AAT1403
DATA SHEET
Serial LED Driver with Filtered PWM and 32-Step S2C Dimming Control
1
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202115B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • December 3, 2012
General Description
The AAT1403 is a step-up single channel LED driver with
an input voltage range of 2.7V to 5.5V. The wide input
voltage range, small solution size, advanced dimming
features and high efficiency is suitable for LED backlight
solutions for single cell Li-ion based equipment. A preci-
sion, high voltage current sink maintains the maximum
LED current set by an external resistor from 10 to 31mA.
The high switching frequency supports ultra small, low
cost filtering components.
Two dimming controls are available; 32 dimming steps
using the S2Cwire™ interface, and filtered PWM control.
The frequency range of the PWM dimming extends up to
100 kHz eliminating audible noise and suitable for CABC
(Content Adaptive Brightness Control) applications.
The device includes over-temperature protection and
programmable over-voltage protection and recovers
automatically when the fault is removed. The AAT1403 is
available in a 10-pin wafer-level chip scale package
(WLCSP) and is rated over the -40°C to +85°C tempera-
ture range.
Features
•Input Voltage Range: 2.7 to 5.5V
•Drives Up to 45V with Typical 10 Series LEDs at 31mA
•1MHz Switching Frequency Allows Small External
Components
•Up to 81% Efficiency with 10µH Inductor
•Dimming Control Options:
▪ 32 Steps - S2Cwire Single Wire Interface
▪ Filtered PWM
•Low Operating Current at 2.3mA
•Shutdown Current < 1µA
•Over-Voltage Protection for Open-LED Faults
•Over-Temperature Protection
•Ultra Small, Low Profile 10-pin 1.55 x 1.15mm
WLCSP Package
Applications
•Digital Still Cameras (DSC)
•Mobile Handsets
•Netbooks and Notebooks
•Portable Media Players
•White LED Drivers
Typical Application
LX
OVP
D1
V
IN
2.7V – 5.5V
AAT1403
CS
L1 10μH
V
OUT
Up to 45V
at 31mA
C
OUT
0.1µF
50V
C
IN
4.7µF
IN
GND
EN/SET
S
2
C
R1
R2
R
SET
10k PGND
RSET
C
COMP
56nF
COMP
PWM
Up to 10
WLEDs
PWM
AAT1403
DATA SHEET
Serial LED Driver with Filtered PWM and 32-Step S2C Dimming Control
2Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202115B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • December 3, 2012
Pin Descriptions
Pin # Symbol Function
A1 LX Switching node of boost converter. Connect an inductor between LX and input supply (VIN); Schott-
ky rectier anode is connected between LX pin while cathode is connected to output capacitor.
A2 IN Supply input for the IC. Connect a 4.7µF 6.3V/10V ceramic capacitor from this pin to GND.
A3 EN/SET Enable on/off control and S2Cwire interface input.
B1 PGND Power ground pin.
B3 PWM Input PWM pin. Pull high to disable the PWM dimming feature.
C1 GND Ground pin.
C3 COMP
Compensation pin. Connect a capacitor from this pin to GND. Compensation components are mainly
related to the output capacitor valued. See the Capacitor Selection section in the Application Infor-
mation section of this datasheet.
D1 CS Connect to the cathode of the last diode of the LED string.
D2 RSET Connect a resistor to GND to set maximum LED current up to 31mA.
D3 OVP Feedback pin for over-voltage protection.
Pin Configuration
WLCSP10 1.1 x1.5
(Top View)
A1 A2 A3
B1
C1
D1 D2
B3
C3
D3
AAT1403
DATA SHEET
Serial LED Driver with Filtered PWM and 32-Step S2C Dimming Control
3
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202115B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • December 3, 2012
1. Stresses above those listed in Absolute Maximum Ratings may cause permanent 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 an FR4 board.
3. Check Electrical Characteristics.
Absolute Maximum Ratings1
Symbol Description Value Units
VIN IN to GND, PGND -0.3 to 6.0 V
VLX LX to GND, PGND -0.3 to 50 V
VCS SINK to GND, PGND -0.3 to 35 V
VEN/SET
,VPWM, VRSET
,
VCOMP, VOVP
EN/SET, PWM, RSET, COMP, OVP to GND/PGND -0.3 to IN +0.3 V
Thermal Information2
Symbol Description Value Units
ΘJA Thermal Resistance 122 OC/W
PDMaximum Power Dissipation 820 mW
TJMaximum Junction Operating Temperature -40 to +155 OC
TLEAD Maximum Soldering Temperature (at leads, 10 sec.) 300
Recommended Operating Conditions
Symbol Description Min Typ Max Units
VIN Input Supply Voltage 2.7 5.5 V
VOUT Boosted Output Voltage VIN + 3V VOUT3V
L1 Inductor Value 4.7 10 22 μH
FPWM-F Input Filtered PWM Frequency 100 100,000 Hz
TAAmbient Temperature Range - 40 85 °C
AAT1403
DATA SHEET
Serial LED Driver with Filtered PWM and 32-Step S2C Dimming Control
4Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202115B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • December 3, 2012
1. The AAT1403 is guaranteed to meet performance specification over the –40°C to +85°C operating temperature range, and is assured by design, characterization and correla-
tion with statistical process controls.
