EVALUATION BOARD DATA SHEET

EVALUATION BOARD DATA SHEET
EV183
Evaluation Board for the AAT2822/2823/2824/2825
TFT-LCD DC-DC Converter with WLED Driver and VCOM Buffer
Introduction
The AAT282x family (AAT2822, AAT2823, AAT2824, AAT2825) of integrated panel power solutions provides the regulated voltages required by an active-matrix thin-film transistor (TFT) liquid-crystal display (LCD). The AAT282x family
includes a boost DC-DC converter for LCD bias up to 14.5V, two charge pumps up to ±30V, a WLED backlight driver
up to 28V, and a VCOM buffer in a 4 mm x 4mm TQFN package. The AAT282x have power sequence of VAVDD -> VGH
-> VGL. The AAT282x-1 have power sequence of VAVDD -> VGL -> VGH.
This document highlights the use of the AAT282x family evaluation board to demonstrate the functions and performance of the AAT282x power ICs. A brief “Getting Started” section is included to help the user to set up and operate
the evaluation board. The board is shown in Figure 1. Figure 2 and Figure 15 depict the board schematic and layout.
For additional information, refer to the AAT282x product datasheets.
Board Pictures
(a) Top
(b) Bottom
Figure 1: AAT282xIBK Evaluation Board.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
202319A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • August 30, 2012
1
EVALUATION BOARD DATA SHEET
EV183
Evaluation Board for the AAT2822/2823/2824/2825
TFT-LCD DC-DC Converter with WLED Driver and VCOM Buffer
Board Schematic
WLED-
VIN
10V C1
4.7μF
VIN-WLED
R20
0Ω
J3
C4
HF-PWM
R1
0Ω
VIN
adj
10V C2
0.1μF
PWM
R21
0Ω
OVP
10μF
16V
15
10kΩ
19
20
21
OVP
WFB
WCOMP
VOPIN
C22
0.1μF
stage 2
C18
0.22μF
25V
6
13
R11
4
C19
0.22μF
50V
J5
3
0.1μF
50V
BAT54SDW
A3
200kΩ
LX
C8
100pF
1
C20
0.22μF
50V
6
0.1μF
50V
5
4
C21
0.22μF
50V
C14
3
BAT54SDW
VAVDD
0.6V R6
J1
FBP
Adj
C26
10pF
R7
6.04kΩ 25V
EN
DRVP
R18
open
A1
C10
3
4
C11
6
1
VAVDD
AVDD
C16
0.22μF
25V
J8
stage2
2
C17
0.22μF
50V
BAT54SDW
A4
3
J9
4
0.1μF
50V
C28
R19
VIN
5
0.1μF
50V
C27
VDD
VIN
0Ω
C15
0.1μF
50V
Adj
R3
6.04kΩ
C3
10μF
10V
L1
2.2μH
D1
VIN
0.1μF
25V
2
stage 3
stage4
C12
C13
1
2
C6
22μF
25V
0.1μF
25V
5
J7
0.6V R2
14
stage3
1
2
1
2
16
R14
R13
1
2
1
1
2
17
C23
0.1μF
25V
2
WEN
1
2
18
5
6
1
C29
0.22μF J10 stage4
50V
1
2
J2
J6
COMP
open
0Ω
R15
10kΩ
VDD
A2
J4
23
FB
7
DRVN
VIN
22
WEN
DRVN
R16
LX
0V
OP+
OPIN
C25
open
12
6
FBN
PGND1
R9
Adj
5
AAT2822
REF
FBP
VGL (negative)
4
11
3
FBN
R10
6.04kΩ
C7
OP-
VDD
0.22μF
6.3V
OUT
R23
open
C9 100Ω
8.2nF R17
U1
PGND2
10
1.2V
WLX
EN
2
9
1
C5
2.2μF
50V
VIN
24
WDIM
WLED+
AGND
D2
DRVP
R4
adj
8
10kΩ
R12
AGND
L2
2.2μH WLX
0.6V
R22
open
C24
10nF
17.4kΩ
OVP
R5
WFB
R8
0.1μF
50V
VGH (positive)
2
BAT54SDW
C30
0.22μF
50V
Figure 2: AAT2822IBK Evaluation Board Schematic.
