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PDF AAT1409 Data sheet ( Hoja de datos )
| Número de pieza | AAT1409 | |
| Descripción | 8 Channel LED Backlight Driver | |
| Fabricantes | Analogic Corporation | |
| Logotipo |  |
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DataSheet.in
PRODUCT DATASHEET
AAT1409
SwitchRegTM 8 Channel LED Backlight Driver with Integrated Boost and High Frequency Direct PWM Dimming
General Description
The AAT1409 is a highly integrated, high efficiency LED
backlight solution for notebook computers, monitors and
portable TVs. The device operates from DC inputs, ciga-
rette lighter adapters, or multi-cell Li-ion batteries over
the 4.5V to 26V voltage range.
An integrated boost (step-up) converter provides up to
45V output for driving series LEDs. Eight precision cur-
rent sinks are programmed up to 45mA per string
through one external RSET resistor, supporting up to 881
white LEDs at 360mA total output current.
LED strings may be disabled or operated in parallel for
increased drive capability. The boost output voltage is
set by the LED string with the highest voltage require-
ment, allowing a wide range of LED characteristics.
The PWM dimming range at 100Hz is up to 1,000:1.
The boost switching frequency is selectable (up to
1.3MHz) to allow optimum efficiency and the smallest
external L/C filtering components. Alternatively, the
device may be synchronized to an external clock.
Boost current mode control provides fast response to
line and load transients. Integrated Light-Load mode
ensures highest efficiency across the entire load range.
Fault tolerant circuitry extends system life by disabling
open LED strings. The unique high voltage current sinks
prevent damage resulting from shorted LEDs.
The AAT1409 is available in the Pb-free, thermally
enhanced 24-pin 3x4 TQFN package.
Features
• VIN Range: 4.5V to 5.5V / 5.0V to 26.0V
• LX Rated to 50V
• Maximum IOUT: 360mA
• Up to 92% Efficiency
• High Efficiency Light-Load Mode
• 8 LED Current Sinks up to 45mA/each
▪ ±2% Accuracy (21mA)
▪ ±2% Matching (21mA)
• Flexible Configurations
▪ Disable or Parallel
• Switching Frequency Options
▪ 675kHz or 1.3MHz
▪ Synchronize to System Clock
• PWM Direct Dimming Input
▪ Up to 100kHz Prevents Audio Interference
▪ Fast Turn-On/Off
▪ Wide 1,000:1 Dimming Range (100Hz)
• Fault Tolerant: Open/Short LED(s)
• Current Limit Protection
• Over-Voltage Protection
• Over-Temperature Protection
• Soft-Start Minimizes Inrush Current
• TQFN34-24 Low Profile Package
• -40°C to +85°C Temperature Range
Applications
• Monitors
• Notebook Computers
• Portable TV
• Portable DVD Players
• White LED Backlight
1. The maximum number of LEDs in each string is dependent upon the maximum VF of the diodes in that string. Under no event should the voltage at LX be exceeded.
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DataSheet.in
PRODUCT DATASHEET
AAT1409
SwitchRegTM 8 Channel LED Backlight Driver with Integrated Boost and High Frequency Direct PWM Dimming
Electrical Characteristics1
VIN = 12V; CIN = 4.7μF, COUT = 2.2μF; CVCC = 2.2μF; L1 = 10μH; RSET =7.5kΩ (ICSx = 21mA); TA = -40oC to 85oC unless
otherwise noted. Typical values are at TA = 25oC.
