Analogic AAT2834 240ma total display solution for portable device Datasheet

AAT2833/34
240mA Total Display Solution
for Portable Devices
General Description
Features
The AAT2833/34 is a total solution IC for portable
display applications. Based on a tri-mode charge
pump power engine, it is capable of delivering
240mA of output current for white LED (WLED)
backlight and RGB applications. The high conversion efficiency and high level of integration make the
AAT2833/34 an optimal solution for battery life and
size-critical applications.
•
•
•
AnalogicTech's AS2Cwire™ (Advanced Simple
Serial Control™) serial digital interface is used to
enable, disable, and set current levels for all of the
light emitting diodes (LEDs). Each backlight channel can be programmed to 16 levels of current, from
a recommended maximum of 30mA programmed by
the RBSET resistor. The RGB module can be adjusted to 8 levels of current, up to a recommended maximum of 60mA. The RGB module is programmable
with up to 4096 (AAT2833) or 64 (AAT2834)
color/intensity (brightness) combinations.
•
The AAT2833/34 is offered in a Pb-free, thermally
enhanced 24-pin 4x4x0.75mm TQFN package.
•
•
•
•
•
Applications
•
•
•
•
•
ChargePump™
Input Supply Voltage Range: 2.7V to 5.5V
Tri-Mode (1X/1.5X/2X) Charge Pump:
— Delivers up to 240mA of Output Current
— Switching Frequency: Up to 2MHz
Total Display Solution for RGB and Backlight
Applications
— 6-Channel Backlight WLED Backlight
• User-Programmable Full-Scale Current,
up to 30mA
— 3-Channel RGB
• User-Programmable Full-Scale Output
Current/Duty Cycle
• AAT2833: 4096 Color/Intensity
Combinations
• AAT2834: 64 Color/Intensity
Combinations
Single-Wire AS2Cwire Serial Interface for
Configuration/Control
— Eleven Addressable Registers
— Fast, 1MHz Serial Interface
True Load Disconnect in Shutdown, IIN < 1µA
Built-in Thermal Protection
Built-in Auto-Disable for Open LED Condition
Automatic Soft-Start Minimizes Inrush Current
Available in 4x4x0.75mm TQFN44-24 Package
Digital Still Cameras
LCD Display Modules
MP3 Players
White LED Drivers
Wireless Handsets
Typical Application
RGB LED
COUT
2.2μF
OUT BL1
IN
VBATTERY
Single-cell Li+
EN/SET
CIN
2.2μF
AS2Cwire
Serial Control
2833.2007.09.1.0
BL2 BL3 BL4 BL5 BL 6
R G B
BSET
AAT2833/34
C1+ C1- C2+ C2-
C1
1μF
PGND
AGND
RBSET
280kΩ
C2
1μF
1
AAT2833/34
240mA Total Display Solution
for Portable Devices
Pin Description
Pin #
Symbol
Function
1
2
3
4
5, 17, 18, 19, 20
6
7
8
9
10
11
12
13
14
15
16
21
BL3
BL2
BL1
AGND
N/C
EN/SET
R
G
B
C2+
C2OUT
IN
C1+
C1PGND
BSET
22
23
24
EP
BL6
BL5
BL4
Power return (cathode) for backlight channel 3. If not used, connect to the OUT pin.
Power return (cathode) for backlight channel 2. If not used, connect to the OUT pin.
Power return (cathode) for backlight channel 1. If not used, connect to the OUT pin.
Signal ground.
Not connected.
Enable and AS2Cwire serial interface control input.
Power return (cathode) for Red LED of the RGB module.
Power return (cathode) for Green LED of the RGB module.
Power return (cathode) for Blue LED of the RGB module.
Positive node of flying capacitor 2.
Negative node of flying capacitor 2.
Output voltage pin. Connect to anode of all LEDs.
Input voltage pin.
Positive node of flying capacitor 1.
Negative node of flying capacitor 1.
Power ground.
Maximum backlight current programming resistor input. Ground this pin to use
default values.
Power return (cathode) for backlight channel 6. If not used, connect to the OUT pin.
Power return (cathode) for backlight channel 5. If not used, connect to the OUT pin.
Power return (cathode) for backlight channel 4. If not used, connect to the OUT pin.
Exposed pad (bottom); connect to GND directly beneath the package.
Pin Configuration
TQFN44-24
(Top View)
N/C
N/C
BSET
BL6
BL5
BL4
19
20
21
22
23
24
BL3
BL2
BL1
AGND
N/C
EN/SET
1
18
2
17
3
16
4
15
5
14
6
13
N/C
N/C
PGND
C1C1+
IN
12
11
9
10
8
7
OUT
C2C2+
B
G
R
2
2833.2007.09.1.0
AAT2833/34
240mA Total Display Solution
for Portable Devices
Absolute Maximum Ratings1
TA = 25°C, unless otherwise noted.
