AAT3176 - Skyworks Solutions, Inc.

DATA SHEET
AAT3176
500mA LED Flash Driver
General Description
Features
The AAT3176 is a high output current, high efficiency, low
noise, low profile charge pump converter IC, ideal for
multi-function LED photo-flash applications where solution cost, size, and efficiency are critical. The charge
pump is capable of delivering up to 500mA of output current and can be easily programmed in 16 steps with a
single GPIO output through Skyworks' S2Cwire™ (Simple
Serial Control) interface. This allows smooth transitions
and flexible adjustment of brightness in flash or other
lighting modes. Operating at a fast 1MHz switching frequency, the dual-mode (1x/2x) operation of the internal
charge pump offers excellent power efficiency for both
flash and movie modes and combined with a low external
parts count (one 1μF flying capacitors and small bypass
capacitors at VIN and OUT), the AAT3176 is ideally suited
for small, battery-powered applications.
• 2.7V to 5.5V Supply Voltage Range
• Up to 500mA Output Drive Capability at 3.6V VIN
• Flexible Brightness Control
▪ 16 Step Output Current by S2Cwire
• Separate External Resistors to Set Maximum Flash and
Movie-Mode Current
• Dual Mode 1x/2x Charge Pump
• < 1.0μA in Shutdown
• Small Application Circuit
• Automatic Soft-Start Limits Inrush Current
• Open- and Short-Circuit Protection
• Thermal Shutdown Protection
• -40 to +85°C Temperature Range
• 10-pin TDFN2.2x2.2 Package
Applications
The maximum current for both Flash and Movie mode is
set by two independent external resistors. The MODE pin
is adopted to select the LED current between Movie
(Torch) and Flash mode.
•
•
•
•
Digital Still Cameras (DSC)
LED Photo Flash/Torch
Mobile Handsets
PDAs and Notebook PCs
The AAT3176 has a thermal management system to protect the device in the event of short-circuit, open-circuit,
and over-temperature condition. Built-in soft-start circuitry prevents excessive in-rush current during startup. The shutdown feature disconnects the load from VIN
and reduces quiescent current to less than 1.0μA.
The AAT3176 is available in the 2.2 x 2.2mm Pb-free
10-pin TDFN package.
Typical Application
C1
1µF
C1+
2.7V to 5.5V
CIN
4.7µF
EN
Flash
Movie
C1VOUT
VIN
COUT
2.2µF
AAT3176
FL
RSETF
RSETM
EN/SET
MODE
GND
Flash
LED
RM
RF
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202102A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 25, 2012
1
DATA SHEET
AAT3176
500mA LED Flash Driver
Pin Descriptions
Pin #
Symbol
1
2
3
4
5
C1+
VOUT
FL
RSETF
RSETM
6
MODE
7
EN/SET
8
9
10
EP
GND
C1VIN
Description
Flying capacitor C1 positive terminal. Connect a 1.0 μF capacitor between C1+ and C1-.
Charge-pump output. Requires 2.2uF bypass capacitor to ground.
Output current source. Connect the flash LED anode to this pin.
Connect a resistor to GND to set maximum FLASH output current.
Connect a resistor to GND to set maximum MOVIE-MODE output current.
Selects between Flash and Movie Mode:
When MODE is HIGH, it is in Flash Mode with RSETF for maximum current.
When MODE is LOW, it is in Movie Mode with RSETM for maximum current .
Charge Pump enable / set input control pin.
When in the low state, the AAT3176 is shut down, and consumes less than 1μA. When connected logic
high level, the AAT3176 is active. This pin must be connected.
Ground connection and flash LED cathode.
Flying capacitor C1 negative terminal.
Input power supply pin. Requires 4.7μF bypass capacitor to ground.
Exposed pad. Connect directly to ground beneath the package.
Pin Configuration
TDFN2.2x2.2-10
(Top View)
C1+
VOUT
FL
RSETF
RSETM
2
1
10
2
8
3
8
4
7
5
6
VIN
C1GND
EN/SET
MODE
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202102A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 25, 2012
DATA SHEET
AAT3176
500mA LED Flash Driver
Absolute Maximum Ratings1
TA = 25°C unless otherwise noted.
