Diodes AL3157 User Manual

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

www.diodes.com

March 2011

© Diodes Incorporated

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

2 of 9

www.diodes.com

March 2011

© Diodes Incorporated

)

)

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

www.diodes.com

March 2011

© Diodes Incorporated