Symbol
VN
VN
VN
TJ
TLEAD
Description
[OUT, IN, BL1, BL2, BL3, BL4, BL5, BL6, R, G, B] to GND
[C1+, C2+] to GND
[EN/SET, BSET, C1-, C2-] to GND
Operating Junction Temperature Range
Maximum Soldering Temperature (at leads, 10 sec)
Value
Units
-0.3 to 6.0
-0.3 to VOUT + 0.3
-0.3 to VIN + 0.3
-40 to +150
300
V
V
V
°C
°C
Value
Units
50
2.0
°C/W
W
Value
Units
-40 to +85
°C
Thermal Characteristics2
Symbol
θJA
PD
Description
Maximum Thermal Resistance
Maximum Power Dissipation
Recommended Operating Conditions
Symbol
T
Description
Ambient Temperature Range
1. Stresses above those listed in Absolute Maximum Ratings may cause damage to the device. Functional operation at conditions other
than the operating conditions specified is not implied. Only one Absolute Maximum Rating should be applied at any one time.
2. Mounted on a demo board (FR4, in still air).
2833.2007.09.1.0
3
AAT2833/34
240mA Total Display Solution
for Portable Devices
Electrical Characteristics1
VIN = 3.6V; CIN = 4.7µF; C1 = C2 = 1µF; COUT = 2.2µF; TA = -40°C to +85°C, unless otherwise noted. Typical
values are TA = 25°C.
Symbol
Description
Conditions
Charge Pump Section
VIN
IN Operating Supply Voltage Range
IIN
IN Operating Supply Current
ISHDN
IOUT
IN Shutdown Current
OUT Maximum Output Current
BL1-BL6, RGB Charge Pump
VTH(HYS)
Mode Transition Hysteresis
VBSET
BSET Pin Voltage
fOSC
Charge Pump Oscillator Frequency
tSS
Charge Pump Soft-Start Delay
TSD
Over-Temperature Shutdown Threshold
TSD(HYS)
Over-Temperature Shutdown Hysteresis
BL1-BL6 Backlight LED Outputs
IBL_(MAX)
BL1-BL6 Maximum Current
ΔIBL
BL1-BL6 Current Matching2
Min Typ Max Units
2.7
Address = 0, Data = 1,
VIN - VF = 1.5V
Address = 0, Data = 1,
VIN - VF = 1.5V
4
mA
5
0.3
1
27
BL1-BL6 Charge Pump Mode
Transition Threshold
RGB LED Outputs
R-G-B Maximum Current
VRGB_(TH)
RGB Charge Pump Mode
Transition Threshold
240
µA
mA
500
mV
0.7
2
200
140
15
V
MHz
µs
°C
°C
30
33
mA
1
%
100
Address = 12, Data = 7,
VIN - VF = 1.5V
V
0.6
VBL_(TH)
IRGB_(MAX)
5.5
1X Mode, Address = 0, Data = 1,
VEN/SET = VIN
1.5X Mode, Address = 0, Data = 1,
VEN/SET = VIN
2X Mode, Address = 0, Data = 1,
VEN/SET = VIN
1X LL Mode, Address = 3,
Data = 1, VEN/SET = VIN
VEN/SET = 0V, TA = 25°C
51
60
100
mV
69
mA
mV
1. The AAT2833/34 is guaranteed to meet performance specifications over the -40°C to +85°C operating temperature range and is
assured by design, characterization, and correlation with statistical process controls.
2. Current matching is defined as the deviation of any sink current from the average of all active channels.
4
2833.2007.09.1.0
AAT2833/34
240mA Total Display Solution
for Portable Devices
Electrical Characteristics1
VIN = 3.6V; CIN = 4.7µF; C1 = C2 = 1µF; COUT = 2.2µF; TA = -40°C to +85°C, unless otherwise noted. Typical
values are TA = 25°C.