Electrical Characteristics1
VIN = 3.6V, CIN = 4.7µF, COUT = 0.1µF, L = 10µH, RSET = 10KΩ, TA = -40°C to 85°C unless otherwise noted. Typical values
are at TA= 25°C.
Symbol Description Conditions Min Typ Max Units
VIN Input Voltage Range 2.7 5.5 V
VOUT Maximum Output Voltage 45 V
IQQuiescent Supply Current VENSET = VIN 430 700 µA
ISHDN Input Shutdown Current VENSET = 0V 1 µA
IQSW Input Switching Current VENSET = VIN 2.3 mA
RDS(ON)N NMOS On-Resistance TA = 25°C 650 mΩ
η Maximum Efciency IOUT = 31mA 81 %
Fosc Switching Frequency TA = 25°C 1.0 MHz
TSS Soft-Start Time VENSET = VIN to 95% of output regulation,
CCOMP = 56nF 5 ms
DMAX Maximum Duty Cycle 94.0 %
VOVP-T OUT Over-Voltage Protection Threshold VOVP rising 1.1 1.2 1.3 V
VOVPH Over-Voltage Protection Hysteresis 75 mV
TSD Over-Temperature Shutdown Threshold 155 °C
THYS Over-Temperature Shutdown Hysteresis 15 °C
VCS Current Sink Voltage IOUT = 31mA 500 mV
ICS(ACC) Current Sink Accuracy RSET = 10KΩ 27.9 31.0 34.1 mA
VRSET RSET Voltage RSET = 10KΩ 1.206 V
EN/SET
VEN/SET (L) EN/SET VIN = 2.7V to 5.5V 0.4 V
VEN/SET (H) EN/SET VIN = 2.7V to 5.5V 1.4 V
tEN/SET(LOW) EN/SET Input Low Time 0.3 75 µs
tEN/SET(HI_MIN) EN/SET Minimum High Time 100 ns
tEN/SET(HIMAX) EN/SET Maximum High Time 75 µs
tEN/SET(OFF) EN/SET Input Off Timeout 500 µs
tEN/SET(LAT) EN/SET Latch Timeout 500 µs
IEN/SET (LK) EN Input Leakage VENSET = 5V, VIN = 5V -1 1 µA
PWM
VPWM(L) Logic Threshold Low 0.4 V
VPWM(H) Logic Threshold High 1.4 V
IPWM(LK) PWM Input Leakage VPWM = 5V, VIN = 5V -1 1 µA
AAT1403
DATA SHEET
Serial LED Driver with Filtered PWM and 32-Step S2C Dimming Control
5
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202115B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • December 3, 2012
Typical Characteristics
Quiescent Current vs. Input Voltage
Input Voltage (V)
Quiescent Current (µA)
2.73.1 3.53.9 4.34.7 5.
15
.5
380
400
420
440
460
480
500
85°C
25°C
-40°C
Shutdown Current vs. Input Voltage
Input Voltage (V)
Shutdown Current (µA)
2.73.1 3.53.9 4.34.7 5.
