Page 1
HIGH EFFICIENCY 1x/2x CHARGE PUMP LED DRIVER
FOR SMALL SCREEN BACKLIGHTING AND FLASHLIGHT
Description
The AL3157 is a low noise, constant frequency charge
pump DC/DC converter that uses a Du al m o de load switch
(1x), and doubling (2x) conversion for driving white LEDs.
Low external part count (one 1µF flying capacitor and two
2.2µF capacitors at V
and V
IN
) make this part ideally
OUT
suited for small, battery-powered applications
The AL3157 drives 3 channels at up to 30mA for small
screen backlighting and an add itional channel up to 210 mA
for LED Flash or LED Flashlight – All from a 2.7V to 5.5V
input.
The AL3157 uses two control inputs (EN1/2) to
enable/disable it and PWM dim the LED current. EN2
controls/PWM dims the backlight LEDs at 30mA per
channel and EN1 controls/PW M dims the Flash/Flash light
LEDs at 210mA.
Each output is equipped with built-in protection for V
short circuit and auto-disable for LED failure conditions.
NEW PRODUCT
Built-in soft-start circuitry prevents excessive in-rush
current during start-up and mode switching. A low-current
shutdown feature disconnects the load from V
IN
quiescent current less than 1µA.
The AL3157 is available in a lead-free, space-saving
thermally enhanced 12-pin 3x3mm DFN package.
Features
OUT
to reduce
Pin Assignments
1
EN2
PGND
Applications
2
3
C
N
4
V
IN
5
C
P
V
OUT
( Top View )
Exposed Pad
U-DFN3030-12
AL3157
12
D1
11
EN1
10
D2
9
GND
8
D3
76
D4
• Dual-Mode 1x and 2x Charge Pump
• Up to 300mA drive capability
o 3-channel for backlight – 30mA/ch
o 1-channel for Flight/light – 210mA
Range: 2.7V to 5.5V
• V
IN
• Smart Touch Phone LED Backlighting
• PDA White LED backlighting
• Backlighting + Torch light
• Two simple PWM dimming control inputs up to
50kHz
• 1.2 MHz Constant Switching Frequency
• Built-In Thermal, Open-Circuit and V
short circu it
OUT
Protection
• Soft Start for reducing in-rush current
• I
<1µA in Shutdown
Q
• Thermally-Enhanced DFN3030-12 Package:
Available in “Green” Molding Compound (No Br, Sb)
• Lead Free Finish/ RoHS Compliant (Note 1)
Notes: 1. EU Directive 2002/95/EC (RoHS). All applicable RoHS exemptions applied. Please visit our website at
http://www.diodes.com/products/lead_free.html
Typical Application Circuit
Flash/
1µF
1µF
C
C
4
IN
IN
2.2µF
2.2µF
C
C
4
V
V
IN
IN
IN
IN
5
5
C
C
P
P
AL3157
AL3157
3
3
C
C
N
N
11
11
EN1
EN1
1
1
EN2
EN2
PGND GND
PGND GND
29
29
V
V
1
1
EN1
EN1
EN2
EN2
Flash/
Light
Light
(EN1)
(EN1)
6
6
V
V
OUT
OUT
12
12
D1
D1
10
10
D2
D2
8
8
D3
D3
7
7
D4
D4
Backlight
Backlight
(EN2)
(EN2)
2.2µF
2.2µF
C
C
OUT
OUT
AL3157
Document number: DS35116 Rev. 1 - 2
1 of 9
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March 2011
© Diodes Incorporated
Page 2
HIGH EFFICIENCY 1x/2x CHARGE PUMP LED DRIVER
FOR SMALL SCREEN BACKLIGHTING AND FLASHLIGHT
Pin Descriptions
Pin Name Pin Number Description
EN2 1 Enable Pin 2: Controls outputs D2, D3 and D4
PGND 2 Charge Pump Switch Ground: Connect to GND
CN 3 Negative Terminal of Flying Capacitor
VIN 4 Input Power Supply. Decouple with a 2.2µF capacitor between this pin and ground.
CP 5 Positive Terminal of Flying Cap a ci to r
V
6
OUT
Charge pump output to driv e D1~D4 lo ad circu i t . Decou pl e w ith a 2. 2 µF capa citor between
this pin and ground.
D4 7 Current sink input #4. Drive up to 30mA LED current. Connect to V
D3 8 Current sink input #3. Drive up to 30mA LED current. Connect to V
GND 9 Ground
D2 10 Current sink input #2. Driv e up to 30mA LED current. Connect to V
EN1 11 Enable Pin 1: Controls output D1
NEW PRODUCT
D1 12 Current sink input #1. Drive up to 210mA LED current. Connect to V
EP EP PAD Exposed Pad (bottom). Connect to GND directly underneath the package.