Symbol
EN/SET Logic
VENS(L)
VENS(H)
IEN/SET
TEN/SET_LO
TEN/SET_HI_MIN
TEN/SET_HI_MAX
TOFF
TLAT
2833.2007.09.1.0
Description
Control
EN/SET Input Low Threshold Voltage
EN/SET Input High Threshold Voltage
EN/SET Input Leakage Current
EN/SET Low Time
Minimum EN/SET High Time
Maximum EN/SET High Time
EN/SET Off Timeout
EN/SET Latch Timeout
Conditions
Min Typ Max Units
0.4
1.4
-1
0.3
1
75
50
75
500
500
V
V
µA
µs
ns
µs
µs
µs
5
AAT2833/34
240mA Total Display Solution
for Portable Devices
Typical Characteristics
AAT2833 Backlight Section Efficiency
Backlight Current Matching vs. Temperature
32
100
30mA/Channel
19mA/Channel
80
70
60
50
2.1mA/Channel
40
LED Current (mA)
Efficiency (%)
90
31.5
31
30.5
Channel 5 Channel 6
30
29.5
29
Channel 3
28.5
30
2.7
3.1
3.5
3.9
4.3
4.7
5.1
Channel 4
28
-40
5.5
Channel 1
-15
10
Input Voltage (V)
85
140
450
120
400
Threshold (mV)
Hysteresis (mV)
60
BL1-BL6 Mode Transition Threshold
vs. Current Setting
500
350
300
250
200
150
100
100
80
60
40
20
50
0
2
0
2
4
6
8
10
12
14
16
25°C
-40°C
1.1
1.0
0.9
0.8
0.7
85°C
0.6
0.5
0.4
0.3
0.2
2.7
3.1
3.5
3.9
4.3
Input Voltage (V)
4.7
5.1
6
8
10
12
14
16
EN/SET Low Threshold Voltage
vs. Input Voltage
EN/SET Low Threshold (V)
EN/SET High Threshold Voltage
vs. Input Voltage
1.2
4
Current Setting (Address 0, Data #)
Current Setting (Address 0, Data #)
EN/SET High Threshold (V)
35
Temperature (°C)
1X Mode Hysteresis vs. Current Settings
6
Channel 2
5.5
1.2
25°C
-40°C
1.1
1.0
0.9
0.8
0.7
85°C
0.6
0.5
0.4
0.3
0.2
2.7
3.1
3.5
3.9
4.3
4.7
5.1
5.5
Input Voltage (V)
2833.2007.09.1.0
AAT2833/34
240mA Total Display Solution
for Portable Devices
Typical Characteristics
EN/SET Latch Timeout vs. Input Voltage
500
600
450
550
500
400
25°C
TOFF (µs)
TLAT (µs)
EN/SET Off Timeout vs. Input Voltage
85°C
350
300
-40°C
250
25°C
450
-40°C
85°C
400
350
300
250
200
150
2.7
200
3.1
3.5
3.9
4.3
4.7
5.1
5.5
150
2.7
3.1
Input Voltage (V)
3.5
3.9
4.3
4.7
5.1
5.5
Input Voltage (V)
Turn On to 1X Mode Backlight
Turn On to 1.5X Mode Backlight
(30mA/channel; Address 0, Data 16; VIN = 4.4V)
(30mA/channel; Address 0, Data 16; VIN = 3.5V)
VEN/SET
(2V/div)
VEN/SET
(2V/div)
VOUT
(2V/div)
VOUT
(2V/div)
VBLX
(0.5V/div)
VBLX
(0.5V/div)
IIN
(0.1A/div)
IIN
(0.2A/div)
Time (200µs/div)
Time (200µs/div)
Turn On to 2X Mode Backlight
Turn Off from 1.5X Mode Backlight
(30mA/channel; Address 0, Data 16; VIN = 2.7V)
(30mA/channel; Address 0, Data 16)
VEN/SET
(2V/div)
VEN/SET
(2V/div)
VOUT
(2V/div)
VDIODE
(2V/div)
VBLX
(0.5V/div)
ILED
(0.02A/div)
IIN
(0.2A/div)
Time (200µs/div)
2833.2007.09.1.0
Time (100µs/div)
7
AAT2833/34
240mA Total Display Solution
for Portable Devices
Typical Characteristics
Operating Characteristics
Operating Characteristics
(VIN = 3.4V; 1.5X Mode;
30mA/channel; AC Coupled)
(VIN = 2.7V; 2X Mode;
30mA/channel; AC Coupled)
VIN
(100mV/div)
VIN
(100mV/div)
VOUT
(100mV/div)
VOUT
(100mV/div)
IIN
(20mA/div)
IIN
(20mA/div)
Time (500ns/div)
8
Time (500µs/div)
2833.2007.09.1.0
AAT2833/34
240mA Total Display Solution
for Portable Devices
Functional Block Diagram
C1+ C1–
IN
C2+ C2–
OUT
Tri-Mode Charge
Pump Control
VF Monitoring
3
6
PGND
BL1
EN/SET
AS2Cwire
Control
Main Ref
BL2
BL3
BL4
Sub Ref
BL5
BL6
BSET
DAC
R
RGB Ref
G
B
AGND
Functional Description
The AAT2833/34 is a multi-functional power solution for display systems in portable devices. It
includes six individual channels for backlight white
LEDs, and three individual channels for RGB LEDs.