15
.5
0.00
0.02
0.04
0.06
0.08
0.10
85°C
25°C
-40°C
Efficiency vs. Output Current
(RSET = 10KΩ, L = 10µH, 10 LEDs)
Output Current (mA)
Efficiency (%)
0816 24 3241220286142
23
02101826
30
35
40
45
50
55
60
65
70
75
80
85
90
VIN = 2.7V
VIN = 3.0V
VIN = 3.6V
VIN = 4.2V
VIN = 5.0V
VIN = 5.5V
LED Current Accuracy vs. Input Voltage
(VIN = 3.6V, RSET = 15KΩ)
Input Voltage (V)
Current (mA)
2.73.1 3.53.9 4.34.7 5.15.5
18.8
19.2
19.6
20.0
20.4
20.8
21.2
LED Current Accuracy vs. S2C
(VIN = 3.6V, L = 10µH)
S2C Data
LED Current (mA)
1917 25537 13 211511 19 23 27 29 31
0
4
8
12
16
20
24
28
32
RSET = 10KΩ
RSET = 15KΩ
RSET = 20KΩ
RSET = 25KΩ
RSET = 30KΩ
Startup Time vs. C
COMP
(10 WLEDs)
CCOMP (nF)
t
SU
(ms)
10 20 30 40 50 60 70 80 90 100
0
2
4
6
8
10
12
AAT1403
DATA SHEET
Serial LED Driver with Filtered PWM and 32-Step S2C Dimming Control
6Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202115B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • December 3, 2012
Typical Characteristics
LED Current Accuracy vs. Temperature
(VIN = 3.6V, RSET = 10kΩ)
Temperature (°C)
Current (mA)
-40-15 10 35 60 85
29.8
30.2
30.6
31.0
31.4
31.8
LED Current Accuracy vs. Temperature
(VIN = 3.6V, RSET = 15kΩ)
Temperature (°C)
Current (mA)
-40-15 10 35 60 85
18.8
19.2
19.6
20.0
20.4
20.8
EN Input High Threshold Voltage
vs. Input Voltage
Input Voltage (V)
V
EN(H)
(V)
2.73.1 3.53.9 4.34.7 5.15.5
0.5
0.6
0.7
0.8
0.9
1.0
1.1
85°C
25°C
-40°C
EN Input Low Threshold Voltage
vs. Input Voltage
Input Voltage (V)
V
EN(L)
(V)
2.73.1 3.53.9 4.34.7 5.15.5
0.4
0.5
0.6
0.7
0.8
0.9
1.0
85°C
25°C
-40°C
PWM Input High Threshold Voltage
vs. Input Voltage
Input Voltage (V)
V
PWM(H)
(V)
2.73.1 3.53.9 4.34.7 5.15.5
0.5
0.6
0.7
0.8
0.9
1.0
1.1
85°C
25°C
-40°C
PWM Input Low Threshold Voltage
vs. Input Voltage
Input Voltage (V)
V
PWM(L)
(V)
2.73.1 3.53.9 4.34.7 5.15.5
0.4
0.5
0.6
0.7
0.8
0.9
1.0
85°C
25°C
-40°C
AAT1403
DATA SHEET
Serial LED Driver with Filtered PWM and 32-Step S2C Dimming Control
7
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202115B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • December 3, 2012
Typical Characteristics
OVP High Threshold Voltage vs. Input Voltage
Input Voltage (V)
V
OVP(H)
(V)
2.73.1 3.53.9 4.34.7 5.15.5
1.12
1.14
1.16
1.18
1.20
1.22
85°C
25°C
-40°C
OVP Low Threshold Voltage vs. Input Voltage
Input Voltage (V)
V
OVP(L)
(V)
2.73.1 3.53.9 4.34.7 5.15.5
1.03
1.05
1.07
1.09
1.11
1.13
85°C
25°C
-40°C
Startup Waveform
(VIN = 3.6V; CIN = 4.7μF, COUT = 0.1μF,
CCOMP = 56nF, RSET = 10KΩ, 10 LEDs)
Time (2ms/div)
EN
(5V/div)
VOUT
(20V/div)
IIN
(200mA/div)
ILED
(20mA/div)
0
0
0
0
Turn Off
(VIN = 3.6V; CIN = 4.7μF, COUT = 0.1μF,
CCOMP = 56nF, RSET = 10KΩ, 10 LEDs)
Time (100µs/div)
EN
(5V/div)
VOUT
(20V/div)
IIN
(200mA/div)
ILED
(20mA/div)
0
0
0
0
Operation Waveform
(VIN = PWM = 3.6V; CIN = 4.7μF, COUT = 0.1μF,
CCOMP = 56nF, RSET = 10KΩ, 10 LEDs)
VLX
(20V/div)
VOUT (AC)
(500mV/div)
IINDUCTOR
(500mA/div)
ILED
(20mA/div)
0
0
0
0
Operation Waveform
(VIN = 3.6V; CIN = 4.7μF, COUT = 0.1μF,CCOMP = 56nF,
RSET = 10KΩ, PWM = 50kHz, 50% Duty Cycle, 10 LEDs)
Time (1µs/div)
VLX
(20V/div)
VOUT (AC)
(500mV/div)
IINDUCTOR
(500mA/div)
ILED
(20mA/div)
0
0
0
0
AAT1403
DATA SHEET
Serial LED Driver with Filtered PWM and 32-Step S2C Dimming Control
8Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202115B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • December 3, 2012
Typical Characteristics
LED Current Transition by PWM
(VIN = 3.6V; CIN = 4.7μF, COUT = 0.1μF, CCOMP = 56nF,
RSET = 10KΩ, PWM = 10KHz, 31mA to 15mA, 10 LEDs)
Time (400µs/div)
PWM
(5V/div)
VOUT
(20V/div)
IIN
(200mA/div)
ILED
(20mA/div)
0
0
0
0
LED Current Transition by PWM
(VIN = 3.6V; CIN = 4.7μF, COUT = 0.1μF, CCOMP = 56nF,
RSET = 10kΩ, PWM = 10KHz, 15mA to 31mA, 10 LEDs)
