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PDF AAT1235 Data sheet ( Hoja de datos )
| Número de pieza | AAT1235 | |
| Descripción | High Efficiency White LED Drivers | |
| Fabricantes | Advanced Analogic Technologies | |
| Logotipo |  |
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General Description
The AAT1235 is a highly integrated, high efficiency
power solution for white LED backlight and keypad
backlights in mobile/portable devices. It is based on a
switching boost converter which steps up the single-
cell lithium-ion/polymer battery voltage to drive 5
strings of series-connected white LEDs with preci-
sion current regulation. The AAT1235 is capable of
driving a total of four LEDs per channel.
www.DataSheet4U.com
The boost converter can produce an output drive of
up to 24V at 100mA. The high switching frequency
(up to 2MHz) provides fast response to load tran-
sients and allows the use of small external compo-
nents. A fully integrated control circuit simplifies the
design and reduces total solution size.
AnalogicTech's Advanced Simple Serial Control™
(AS2Cwire™) serial digital input is used to individual-
ly turn each output sink on/off and adjust the LED
current by group. Unlike conventional pulse width
modulation (PWM) control of LED brightness, the
AAT1235 drives the LEDs with constant, non-pulsat-
ing current.
A similar device is also available with an I2C two-
wire interface; please see the AAT1236 datasheet.
The AAT1235 is available in a Pb-free, thermally-
enhanced 16-pin 3x4mm TDFN package and is
specified for operation over the -40°C to +85°C tem-
perature range.
Typical Application
L= 2.2µH
D1
COUT
2.2µF
AAT1235
High Efficiency White LED Drivers
for Backlight and Keypad
Features
SwitchReg™
• Input Supply Voltage Range: 2.7V to 5.5V
• Maximum Boost Output Drive: Up to 24V at 100mA
• Up to 85% Efficient Operation
• Up to 2MHz Switching Frequency with Small
Inductor
• User-Programmable Full-Scale LED Current, Up
to 30mA
• Single-Wire AS2Cwire Serial Interface
— Five Addressable Registers
• Independent LED Current Control by Group
— Backlight Group B1-B2, 16 Settings
— Auxiliary Group A1-A3, 16 Settings
• Independent LED ON/OFF Control
— Fast, 1MHz Serial Interface
• Non-Pulsating, High-Performance LED Current
Drive for Uniform Illumination
— 10% Absolute Accuracy
— 2% Channel-to-Channel Matching
• Over-Voltage and Over-Temperature Protection
• Automatic Soft-Start Minimizes Large Inrush
Current at Startup
• Available in 3x4mm TDFN34-16 Package
Applications
• Digital Still Cameras (DSCs)
• Keypad Backlight
• Large Panel Displays
• Mobile Handsets
• Personal Media Players
• PDAs and Notebook PCs
• White LED Backlight
Up to 24V Max
Keypad or
RGB LEDs
1235.2007.02.1.1
Input :
2.7V~5.5V
CIN
2.2µF
LIN
VIN
IN
AS 2Cwire Control
Backlight
LEDs
SW B 1 B 2 A 1 A 2 A 3
AAT1235
OV
EN /SET
RSET
R1
22.6kΩ
GND AGND
R2
187kΩ
R3
12.1kΩ
1
1 page  
Typical Characteristics
83
82
81
80
79
www.DataSheet4U.com 78
77
76
1.6
Efficiency vs. LED Current
(Group B On; Group A Off)
VIN = 5V
VIN = 3.6V
VIN = 4.2V
3.9 6.2 8.5 10.8 13.1 15.4 17.7 20
Output LED Current (mA)
AAT1235
High Efficiency White LED Drivers
for Backlight and Keypad
84
83
82
81
80
79
78
77
1.6
Efficiency vs. LED Current
(Group B Off; Group A On)
VIN = 5V
VIN = 4.2V
VIN = 3.6V
3.9 6.2 8.5 10.8 13.1 15.4 17.7
Output LED Current (mA)
20
86
85
84
83
82
81
80
79
1.6
Efficiency vs. LED Current
(Group A and B On)
VIN = 5V
VIN = 3.6V
VIN = 4.2V
3.9 6.2 8.5 10.8 13.1 15.4 17.7
Output LED Current (mA)
20
LED Current Accuracy vs. Supply Voltage
3
2
IB1, B2, A1, A2, A3
1
0
-1
-2
-3
2.7 3.1 3.4 3.8 4.1 4.5 4.8 5.2 5.5
Supply Voltage (V)
LED Current vs. Supply Voltage
20.0
IB1
19.8
19.6 IA1
19.4
19.2
19.0
IA3
18.8 IB2 IA2
18.6
18.4
2.7 3.1 3.4 3.8 4.1 4.5 4.8 5.2 5.5
Supply Voltage (V)
Shutdown Current vs.