All of these functionalities are powered by a highly
efficient tri-mode charge pump power engine that is
capable of delivering 240mA of output current.
The six backlight channels can be turned on or off
all together, in two groups, or individually. The twogroup operation allows LEDs to be turned on and
off in for dual display applications: the main display
(BL1-BL4) and sub-display (B5-B6). The individual
on/off feature supports applications other than
main/sub-display backlighting, such as keypad
lighting. The maximum backlight current is programmable with an external resistor, RBSET.
The RGB channels can be programmed with up to
4096 or 64 different combinations of colors and lighting intensities (brightness). R, G, and B channels
are individually controlled and can be used for alternative functions, such as keyboard lighting, "fun"
lighting, etc.
2833.2007.09.1.0
AS2Cwire Serial Interface
Each current channel input on the AAT2833/34 is
controlled by AnalogicTech's AS2Cwire serial digital
interface. The AS2Cwire interface uses the number
of rising edges on the EN/SET pin to address and
load the LED configuration registers. AS2Cwire
latches data or addresses after the EN/SET pin has
been held logic high for longer than TLAT (500µs).
Addresses and data are 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, Address 2 by
19 rising edges, and so on. Data is set to any number of rising edges between 1 and including 16.
A typical write protocol consist of the following: first
a burst of EN/SET rising edges that identify/target a
particular address followed by EN/SET being held
logic high for the TLAT timeout period to latch the
address value in the registers, then another burst of
rising edges that signify data with the accompanying
TLAT timeout period to latch the data value in the registers. Once an address is set, then multiple writes
to the corresponding data register are allowed without having to write to the address for every change
9
AAT2833/34
240mA Total Display Solution
for Portable Devices
in data values. When EN/SET is held low longer
than TOFF (500µs), the AAT2833/34 enters shutdown
mode operation and draws less than 1µA from the
input supply voltage. Data and address registers are
cleared (reset to 0) in shutdown mode operation.
Table 1a contains the AS2Cwire serial interface
address functionality when independent channel
control is disabled (independent channel control is
disabled by default) and conversely Table 1b contains the AS2Cwire serial interface address functionality when independent channel control is enabled.
EN/SET
Rising
Address Edges
0
1
2
3
7
8
9
10
11
12
15
17
18
Function
Backlight Current BL1-BL6
Main Backlight Current
BL1-BL4
Sub Backlight Current BL5-BL6
Low Backlight Current
Red Color
Green Color
Blue Color
RGB Intensity
RGB Mode
RGB Current
Backlight Independent
Channel Control
19
20
24
25
26
27
28
29
32
Table 1a: AS2Cwire Serial Interface Addressing
with Independent Channel Control Disabled.
Backlight Current Control
(Addresses 0-2)
The six channel backlight inputs, BL1-BL6, can
drive six individual LEDs to a maximum current of
30mA per channel. The EN/SET AS2Cwire serial
interface enables all channels and sets the current
magnitude as a percentage of the maximum current, programmed by an external resistor at BSET
(see Figure 4). To set the backlight current (minimum to maximum current) of the main display
LEDs (BL1-BL4), the user would write data to
Address 1. To set the backlight current for the sub
display LEDs (BL5-BL6), the user would write data
to Address 2. To write to both main display and sub
display LEDs (BL1-BL6) at the same time, the user
would write to Address 0.
Data BL % of BSET
1
2
3
4
5
6
7
8
0
21
22
25
29
32
35
40
Address
Function
0
1
2
3
7
8
9
10
11
12
15
17
18
19
20
24
25
26
27
28
29
32
Not Applicable
Backlight Current BL1-BL6
BL1-BL4 On/Off Control
BL5-BL6 On/Off Control
Red Color
Green Color
Blue Color
RGB Intensity
RGB Mode
RGB Current
Not Applicable
BL % of BSET
9
10
11
12
13
14
15
16
44
51
56
63
71
79
89
100
Table 2a: Addresses 0-2 with Independent
Channel Control Disabled, Backlight
Current Level.
Data BL % of BSET
EN/SET
Rising
Edges
Data
1
2
3
4
5
6
7
8
0
21
22
25
29
32
35
40
Data
BL % of BSET
9
10
11
12
13
14
15
16
44
51
56
63
71
79
89
100
Table 2b: Address 1 with Independent
Channel Control Enabled, Backlight
Current Level.
Table 1b: AS2Cwire Serial Interface Addressing
with Independent Channel Control Enabled.
