1 = 2011
ID Code: Internal
AYW X
AX2012
Year : A = 2010
1 = 2011
Week: 01~26(A~Z)
27~52(a~z)
ID Code: Internal
Y
W X
J
A
Characteristics
Symbol
Rating
Unit
VCC Pin Voltage
VCC
GND - 0.3 to GND + 6
V
EN,FB, OV Pin Voltage
GND - 0.3 to VCC + 0.3
V
SW, OV Pin Voltage
VSW
30
V
Power Dissipation
PD
( TJ-TA ) / θJA
mW
Storage Temperature Range
TST
-65 to +150
°C
Operating Junction Temperature Range
TOP
-40 to +125
°C
Thermal Resistance from Junction to
case
TSOT-23-6L
θJC
180
°C /W
TDFN-8L
25
Thermal Resistance from Junction to
ambient
TSOT-23-6L
θJA
250
°C /W
TDFN-8L
120
ORDER/MARKING INFORMATION
ABSOLUTE MAXIMUM RATINGS (at T
Note: θJA is measured with the PCB copper area of approximately 1 in2(Multi-layer).
=25°C)
A
Axelite Confidential Materials, do not copy or distribute without written consent.
3/11
Rev.1.1 Nov.05, 2010
Page 4
AX2012
Characteristics
Symbol
Conditions
Min
Typ
Max
Units
Input Voltage Range
VCC
2.5 - 5.5
V
Step-Up Voltage Range
V
OUT
3 -
27
V
OV Sense Voltage
VOV
27.5
29
30.5
V
Under Voltage Lockout
U
VLO
Rising
-
2.25
2.45
V
UVLO Hysteresis
-
100 - mV
Feedback Voltage
VFB
285
300
315
mV
EN Threshold
Logic-High Voltage
VIH
1.4 - - V Logic-Low Voltage
VIL - - 0.4
V
EN Hysteresis
-
200 - mV
Operating Quiescent Current
I
CCQ
I
OUT
= 0mA, VFB =0.5V
-
170 - μA
Shutdown Current
ISD
VEN=0V, tEN > 20ms
- - 1
μA
N-Channel MOSFET Current Limit
(Note1)
I
LIM
Duty=50%
-
1.9 - A
MOSFET On-Resistance (Note1)
R
DS(on)
VCC=3V, ISW=1A
-
0.6
-
Ω
VCC=5V, ISW=1A
-
0.45
-
Maximum Duty Cycle
D
MAX
85
90 - %
Line Regulation
VCC = 3V to 5V
- 1 -
%
Switching Frequency
F
OSC
0.9
1.2
1.5
MHz
Dimming Clock Rate
F
DIM
0.2 - 200
KHz
FB Input Leakage Current
I
FB-LKG
VFB = 0.5V
-
0.01
100
nA
SW Leakage Current
I
SWL
Vsw = 27V, VFB =0.5V
- - 1
µA
EN Input Leakage Current
I
EN-LKG1
VEN= VCC
-
1.5 3 μA
I
EN-LKG2
VEN= GND
-
0.01
0.1
μA
Shutdown Delay
T
SHDN
- 10 - mS
Thermal Shutdown
TSD -
150
-
°C
Thermal Shutdown Hysteresis
TSH -
30
-
ELECTRICAL CHARACTERUSTICS
(VCC=5V, I
= 20mA, TA = 25°C , unless otherwise noted)
OUT
Note1: Guaranteed by design.
Axelite Confidential Materials, do not copy or distribute without written consent.
4/11
Rev.1.1 Nov.05, 2010
Page 5
AX2012
VIN=5V
C1
4.7uF
L1
4.7uH
U1
AX2012
4
6
5
1
VCC
EN
OV
GND
SW
C2
1uF
D1
B240A
I
LED
= VFB/R3, VFB=300mV
ON
OFF
2
FB
R3
3
8-WLEDs
VIN=5V
C1
4.7uF
L1
4.7uH
U1
AX2012
4
6
5
1
VCC
EN
OV
GND
SW
C2
1uF
D1
B240A
I
LED
= VFB/R3, VFB=300mV
200~200KHz
2
FB
R3
3
8-WLEDs
Dimming
APPLICATION CIRCUIT
(1) 8 series LED application
(2) LED Dimming application
Axelite Confidential Materials, do not copy or distribute without written consent.
5/11
Rev.1.1 Nov.05, 2010
Page 6
AX2012
)
R3
300mV
(=I
LED
I
LED
R3
20mA
15Ω
6mW
350mA
0.857Ω
105mW
APPLICATION INFORMATION
Setting the I
Current
LED
Application circuit item shows the basic application circuit with AX2012 adjustable
output version. The external resistor sets the LED output current according to the following
equation:
Over Voltage Protection
OV measure the output voltage for open circuit protection. Connect OV pin to the
output at the top of the LED string. If V
stops the internal driver until V
below 29V.
OUT
above 29V, the OVP protection is happened that
OUT
Under Voltage Lockout (UVLO)
To avoid mis-operation of the device at low input voltages an under voltage lockout is
included that disables the device, if the input voltage falls below (2.25V-100mV).