2
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
202319A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • August 30, 2012
EVALUATION BOARD DATA SHEET
EV183
Evaluation Board for the AAT2822/2823/2824/2825
TFT-LCD DC-DC Converter with WLED Driver and VCOM Buffer
WLED-
VIN
10V C1
4.7μF
VIN-WLED
R20
0Ω
J3
C4
HF-PWM
R1
0Ω
VIN
adj
10V C2
0.1μF
PWM
10μF
16V
DRVN
7
200kΩ
LX
C8
100pF
stage 2
C18
0.22μF
25V
6
4
C19
0.22μF
50V
J5
3
C13
0.1μF
50V
BAT54SDW
A3
1
stage4
C12
20
21
22
19
WFB
WCOMP
D1
C20
0.22μF
50V
6
C21
0.22μF
50V
C14
0.1μF
50V
5
4
3
BAT54SDW
VAVDD
0.6V R6
VIN
J1
FBP
C26
R18
open
A1
C10
3
4
C11
6
1
VAVDD
AVDD
C16
0.22μF
25V
J8
stage2
2
C17
0.22μF
50V
BAT54SDW
A4
3
J9
4
0.1μF
50V
C28
R19
VIN
5
0.1μF
50V
C27
VDD
VIN
0Ω
C15
0.1μF
50V
Adj
10pF
R7
6.04kΩ 25V
EN
DRVP
0.1μF
25V
2
stage 3
L1
2.2μH
C6
22 μF
25V
0.1μF
25V
5
Adj
R3
6.04kΩ
C3
10μF
10V
stage3
1
2
1
2
0.6V R2
R11
1
2
1
1
2
13
C23
0.1μF
25V
2
WEN
1
2
COMP
15
14
5
6
1
C29
0.22μF J10 stage4
50V
1
2
J2
J6
OVP
FB
16
VDD
A2
J4
23
WEN
DRVN
VIN
N/C
17
LX
0V
N/C
18
12
6
PGND1
R9
Adj
5
AAT2823
FBN
11
VGL (negative)
4
REF
FBP
FBN
R10
6.04kΩ
C7
N/C
N/C
VDD
0.22μF
6.3V
3
C9
8nF
U1
PGND2
10
1.2V
WLX
EN
2
9
1
C5
2.2μF
50V
VIN
24
WDIM
WLED+
AGND
D2
C25
open
R12
DRVP
R4
adj
8
10kΩ
R23
open
17.4kΩ
AGND
L2
2.2μH WLX
0.6V
R22
open
R21
0Ω
OVP
OVP
R5
WFB
R8
0.1μF
50V
VGH (positive)
2
BAT54SDW
C30
0.22μF
50V
Figure 3: AAT2823IBK Evaluation Board Schematic.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
202319A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • August 30, 2012
3
EVALUATION BOARD DATA SHEET
EV183
Evaluation Board for the AAT2822/2823/2824/2825
TFT-LCD DC-DC Converter with WLED Driver and VCOM Buffer
VIN
10V C1
4.7μF
R1
0Ω
10V C2
0.1μF
C24
10nF
100Ω
R17
7
stage 2
C18
0.22μF
25V
6
19
20
N/C
22
21
VIN
N/C
13
R11
4
C19
0.22μF
50V
J5
3
0.1μF
50V
BAT54SDW
A3
200kΩ
LX
C8
100pF
1
C20
0.22μF
50V
6
C14
0.1μF
50V
5
4
C21
0.22μF
50V
C3
10μF
10V
L1
2.2μH
D1
VAVDD
0.6V R6
VIN
J1
FBP
3
BAT54SDW
C26
R18
open
A1
C10
3
4
C11
6
1
VAVDD
