AAT2825 Advanced Analogic Technologies, AAT2825 Datasheet

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AAT2825

Manufacturer Part Number
AAT2825
Description
(AAT2822 - AAT2825) TFT-LCD DC-DC Converter
Manufacturer
Advanced Analogic Technologies
Datasheet
1.AAT2825.pdf (28 pages)
General Description
The AAT2822-AAT2825 family of integrated panel power
solutions provides the regulated voltages required by an
active-matrix thin-film transistor (TFT) liquid-crystal dis-
play (LCD). The AAT2822 includes a triple-output DC-DC
converter, a LED backlight driver, and a VCOM buffer in
a 4 mm x 4mm TQFN package. The primary 1.3MHz
DC-DC boost converter uses an ultra-small inductor and
ceramic capacitor to generate output voltage (V
up to 14.5V for the charge pumps. The low on-resistance
of the integrated power MOSFET allows for efficiency up
to 93%.
The two charge pumps independently regulate a positive
output (VGH) and a negative output (VGL). These low-
power outputs use external diode and capacitor stages
to regulate output voltages up to +30V and down to
-30V. A proprietary regulation algorithm minimizes out-
put ripple when using small capacitors.
The high efficiency backlight driver provides a constant
current output capable of boosting up to 28V. The driver
is an ideal power solution for backlight applications with
up to seven white LEDs in series or up to 39 white LEDs
in a parallel and series configuration. LED brightness is
PWM controlled up to 1kHz. Filtered PWM is supported
for higher frequencies.
The high slew rate operational amplifier is suitable for
VCOM buffering and gain adjustment.
The sequencing of the power supplies ensures proper
panel startup and avoid damage to the device.
The AAT2822 family is available in a Pb-free, 24-pin 4 x
4mm TQFN package and operates over the -40°C to
+85°C temperature range.
2822.2010.02.1.0
SystemPower
TM
TFT-LCD DC-DC Converter with WLED Driver and VCOM Buffer
w w w . a n a l o g i c t e c h . c o m
AVDD
) of
Features
LCD Bias Power
• 2.5V to 5.5V Input Supply Range
• 1.3MHz Fixed Frequency Current-Mode Step-Up
• Fast Transient Response
• Adjustable Voltage up to 14.5V
• High Efficiency (93%) @ 50mA Output Current
• Small External Inductor and Capacitors
• Integrated Soft Start and Sequencing of All Rails
• Short-Circuit, Over-Voltage, and Over-Temperature
Positive Output, VGH
• Up to 13.2V Input Supply (V
• Adjustable Voltage up to 30V @ 20mA
Negative Output, VGL
• Up to 13.2V Input Supply (V
• Adjustable Voltage down to -30V @ 20mA
WLED Driver
• Input Voltage Range: 2.5V to 25V
• Maximum Continuous Output:
• Panel sizes from 5" – 10"
• Constant LED Current with 6% Accuracy
• PWM Dimming Control
• 1.3MHz Switching Fixed Frequency
VCOM Buffer
• High-Performance
• ±75mA Output Short-Circuit Current
• Low 1.5mA Quiescent Current
Applications
• Automotive Displays
• Digital Photo Frames
• Netbooks
• PNDs
Regulator
▪
Protection
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±1% Typical Accuracy
±3% Typical Accuracy
± 3% Typical Accuracy
12V @ 260mA
28V @ 50mA
5.0" 3S5P
5.6" 3S6P
7.0" 3S9P
8.0" 3S10P/11P
10" 3S13P
Up to 1kHz
Up to 90% Efficiency
13V/μs Slew Rate
12MHz, -3dB Bandwidth
AAT2822/23/24/25
PRODUCT DATASHEET
DD
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www.DataSheet4U.com
1

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AAT2825 Summary of contents

Page 1

... TM SystemPower TFT-LCD DC-DC Converter with WLED Driver and VCOM Buffer General Description The AAT2822-AAT2825 family of integrated panel power solutions provides the regulated voltages required by an active-matrix thin-film transistor (TFT) liquid-crystal dis- play (LCD). The AAT2822 includes a triple-output DC-DC converter, a LED backlight driver, and a VCOM buffer 4mm TQFN package ...