10
2833.2007.09.1.0
AAT2833/34
240mA Total Display Solution
for Portable Devices
Backlight Independent Channel Control
(Address 15)
IBLED (% of BSET)
120
100
80
60
40
20
0
1
2
3
4
5
6
7
8
9
10
11
12 13
14 15
16
Data Code
Figure 1: Addresses 0-2 Backlight Current Level.
The AAT2833/34 can also individually control each
backlight channel. This mode allows the user to turn
on some or all of the channels in any desired combination. This control is achieved by changing the
functionality of the AS2Cwire registers. To enable
individual LED control mode, a user would write
Data 8 to Address 15. All channels that are enabled
must carry the same current, which is set using the
new functionality of Address 1 (see Table 2b).
Data
Individual BL Control
8
On
Low Backlight Current (Address 3)
In addition to the current levels set by Addresses 0,
1, and 2 (shown in Table 2a and Figure 1), there is
also a low backlight current level that can be set. To
set the low backlight current level, the user would
write data to Address 3, as shown in Table 3.
For example, to toggle between 1.7% and 25% of the
maximum backlight current on all LEDs, write Data =
14 to Address 3 and Data 4 to Address 0. To set BL1BL4 to 25% and BL5-BL6 to 0.2%, write Data = 5 to
Address 3, and Data = 4 to Address 2.
Data
BL1-BL4
Current On
BL5-BL6
Current On
BL %
of BSET
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
No
No
No
No
No
No
No
No
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
No
No
No
No
Yes
Yes
Yes
Yes
No
No
No
No
Yes
Yes
Yes
Yes
0
0
0
0
0.2
1.7
3.5
7.0
0.2
1.7
3.5
7.0
0.2
1.7
3.5
7.0
Table 4: Address 15, Backlight Independent
Channel Control
Data
BL6
BL5
BL4
BL3
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
Off
Off
Off
Off
Off
Off
Off
Off
On
On
On
On
On
On
On
On
Off
Off
Off
Off
On
On
On
On
Off
Off
Off
Off
On
On
On
On
Off
Off
On
On
Off
Off
On
On
Off
Off
On
On
Off
Off
On
On
Off
On
Off
On
Off
On
Off
On
Off
On
Off
On
Off
On
Off
On
Table 5: Address 2 with Independent
Channel Control Enabled, BL3-BL6
On/Off Control.
Table 3: Address 3 with Independent Channel
Control Disabled, Low-Backlight Current
Levels (RBSET = 280kΩ).
2833.2007.09.1.0
11
AAT2833/34
240mA Total Display Solution
for Portable Devices
Data
BL2
BL1
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
Off
Off
Off
Off
Off
Off
Off
Off
On
On
On
On
On
On
On
On
Off
Off
Off
Off
On
On
On
On
Off
Off
Off
Off
On
On
On
On
With independent channel control enabled, the
functionality of Addresses 1, 2, and 3 will conform to
what is described in Tables 2b, 5, and 6. Also,
Addresses 0 and 15 are no longer applicable after
independent channel control has been enabled. As
indicated by the possible settings listed in the
tables, any combination of backlight channels can
be enabled and disabled. The original functionalities (Sub Backlight Current BL5-BL6 and Low
Backlight Current) of Addresses 2 and 3 are no
longer available unless the internal state machine
has been reset to default mode operation (when
EN/SET is logic low for >500µs). The functionality
of Addresses 7-12 are unmodified by the enabling of
independent channel control.
Table 6: Address 3 with Independent
Channel Control Enabled, BL1-BL2
On/Off Control.
Data
Address
THI
TLO
TLAT
EN/SET
1
Address
2
17
18
1
0
2...
n ≤ 16
1
DATA1
1
DATA0
1
n
Figure 2: AS2Cwire Serial Interface Timing Details.
12
2833.2007.09.1.0
AAT2833/34
240mA Total Display Solution
for Portable Devices
RGB Control
The Red, Green, and Blue LED PWM timing, along
with the overall period, is controlled by five registers.
The current level for the RGB LEDs is controlled by
another register (Address 12) which makes it possible to change the peak currents from 33% up to
200% of the backlight maximum current set by
RBSET. A mode register (Address 11) sets the
method of update for the color and intensity registers. All registers are updated simultaneously or individually, depending on how the mode register is set.
If updated simultaneously, the color registers are
updated when the period register is updated. Up to
4096 different color/brightness combinations are programmable in the AAT2833 and 64 color/brightness
combinations are programmable in the AAT2834.
Address 7, 8, 9: RGB Color Registers
The AAT2833's RGB color registers store up to 16
levels of lighting intensity for a given color channel.
The first level (DATA = 1) is reserved for the off-state.