Functional Block Diagram
CNC
P
AL3157
when un-used.
OUT
when un-used.
OUT
when un-used.
OUT
when un-used.
OUT
V
EN1
EN2
V
OUT
IN
OSCILLATOR
TEMPERATURE
PROTECTION
BANDGAP
OVER
UNDER
VOLTAGE
LOCKOUT
CHARGE PUMP
SWITCHES
DIGITAL CONTROL BLOCK
CURRENT
CONTROL
SHORT
CIRCUIT
PROTECTION
GND
OVER
VOLTAGE
PROTECTION
D1
D2
D3
D4
AL3157
Document number: DS35116 Rev. 1 - 2
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March 2011
© Diodes Incorporated
Page 3
)
)
HIGH EFFICIENCY 1x/2x CHARGE PUMP LED DRIVER
FOR SMALL SCREEN BACKLIGHTING AND FLASHLIGHT
Absolute Maximum Ratings (Note 2)
Symbol Description Rating Unit
ESD HBM Human Body Model ESD Protection 2 kV
ESD MM Machine Model ESD Protection 200 V
VIN Input Voltage -0.3 to 6 V
V
EN1, EN2, EN3 to GND Voltage -0.3 to VIN +0.3 V
EN1,2,3
I
Maximum DC Output Current 300 mA
OUT
TJ Operating Junction Temperature Ra ng e 125 °C
T
Maximum Soldering Temp e rat ure (at le ads , 10 sec) 300 °C
LEAD
Notes: 2. Exceeding Absolute Maximum Ratings will cause permanent damage to the device.
Recommended Operating Conditions
Symbol Parameter Min Max Unit
VIN Input Voltage 2.7 5.5 V
V
EN1,2 Threshold Low 0 0.4 V
NEW PRODUCT
ENL(1, 2
V
EN1,2, Threshold High 1.4 VIN V
ENH(1,2
TA Operating Ambient Temperature -40 85 °C
AL3157
Electrical Characteristics
VIN = 4V, CIN = C
Symbol Parameter Test Conditions Min Typ. Max Unit
IQ Quiescent Current
I
Shutdown Current EN1, EN2 = 0 1 µA
SHDN
Backlight LED Drive Sink Current
I
D2~4
Accuracy (Note 3)
Flash/light LED Drive Sink Current
ID1
Accuracy (Note 3)
Current Matching Between Any
I
D-Match
V
V
Two Backlight LED Drive Current
Sink Outputs (Note 4)
Charge Pump V
R
out
Resistance
1x to 2x Transition Threshold at
TH-Dx
D2, D3 and D4 Pins
1x to 2x Transition Threshold at D1
TH-D1
Pin
VHS Mode Transition Threshold 500 mV
tSS Soft-Start Time 100 µs
fSW Switching Frequency 1.2 MHz
t
EN1,2 Off Timeout 20 ms
EN1,2
UVLO VIN Under-Voltage Lockout 1.8 2 2.2 V
I
EN1, 2 Input Leakage -1 1 µA
EN1,2
T
Thermal Shutdown Protection 160
SHDN
T
Thermal Shutdown Hysteresis 10
HYS
Thermal Resistance
θ
JA
Junction-to-Ambient
Notes: 3. Determined by the mean of channels 2,3 and 4 currents, EG (ID2 + ID3 + ID4)/3
4. Determined by the maximum sink current (MAX), the minimum sink current (MIN), and the average sink current (AVG). Two matching
5. Device mounted on FR-4 substrate, 2"*2", 2oz, copper, double-sided PC board.
= 2.2µF, C1 = 1µF; TA = 25°C unless otherwise noted.
OUT
1x Mode, 3.0≤V
No Load Current
2x Mode, 3.0≤VIN≤5.5, Active,
No Load Current
≤5.5, Active,
IN
0.3 0.6
mA
2 5
IDX = 30mA 28.5 30 31.5 mA
ID1 = 210mA 199.5 210 220.5 mA
VF: D2:D4 = 4V 1 2 %
Open Loop
OUT
1x mode 0.5
2x mode 4.5
Ω
ID = 30mA 150 mV
ID1 = 210mA 150 mV
oC
oC
U-DFN3030-12 (Note 5) 55.29 oC/W
numbers are calculated as (MAX-AVG)/AVG and (AVG-MIN)/AVG. The largest num ber of the two (worst case) is as th e matching data.