Symbol Description
Power Supply, Current Sinks
VIN Input Voltage Range
VUVLO
Under Voltage Threshold
VCC
VCX
IQ
ISD
ICSx
ICSx-Matching
VOVP
RDS(ON)LO
DMAX
TMIN
ICSx / IRSET
ILIMIT
ILEAK
VCC Output Voltage
Current Sink Voltage
IN Quiescent Current (no switching)
IN Pin Shutdown Current
Current Sink Accuracy
Current Matching Between Any Sink Channel
Over-Voltage Threshold
Over-Voltage Hysteresis
Low Side Switch On Resistance
Maximum Duty Cycle
Minimum On-Time
Current Set Ratio
Low Side Switch Current Limit
LX Pin Leakage
CSx Pin Leakage
FOSC
Oscillator Frequency
FSYNC
Sync Frequency
FSYNC
Sync Duty Cycle Range
FPWM(MAX) Maximum Direct PWM Frequency
TSS Soft-Start Time
Logic Level Inputs: EN Pin
VEN(L)
Threshold Low
VEN(H)
Threshold High
ILEN Input Leakage Enable Pin
Logic Level Inputs: SYNC, PWM, FSET Pins
V(H) Threshold Low
V(H) Threshold High
ILK Input Leakage
TPWM(ON/OFF) PWM Turn On/Off Delay
Thermal Protection
TJ(SD)
TJ(HYS)
TJ Thermal Shutdown Threshold
TJ Thermal Shutdown Hysteresis
Conditions
VIN = VCC
VCC = Open
VIN Rising
Hysteresis
VIN Falling
EN = Logic High, ICC(OUT) = 0mA
EN = Logic High, ICSx = 21mA (RSET =
7.5kΩ)
ICSx = 0% , VCSx = 0.5V, EN = Logic High
CS1-CS8 = Open, EN = Logic Low, does
not include LX leakage current
ICSx = 21mA
ICSx = 21mA
VOUT Rising
VOUT Falling
VCC = 4.5V
ICSx/IRSET , VRSET = 0.6V
EN = Logic Low; VLX = 40V
EN = Logic Low, CSx = 30V
FSET = Logic Low; VIN = 5.0 to 26.0V;
VIN = VCC = 4.5 to 5.5V
FSET = Logic High; VIN = 5.0 to 26.0V;
VIN = VCC = 4.5 to 5.5V
FOSC ± 20%
VOUT = 35V, CCOMP = 18nF, RCOMP = 10kΩ
VEN = 5V, VIN = 5V
VSYNC = VPWM = VFSET = 5V
PWM transition to 95%/5% IRSET
Min
4.5
5.0
3.2
4.0
-5
-3
1.1
90
3.0
550
1100
10
2.5
1.4
-1
Typ
500
4.5
0.5
1.5
±2
±2
1.2
100
200
100
262
675
1300
FOSC
±20%
50
1
1
140
15
Max
5.5
26.0
4.3
6
40.0
+5
+3
1.3
6.5
1
10
800
1500
90
100
0.4
3
0.4
1
Units
V
V
mV
V
V
V
mA
μA
%
%
V
mV
mΩ
%
ns
A/A
A
μA
μA
kHz
kHz
kHz
%
kHz
ms
V
V
μA
V
V
μA
μs
°C
°C
1. The AAT1409 is guaranteed to meet performance specifications over the -40°C to +85°C operating temperature range and is assured by design, characterization, and correla-
tion with statistical process controls.
2. Output voltage must result in a voltage lower than the LX maximum rating under all operating conditions.
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DataSheet.in
PRODUCT DATASHEET
AAT1409
SwitchRegTM 8 Channel LED Backlight Driver with Integrated Boost and High Frequency Direct PWM Dimming
Application Information
OVP Protection with Open LED Failure
The OVP protection consists of a resistive divider net-
work (R3 and R4) as shown in Figure 2. The resistor
divider must be selected so that the voltage at the OVP
pin exceeds the OVP rising threshold when the output is
at VOUT(MAX).
R3 = R4 ·
VOUT(MAX)
V - 1OVP(MAX)
When the OVP rising threshold is exceeded, the con-
verter stops switching. The open LED channel is removed
from the boost converter feedback loop. When the volt-
age at the OVP pin falls below the OVP hysteresis volt-
age, the boost converter can resume switching.
It is important that during normal operation the current
sinks are given enough headroom so that the OVP
threshold is not tripped.
The output voltage at the minimum OVP threshold is
V = V ·OUT(MIN)
OVP(MIN)
R3
R4
+
1
The maximum voltage of each LED string including the
current sink headroom should not exceed VOUT(MIN).
VOUT(MIN) > VCSX + N · VFLED(MAX)
V ·OVP(MIN)
R3
R4
+
1
> VCSX + N · VFLED(MAX)
R3 > R4 ·
VCSX + N · VFLED(MAX) - VOVP(MIN)
VOVP(MIN)
Where:
N is the number of LEDs in each string.
VOVP(MIN) = 1.1V is minimum over voltage threshold.
VCSX = 0.5V is the current sink voltage.
VFLED(MAX) is the maximum LED forward voltage at 20mA.
VCC
VOUT
VRSET = 0.6V
IR2
262 .IR2
R2
L1
D1
C4
LX
R3
OVP
R4
1.2V
VIN
C1
Figure 2: Over-Voltage Protection and Current Sink Setting Circuit.
1409.2010.05.1.1
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| Páginas | Total 18 Páginas | |
| PDF Descargar | [ Datasheet AAT1409.PDF ] | |
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