Every setting thereafter increases the on-time of the
respective LED by 128µs. The settings can be calculated as follows:
R = (DATA7 - 1) · 128μs
G = (DATA8 - 1) · 128μs
B = (DATA9 - 1) · 128μs
Where R, G, and B are the on-times of the respective LEDs and DATA7, DATA8, and DATA9 are the
data inputs into Registers 7, 8, and 9, respectively.
DATAN can be set to a value from 1 to 16 with the
default DATAN value equal to 1. Since the AAT2834
supports 64 color/brightness combinations, DATAN
can be set from 1 to 4.
Address 10: RGB Timebase Register - T
The overall period is set by the AAT2833/34's T register. Adjusting this register allows a user to adjust
how often the RGB LED sequence is repeated. The
longer the period, the smaller the effective duty cycle,
and thus RGB light intensity (brightness) is reduced.
2833.2007.09.1.0
The RGB period can be calculated using the following equation:
T = [(DATA10 - 1) · 3 + 15] · 128μs
Where T is the period of repetition and DATA10 is
the data input into Register 10. In the AAT2833,
DATA10 can be set to a value from 1 to 16, with the
default DATA10 value equal to 1. In the AAT2834,
DATA10 can be set from 1 to 4, with the default
DATA10 value equal to 1.
Please note that if the user sets the period to be
smaller than the combined on-times (R+G+B),
then the RGB sequence will automatically begin
again once time T has been reached, whether or
not all on-times have been completed.
Address 11: RGB Mode Register
The AAT2833/34's RGB mode register can have
one of two DATA11 values. If DATA11 is set to 1 (the
default), then each RGB LED on-time will be updated immediately after their respective register is set.
If DATA11 is set to 2, then as the user sets the Red,
Green, and Blue on-time registers, none of the
LEDs will be updated until the timebase register is
set. For example, if the user wants to set a certain
Red-Green-Blue combinations, the Red on-time
can be programmed first, followed by the Green ontime, followed by the Blue on-time, and then the
RGB period T last. If DATA11 is set to 1, then after
the Red on-time is programmed the user will see
the Red LED turn on immediately. After the Green
on-time is programmed, the Red-Green color combinations will appear, etc. If DATA11 is set to 2, then
none of those intermediate colors will appear until
the RGB period register T has been set and loaded.
Address 12: RGB Current Level Register, ISINK
The ISINK current level in the RGB LED can be
adjusted by writing data to Register 12. The maximum current is two times (200%) the maximum
backlight current set by RBSET (see Table 7). By
increasing or decreasing the current, the brightness
level can easily be changed for any particular color
combination.
13
AAT2833/34
240mA Total Display Solution
for Portable Devices
Data
RGB Current as % of BSET
1
2
3
4
5
6
7
0
33
66
100
133
167
200
IR = ISINK ·
R
T
G
T
B
IB = ISINK ·
T
IG = ISINK ·
Shutdown
Table 7: Address 12, RGB Current Level
Register (ISINK).
RGB LED Current Calculation
The average current in a particular color channel is
a function of the values in the R, G, B, T, and ISINK
registers, as follows:
Since the channel backlight power returns are the
only power returns for all the LEDs, there is no
leakage current if all channels are disabled.
Applying a HIGH-to-LOW transition on the EN/SET
pin and holding LOW for at least TOFF (500µs) will
activate the AAT2833/34's shutdown mode. Data
and Address registers are cleared (reset to 0) during shutdown.
R
Red
ISINK
ISINK
T
G
Green
ISINK
B
Blue
ISINK
Figure 3: RGB Diode Current Timing.
14
2833.2007.09.1.0
AAT2833/34
240mA Total Display Solution
for Portable Devices
Applications Information
Adjusting the Maximum Backlight LED
Current Level
The value of RBSET determines the maximum LED
current level for the backlight section. In the typical
application, selecting RBSET = 280kΩ results in a
maximum 30mA/channel LED current level.
The relationship between RBSET and the maximum
backlight current is illustrated graphically in Figure 4.
The AAT2833/34's LED current control circuits have
been optimized for full-scale current settings higher
than 15mA, RBSET > 550kΩ.
PLEDs VLED1 · ILED1 + ... + VLED4 · ILED4
=
PIN
VIN · IIN
η=
4 · VLEDX · ILEDX
; x = 1, 2, 3 or 4 and IIN = 4 · ILEDX
VIN · IIN
VLEDX
η= V
IN
Due to the very low 1X mode quiescent current, the
input current nearly equals the total output current
delivered to the LEDs. Further, the low resistance
bypass switch introduces a negligible voltage drop
from input to output.
The AAT2833/34 further maintains optimized performance and efficiency by detecting when the
input voltage is not sufficient to sustain the LED
bias current. The device automatically switches to
1.5X mode when the input voltage drops too low in
relation to the LED forward voltages.