Page 2

TM SystemPower TFT-LCD DC-DC Converter with WLED Driver and VCOM Buffer Typical Application COMP VGL R5 C REF ON OFF ON OFF PWM R WCOMP C WCOMP VAVDD ...

Page 3

... TM SystemPower TFT-LCD DC-DC Converter with WLED Driver and VCOM Buffer Pin Descriptions Pinout is preliminary and subject to change during development. Pin Number AAT2822 AAT2823 AAT2824 AAT2825 n n ...

Page 4

... COMP PRODUCT DATASHEET www.DataSheet4U.com AAT2823 WLX N PGND2 N REF N FBN N WEN DRVN COMP 6 13 AAT2825 N/C N PGND2 N REF N FBN N GND DRVN COMP 6 13 2822.2010.02.1.0 ...

Page 5

... TM SystemPower TFT-LCD DC-DC Converter with WLED Driver and VCOM Buffer Part Number Descriptions Part Number LCD Bias AAT2822 AAT2822-1 AAT2823 AAT2823-1 AAT2824 AAT2824-1 AAT2825 AAT2825-1 Absolute Maximum Ratings T = 25°C unless otherwise noted. A Description OPIN, OUT, OP+, OP- DD LX, WLX WCOMP, COMP, FB, FBP, FBN, REF, WEN, PWM, WFB, OVP ...

Page 6

TM SystemPower TFT-LCD DC-DC Converter with WLED Driver and VCOM Buffer Electrical Characteristics WEN = WDIM = 25°C. A Symbol Description Power Supply V Input Voltage Range IN V ...

Page 7

TM SystemPower TFT-LCD DC-DC Converter with WLED Driver and VCOM Buffer Electrical Characteristics WEN = WDIM = Symbol Description WLED Driver (AAT2822, AAT2823 Only) ...

Page 8

TM SystemPower TFT-LCD DC-DC Converter with WLED Driver and VCOM Buffer Typical Characteristics Oscillator Frequency vs. Temperature 1.285 1.280 1.275 1.270 1.265 1.260 1.255 1.250 1.245 1.240 1.235 -40 - Temperature (°C) Power Up Sequencing (VAVDD->VGL->VGH ...

Page 9

TM SystemPower TFT-LCD DC-DC Converter with WLED Driver and VCOM Buffer Typical Characteristics VGH vs. Temperature 30.5 30.4 30.3 30.2 30.1 30.0 29.9 29.8 29.7 29.6 29.5 -40 - Temperature (°C) VGL vs. Temperature -29.50 -29.60 -29.70 -29.80 ...

Page 10

TM SystemPower TFT-LCD DC-DC Converter with WLED Driver and VCOM Buffer Typical Characteristics VCOM Buffer Supply Current vs. Temperature (V = 5.0V 12V) IN OPIN 2.00 1.95 1.90 1.85 1.80 1.75 1.70 1.65 1.60 1.55 1.50 -40 -15 ...

Page 11

TM SystemPower TFT-LCD DC-DC Converter with WLED Driver and VCOM Buffer Functional Block Diagram VIN EN COMP VDD DRVN FBN OPIN OP- OP+ WEN WDIM Functional Description Main Boost Converter The main boost regulator contains a current-mode, fixed-frequency PWM architecture ...

Page 12

TM SystemPower TFT-LCD DC-DC Converter with WLED Driver and VCOM Buffer converter. Integrated soft-start circuitry minimizes the start-up inrush current and eliminates output voltage overshoot across the full input voltage range and all load conditions. The backlight current is set ...

Page 13

TM SystemPower TFT-LCD DC-DC Converter with WLED Driver and VCOM Buffer Start EN High No Yes MAIN BOOST No V >FB Fault Trip FB Level and Persist Yes NEGATIVE >FBN Fault Trip FBN Level and Persist Yes ...

Page 14

TM SystemPower TFT-LCD DC-DC Converter with WLED Driver and VCOM Buffer Selecting the Schottky Diode To ensure minimum forward voltage drop and no recov- ery, high voltage Schottky diodes are the best choice for the primary step-up converter. The output ...

Page 15

TM SystemPower TFT-LCD DC-DC Converter with WLED Driver and VCOM Buffer R = 6.04kΩ (V) R (kΩ) AVDD 2 9 84.5 10 93.1 11 105 12 115 13 124 15 143 20 196 22 215 24 237 Table ...