AVDD
C16
0.22μF
25V
J8
stage2
2
C17
0.22μF
50V
BAT54SDW
A4
3
J9
4
0.1μF
50V
C28
R19
VIN
5
0.1μF
50V
C27
VDD
VIN
0Ω
C15
0.1μF
50V
Adj
10pF
R7
6.04kΩ 25V
EN
DRVP
0.1μF
25V
2
stage 3
stage4
C12
C13
1
2
Adj
R3
6.04kΩ
C6
22 μF
25V
0.1μF
25V
5
J7
0.6V R2
14
LX
PGND1
C22
0.1μF
stage3
1
2
1
2
10kΩ
1
2
1
1
2
15
VOPIN
C23
0.1μF
25V
2
WEN
1
2
16
R14
R13
5
6
1
0.1μF
50V
C29
0.22μF
50V
VGH (positive)
2
BAT54SDW
J10 stage4
1
2
J2
J6
COMP
18
17
VDD
A2
J4
open
0Ω
R15
10kΩ
12
DRVN
DRVN
VIN
OPIN
FB
11
0V
OP+
WEN
FBP
R9
Adj
6
FBN
VDD
VGL (negative)
5
AAT2824
REF
EN
R10
6.04kΩ
C7
OP-
9
4
OUT
PGND2
10
3
FBN
R16
U1
N/C
8
1.2V
0.22μF
6.3V
N/C
24
N/C
2
DRVP
1
AGND
23
AGND
C30
0.22μF
50V
Figure 4: AAT2824IBK Evaluation Board Schematic.
4
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
202319A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • August 30, 2012
EVALUATION BOARD DATA SHEET
EV183
Evaluation Board for the AAT2822/2823/2824/2825
TFT-LCD DC-DC Converter with WLED Driver and VCOM Buffer
VIN
10V C1
4.7μF
R1
0Ω
10V C2
0.1μF
20
21
19
N/C
N/C
N/C
0.6V R2
14
13
R11
LX
200kΩ
LX
C8
100pF
L1
2.2μH
D1
C19
0.22μF
50V
J5
3
C13
0.1μF
50V
BAT54SDW
A3
1
C20
0.22μF
50V
6
C21
0.22μF
50V
C14
0.1μF
50V
5
4
3
BAT54SDW
0.6V R6
VIN
J1
FBP
C26
R18
open
A1
C10
3
4
C11
6
1
VAVDD
AVDD
C16
0.22μF
25V
J8
stage2
2
C17
0.22μF
50V
BAT54SDW
A4
3
J9
4
0.1μF
50V
C28
R19
VIN
5
0.1μF
50V
C27
VDD
VIN
0Ω
C15
0.1μF
50V
Adj
10pF
R7
6.04kΩ 25V
EN
DRVP
0.1μF
25V
2
stage 3
stage4
C12
0.1μF
25V
5
4
VAVDD
C6
22 μF
25V
stage3
1
2
stage 2
C18
0.22μF
25V
6
Adj
R3
6.04kΩ
C3
10μF
10V
5
6
1
C29
0.22μF J10 stage4
50V
1
2
1
2
15
1
2
1
1
2
16
C23
0.1μF
25V
2
WEN
1
2
17
12
7
J2
J6
COMP
18
VDD
A2
J4
22
23
DRVN
DRVN
VIN
VIN
FB
PGND1
R9
Adj
N/C
WEN
FBP
6
0V
AAT2825
FBN
11
5
N/C
10
VGL (negative)
4
REF
EN
FBN
R10
6.04kΩ
C7
N/C
VDD
0.22μF
6.3V
3
N/C
PGND2
8
1.2V
U1
N/C
DRVP
2
9
1
AGND
N/C
24
AGND
0.1μF
50V
VGH (positive)
2
BAT54SDW
C30
0.22μF
50V
Figure 5: AAT2825IBK Evaluation Board Schematic.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