Input Capacitor Selection
The input capacitor reduces the surge current drawn from the input and switching
noise from the device. The input capacitor impedance at the switching frequency shall be
less than input source impedance to prevent high frequency switching current passing to the
input. A low ESR input capacitor sized for maximum RMS current must be used. Ceramic
capacitors with X5R or X7R dielectrics are highly recommended because of their low ESR
and small temperature coefficients. A 4.7µF ceramic capacitor for most applications is
sufficient. For a lower output power requirement application, this value can be decreased.
Output Capacitor Selection
The output capacitor is required to keep the output voltage ripple small and to ensure
regulation loop stability. The output capacitor must have low impedance at the switching
frequency. Ceramic capacitors with X5R or X7R dielectrics are recommended due to their
low ESR and high ripple current. A 1uF ceramic capacitors works for most of the
applications. Higher capacitor values can be used to improve the load transient response.
6/11
Axelite Confidential Materials, do not copy or distribute without written consent.
Rev.1.1 Nov.05, 2010
Page 7
AX2012
Efficiency vs. Output Current
Efficiency vs. Input Voltage
Output Voltage vs. Output Current
Quiescent Current vs. Input Voltage
Frequency vs. Input Voltage
Frequency vs. Temperature
TYPICAL CHARACTERISTICS
Axelite Confidential Materials, do not copy or distribute without written consent.
7/11
Rev.1.1 Nov.05, 2010
Page 8
AX2012
Reference Voltage vs. Input Voltage
Reference Voltage vs. Temperature
LED Current vs. Duty
Enable Threshold vs. Input Voltage
TYPICAL CHARACTERISTICS (CONTINUOUS)
Axelite Confidential Materials, do not copy or distribute without written consent.
8/11
Rev.1.1 Nov.05, 2010
Page 9
AX2012
Power ON from V
IN
Power ON from EN
Steady State Operation
Normal Operation into OVP
PWM Dimming from EN (200Hz)
PWM Dimming from EN (20KHz)
VIN
VSW
V
OUT
I
OUT
EN
VSW
V
OUT
I
OUT
VIN=5V
4WLEDs
I
OUT
=150mA
VIN=5V, 4WLEDs, I
OUT
=150mA
VSW
VFB
V
OUT
I
OUT
VIN
VSW
V
OUT
I
OUT
( V
OUT
, I
OUT
: measured by AC coupled mode )
V
=5V, 3WLEDs, I
=150mA
VEN
VSW
V
OUT
I
OUT
VEN
VSW
V
OUT
I
OUT
VIN=5V, 4WLEDs, I
OUT
=150mA
V
=5V, 4WLEDs, I
=150mA
VIN=5V
4WLEDs
I
OUT
=150mA
TYPICAL CHARACTERISTICS (CONTINUOUS)
Axelite Confidential Materials, do not copy or distribute without written consent.
9/11
Rev.1.1 Nov.05, 2010
Page 10
AX2012
E1
E
e
e1
b
D
A
A1
A2
y
L1
R
L
C
L2
θ
Symbol
Dimensions in Millimeters
Dimensions in Inches
Min.
Nom.
Max.
Min.
Nom.
Max. A - - 1.10 - -
0.043
A1
0.00 - 0.10 0 -
0.004
A2
0.70
0.90
1.00
0.028
0.035
0.039
b
0.30
0.40
0.50
0.012
0.016
0.020
C
0.08
0.14
0.20
0.003
0.006
0.008
D
2.80
2.90
3.00
0.110
0.114
0.118
E
2.60
2.80
3.00
0.102
0.110
0.118
E1
1.50
1.60
1.70
0.059
0.063
0.067
e
0.95 BSC.
0.037 BSC.
e1
1.90 BSC.
0.075 BSC.
L
0.30
0.45
0.60
0.012
0.018
0.024
L1
0.60 REF.
0.024 REF.
L2
0.25 BSC.
0.010 BSC.
y - -
0.10 - -
0.004
R
0.10 - -
0.004 - - θ 0o - 8o
0o - 8o
PACKAGE OUTLINES
(1) TSOT-23-6L
JEDEC outline: MO-193 AA
Axelite Confidential Materials, do not copy or distribute without written consent.
10/11
Rev.1.1 Nov.05, 2010
Page 11
AX2012
1
D2
1
E2
L
b
e
1
E
1
D
PIN 1 INDENT
C
A1
y
Symbol
Dimensions in Millimeters
Dimensions in Inches
Min.
Nom.
Max.
Min.
Nom.
Max.
A
0.70
0.75
0.80
0.028
0.030
0.031
A1
0.00
0.02
0.05
0
0.001
0.002
b
0.15
0.20
0.25
0.006
0.008
0.010
C
0.19
0.20
0.25
0.007
0.008
0.010
D
1.90
2.00
2.10
0.075
0.079
0.082
D2
1.55
1.60
1.65
0.061
0.063
0.065
E
1.90
2.00
2.10
0.075
0.079
0.082
E2
0.85
0.90
0.95
0.033
0.035
0.037 e -
0.50 - -
0.020 - L
0.30
0.35
0.40
0.012
0.014
0.016
y
0.00
-
0.075 0 -
0.003
(2) TDFN-8L (2*2 0.75mm)
Axelite Confidential Materials, do not copy or distribute without written consent.
11/11
Rev.1.1 Nov.05, 2010
Page 12
Loading...