Symbol
VIN
VEN
Description
Input Voltage
EN to GND Voltage
Maximum EN to Input Voltage
Maximum DC Output Current2
Maximum Peak Output Current (lasting 1 second)
Maximum Junction Operating Temperature
Storage Temperature Range
Maximum Soldering Temperature (at leads, 10 sec)
VEN(MAX)
IOUT
TJ
TS
TLEAD
Value
Units
-0.3 to 6.0
-0.3 to 6.0
VIN + 0.3
150
550
-40 to 150
-65 to 150
300
V
V
V
mA
mA
Value
Units
71.4
1.4
°C/W
W
°C
Thermal Information3
Symbol
JA
PD
Description
Thermal Resistance
Maximum Power Dissipation (TA = 25°C)
4
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. Based on long-term current density limitation.
3. Mounted on an FR4 board.
4. Derate 71.4mW/°C above 25°C.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202102A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 25, 2012
3
DATA SHEET
AAT3176
500mA LED Flash Driver
Electrical Characteristics1
VIN = 3.6V; CIN = 4.7μF; COUT = 2.2μF; CFLY = 1μF; RSETF = 21kΩ; RSETM = 105kΩ; TA = -40°C to 85°C, unless otherwise
noted. Typical values are TA = 25°C.
Symbol
Description
Conditions
Power Supply
VIN
Input Voltage Range
VOUT (max)
Maximum Output Voltage
IINQ
ISHDN(MAX)
IIN_Short
IDM
IDF
Input Operating Current
VIN Pin Shutdown Current
Input Current at Short Circuit
Movie Output Current
Flash Output Current
IOUT(MAX)
Maximum Output Current
ILED/ISET
LED Current Ratio
FCLK
Charge Pump Clock Frequency in 2X Mode
Soft-Start Time
TSS
EN/SET, MODE
VRSET
RSETF and RSETM Pin Voltage
VEN/MODE(L)
EN/MODE Threshold Low
EN/MODE Threshold High
VEN/MODE(H)
ILEAK
EN/SET, MODE input leakage
S2C Control
TEN/SET LO
EN/SET Low Time
TEN/SET HI(MIN) Minimum EN/SET High Time
TEN/SET HI(MAX) Maximum EN/SET High Time
TOFF
EN/SET Off Timeout
TLAT
EN/SET Latch Timeout
Thermal Protection
Thermal Shutdown Threshold
TSD
Thermal Shutdown Hysteresis
THYS
Min
Typ
2.7
EN/SET = IN, 1x mode, IF = 100mA
EN/SET = IN, 2x mode, IF = 100mA
EN = GND
VF = 0V
RSETM = 105kΩ
RSETF = 21kΩ, TA = 25°C
RSETF = 21kΩ, VIN = 3.0V
VF = 3.6V
Max
Units
5.5
V
V
5.5
0.5
3.0
mA
1.0
450
25
100
500
350
550
500
0.5
8652
1
100
1.5
1.22
0.4
1.4
-1
1
0.3
75
50
75
500
500
140
15
μA
mA
mA
mA
mA
mA
MHz
μs
V
V
V
μA
μs
ns
μs
μs
μs
O
C
1. The AAT3176 is guaranteed to meet performance specifications over the -40°C to +85°C operating temperature range and is assured by design, characterization, and correlation with statistical process controls.