202319A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • August 30, 2012
5
EVALUATION BOARD DATA SHEET
EV183
Evaluation Board for the AAT2822/2823/2824/2825
TFT-LCD DC-DC Converter with WLED Driver and VCOM Buffer
Getting Started
Setup
1. Connect an input power source (to supply between 2.5V and 5.5V) between VIN and ground.
2. Connect the jumpers to the positions shown in Figure 6.
3. Place the J2 jumper to the ON position before connecting the external WLED.
To reduce inrush current, do not enable the main boost and the white LED driver concurrently.
(a) Jumper Position when WLED Disabled
b) Jumper Position when WLED Enabled
Figure 6: AAT282x Evaluation Board Measurement Configuration.
Table 1 shows the jumper functions.
Jumper
Description
J1
J2
Enable the VAVDD, VGH, and VGL channels by setting the jumper EN from OFF to ON position.
Enable the WLED by setting the jumper WEN from OFF to ON position.
LED dimming control input to WDIM. Set to “100” position for maximum brightness and “0” position for
shut down. Apply an external PWM signal up to 1 kHz to pin 2 of J3 by removing the jumper and adjust the
duty cycle of the PWM signal from 100% to 5%, the LED brightness will change proportionally.
Stage select for VGL channel with one of the three jumpers: J4 for two stages selection; J5 for three and J6
for four. Detail stage selection is discussed in section: “Boost and Dual Charge Pump Output Setting.”
Stage select for VGH channel with one of the three jumpers: J4 for two stages selection; J5 for three and J6
for four. Detail stage selection is discussed in section: “Boost and Dual Charge Pump Output Setting.”
Connect J7 OPIN for using VAVDD as VCOM buffer input voltage (VOPIN). The maximum input bias voltage for
the VCOM buffer cannot exceed 13V. To prevent damage to the device when VAVDD is greater than 13V, OPIN
should be connected to an external supply to the top pin of J7 by removing the jumper.
J3
J4, J5, J6
J8, J9, J10
J7
Table 1: AAT282x Evaluation Board Jumper Functionality.
6
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
202319A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • August 30, 2012
EVALUATION BOARD DATA SHEET
EV183
Evaluation Board for the AAT2822/2823/2824/2825
TFT-LCD DC-DC Converter with WLED Driver and VCOM Buffer
Functional Testing and Evaluation
Measurement for Boost and Dual Charge Pumps
The boost of LCD bias and dual charge pumps can be measured by test points of VAVDD, VGH and VGL. The boost
output voltage can be set up to 14.5V and the outputs, VGH and VGL, of the two charge pumps can be set up to +30V
and -30V by external resistor dividers. For details refer to the section: “Boost and Dual Charge Pumps Output
Setting”.
Figure 7 shows the configuration and the waveforms for the power up sequencing of the AAT282x-1 boost and the dual
charge pumps. A 1Hz pulse signal is fed in to the Enable pin, EN. VIN is 5V, VAVDD is 10V, VGH is 18V, VGL is 20V. The
waveform shows the power sequence is VAVDD -> VGL -> VGH.
(a) Measurement Configuration
(b) Waveform of AAT2822-1 Power-up Sequence
Figure 7: AAT2822 Evaluation Board Boost and Dual Charge Pump Measurement.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
202319A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • August 30, 2012
7
EVALUATION BOARD DATA SHEET
EV183
Evaluation Board for the AAT2822/2823/2824/2825
TFT-LCD DC-DC Converter with WLED Driver and VCOM Buffer
Measurement for WLED Backlight Driver
The WLED backlight driver is a step-up DC-DC converter with sense resistor to provide feedback voltage. Its input voltage, VDD, on the board is either VAVDD with R19 set to 0Ω or external VIN with R18 set to 0Ω.