Page 16

TM SystemPower TFT-LCD DC-DC Converter with WLED Driver and VCOM Buffer Positive Output Voltage (V GH The positive output voltage is set by a resistive divider from the output ( the FBP and ground pins. GH Limiting the ...

Page 17

TM SystemPower TFT-LCD DC-DC Converter with WLED Driver and VCOM Buffer When the rising OVP threshold is exceeded, switching is stopped and the output voltage decays. Switching auto- matically restarts when the output drops below the lower OVP hysteresis voltage ...

Page 18

TM SystemPower TFT-LCD DC-DC Converter with WLED Driver and VCOM Buffer R21 PWM 0 1 WLX 2 PGND2 3 AAT2822 FBN WEN DRVN COMP Figure 4: PWM Dimming Control. For applications requiring a PWM frequency higher than 1KHz, an external ...

Page 19

... The I rating drops with increasing conduction FSM period. Manufacturers’ datasheets should be consulted to verify reliability under peak load conditions. The diode’s published current rating may not reflect actual operating conditions and should be used only as a com- parative measure between similarly rated devices ...

Page 20

TM SystemPower TFT-LCD DC-DC Converter with WLED Driver and VCOM Buffer MLC capacitors exhibit significant capacitance reduction with applied voltage. Output ripple measurements should confirm that output voltage droop and operating stability are acceptable. Voltage derating can minimize this fac- ...

Page 21

TM SystemPower TFT-LCD DC-DC Converter with WLED Driver and VCOM Buffer WLED - VIN-WLED C4 10μF 16V OVP R5 10k R4 D2 Adj. C5 WLED + 2.2μF 1.2V 50V R10 C7 6.04k VGL (negative) 0.22μF 6.3V R9 Adj. VIN A2 ...

Page 22

TM SystemPower TFT-LCD DC-DC Converter with WLED Driver and VCOM Buffer Symbol Part Number U1 AAT2822IBK C10, C12, C13, C22, C23 C11, C14, C15 C16, C17, C18, C19, C20, C21 C24 ...

Page 23

TM SystemPower TFT-LCD DC-DC Converter with WLED Driver and VCOM Buffer WLED - VIN-WLED C4 10μF 16V OVP 10k Adj. WLED + C5 2.2μF 50V R10 C7 6.04k VGL (negative) 0.22μF R9 6.3V Adj. VIN A2 J2 ...

Page 24

TM SystemPower TFT-LCD DC-DC Converter with WLED Driver and VCOM Buffer C7 R10 0.22μF 6.04k VGL (negative) 6.3V R9 Adj. VIN WEN 1 C18 Stage 2 0.22μ 25V C19 0.22μF BAT54SDW 50V ...

Page 25

... J4 5 0.22μ 25V 4 C19 BAT54SDW 0.22μF A3 Stage 3 50V Stage 4 C20 J6 5 0.22μ 50V 4 C21 BAT54SDW 0.22μF 50V Figure 9: AAT2825IBK Evaluation Board Schematic. 2822.2010.02.1.0 AAT2822/23/24/ 0.1μF 4.7μF 0 10V 10V N/C N PGND2 N N/C REF 4 15 AAT2825 FBN ...

Page 26

TM SystemPower TFT-LCD DC-DC Converter with WLED Driver and VCOM Buffer Figure 10: AAT28XXIBK Evaluation Board Top Side Layout. 26 AAT2822/23/24/25 Figure 11: AAT28XXIBK Evaluation Board Bottom Side Layout ...

Page 27

... Bottom View Side View PRODUCT DATASHEET www.DataSheet4U.com Part Number (Tape and Reel) 2 AAT2822IBK-T1 AAT2822IBK-1-T1 AAT2823IBK-T1 AAT2823IBK-1-T1 AAT2824IBK-T1 AAT2824IBK-1-T1 AAT2825IBK-T1 AAT2825IBK-1-T1 Pin 1 Identification Chamfer 0.300 × 45° 1 0.214 ± 0.036 27 ...

Page 28

... Testing and other quality control techniques are utilized to the extent AnalogicTech deems necessary to support this warranty. Specifi c 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 ...

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