4
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202102A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 25, 2012
DATA SHEET
AAT3176
500mA LED Flash Driver
Typical Characteristics
Quiescent Current vs. Input Voltage
Shutdown Current vs. Input Voltage
(VF = 3.6V; RSET = 105kΩ)
(VF = 3.6V; EN = 0V)
Quiescent Current (mA)
-40°C
25°C
85°C
0°C
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
Shutdown Current (μA)
1
5.0
-40°C
0°C
25°C
85°C
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
0.0
2.7
3.1
3.5
3.9
4.3
4.7
5.1
5.5
2.7
3.1
3.5
Input Voltage (V)
Efficiency vs. Input Voltage
100%
Efficiency (%)
5.1
5.5
80%
70%
60%
50%
VF = 2.7V
VF = 3.0V
VF = 3.3V
VF = 3.6V
90%
Efficiency (%)
VF = 2.7V
VF = 3.0V
VF = 3.3V
VF = 3.6V
90%
40%
80%
70%
60%
50%
40%
3.1
3.5
3.9
4.3
4.7
5.1
30%
2.7
5.5
3.1
3.5
Input Voltage (V)
3.9
4.3
4.7
5.1
5.5
Input Voltage (V)
Efficiency vs. Input Voltage
Efficiency vs. Input Voltage
(RSETF = 35.7kΩ; IF = 300mA)
(RSETF = 21kΩ; IF = 500mA)
VF = 2.7V
VF = 3.0V
VF = 3.3V
VF = 3.6V
90%
80%
70%
60%
50%
40%
100%
VF = 2.7V
VF = 3.0V
VF = 3.3V
VF = 3.6V
90%
Efficiency (%)
100%
Efficiency (%)
4.7
(RSETF = 52.3kΩ; IF = 200mA)
100%
30%
2.7
4.3
Efficiency vs. Input Voltage
(RSET = 105kΩ; IF = 100mA)
30%
2.7
3.9
Input Voltage (V)
80%
70%
60%
50%
40%
3.1
3.5
3.9
4.3
Input Voltage (V)
4.7
5.1
5.5
30%
2.7
3.1
3.5
3.9
4.3
4.7
5.1
5.5
Input Voltage (V)
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202102A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 25, 2012
5
DATA SHEET
AAT3176
500mA LED Flash Driver
LED Current vs. Input Voltage
LED Current vs. Input Voltage
(RSET = 105kΩ; IF = 100mA)
(RSET = 52.3kΩ; IF = 200mA)
120
120
115
115
110
110
105
105
IF (mA)
IF (mA)
Typical Characteristics
100
95
VF = 2.7V
VF = 3.0V
VF = 3.3V
VF = 3.6V
90
85
3.1
3.5
3.9
4.3
4.7
5.1
95
VF = 2.7V
VF = 3.0V
VF = 3.3V
VF = 3.6V
90
85
80
2.7
100
80
2.7
5.5
3.1
3.5
Input Voltage (V)
3.9
4.3
4.7
5.1
5.5
Input Voltage (V)
LED Current vs. Input Voltage
LED Current vs. Input Voltage
(RSET = 35.7kΩ; IF = 300mA)
(RSET = 21kΩ; IF = 500mA)
400
600
550
350
500
IF (mA)
IF (mA)
300
250
200
VF = 2.7V
VF = 3.0V
VF = 3.3V
VF = 3.6V
150
100
2.7
3.2
3.7
4.2
4.7
450
400
350
VF = 2.7V
VF = 3.0V
VF = 3.3V
VF = 3.6V
300
250
200
2.7
5.2
3.1
3.5
Input Voltage (V)
3.9
4.3
4.7
5.1
5.5
Input Voltage (V)
Maximum Output Current vs. Input Voltage
Maximum Output Current vs. Input Voltage
(RSETM = 105kΩ; VF = 3.6V)
(RSETF = 21kΩ; VF = 3.6V)
140
550
130
500
IF_MAX (mA)
IF_MAX (mA)
120
110
100
90
80
-40°C
25°C
85°C
70
60
2.7
3.1
3.5
3.9
4.3
Input Voltage (V)
6
4.7
5.1
5.5
450
400
-40°C
25°C
85°C
350
300
3.6
3.8
4.0
4.2
4.4
4.6
4.8
5.0
Input Voltage (V)
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202102A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 25, 2012
5.2
5.4
DATA SHEET
AAT3176
500mA LED Flash Driver
Typical Characteristics
EN/MODE Threshold High vs. Temperature
EN/MODE Threshold Low vs. Temperature
1.4
1.4
1.3
1.2
1.2
1.0
VIL (V)
VIH (V)
1.1
1.0
0.9
0.8
0.7
0.5
0.4
-40
-15
10
35
60
0.6
0.4
VIN = 2.7V
VIN = 3.6V
VIN = 4.2V
0.6
0.8
VIN = 2.7V
VIN = 3.6V
VIN = 4.2V
0.2
0.0
-40
85
-15
10
Temperature (°C)
35
60
85
Temperature (°C)
LED Current vs. RSET
EN Leakage Current vs. Input Voltage
(VF = 3.6V; VEN = 5.5V; RSET = 21kΩ)
0.8
EN Leakage Current (μA)
LED Current (mA)
600
RSETF
RSETM
500
400
300
200
100
0.7
0.6
0.5
0.4
0.3
-40°C
0°C
25°C
85°C
0.2
0.1
0.0
0
0
50
100
150
200
2.7
3.1
3.5
3.9
4.3
4.7
5.1
5.5
Input Voltage (V)
RSET (kΩ)
Oscillator Frequency vs. Input Voltage
Frequency (MHz)
1.10
1.05
1.00
-40°C
0°C
25°C
85°C
0.95
0.90
2.7
3.1
3.5
3.9
4.3
4.7
5.1
5.5
Input Voltage (V)
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202102A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 25, 2012