The WLED brightness can be adjusted by either the PWM dimming or the ballast resistor (R8). The PWM signal can be
fed in through WDIM pin at pin2 of jumper J3. The ballast resistor is used to set the maximum WLED current. For details
refer to the section: “WLED Backlight”.
Figure 8 shows the configuration and the measurement waveforms with R8 = 3Ω at 5V VIN. The current for each string
is 20mA. In this configuration, 3 series 5 parallels WLEDs (3S5P), the total current is 100mA.
(a) Measurement Configuration
(b) Waveform for WLED 3S5P Configuration
Figure 8: AAT2822 Evaluation Board Backlight Driver Measurement Operation.
8
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
202319A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • August 30, 2012
EVALUATION BOARD DATA SHEET
EV183
Evaluation Board for the AAT2822/2823/2824/2825
TFT-LCD DC-DC Converter with WLED Driver and VCOM Buffer
Measurement for LCD VCOM Buffer
The VCOM buffer is designed to drive the voltage on the backplane of an LCD display. The VCOM output voltage is
typically set to half of the main boost output (VAVDD). Figure 9 shows the configuration for the measurement. The
maximum input bias voltage for the VCOM buffer (VOPIN) cannot exceed 13V. To prevent damage to the device, connect
VOPIN to an external supply when VAVDD is greater than 13V and leave the jumper J7 open to disconnect VAVDD from VOPIN.
Figure 9: AAT282x Evaluation Board: Measurement Configuration for VCOM Buffer Output.
Boost and Dual Charge Pump Output Setting
The output voltage VAVDD of the LCD bias boost is set by external resistor divider R2 and R3. The dual charge pumps
output voltages are determined by both resistor divider and charge pump stages. Table 2 shows the resistor divider
selection equation and table 3 shows the charge pump stage selection equation.
Output Channel
Output Range
VAVDD
VIN - VDIODE to 14.5V
VGL
VDD to 30V
VGH
-VDD to -30V
Equation For Adjustable Resistor
R2 = R3 ·
VAVDD
VAVDD
VFB -1 = R3 · 0.6V - 1
VGL
VGL
R9 = V
· R10 = 1.2V · R10
REF
R6 = R7 ·
VGH
VGH
- 1 = R7 ·
-1
VFBP
0.6V
Eq.1
Eq.2
Eq.3
Table 2: Resistor Divider Equations for Boost and Dual Charge Pumps.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
202319A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • August 30, 2012
9
EVALUATION BOARD DATA SHEET
EV183
Evaluation Board for the AAT2822/2823/2824/2825
TFT-LCD DC-DC Converter with WLED Driver and VCOM Buffer
Charge Pump
Equation For Stage Selection
VGL
nN =
VGL
2VF - VAVDD(MIN)
Eq.4
VGH
nP =
VGH - VAVDD(MIN)
VAVDD(MIN) - 2VF
Eq.5
Table 3: Charge Pump Stage Selection Equations.
For example, if VAVDD = 5V, VGH = 18V and the forward voltage of the Schottky diode VF is 0.31V.
nP =
18 - 5
= 2.97
5 - 2 · 0.31
So, to set VGH to 18V, three stages need to be used (J5 must be connected and J4, J6 left open).
WLED Backlight
WLED brightness can be adjusted either by setting the ballast resistor for max WLED current or by varying the duty
cycle of the PWM signal.
Ballast Resistor Selection
The white LED driver can be enabled by setting J2 from OFF to ON position. The backlight current is set by an external
ballast resistor (R8) up to a maximum of 260mA at 12V or 50mA at 28V. The AAT282x can drive from 3 WLEDs up to
a maximum of 7 WLEDs in series. The number of WLEDs depends on the LCD panel size. Table 4 gives some examples
of different LCD panel size and corresponding WLED configurations. The brightness of the white LED can be controlled
by a PWM signal. By connecting a 1 kHz PWM signal to the WDIM pin and adjusting the duty cycle of the PWM signal
from 100% to 5%, the brightness of the LED will change proportionally. The higher frequencies are achieved by filtered
PWM and the value of R21, R22, R23, C25 should be calculated. See AAT2282 datasheet for more details.