45
40
35
IBLED (mA)
η=
30
25
20
15
10
5
0
100
200
300
400
500
600
700
800
900
1000
RBSET (kΩ
Ω)
Figure 4: Maximum Backlight LED
Current vs RBSET.
Device Power Efficiency
The AAT2833/34's power conversion efficiency
depends on the charge pump mode of operation.
By definition, device efficiency is expressed as the
output power delivered to the LEDs divided by the
total input power consumed.
η=
PLEDs VLED1 · ILED1 + ... + VLED4 · ILED4
=
PIN
VIN · IIN
When the input voltage is sufficiently greater than
the LED forward voltages, the device optimizes
efficiency by operating in 1X mode. In 1X mode,
the device is working as a bypass switch and passing the input supply directly to the output. By simplifying the conditions such that the LEDs have uniform VF, the power conversion efficiency can be
approximated by:
2833.2007.09.1.0
In 1.5X mode, the output voltage can be boosted to
1.5X the input voltage. The 1.5X conversion ratio
introduces a corresponding 0.5X increase in input
current. For ideal conversion, the 1.5X mode efficiency is given by:
η=
η=
PLEDs VLED1 · ILED1 + ... + VLED4 · ILED4
=
PIN
VIN · IIN
4 · VLEDX · ILEDX
; x = 1, 2, 3 or 4 and IIN = 1.5(4 · ILEDX)
VIN · IIN
VLEDX
η = 1.5V
IN
Similarly, when the input falls further, such that
1.5X mode can no longer sustain the LED bias currents, the AAT2833/34 will automatically switch to
2X mode. In 2X mode, the output voltage can be
boosted to 2X the input voltage. The 2X conversion
ratio introduces a corresponding 1X increase in
input current. For ideal conversion, the 2X mode
efficiency is given by:
η=
PLEDs VLED1 · ILED1 + ... + VLED4 · ILED4
=
PIN
VIN · IIN
η=
4 · VLEDX · ILEDX
; x = 1, 2, 3 or 4 and IIN = 2(4 · ILEDX)
VIN · IIN
VLEDX
η = 2V
IN
15
AAT2833/34
240mA Total Display Solution
for Portable Devices
LED Selection
PCB Layout
The AAT2833/34 is designed to drive high-intensity
white LEDs. It is particularly suitable for LEDs with
an operating forward voltage in the range of 4.2V
to 1.5V.
To achieve adequate electrical and thermal performance, careful attention must be given to the
printed circuit board (PCB) layout. In the worst-case
operating condition, the chip must dissipate considerable power at full load. Adequate heat-sinking
must be achieved to ensure intended operation.
The AAT2833/34 can also drive other loads that
have similar characteristics to white LEDs. For various load types, the AAT2833/34 provides a high
current, programmable, ideal constant current
channel/sink.
Capacitor Selection
Careful selection of the four external capacitors
CIN, C1, C2, and COUT are important because they
will affect turn-on time, output ripple, and transient
performance. Optimum performance will be
obtained when low equivalent series resistance
(ESR) ceramic capacitors are used. In general, low
ESR is defined as a resistance that is less than
100mΩ.
X7R and X5R ceramic capacitors are highly recommended over all other types of capacitors for
use with the AAT2833/34. For the input (CIN) and
output (COUT) capacitors, a 2.2µF or greater value
is recommended, and a 1µF or greater value is recommended for the flying (C1/C2) capacitors.
Ceramic capacitors offer many advantages over
their tantalum and aluminum electrolytic counterparts. A ceramic capacitor typically has very low
ESR, is lowest cost, has a smaller PCB footprint,
and is non-polarized. Low ESR ceramic capacitors
help maximize charge pump transient response.
16
Figures 6 and 7 illustrate an example PCB layout.
The bottom of the package features an exposed
metal pad. The exposed pad acts, thermally, to
transfer heat from the chip and, electrically, as a
ground connection.
The junction-to-ambient thermal resistance (θJA) for
the AAT2833/34 package can be significantly
reduced by following a couple of important PCB
design guidelines. The PCB area directly underneath the package should be plated so that the
exposed pad can be mated to the top layer PCB
copper during the reflow process. Multiple copper
plated thru-holes should be used to electrically and
thermally connect the AAT2833/34’s exposed pad
area to additional ground plane(s).
The chip ground is internally connected to both the
paddle and to the AGND and PGND pins. It is good
practice to connect the GND pins to the exposed
pad area with traces as shown in Figure 5.
The flying capacitors (C1 and C2), input capacitor
(C4), and output capacitor (C3) should be connected as close as possible to the IC. In addition to the
external passive components being placed as
close as possible to the IC, all traces connecting
the AAT2833/34 should be as short and wide as
possible to minimize path resistance and potential
coupling.