Time (400µs/div)
PWM
(5V/div)
VOUT
(20V/div)
IIN
(200mA/div)
ILED
(20mA/div)
0
0
0
0
LED Current Transition by S2C
(VIN = 3.6V; CIN = 4.7μF, COUT = 0.1μF, CCOMP = 56nF,
RSET = 10KΩ, S2C Data 1 to 16, 10 LEDs)
Time (400µs/div)
EN/SET
(5V/div)
VOUT
(20V/div)
IIN
(200mA/div)
ILED
(20mA/div)
0
0
0
0
LED Current Transition by S2C
(VIN = 3.6V; CIN = 4.7μF, COUT = 0.1μF, CCOMP = 56nF,
RSET = 10KΩ, S2C Data 16 to 1, 10 LEDs)
Time (400µs/div)
EN/SET
(5V/div)
VOUT
(20V/div)
IIN
(200mA/div)
ILED
(20mA/div)
0
0
0
0
AAT1403
DATA SHEET
Serial LED Driver with Filtered PWM and 32-Step S2C Dimming Control
9
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202115B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • December 3, 2012
Functional Description
The AAT1403 is a high frequency current mode controlled
step-up (boost) converter LED driver. The device utilizes
a single current sink to regulate the LED current by con-
trolling the output voltage. The wide voltage range is
suitable for single cell Li-ion / Li-polymer battery applica-
tions. The internal current sink is programmed by an
external resistor to a current from 10mA to 31mA. The
minimum output voltage must be greater than the input
voltage. The AAT1403 is capable of driving up to 45V with
10 series connected LEDs with currents up to 31mA. The
LED dimming method is through either the S2Cwire inter-
face with 32 steps or varied duty cycle of the PWM signal
with frequency up to 100kHz after the maximum LED
current is set by S2Cwire.
The over-voltage protection function is designed to pro-
tect the boost converter during the fault of the open
circuit of the LED string. The over-temperature function
is targeted to protect the converter if an over-tempera-
ture fault occurs. The AAT1403 will recover to normal
operation automatically when the OVP or OTP fault is
removed.
Soft Start / Enable
The AAT1403 is enabled by EN/SET pulled to high after
power on with a certain delay time. Internal soft start
circuitry limits the input inrush current and eliminates
output voltage overshoot. When ENSET is pulled low the
AAT1403 enters a low-power, non-switching state. The
total input current during shutdown is less than 1μA. An
external diode limits VOUT to the level of VIN during shut-
down. The diode consumes a small amount of additional
input current depending on the OVP resistor divider
value.
Over-Temperature Protection
Thermal protection disables the AAT1403 when internal
dissipation becomes excessive. Thermal protection dis-
ables the power MOSFET. The junction over-temperature
threshold is 155°C with 15°C of temperature hysteresis.
The output voltage automatically recovers when the
over-temperature fault condition is removed.
Functional Block Diagram
GND
PWM
EN/SET
COMP
IN
LX PGND
OVP
OSC
REF
Interface
Control
CS
RSET
OVP
AAT1403
DATA SHEET
Serial LED Driver with Filtered PWM and 32-Step S2C Dimming Control
10 Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202115B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • December 3, 2012
Over-Voltage Protection
Over-voltage protection prevents damage to the AAT1403's
LX pin during open-circuit or high output voltage condi-
tions. An over-voltage event is defined as a condition
where the voltage on the OVP pin exceeds the over-volt-
age protection threshold (VOVP-T). When VOVP has reached
the threshold limit, the converter stops switching and the
output voltage decays. Switching resumes when the lower
hysteresis limit of VOVP is reached, thereby maintaining an
average output voltage between the upper and lower OVP
thresholds.
LED Current Setting
The maximum LED current is determined by the RSET
resistor value. With a fixed 1.2V voltage on RSET
, the LED
maximum current is a linear ratio to the current flowing
through RSET
.