The equation for calculating OVP adjustable resistor (R4) is:
R4 = R5 ·
VLED(MAX)
VLED(MAX)
VOVP -1 = R5 ·
0.6V -1
where
VLED(MAX) equals the forward voltage of the WLED series plus 0.3V VWFB.
The equation for the number of series-connected LEDs is given by:
N=
VOVP(MIN) - VWFB(MAX)
=
VFLED(MAX)
VOVP(MIN) - 0.3V
3.5V
So, for example, when VOVP(MIN) = 28V, VWFB(MAX) = 0.3V, and VFLED(MAX) = 3.5V
N=
28V - 0.6V
3.5V
= 7.8 LEDs
The maximum number of WLEDs in series for the given VOVP output range is, therefore, seven.
10
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
202319A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • August 30, 2012
EVALUATION BOARD DATA SHEET
EV183
Evaluation Board for the AAT2822/2823/2824/2825
TFT-LCD DC-DC Converter with WLED Driver and VCOM Buffer
The equation for calculating ballast resistor (R8) is:
R8 =
0.3V
ILED(MAX)
VWFB(MAX)
=
ILED(MAX)
For example, for a 10-inch panel with 3 series and 13 parallel (3S13P) string configuration and the maximum current
in each string being 20mA:
R8 =
WLED Matrix
(Series and
Parallel)
3S5P
0.3V
= 1.15Ω
13 · 20mA
Maximum ILED
Current (mA)
Ballast Resistor
R8 (Ω)
5
10
15
20
25
30
12.0
6.0
4.0
3.0
2.4
2.0
WLED Matrix
(Series and
Parallel)
3S13P
Maximum ILED
Current (mA)
Ballast Resistor
R8 (Ω)
5
10
15
20
25
30
4.62
2.31
1.54
1.15
0.92
0.77
Table 4: Ballast Resistor Selection.
Maximum WLED Output Current
Maximum WLED output current is determined by both WLED driver input voltage VIN_WLED and WLED string voltage VLED.
Figure 10 shows the relationship of the three factors.
600
ILED_MAX (mA)
500
V IN_WLED = 3.6V
V IN_WLED = 4.2V
400
V IN_WLED = 5V
V IN_WLED = 8V
300
V IN_WLED = 10V
V IN_WLED = 12V
V IN_WLED = 15V
200
V IN_WLED = 18V
V IN_WLED = 20V
100
0
6
10
14
18
22
26
VLED (V)
Figure 10: WLED Driver Maximum Output Current for different VLED Voltage.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
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11
EVALUATION BOARD DATA SHEET
EV183
Evaluation Board for the AAT2822/2823/2824/2825
TFT-LCD DC-DC Converter with WLED Driver and VCOM Buffer
PWM Dimming
The brightness of the white LED can be controlled using a PWM signal. By connecting a 1 kHz PWM signal to pin 2 of
jumper J3 and adjusting the duty cycle of the PWM signal from 5% to 100%, the brightness of the LED will change
proportionally. Figure 11 shows the variation of ILED with the PWM duty cycle.
20
18
16
ILED (mA)
14
12
10
8
6
4
2
0
5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100
PWM Duty Cycle (%)
Figure 11: 1kHz PWM control (VIN = 5V, ILED(MAX) is set to 20mA).
For applications requiring a PWM frequency higher than 1kHz, an external filter PWM is connected to the WFB pin to
control the dimming of the white LED. Connect the PWM signal from "HF-PWM" test point and connect WDIM Pin to
VIN. Figure 12 shows a low path filter used in the high frequency PWM control application. In this method, the LED
dimming has relationship with both PWM high voltage level and duty cycle.