Supply Voltage and Temperature
0.7
0.6
25°C
0.5
85°C
0.4
0.3
0.2
0.1 -40°C
0.0
2.7 3.1 3.5 3.9 4.3 4.7 5.1
Supply Voltage (V)
5.5
1235.2007.02.1.1
5
5 Page 
AAT1235
High Efficiency White LED Drivers
for Backlight and Keypad
Constant Current Output Level Settings
and AS2Cwire Serial Interface
The LED current sink level of each group and the
on/off status of each channel is controlled by
AnalogicTech's AS2Cwire serial digital input. Since
each current sink is programmable, no PWM or
additional control circuitry is needed to control LED
brightness. This feature greatly reduces the burden
on a microcontroller or system IC to manage LED
or display brightness, allowing the user to "set it
www.DataSheet4U.caonmd forget it." With its high-speed serial interface
(1MHz data rate), the input sink current can be
changed quickly and easily. Also the non-pulsating
LED current reduces system noise and improves
LED reliability.
AS2Cwire relies on the number of rising edges of
the EN/SET pin to address and load the registers.
AS2Cwire latches data or address after the EN/SET
pin has been held high for time TLAT (500µs).
Address or data is differentiated by the number of
EN/SET rising edges. Since the data registers are
4 bits each, the differentiating number of pulses is
24 or 16, so that Address 0 is signified by 17 rising
edges, Address 1 by 18 rising edges, and so forth.
Data is set to any number of rising edges between
1 and including 16. A typical write protocol is a
burst of EN/SET rising edges, signifying a particu-
lar address, followed by a pause with EN/SET held
high for the TLAT timeout period, a burst of rising
edges signifying data, and a TLAT timeout for the
data registers. Once an address is set, then multi-
ple writes to that address are allowed where only
data is issued. When EN/SET is held low for an
amount of time longer than TOFF (500µs), the
AAT1235 enters into shutdown mode and draws
less than 1µA from the input. Data and Address
registers are cleared (reset to 0) during shutdown.
Address
0
1
2
3
4
EN/SET
Rising Edges
17
18
19
20
21
Data
Register
B1-B2 current
A1-A3 current
B1-B2 on/off
A1-A3 on/off
A1-A3, B1-B2 on
Table 1: AS2Cwire Serial Interface Addressing.
Address 0 and 1: LED Brightness Control
Outputs A1, A2, A3, B1, B2 are each capable of
sinking up to 30mA. The maximum current can be
programmed by an external resistor at the RSET
pin. It is suggested to connect up to four white
LEDs in series for each channel and to keep the
same number of LEDs in each channel.
Outputs B1 and B2 are intended to drive the white
LEDs for the backlight in a phone, while A1:A3 can
supply the keypad LEDs. For large displays, all five
outputs can be used.
Data
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
All Outputs (%)
100
84
71
60
51
43
35
31
26
21
18
15
13.5
12.0
10.5
9.0
Table 2: Address 0 and 1 for Current Setting as
Percentage of the Maximum Level Set by RSET.
Address 2: LED Group B ON/OFF
Control
Data
1
2
3
4
B1
Off
Off
On
On
B2
Off
On
Off
On
Table 3: Address 2 for Group B ON/OFF State.
1235.2007.02.1.1
11
11 Page | ||
| Páginas | Total 21 Páginas | |
| PDF Descargar | [ Datasheet AAT1235.PDF ] | |
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