V
SET
R
SET
I
LED
= · 258
The LED dimming is controlled via one of two options,
either using the 32-step S2Cwire single-wire interface via
the EN/SET pin or PWM control with varied duty cycle up
to 100kHz frequency. 32 S2Cwire rising-edge steps set the
LED current from 100% to 2% percentage of the maxi-
mum LED current value when PWM control is disabled by
pulling the PWM pin high. S2Cwire can also be used to set
maximum LED current along with a PWM signal to dim the
LED lighting from 100% to 1% of duty cycle.
S2Cwire™ Serial Interface
The LED current magnitude can be controlled by the EN/
SET pin using the S2Cwire interface. The interface records
rising edges of the EN/SET pin and decodes them into 32
individual current level settings. Code 1 is full scale
(maximum LED current), and Code 32 is 2% of the full
scale. The modulo 32 interface wraps states back to state
1 after the 32nd clock. The counter can be clocked at
speeds up to 1MHz, so intermediate states are not visi-
ble. The first rising edge of EN/SET enables the IC and
initially sets the output LED current to full scale after
500µs tLAT. Once the final clock cycle is input for the
desired brightness level, the EN/SET pin should be held
high to maintain the device output current at the pro-
grammed level. The device is disabled 500μs after the
EN/SET pin enters a logic low state. The EN/SET timing
is designed to accommodate a wide range of data rates
from 20kHz to 1MHz.
After the first rising edge of EN/SET, the boost converter
is enabled and reaches full capacity after the soft-start
time. Exact counts of clock pulses for the desired current
level should be entered on the EN/SET pin with a single
burst of clocks. The counter refreshes each time a new
clock input to the EN/SET pin is detected. A constant cur-
rent is maintained as long as EN/SET remains in a logic
high state. To save power, the boost converter is switched
off after EN/SET has remained in the low state for at least
the tOFF timeout period as shown in Figure 1.
S2Cwire Serial Interface Timing
1
EN/SET
2n-1 n ≤32
Data Reg
0n
0
THI
TLO TLAT TOFF
Figure 1: S2Cwire Timing Diagram.
AAT1403
DATA SHEET
Serial LED Driver with Filtered PWM and 32-Step S2C Dimming Control
11
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202115B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • December 3, 2012
Application Information
LED Current Setting
The maximum LED current is determined by value of the
external resistor RSET from 10mA to 31mA. The value of
RSET is determined by the voltage of RSET and the LED
current, and can be calculated by:
V
SET
· 258
I
LED
R
SET
=
Where VSET = 1.2V. Table 1 lists examples of standard 1%
metal film RSET values for different maximum LED current
requirements.
Maximum LED Current (mA) RSET (kΩ)
31 10
20 15
15 20
12 25
10 30
Table 1: Examples of Standard 1% RSET Values for
Setting Maximum LED Current Levels.
LED current dimming is controlled either via the S2Cwire
single-wire interface through the EN/SET pin in 32 steps
or via PWM control with varied duty cycle up to 100kHz
frequency. The S2Cwire interface programs the LED cur-
rent from the maximum LED current set by RSET to 2%
of the maximum LED current as shown in Table 2.
S2Cwire
Data
LED Current
(% IMAX)
S2Cwire
Data
LED Current
(% IMAX)
1 100 17 48
2 97 18 45
3 94 19 42
4 90 20 39
5 87 21 35
6 84 22 32
7 81 23 29
8 77 24 26
9 74 25 23
10 71 26 19
11 68 27 16
12 65 28 13
13 61 29 10
14 58 30 6
15 55 31 3
16 52 32 2
Table 2: S2Cwire Dimming Control
Current Settings.
Figure 2 illustrates the LED current value at different
S2Cwire code settings when RSET is 15kΩ with a maximum
LED current of 20mA.
I
LED
(mA)
ILED (mA)
135791113151719212325272931246810 12 14 16 18 20 22 24 26 28 30 32
0
2
4
6
8
10
12
14
16
18
20
22
Figure 2: S2Cwire Dimming Control
at Maximum LED Current (20mA max).
Filtered PWM Dimming
The AAT1403 provides a PWM input as an additional
means of providing dimming control for CABC applica-
tions. The LED current reduces percentage linearly as
the duty cycle decreasing. Frequencies of up to 100kHz
can be applied. To avoid output flicker and noise, the
input control PWM frequency is filtered by the low pass
filter composed of the error amplifier and the external
compensation capacitor.
Figure 3 shows LED current dimming controlled by vary-
ing the PWM duty cycle at RSET = 15kΩ.
