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AAT2404 PDF Datasheet - Skyworks Solutions

Part Number AAT2404
Description Voltage-Variable Current Sourcing Boost Controller
Manufacturers Skyworks Solutions 
Logo Skyworks Solutions Logo 
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AAT2404 datasheet, circuit
DATA SHEET
AAT2404
Voltage-Variable Current Sourcing Boost Controller For LED Lighting Applications
General Description
The AAT2404 is a highly integrated high-efficiency vari-
able voltage current sourcing boost controller for white
LED backlight applications intended for use in large size
LCD panels and LCD TVs. To accommodate various LED
backlighting configurations in both direct and edge light-
ing applications, the device uses a high voltage external
power MOSFET. The AAT2404 contains an integrated cur-
rent sense architecture eliminating the need for an
expensive low resistance/high accuracy sense resistor.
The device operates ideally from a regulated 12V or 24V
DC power supply, but can also operate over a 10.8V to
28V range.
The AAT2404 provides an output voltage up to 100V
regulated by the CSFB pin provided by the ICs in
Skyworks' family of white LED drivers for TV applications.
The CSFB pin is an analog voltage representing the LED
string with the highest voltage requirement. Regulating to
this voltage allows for a wide range of LED characteristics,
while maintaining the lowest possible power dissipation.
The CSFB regulation point can be set by adjusting a resis-
tor to ground from the RSET pin.
The boost switching frequency is nominally 400kHz to
allow for optimum efficiency with the smallest external
filter. However, the device switching frequency may be
adjusted with an external resistor to optimize system
performance. Current mode control provides fast response
to line and load transients.
Thermal protection circuitry shuts down the boost con-
verter in the event of an over-temperature condition.
The AAT2404 is available in the Pb-free, thermally
enhanced 24-pin 3 x 4mm TQFN package.
Features
VIN Range: 10.8V – 28.0V
Maximum VLED: 100V
Up to 95% Boost Conversion Efficiency
Integrated Current Sense Eliminates Need for Ballast
Resistors
Switching Frequency Options
400KHz Nominal
Adjustable Range from 100kHz to 800kHz
Adjustable Regulation Voltage
Analog Input from LED Driver
User Adjustable for Fixed Output
Integrated Low Impedance Gate Drive = VCC
Flexible Current Sense Feedback Control
Power OK Output
Integrated Over-Voltage Protection
Soft-Start to Minimize Inrush Current
TQFN34-24 Low Profile Package
-40°C to +85°C Temperature Range
Applications
Large Size LCD TV, Panels
LCD Monitors
Video Walls
White LED Backlighting
Typical Application
VIN = 10.8V to 28V
CIN
CVCC
D1
L1 Q1
VIN GATE LXS OVP
VCC
AAT2404
R1
R2
VLED
COUT
On/Off Enable Input
CC
RC
RFREQ
RSET
EN
COMP
POK
FREQ
RSET
CSFB
PGND AGND
Power OK Output
Current Sense Feedback Input
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202247A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • August 7, 2012
1

1 page
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AAT2404 pdf, schematic
DATA SHEET
AAT2404
Voltage-Variable Current Sourcing Boost Controller For LED Lighting Applications
Pin Descriptions
Pin #
1, 2, 3,
23, 24
4
5
6
7, 8
9
10
11
12
13
14
15
16
17, 18, 19,
20, 21, 22
EP
Symbol
LXS
GATE
VIN
VCC
AGND
COMP
NC
CSFB
FREQ
OVP
RSET
EN
POK
PGND
EP
Function
I
O
I
I/O
GND
I
I
O
I
O
I
O
GND
GND
Description
Boost converter current sense node. Connect to the source terminal of the external low re-
sistance power MOSFET to this pin.
Output drive pin. Connect directly to the gate terminal of the external low resistance power
MOSFET. The gate voltage range is from 0V to VCC
Input power supply.
Internally regulated power supply. Decouple with 2.2µF or greater value capacitor between
this pin and AGND.
Analog ground.
Boost converter compensation. Connect external resistor and capacitor to this pin and AGND.
Not connected.
Current sink feedback. When used with compatible Skyworks LED driver devices1, connect
the driver CSFBO output directly to this pin for the current sink feedback from current sink
device.
Boost converter PWM switching frequency adjust pin. Connect a RFREQ resistor between this
pin and AGND to set the switching frequency.
Over-voltage protection. Connect a resistive divider between VLED, this pin, and ground.
Current sink regulation voltage set resistor. Connect the RSET resistor between this pin and
AGND.
Logic High enable pin. Apply a logic high voltage or connect to VIN to enable the device. Use
a 10kΩ resistor between this pin and AGND to for a logic pull-down to shut the device off
when an enable signal is not applied.
Open drain output. Connect to LED cathode with the anode connected via a resistor to VCC or
drive an active low logic signal to a system controller. If not used, leave open / not connected.
Power ground.
Exposed paddle. Connect to PCB GND plane. PCB paddle heat sinking should maintain
acceptable junction temperature.
Pin Configuration
TQFN34-24
(Top View)
LXS
LXS
LXS
GATE
VIN
VCC
AGND
24 23 22 21 20
1 19
2 18
3 17
EP4 16
5 15
6 14
7 13
8 9 10 11 12
PGND
PGND
PGND
POK
EN
RSET
OVP
1. Compatible Skyworks LED backlight driver products include the AAT2401, AAT2402 and AAT2403.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
2 202247A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • August 7, 2012