WLEDadj
VR8
I3
R8
R21
4.99k
Connect WDIM to VIN
I2
R22
VWFB
28k
REF
WCOMP
20
19
22
21
VIN
OVP
WFB
OP+
AAT2822
FBN
OPIN
18
17
16
15
14
13
LX
COMP
HF-PWM
12
11
8
7
10
DRVN
PGND1
FB
FBP
WEN
VDD
6
OP-
EN
5
OUT
R23
4.99k
C25
0.1uF
U1
PGND2
DRVP
4
WLX
9
3
AGND
24
2
WDIM
1
23
I1
VC25
Figure 12: Low-Pass Filter PWM Dimming Control.
Figure 9: Low-Pass Filter PWM Dimming Control.
12
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
202319A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • August 30, 2012
EVALUATION BOARD DATA SHEET
EV183
Evaluation Board for the AAT2822/2823/2824/2825
TFT-LCD DC-DC Converter with WLED Driver and VCOM Buffer
When the PWM duty cycle is adjusted, the average voltage on C25(VC25) will change. Because the VWFB is fixed at 0.3V,
so I2 and I3 will change. The changed I3 will adjust the voltage drop, VDROP, across R21. The voltage across resistor R8,
VR8, changes, leading to the change of the white LED current. Figure 13 shows PWM control by changing the PWM duty
cycle with 2.4V high level and 0V low level. Figure 14 shows PWM control by varying the PWM high level with 50% fixed
duty cycle.
The following example illustrates the calculations for ILED in a 3S5P matrix where the PWM high level voltage is 1.2V,
the frequency is 10kHz the duty cycle is 50%, and R8 = 3Ω.
I3 = I1 + I2 = 0 +
1.2
- 0.3
2
28kΩ
= 0.01mA
VR8 = VWFB − I3 · R21 = 0.3 − 0.01mA · 4.99kΩ = 0.2501V
ILED =
VR8
R8
= 0.2501 = 83mA (Total current in 5 parallel strings)
3
Note: If the voltage in C25 is lower than VWFB, the current direction will reverse and I3 will equal I1 - I2. This will cause
VR8 to be pulled up and decrease ILED.
20
18
16
I LED ᧤mA)
14
12
10
8
6
4
2
0
0
5
10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95
HF_PWM Duty Cycle (%)
Figure 13: 10kHz High Frequency PWM Control by PWM Duty Cycle (VIN = 5V, ILED(MAX) = 20mA).
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
202319A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • August 30, 2012
13
EVALUATION BOARD DATA SHEET
EV183
Evaluation Board for the AAT2822/2823/2824/2825
TFT-LCD DC-DC Converter with WLED Driver and VCOM Buffer
20
18
16
14
I LED (mA)
12
10
8
6
4
2
0
0.6
1.2
1.8
2.4
3
3.6
4.2
4.8
High level of PWM Signal (V)
Figure 14: 10kHz High Frequency PWM Control by PWM High Level Voltage (VIN = 5V, ILED(MAX) = 20mA).
Printed Circuit Board
(a) Top Layer
(b) Bottom Layer
Figure 15: AAT282xIBK Evaluation Board.
14
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
202319A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • August 30, 2012
EVALUATION BOARD DATA SHEET
EV183
Evaluation Board for the AAT2822/2823/2824/2825
TFT-LCD DC-DC Converter with WLED Driver and VCOM Buffer
Layout Guidelines
Use the following guidelines to ensure proper operation of the AAT282x:
1. Minimize the distance from the input capacitor negative terminal to the GND pins.
2. Maintain a ground plane and connect to the IC GND pin(s) as well as the GND connections of CIN and COUT.
3. Connect PGND and AGND as close as possible to the package and maximize the heat sinking space for overall performance.
4. To maximize package thermal dissipation and power handling capacity of the TQFN44-24 package, solder the
exposed paddle of the IC onto the thermal landing of the PCB, where the thermal landing is connected to the ground
plane.