LED
100 90 80 70 60 50 40 30 20 10 0
0
2
4
6
8
10
12
14
16
18
Figure 3: Filtered PWM Dimming Duty Cycle vs.
Maximum LED Current (20mA max).
AAT1403
DATA SHEET
Serial LED Driver with Filtered PWM and 32-Step S2C Dimming Control
12 Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202115B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • December 3, 2012
Capacitor Selection
A compensation capacitor CCOM is used for step-up con-
verter loop compensation, soft startup time control, and
PWM digital signal filtering. Loop compensation requires
matching values for CCOM, COUT
, ILED, and VOUT:
I
LED
30 · 10
-6
· V
OUT
C
OUT
C
COM
<
The AAT1403 can drive up to 10 white LEDs with forward
voltages up to 4V each. In a worst case with VF of 4V, a
COUT value of 0.1µF, and LED maximum current of 20mA,
the value of CCOM should be higher than 6.0nF.
C
OUT
· 30 · V
OUT
I
LED
0.1 · 30 · 40
20
C
COM
> (nF) = (nF) = 6.0nF
A higher value for CCOM lengthens the soft startup time.
The relationship between CCOM and startup time is almost
linear, with startup time x 105 magnification of CCOM; thus
56nF CCOM leads to a soft startup time of 5.6ms. Table 3
gives several examples of minimum CCOM values at differ-
ent COUT and ILED and the step-up converter's operation
stable. Values of 56nF for CCOM and 0.1µF for COUT are
suitable in most cases.
ILED (mA) COUT (µF) VOUT (V) CCOM_MIN (nF)
31 0.1 40 3.9
31 1 40 39
20 0.1 40 6.0
20 1 40 60
10 0.1 40 12
10 1 40 120
Table 3: Minimum CCOM Values vs. ILED and COUT
(Step-Up Converter Operation Stable).
Multi-layer ceramic (MLC) capacitors provide small size
and adequate capacitance, low parasitic equivalent series
resistance (ESR) and equivalent series inductance (ESL),
and are well suited for use as input, output and compen-
sation capacitors in the AAT1403 step-up converter LED
driver application. MLC capacitors of type X7R or X5R are
recommended to ensure good capacitance stability over
the full operating temperature range. A 4.7µF/6.3V input
capacitor is recommended and a 0.1µF/50V output capac-
itor is suitable as noted above. Table 4 lists some recom-
mended capacitors for use with the AAT1403.
Inductor Selection
Inductor value, saturation current and DCR is most impor-
tant parameter in selecting an inductor for the AAT1403.
The suitable inductance range for the AAT1403 is 4.7µH
to 22µH. Higher inductance lowers the step-up convert-
er's RMS current value. Together with lower DCR value
of the inductor, it makes the total inductor power loss
become much lower. Considering inductor size and cost,
10µH inductance is most suitable. Figure 4 illustrates
AAT1403 efficiency at different inductance with similar
DCR value.
Efficiency (%)
ILED (mA)
40812 16 20 24 28 32
30
35
40
45
50
55
60
65
70
75
80
85
90
4.7µH
10µH
22µH
Figure 4: AAT1403 Efficiency at Different
Inductance with Similar DCR (VIN = 3.6V).
Manufacturer Part Number Value (µF) Voltage (V) Temperature Range Case Size
Murata GRM188R60J475K 4.7 6.3 X5R 0603
GRM188R71H104KA93 0.1 50 X7R 0603
Table 4: Examples of AAT1403 Input and Output Capacitor Selection.
AAT1403
DATA SHEET
Serial LED Driver with Filtered PWM and 32-Step S2C Dimming Control
13
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Manufacturer Part Number
Inductance
(µH)
Maximum DC ISAT
Current (mA)
DCR
(mΩ, typ)
Size (mm)
LxWxH Type
Sumida CDRH3D18-100 10 900 164 4.0x4.0x2.0 Shielded
CDRH3D23-220 22 550 219 3.9x3.9x2.5 Shielded
Murata LQH44PN100MP0L 10 1150 160 4.0x4.0x1.65 Non-shielded
LQH44PN220MP0L 22 800 370 4.0x4.0x1.65 Non-shielded
Coilcraft EPL2014-103MLC 10 600 440 2.1x2.2x1.0 Shielded
LPS4012-223MLC 22 790 600 4.1x4.1x1.2 Shielded
Coiltronics SD18-100-R 10 982 158 5.8x5.8x1.8 Shielded
Table 5: Example of AAT1403 Inductor Selection.
