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Lighting Management for Portable Application Lighting Management for
Portable Application
1
2
Market for portable lighting
Gaming Device
Lighting
Glucometer
Blood Pressure Meter
Pulse CO-Oximeter
Barcode Scanner
Handheld Scope
Mp3 Player
Satellite
Radio
GPS
Cellphone
Digital Camera 3
Whats new for portable
lighting Multi display: Dual LCD panel; LCD+ OLED High brightness camera flash: Fun lighting; Audio synchronous; Programmable LED lighting patterns;
4
Challenges For white LED driver: more advanced
brightness control: True linear; More steps; No audio band noise; For Flash LED driver: Current safety control; Improve the integration; Standard LED Lighting
Solution
5
6
White LED Backlighting
Configurations
Switched Capacitor
LEDs in Parallel
Advantage
Doesnt Require Inductive Boost
Disadvantage
Requires separate wire per LED
Matched current sources needed
Advantage
Size Both area & height
Cost
Disadvantage
Efficiency
Inductive Boost
LEDs in Series
Advantage
Few Wires in/out of display
Disadvantage
Requires high voltage boost
Advantages
Highest Efficiency
Guaranteed Current
Match
Disadvantages
EMI
Size
Cost
OR
OR 7
Direct PWM using Enable or
Dedicated PWM Pins
1kHz
EN
Sw. Cap
LM2751
1kHz
EN
Sw. Cap
LM2796
30kHz.
EN
Inductive
LM3519
100kHz.
PWM
Inductive
LM3508
1kHz.
EN
Inductive
LM3500
1kHz.
PWM
Sw. Cap
LM27951/2
1kHz.
EN
Inductive
LM3502
50kHz.
EN
Inductive
LM2707
Maximum
Frequenc
y
EN / PWM
Converter Type
Part Number Direct PWM is the
simplest PWM
brightness control
method because it does
not require any extra
external components. Main draw back are that
customers PWM clock
may exceed the
maximum allowable
PWM frequency of a part,
and potential audio
band noise.
8
Analog Brightness Control
Using External Components If the Customer has a
DAC available, LED
drivers can gain analog
brightness control
functionality through the
addition of external
resistors. The analog voltage and
extra resistor changes
the brightness through
the LEDs by tricking the
feedback loop into
believing it is already
supplying the proper
amount of current. 9
Digital Brightness Control (1) If the customers µP or µC has spare digital control lines, many levels
of brightness can be realize utilizing external resistors Number of Levels = 2
(N° of GPIO)
10
Digital Brightness Control (2) If the customers
µP or µC does not have control pins that can sink or
source mAs of current, digital brightness control can still be realized
using external resistors and control FETs Number of Levels = 2
(N° of GPIO) 11
Summary of brightness
methods Direct PWM Using Enable or Dedicated PWM Pins Analog Brightness Control Using Dedicated Pins or
External Components Digital Brightness Control Using External FETs and
Resistors Internally Programmable Brightness Control
I
2
C
Compatible Interface
12
OLED Bias & LED Driver
Portfolio
Single
-
Display
Multi -
Display
TIME (CY)
Application Segment
04-06
07
08
09
LM2796TL
LM27964SQ
LM27965SQ
LM3508TL
Synchronous
Micro SMD 0.5mm
LM3509SD
OLED+LED
LLP-10
Magnetic
Charge Pump
OLED Bias + LED Driver
LM3557SD
LM3519MF
LM3500/1TL
LM27966SQ
LM27951/2SD
LM2707MF
LM3502/3TL
LM3502/03SQ
LM2751SD 13
Single-Display Applications
PWM
I
2
C
6
Maximum N° LEDs
Control Interface
LM3500TL
4
5
Magnetic
Charge Pump
9
LM27952SD
LM27951SD
LM3557SD
LM3519MF
LM3508TL
LM27966SQ
LM3501TL
Analog
14
Multi-Display Applications
I
2
C
7
Maximum N° LEDs
Control Interface
LM3503SQ
LM3503TL
3
5
Magnetic
Charge Pump
OLED Bias/LED Driver
9
10
LM27964SQ
LM3502SQ
LM3502TL
LM3509SD
LM27966SQ
LM27965SQ
LM2796TL
Analog
PWM 15
LM27965: Charge Pump LED
Driver with I2C Interface
LM27965
SCL
SDIO
D1A
V
IN
P
OUT
GND
R
SET
I
SET
C
OUT
C
IN
C
1
C
2
-
+
V
IN
D2A D3A D4A
D3B
D5A
MAIN DISPLAY
KEYPAD or SUB
DISPLAY
D1B D2B
VIO
I
2
C
Compatible
Interface
D1C
INDICATOR
LED
1
µF
1
µF
1
µF
1
µF
RESET
16