AAT282x EVAL Board Component Listing
Component
Part Number
Description
U1
AAT2822/3/4/5IBK
C1
C2
C3, C4
C5
C6
C7
C8
C9
C10, C12, C22, C23
C11, C13, C14,
C15, C27, C28
C16, C18
C17, C19, C20,
C21, C29, C30
C24
C25
C26
A1, A2, A3, A4
D1, D2
L1, L2
GRM188R61A475K
GRM188R71C104K
GRM21BR61C106K
GRM31CR71H225K
GRM31CR61E226M
GRM188R71A224K
GRM1885C1H101J
GRM2195C1H822J
GRM188R61E104K
TFT-LCD DC-DC Converter with WLED
Driver and VCOM Buffer
CAP CERAMIC 4.7μF 0603 X5R 10V 10%
CAP CERAMIC 0.1μF 0603 X7R 16V 10%
CAP CERAMIC 10μF 0805 X5R 16V 10%
CAP CERAMIC 2.2μF 1206 X7R 50V 10%
CAP CERAMIC 22μF 1206 X5R 25V 20%
CAP CERAMIC 0.22μF 0603 X7R 10V10%
CAP CERAMIC 100pF 0603 COG 50V 5%
CAP CERAMIC 8.2nF 0805 X7R 50V 10%
CAP CERAMIC 0.1μF 0603 X5R 25V 10%
GRM188R71H104K
CAP CERAMIC 0.1μF 0603 X7R 50V 10%
GRM188R61E224K
CAP CERAMIC 0.22μF 0603 X5R 25V10%
GRM21BR71H224K
CAP CERAMIC 0.22μF 0805 X7R 50V10%
GRM188R71H103K
NC
GRM1885C1H100J
BAT54SDW-7-F
SS16L
CDRH5D16-2R2
CAP CERAMIC 10nF 0603 X7R 50V 10%
R2, R4, R6, R8, R9
R3, R7, R10
R5, R13, R14
R11
R12
R15, R19, R20, R21
R17
R16, R18, R22, R23,
R25
RC0603FR-076K04L
RC0603FR-0710KL
RC0603FR-07200KL
RC0603FR-0717K4L
RC0603FR-070RL
RC0603FR-07100RL
CAP CERAMIC 10pF 0603 COG 50V 5%
Schottky Diode Array 30V SC70-6
Schottky Diode 1A 60V Micro SMP
POWER INDUCTOR 2.2μH 3.0A SMD
Adjustable Value (See Equations 1 – 5
and Table 4); 0603 SMD
Res 6.04kΩ 1/10W 1% 0603 SMD
Res 10kΩ 1/10W 1% 0603 SMD
Res 200kΩ 1/10W 1% 0603 SMD
Res 17.4kΩ 1/10W 1% 0603 SMD
Res 0Ω 1/10W 1% 0603 SMD
Res 100Ω 1/10W 1% 0603 SMD
Manufacturer
Skyworks
Murata
Diode Inc
Taiwan Semiconductor
Sumida
Yageo
Not Populated
Table 5: AAT2822 Evaluation Board Bill of Materials.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
202319A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • August 30, 2012
15
EVALUATION BOARD DATA SHEET
EV183
Evaluation Board for the AAT2822/2823/2824/2825
TFT-LCD DC-DC Converter with WLED Driver and VCOM Buffer
Copyright © 2012 Skyworks Solutions, Inc. All Rights Reserved.
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Customers are responsible for their products and applications using Skyworks products, which may deviate from published specifications as a result of design defects, errors, or operation of products outside of published parameters or design specifications. Customers should include design and operating safeguards to minimize these and other risks. Skyworks assumes no liability for applications assistance, customer product
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Skyworks, the Skyworks symbol, and “Breakthrough Simplicity” are trademarks or registered trademarks of Skyworks Solutions, Inc., in the United States and other countries. Third-party brands and names are for
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16
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
202319A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • August 30, 2012