Considering the inductor copper loss, the inductor DCR
value together with the RMS current value flowing
through the inductor leads to inductor conduction loss
and also affects total efficiency. Larger DCR leads to
larger conduction loss and decreases total efficiency. The
inductor conduction loss can be estimated as shown in
the equation:
1
3
P
L_LOSS
= I
2
L_RMS
· DCR
=· (I
2
L_MAX
+ I
2
L_MIN
+ I
L_MAX
· I
L_MIN
) · DCR
IL_MAX and IL_MIN are the inductor peak current and mini-
mum current. Figure 5 shows DCR effects on efficiency
with a 10µH inductor.
Efficiency (%)
ILED (mA)
24068101214161820222426283
03
2
30
34
38
42
46
50
54
58
62
66
70
74
78
82
DCR 235mΩ 3.2x3.2x1.55mm
DCR164mΩ 4.0x4.0x2.0mm
DCR 36mΩ 8.3x8.3x3.0mm
Figure 5: Inductor DCR Effects on
Total Efficiency with 10µH at 3.6V VIN.
Inductor saturation current is also a key parameter in
selecting an inductor. For the step-up converter, the peak
inductor current is the DC input current plus half the
inductor peak-to-peak current ripple.
DC input current:
V
OUT
· I
LED
V
IN
· η
I
IN
=
Inductor peak-to-peak current ripple:
V
IN
· (V
OUT
- V
IN
)
V
OUT
· L · f
I
L_PP
=
Inductor peak current:
V
IN
· (V
OUT
- V
IN
)
2 · V
OUT
· L · f
V
OUT
· I
LED
V
IN
· η
I
L_PP
2
I
L_PEAK
= I
IN
+ = +
For example, for a white LED with 3.2V VF and 20mA
current at 80% efficiency at 3.6V VIN, the inductor peak
current is
3.6 · (3.2 · 10 - 3.6)
2 · 3.2 · 10 · 10µ · 1M
3.2 · 10 · 0.02
3.6 · 0.8
I
L_PEAK
= + = 382mA
Table 5 gives some examples of recommended inductors
for use with the AAT1403.
OVP Setting
Over-voltage protection is designed to protect the step-up
converter from a LED string open fault. The OVP threshold
is 1.2V. For 6 white LEDs with VF up to 4V, the resistor
divider values for R1 and R2 can be calculated by:
V
OUT
V
OVP_TH
R
1
= - 1· R
2
Higher resistor divider values decrease the power loss on
the resistors. The total resistor value for 40V VOUT should
be less than 4MΩ for better noise immunity. Values of
2.2MΩ for resistor R1 and 68kΩ for resistor R2 are rec-
ommended.
AAT1403
DATA SHEET
Serial LED Driver with Filtered PWM and 32-Step S2C Dimming Control
14 Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202115B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • December 3, 2012
Manufacturer
Part
Number
Maximum
DC Blocking
Voltage VR (V)
Maximum DC
Forward Current
IF (mA)
Non-repetitive Peak
Forward Surge
Current IFSM (A)
Forward
Voltage
VF (V) Case
Size
WxLxH
(mm)
Diodes DFLS160 60 1000 5.0 0.5@1A PowerDI 123 1.93x3.0x1.0
TSC SS15L 50 1100 30 0.51@0.5A Sub SMA 1.9x3.8x1.43
SS16L 60 1100 30 0.51@0.5A Sub SMA 1.9x3.8x1.43
Table 6: Example of Typical Rectifier Diodes.
Rectifier Diode Selection
An external rectifier diode is required for the non-syn-
chronous step-up converter. A low VF Schottky diode is
recommended. The diode voltage rating should be higher
than the OVP voltage. For an AAT1403 driving 10 white
LEDs with up to 4V forward voltage, the diode voltage
rating should be higher than 40V. Select a diode with DC
rated current equal to the input current to allow an ade-
quate margin for safe use.
Table 6 gives some examples of recommended rectifier
diodes for use with the AAT1403.
Printed Circuit Board
Layout Recommendations
For best performance of the AAT1403, the following
guidelines should be followed when designing the PCB
layout:
1. Make the power trace as short and wide as possible,
including the input/output power lines and switching
node, etc.
2. Make sure the ground bump connected to the print-
ed circuit board with large copper area for better
thermal dissipation.
3. Put the input and output capacitor close to the IC as
close as possible to get the best filter result.