2 Page
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AAT2404 equivalent
DATA SHEET
AAT2404
Voltage-Variable Current Sourcing Boost Controller For LED Lighting Applications
Typical Characteristics
UVLO vs. Temperature
9.8
9.6
9.4
9.2
9.0
8.8
8.6
8.4
8.2
-40
Rising
Falling
-15 10 35 60
Temperature (°C)
85
Quiescent Current vs. Temperature
(VIN = 24V; VEN = VIN; Non-switching)
1.4
1.3
1.2
1.1
1.0
0.9
0.8
0.7
0.6
-40
-15
10
35 60
85
Temperature (°C)
Shutdown Current vs. Temperature
(VIN = 24V; VEN = GND)
16
14
12
10
8
6
4
2
0
-40 -15 10 35 60 85
Temperature (°C)
Efficiency vs. Load Current
(VIN = 24V; VLED = 31V; COUT = 20µF; L = 10µH)
100
96
92
88
84
80
76
72
68
0 0.4 0.8 1.2 1.6 2.0 2.4 2.8 3.2 3.6 4.0
Output Current (A)
Input Logic Threshold vs. Temperature
(VIN = 24V)
1.7
1.6
1.5
1.4
1.3
1.2
1.1
1.0
0.9
-40
-15
10
Logic Threshold High
Logic Threshold Low
35 60 85
Temperature (°C)
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202247A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • August 7, 2012
5

5 Page
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AAT2404 diode, scr
DATA SHEET
AAT2404
Voltage-Variable Current Sourcing Boost Controller For LED Lighting Applications
Maximum Output Voltage Compliance
When using the AAT2404 in a given application, one
must first determine what the maximum combined LED
string voltage will be at the specified maximum forward
current. The maximum practical operating duty cycle for
the DC-DC boost function is approximately 80%.
The maximum output voltage can be approximated using
Equation 1:
Eq.
1: VLED =
VIN
1-D
Where D = DC-DC boost switching duty cycle.
However, the maximum output voltage should not exceed
100V.
Internal Linear Voltage Regulator
The AAT2404 has an internal linear regulator to produce
5V from the VIN high voltage input for internal logic,
clock, and control functions. The regulator output is con-
nected to the VCC pin and should be bypassed with a
2.2µF or larger ceramic capacitor. The 5V may be used
as a logic pull-up reference termination for all AAT2404
logic functions such as a pull up for the open drain power
OK (POK) function. This output is not intended to sup-
port external loads from circuits other than low current
logic terminations.
IC Enable and Soft Start
An enable pin is provided as a master on/off function that
may be toggled by an external system controller or con-
nected directly to VIN. This is a logic active high function.
If the IC enable is not needed, connect the EN pin to VCC
to turn the AAT2404 on. The slew rate limited turn-on is
guaranteed by the built-in soft-start circuitry. Soft start
eliminates output current overshoot across the full input
voltage range and all load conditions. After the soft start
sequence has terminated, the initial output voltage is
determined by the level sensed on the CSFB pin.
Boost Converter Switching Frequency
The AAT2404 is designed to operate over a wide input to
output voltage range with a nominal 400kHz switching
frequency. However, if a specific system or application
demands a different operating switching frequency, the
frequency can be user adjusted by changing the resistor
value between the FREQ pin and ground. To set a recom-
mend 400kHz switching frequency, the nominal value
RFREQ value is 10kΩ. Refer to Figure 2 for resistor values
to program a specific switching frequency.
1
0.8
0.6
0.4
0.2
0
0 5 10 15 20 25 30 35 40 45
RFREQ (kΩ)
Figure 2: AAT2404 DC_DC Boost Switching
Frequency vs. RFREQ Resistor Value.
OVP
The over-voltage protection (OVP) circuit is provided to
shut down the boost control switching to the external
N-channel MOSFET if the output voltage exceeds a user
preset level, which can occur if the load circuit becomes
disconnected (open). The OVP pin input threshold is 1.2V
and the OVP shutdown voltage should be selected so
that the circuit is active within a reasonable margin
above the normal output operation voltage. To program
a desired OVP output limit level, place a resistor divider
between the voltage output node, the OVP pin, and
ground. Set the OVP voltage using Equation 2:
Eq. 2: R1 = R2
VOUTPUT PROTECTION
VOVP
-1
Where:
VOVP = OVP threshold = 1.2V
VOUTPUT PROTECTION = Desired output protection voltage
level
R2 should typically be set to 12.1kΩ (Nominal range for
R2 should be between 10kΩ and 47kΩ). The maximum
OVP is 120V.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202247A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • August 7, 2012
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