AL3157
Document number: DS35116 Rev. 1 - 2
3 of 9
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March 2011
© Diodes Incorporated
Page 4
HIGH EFFICIENCY 1x/2x CHARGE PUMP LED DRIVER
FOR SMALL SCREEN BACKLIGHTING AND FLASHLIGHT
Typical Performance Characteristics
Turn-On in 1x Mode
AL3157
Turn-On in 2x Mode
NEW PRODUCT
EN1,2
2V/div
Vout
2V/div
Iin
300mA/div
100us/div
Turn-Off in 1x Mode
VIN=4.2V
=25°C
T
A
VIN=4.2V
=25°C
T
A
EN1,2
2V/div
Vout
2V/div
Iin
300mA/div
EN1,2
2V/div
Vout
2V/div
Iin
300mA/div
100us/div
Turn-Off in 2x Mode
VIN=3.0V
=25°C
T
A
VIN=3.0V
=25°C
T
A
EN1,2
2V/div
Vout
2V/div
Iin
300mA/div
200ms/div
Load Characteristics in 2x Mode
VIN=3.0V
T
500ns/div
AL3157
Document number: DS35116 Rev. 1 - 2
200ms/div
PWM Dimming Control (Duty Cycle=50%)
Vin
AC/div
=25°C
A
100mV
Vout
AC/div
100mV
Iin
100mA
AC/div
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VIN=4V
Freq=20kHz
Duty Cycle=50%
TA=25°C
10us/div
EN
2V/div
Id1
200mA/div
Iin
300mA/div
March 2011
© Diodes Incorporated
Page 5
HIGH EFFICIENCY 1x/2x CHARGE PUMP LED DRIVER
FOR SMALL SCREEN BACKLIGHTING AND FLASHLIGHT
Typical Performance Characteristics (Continued)
VF=3.27V
=25°C
T
A
AL3157
Channels 2 to 4
V
=4V
IN
NEW PRODUCT
TA=25°C
Channels 2 to 4
V
=4V
IN
V
EN(H)
AL3157
Document number: DS35116 Rev. 1 - 2
=4.0V
V
IN
www.diodes.com
5 of 9
VIN=2.7V
V
EN(L)
March 2011
© Diodes Incorporated
Page 6
AL3157
Functional Description
The AL3157 is a dual-mode high efficiency charge pump (1x and 2x) device, driving 3-channel standard backlight LEDs
and one high-current Flash/Torch LED, int ended for white LED backlight applications. An internal comparator circuit
compares the voltage at each constant current sink input against a reference voltage. To ensure maximum power
efficiency, the most appr opriate switching mode (1x an d 2x) is automatically selected.
The APL3157 requires only three external comp onents: one 1µF ceramic f lying capaci tor (C
2.2µF ceramic input capacitor (C
The each output channel of the AL3157 can drive three individual LEDs with a maximum current of 30mA per channel and
a Flash/Torch LED with a max imum curre nt of 210m A. These can be paralleled to give a total output current of 300mA.
LED Control Table
NEW PRODUCT
EN1
0 0 OFF OFF
0 1 OFF ON
1 0 ON OFF
1 1 ON ON
EN2
Disabled Current Sinks
Unused current channels must b e disabled by connecting the sinks to VOUT with only a small sense current flowing
through the disabled channel.
Soft-Start
Soft-start is incorporated to prevent excessive in-rush current during power-up, mode switching, and transitioning out of
stand-by mode.
Short-Circuit Protection
Short-circuit protection f unction is incorpo rated to prevent exce ssive load current when either flying cap term inals or output
pin electrically tied to a very lower voltage or ground.
Over-Voltage Protection
Over-Voltage Protection function is incorporated to limit the output voltage under a safe value to avoid on-chip device
breakdown.
Under-Voltage Lockout
Under-Voltage lockout feature disabl es the device when the input voltage drops below UVLO threshold.
Thermal Auto Shutdown
When the die temperature exceeds the thermal limit , the device will be disa bled and enter stand-b y mode. The operati on
resumes whenever the die cools off sufficiently.
PWM Dimming Control
The AL3157 provides simp l e PWM dim mi ng cont ro l thro ug h ENx pi n s, an d t he curre nt is adjusted by the duty cycle of the
signal applied on ENx pin. The recommended PWM frequen cy is from 200Hz to 50kHz depending on applications.
.
), and one 2.2µF ceramic charge pump output capacitor (C
IN
HIGH EFFICIENCY 1x/2x CHARGE PUMP LED DRIVER
FOR SMALL SCREEN BACKLIGHTING AND FLASHLIGHT
) for the charge pump, one
1
).