AAT1403
DATA SHEET
Serial LED Driver with Filtered PWM and 32-Step S2C Dimming Control
15
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202115B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • December 3, 2012
Schematic and Layout
S2Cwire/PWM
Microcontroller
AAT1403
White LED
Driver
CIN
4.7µF
L1 10µH
2.2M
R1
68k
R2
COUT
0.1μF/50V
DS1
SS16L
DC+
DC-
J2
PWM
CCOM
56nF
RSET
15k
VIN
R3
51k
R4
51k
C1
0.1µF
R7
1k
R8
1k
R9
1k
R5
1k
R6 51k
V_MCU
VMCU
EN/SET
UP
DOWN
CYCLE
PIC12F675
VDD
1
GP5
2
GP4
3
GP3
4GP2 5
GP1 6
GP0 7
VSS 8
U2
LED1
Red
J1
VIN
PGND
B1
LX A1
GND
C1
CS D1
RSET
D2
PWM
B3
COMP
C3
IN
A2
EN/SET
A3
OVP D3
AAT1403IUQ
U1
1
2
3J3
VMCU
PWM
D1
D2
D3
D4
D5
D6
D10D8 D7D9
Figure 6: AAT1403 Evaluation Board Schematic.
AAT1403
DATA SHEET
Serial LED Driver with Filtered PWM and 32-Step S2C Dimming Control
16 Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202115B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • December 3, 2012
Figure 7: AAT1403 Evaluation Board Figure 8: AAT1403 Evaluation Board
Top Side Layout. Top Side Layout (detail).
Figure 9: AAT1403 Evaluation Board Bottom Side Layout.
AAT1403
DATA SHEET
Serial LED Driver with Filtered PWM and 32-Step S2C Dimming Control
17
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202115B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • December 3, 2012
Component Part Number Description Manufacturer
U1 AAT1403IUQ High Efciency Serial LED Driver for 6 White LEDs Skyworks
U2 PIC12F675 8-Pin Flash-Based 8-Bit CMOS Microcontroller Microchip
R1 RC0603FR-072M2L Res 2.2MΩ 1/10W 1% 0603 SMD
Yageo
R2 RC0603FR-0768KL Res 68KΩ 1/10W 1% 0603 SMD
R3, R4, R6 RC0603FR-0751KL Res 51KΩ 1/10W 1% 0603 SMD
RSET RC0603FR-0715KL Res 15KΩ 1/10W 1% 0603 SMD
R5, R7, R8, R9 RC0603FR-071KL Res 1KΩ 1/10W 1% 0603 SMD
CIN GRM188R60J475K Cap Ceramic 4.7μF 0603 X5R 6.3V 10%
Murata
COUT GRM21BR71H104K Cap Ceramic 0.1μF 0805 X7R 50V 10%
C1 GRM188R71C104K Cap Ceramic 0.1μF 0603 X7R 16V 10%
CCOM GRM188R71C563K Cap Ceramic 0.056μF 0603 X7R 16V 10%
D1, D2, D3, D4,
D5, D6, D7, D8,
D9, D10
RS-0805UW 20mA White LED 0805 Realstar
DS1 SS16L Surface Mount Schottky Barrier Diode TSC
L1 CDRH3D18-100NC Power Inductor 10μH 0.9A SMD Sumida
LED1 0805KRCT Red LED 0805 HB
CYCLE, UP, DOWN 6*6*5 12V 50mA Pushbutton E-LT
Table 7: AAT1403 Evaluation Board Bill of Materials (BOM).
AAT1403
DATA SHEET
Serial LED Driver with Filtered PWM and 32-Step S2C Dimming Control
18 Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202115B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • December 3, 2012
1. YY = date code.
2. Sample stock is generally held on part numbers listed in BOLD.
Ordering Information
Package Maximum # of LEDs Interface Marking1Part Number (Tape and Reel)2
WLCSP-10 10 S2C, Filtered PWM H5YY AAT1403IUQ-T1
Skyworks Green™ products are compliant with
all applicable legislation and are halogen-free.
For additional information, refer to Skyworks
Definition of Green™, document number
SQ04-0074.
Package Information
WLCSP-10
1.145 ± 0.035
0.800 BSC
0.265 ± 0.015
1.545 ± 0.035
0.200 BSC
1.200 BSC
0.400 BSC
ø 0.2 (Ref.)
Pin A1 indication
Line_1 Line_2
0.100
0.100
0.300
0.300
0.380 ± 0.025
0.200 ± 0.025 0.070 ± 0.035
Bottom View Top View
End View
0.650 ± 0.085
Side View
All dimensions in millimeters.
AAT1403
DATA SHEET
Serial LED Driver with Filtered PWM and 32-Step S2C Dimming Control
19
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202115B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • December 3, 2012
Copyright © 2012 Skyworks Solutions, Inc. All Rights Reserved.
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