Product Info & Target Applications Product Description Multi-Output Constant Current LED Driver Key Specifications Up to 90% Efficiency Adaptive 1x-3/2x Charge Pump Drives 9 LEDs with 30mA Supports Multiple LED Configurations:
5+3+1, 4+3+1, 5+2+1, 4+2+1 Indicator LED Output Requires Only 5 External Components:
C
IN
, C
OUT
2x C
FLY
and R
SET 1% Current Matching Soft-Start I
2
C Programmable Brightness Control 32 Non-linear Brightness Steps LLP-24 (4mm x4mm x0.8mm) Target Applications Single and/or Dual Display Backlight Keypad Backlight Indicator LEDs
17
Brightness Level Control
Brightness Profiles
0.00%
10.00%
20.00%
30.00%
40.00%
50.00%
60.00%
70.00%
80.00%
90.00%
100.00%
0
5
10
15
20
25
30
35
Codes
%
F
u
ll S
c
a
l
e
ideal b0.9
LM27965's b0.9 fit
18
P
LED
/P
IN
(%) Up to 90%
P
LED
/P
IN
: 5 LEDs @ 25C
50
55
60
65
70
75
80
85
90
95
3
3.1
3.2
3.3
3.4
3.5
3.6
3.7
3.8
3.9
4
4.1
4.2
4.3
4.4
4.5
V
IN
(V)
E
f
f
i
ci
en
cy
(
%
)
VLED = 3.6V
VLED = 3.3V
VLED = 3.0V
P
LED
/P
IN
: 4 LEDs @ 25C
50
55
60
65
70
75
80
85
90
95
3
3.1
3.2
3.3
3.4
3.5
3.6
3.7
3.8
3.9
4
4.1
4.2
4.3
4.4
4.5
V
IN
(V)
E
ffic
i
e
n
c
y
(%)
VLED=3.6V
VLED=3.3V
VLED=3.0V 19
LM27966 Application Circuit
-
+
20
Product Info & Target Applications Product Description Constant Current LED Driver Key Specifications Up to 90% Efficiency Adaptive 1x-3/2x Charge Pump Drives 5 LEDs with 30mA Supports Multiple LED Configurations:
5+1 anfd 4+1 Indicator LED Output Requires Only 5 External Components:
C
IN
, C
OUT
2x C
FLY
and R
SET 1% Current Matching Soft-Start I
2
C Programmable Brightness Control 32 Non-linear Brightness Steps LLP-24 (4mm x4mm x0.8mm) Target Applications Single and/or Dual Display Backlight Keypad Backlight
21
LM3509SD: Typical Application
Circuits
SW
IN
OVP
MAIN
SUB/FB
SCL
SDA
GND
VIO
SET
R
SET
LM3509
Dual White LED Bias Supply
SW
IN
OVP
MAIN
SUB/FB
SCL
SDA
GND
RESET/
GPIO
VIO
SET
R
SET
LM3509
R1
R2
OLED
Display
V
OLED
= 18V
OLED Panel Power Supply
10
µH
10
µH
1
µF
1
µF
2.2µF
1
µF
C
IN
C
OUT
8.3k 30mA per string
20mA
40mA
10k 136k C
IN
C
OUT
8.3k 2.7V to 5.5V
2.7V to 5.5V
10k 10k 10k 10k RESET/
GPIO
22
Overview & Target
Applications Product Description Dual-Output LED/OLED Driver Key Specifications 87% Peak Efficiency Drives 10 LEDs with 30mA and
0.2% Current Matching Simultaneously Drives 5 LEDs at
20mA and Delivers 21V at 40mA I
2
C Brightness Control 32 Non-linear Brightness Steps Auto-Dimming General Purpose I/O Soft Start Hardware Reset Target Applications Mobile Phones, PDAs,
Smartphones GPS, Handheld Games MP3 Players, DSCs, Portable
DVD Players OLED Displays Package: LLP-10 3mm x 3mm x 0.8mm
23
LED Dimming Scheme Non-Linear Brightness Steps Automatic Fade-In/Fade-Out Selectable Rate Changes:
51
µs/13ms/26ms/52ms/step
100.00%
31
7.50%
15
87.50%
30
6.25%
14
70.00%
29
5.25%
13
61.25%
28
4.38%
12
52.50%
27
3.75%
11
43.75%
26
3.13%
10
37.50%
25
2.81%
9
31.25%
24
2.44%
8
26.25%
23
2.06%
7
22.50%
22
1.69%
6
18.75%
21
1.31%
5
16.88%
20
1.13%
4
15.00%
19
1.00%
3
12.50%
18
0.63%
2
10.00%
17
0.13%
1
8.75%
16
0.00%
0
% of
I
LED_MAX
BMAIN or
BSUB Code
% of
I
LED_MAX
BMAIN or BSUB
Hex Code
LED Curre
nt

(
%
of I
LED
M
A
X
)
24
LED Efficiency (P
LED
/P
IN
): Up to
85% 4 LED String
L = 10
µH, VLF4012
0
10
20
30
40
50
60
70
80
90
0
5
10
15
20
25
30
I
LED
(mA)
E
ffi
c
i
e
n
cy
(
%
)
VIN = 3.33V
VIN = 3.65V
VIN = 4.25V 25
LED Efficiency (P
LED
/P
IN
): Up to
83% 5 LED String
L = 10
µH, VLF4012
0
10
20
30
40
50
60
70
80
90
0
5
10
15
20
25
30
I
LED
(mA
)
E
f
f
i
ci
e
n
cy (
%
)
VIN = 3.33V
VIN = 3.65V
VIN = 4.25V
26
LED Efficiency (P
LED
/P
IN
): Up to
87% Dual (4+4) LED String
0
10
20
30
40
50
60
70
80
90
0
10
20
30
40
50
60
70
I
LED
(mA)
E
f
f
i
ci
e
n
cy (
%
)
VIN = 3.33V
VIN = 3.65V
VIN = 4.25V 27
OLED Bias Efficiency: Up to
86% V
OUT
= 18V
L = 10
µH, VLF4012
0
10
20
30
40
50
60
70
80
90
0
10
20
30
40
50
60
70
I
OUT
(mA)
E
f
fi
ci
e
n
cy (
%
)
VIN = 3.33V
VIN = 3.65V
VIN = 4.25V
28
OLED Bias Efficien