2833.2007.09.1.0
AAT2833/34
240mA Total Display Solution
for Portable Devices
Pin #1
Figure 5: AAT2833/34 Package PCB Layout.
Evaluation Board Layout
Figure 6: AAT2833/34 Evaluation Board
Component Side Layout.
2833.2007.09.1.0
Figure 7: AAT2833/34 Evaluation Board
Solder Side Layout.
17
AAT2833/34
240mA Total Display Solution
for Portable Devices
Evaluation Board Schematic
VOUT
D1
D2
D3
D4
D5
D6
DC+
VIN
R9 = 280K for
30mA/chnl backlight.
J1
R9
280K
C7
5
6
N/C
N/C
BL6
BSET
N/C
BL2
N/C
BL1
PGND
AGND
C1-
N/C
C1+
EN/SET
VIN
8
9
10
C2
1.0μF
4
3
7
Optional footprints for
R
auxiliary lighting LEDs .
U1
AA T2833
BL3
R
EN
19
11
18
17
16
15
C1
14
1.0μF
13
OUT
4
20
C2-
3
21
C2+
2
G
1
22
BL5
23
BL4
24
B
Optional 100μF
lab supply bypass
C4
4.7μF
12
C3
2.2μF
RGB
G
B
Figure 8: AAT2833/34 Evaluation Board Schematic.
R7
EN
220
J2
R8
100K
VIN
VIN
R1 R2 R3 R4 R5
1K 1K 1K 1K 1K
U2
SW1
SW2
1
2
3
4
VDD
GP5
GP4
GP3
VSS
GP0
GP1
GP2
8
7
6
5
C6
1μF
R6
330
PIC12F675
LED7
RED
SW3
SW4
SW5
Figure 9: AAT2833/34 Microcontroller Section Schematic.
18
2833.2007.09.1.0
AAT2833/34
240mA Total Display Solution
for Portable Devices
Options
Option
Flash
Backlight
RGB
Package
AAT2833
AAT28343
N
N
Y
Y
Y
Y
TQFN44-24
TQFN44-24
Function
Backlight Plus 4096-Combination RGB
Backlight Plus 64-Combination RGB
Ordering Information
Package
Marking1
Part Number (Tape and Reel)2
TQFN44-24
TQFN44-24
SVXYY
AAT2833IBK-T1
AAT2834IBK-T13
All AnalogicTech products are offered in Pb-free packaging. The term “Pb-free” means
semiconductor products that are in compliance with current RoHS standards, including
the requirement that lead not exceed 0.1% by weight in homogeneous materials. For more
information, please visit our website at http://www.analogictech.com/pbfree.
1. XYY = assembly and date code.
2. Sample stock is generally held on part numbers listed in BOLD.
3. Contact factory for AAT2834 availability.
2833.2007.09.1.0
19
AAT2833/34
240mA Total Display Solution
for Portable Devices
Package Information
Pin 1 Identification
Chamfer 0.300 ×45°
0.255 ± 0.025
1
2.700 ± 0.050
4.000 ± 0.050
2.700 ± 0.050
Top View
0.000 −0.050
Bottom View
0.214 ± 0.036
0.750 ± 0.050
4.000 ± 0.050
Pin 1 Dot By Marking
0.500 BSC
0.400 ± 0.050
TQFN44-24
Side View
All dimensions in millimeters.
© Advanced Analogic Technologies, Inc.
AnalogicTech cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in an AnalogicTech product. No circuit patent licenses, copyrights, mask work
rights, or other intellectual property rights are implied. AnalogicTech reserves the right to make changes to their products or specifications or to discontinue any product or service without notice. Except as provided in AnalogicTech’s terms and conditions of sale, AnalogicTech assumes no liability whatsoever, and AnalogicTech disclaims any express or implied warranty relating to the sale and/or use of AnalogicTech products including liability or warranties relating to fitness for a particular purpose, merchantability, or infringement of any patent,
copyright or other intellectual property right. In order to minimize risks associated with the customer’s applications, adequate design and operating safeguards must be provided by the
customer to minimize inherent or procedural hazards. Testing and other quality control techniques are utilized to the extent AnalogicTech deems necessary to support this warranty.
Specific testing of all parameters of each device is not necessarily performed. AnalogicTech and the AnalogicTech logo are trademarks of Advanced Analogic Technologies Incorporated.
All other brand and product names appearing in this document are registered trademarks or trademarks of their respective holders.
Advanced Analogic Technologies, Inc.
3230 Scott Boulevard, Santa Clara, CA 95054
Phone (408) 737- 4600
Fax (408) 737- 4611
20
2833.2007.09.1.0