OUT
D1
D2, D3, D4
AL3157
Document number: DS35116 Rev. 1 - 2
6 of 9
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March 2011
© Diodes Incorporated
Page 7
Seating plane
Ordering Information
AL3157
HIGH EFFICIENCY 1x/2x CHARGE PUMP LED DRIVER
FOR SMALL SCREEN BACKLIGHTING AND FLASHLIGHT
AL3157 X - 7
AL3157 X - 7
Package
Package
F : U-DFN3030-12
F : U-DFN3030-12
Packing
Packing
7 : 7” Tape & Reel
7 : 7” Tape & Reel
Device
AL3157F-7 F U-DFN3030-12 3000/Tape & Reel -7
Notes: 7. Pad layout as shown on Diodes Inc. suggested pad layout document AP02001, which can be found on our website at
http://www.diodes.com/datasheets/ap02001.pdf
Package
Code
Packaging
(Note 7)
Quantity Part Number Suffix
7” Tape and Reel
Marking Information
(1) U-DFN3030-12
NEW PRODUCT
( Top View )
XX
Y
W
: B7 : AL3157
XX
: Year : 0~9
Y
: Week : A~Z : 1~26 week;
W
X
a~z : 27~52 week;
z : represents 52 and 53
X
: A~Z : Green
Part Number Package Identification Code
AL3157F U-DFN3030-12 B7
Package Information
(1) Package type: U-DFN3030-12
AL3157
Document number: DS35116 Rev. 1 - 2
2x-
0.10 C
0.08 C
0.25 B
0.57/0.63
B
2.9 / 3.1
A
0.25
2x
0/0.05
R
0
.3
1.5 / 1.7
0.45typ
www.diodes.com
2.9 / 3.1
2.3 / 2.5
0.18/0.28
Bottom View
7 of 9
0.10
0.15max.
A
0.25/0.55
M C A B
C
March 2011
© Diodes Incorporated
Page 8
Tape Orientation (Note 8)
AL3157
HIGH EFFICIENCY 1x/2x CHARGE PUMP LED DRIVER
FOR SMALL SCREEN BACKLIGHTING AND FLASHLIGHT
NEW PRODUCT
Notes: 8. The taping orientation of the other package type can be found on our website at http://www.diodes.com/datasheets/ap02007.pdf
AL3157
Document number: DS35116 Rev. 1 - 2
8 of 9
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© Diodes Incorporated
Page 9
AL3157
HIGH EFFICIENCY 1x/2x CHARGE PUMP LED DRIVER
FOR SMALL SCREEN BACKLIGHTING AND FLASHLIGHT
DIODES INCORPORATED MAKES NO WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, WITH REGARDS TO THIS
DOCUMENT, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
PARTICULAR PURPOSE (AND T HEIR EQUIVALENTS UNDER THE LAWS OF ANY JURISDICTIO N).
Diodes Incorporated and its subsidiaries reserve the right to make modifications, enhancements, improvements, corrections or other
changes without further notice to this document and any product described herein. Diodes Incorporated does not assume any
liability arising out of the application or use of this document or any product described herein; neither does Diodes Incorporated
convey any license under its patent or trademark rights, nor the rights of others. Any Customer or user of this document or products
described herein in such applications shall assume all risks of such use and will agree to hold Diodes Incorporated and all the
companies whose products are represented on Diodes Incorporated website, harmless against all damages.
Diodes Incorporated does not warrant or accept any liability whatsoever in respect of any products purchased through unauthorized
sales channel.
Should Customers purchase or use Diodes Incorporated products for any unintended or unauthorized application, Customers shall
indemnify and hold Diodes Incorporated and its representatives harmless against all claims, damages, expenses, and attorney fees
arising out of, directly or indirectly, any claim of personal injury or death associated with such unintended or unauthorized
application.
Products described herein may be covered by one or more United States, international or foreign patents pending. Product names
NEW PRODUCT
and markings noted herein may also be covered by one or more United States, international or foreign trademarks.
Diodes Incorporated products are specifically not authorized for use as critical components in life support devices or systems
without the express written approval of the Chief Executive Officer of Diodes Incorporated. As used herein:
A. Life support devices or systems are devices or systems which:
1. are intended to implant into the body, or
B. A critical component is any component in a life support device or system whose failure to perform can be reasonably expected
Customers represent that they have all necessary expertise in the safety and regulatory ramifications of their life support devices or
systems, and acknowledge and agree that they are solely responsible for all legal, regulatory and safety-related requirements
concerning their products and any use of Diodes Incorporated products in such safety-critical, life support devices or systems,
notwithstanding any devices- or systems-related information or support that may be provided by Diodes Incorporated. Further,
Customers must fully indemnify Diodes Incorporated and its representatives against any damages arising out of the use of Diodes
Incorporated products in such safety-critical, life support devices or systems.
Copyright © 2011, Diodes Incorporated
www.diodes.com
2. support or sustain life and whose failure to perform when properly used in accordance with instructions for use provided
in the labeling can be reasonably expected to result in significant injury to the user.
to cause the failure of the life support device or to affect its safety or effectiveness.
IMPORTANT NOTICE
LIFE SUPPORT
AL3157
Document number: DS35116 Rev. 1 - 2
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