7
DATA SHEET
AAT3176
500mA LED Flash Driver
Typical Characteristics
LED Current 7.5mA to 100mA Transient
LED Current 100mA to 7.5mA Transient
(VIN = 5.0V; VF = 3.6V; RSET = 105kΩ)
(VIN = 5.0V; VF = 3.6V; RSET = 105kΩ)
VEN
(2V/div)
VEN
(2V/div)
100mA
100mA
IF
(50mA/div)
IF
(50mA/div)
Time (40μs/div)
Time (40μs/div)
LED Current 40mA to 500mA Transient
LED Current 500mA to 40mA Transient
(VIN = 5.0V; VF = 3.6V; RSET = 21kΩ)
(VIN = 5.0V; VF = 3.6V; RSET = 21kΩ)
VEN
(2V/div)
VEN
(2V/div)
500mA
500mA
IF
(200mA/div)
IF
(200mA/div)
Time (40μs/div)
8
Time (40μs/div)
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202102A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 25, 2012
DATA SHEET
AAT3176
500mA LED Flash Driver
Functional Block Diagram
C+
C-
VIN
1MHz
Oscillator
Charge
Pump
OUT
Soft Start
Control
FL
EN/SET
System Control;
S2CWire;
Timing
GND
RSETF
MODE
RSETM
Functional Description
The AAT3176 is a high efficiency, low noise, 1x/2x regulating charge pump device is intended for photo flash
LED applications. The AAT3176 requires only 3 external
components: one 1.0μF ceramic capacitor for the charge
pump flying capacitor, one 4.7μF ceramic capacitor for
CIN, and one 2.2μF to 4.7 μF ceramic capacitor for COUT
filtering.
The charge pump is designed to deliver up to 500mA
load current at VIN = 3.6V. The dual mode charge pump
section contains soft start circuitry to prohibit an excessive in rush current during start up. System efficiency is
maximized with a 1x/2x mode, dual mode charge-pump
topology. The internal clock oscillator frequency of 1MHz
allows the use of small external components.
Depending upon the variation of load current (at different modes), input voltage, and LED forward voltage, the
charge pump will operate in 1x or 2x mode to generate
the output voltage required to power the load for the
required current. This results in significant power savings over pure voltage doubling architectures, especially
when the LEDs are operated at lower current levels in
movie, viewing, or flash modes.
The AAT3176 also includes open- and short-circuit protection to deal with fault situations. When the flash LED
is not connected (an open fault occurs), the VOUT will be
limited to 6V; When a flash LED short fault occurs, the
total input current is limited to typical 25mA.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202102A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 25, 2012
9
DATA SHEET
AAT3176
500mA LED Flash Driver
S2Cwire Serial Interface
The AAT3176 utilizes Skyworks’ single-wire S Cwire
interface to enable/disable the charge pump and adjust
the output current level to one of sixteen different current levels. Each DATA defines the output current as a
percentage of the maximum current set by the resistor
at the RSET pin, as detailed in Table 1.
2
The S2Cwire interface records rising edges of the EN/SET
pin and decodes them into 16 individual current level
settings, with DATA 1 reserved for maximum current.
Once EN/SET has been held in the logic high state for
time TLAT, the programmed current is set at the current
source outputs. For subsequent current level programming, the number of rising edges corresponding to the
desired DATA must be entered on the EN/SET pin. Figure
1 shows the S2CwireTM interface timing.
DATA
Output Current (% of IMAX)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
100.0%
89.1%
79.4%
70.8%
63.1%
56.2%
50.1%
44.7%
39.8%
35.5%
31.6%
28.2%
25.1%
22.4%
20.0%
7.5%
Table 1: Output Current at
Different S2Cwire DATA.1
When EN/SET is held low for an amount of time greater
than TOFF, the AAT3176 enters shutdown mode and draws
less than 1μA from VIN. Data and Address registers are
reset to 0 during shutdown.
S2Cwire Serial Interface Timing
THI
TLO
TOFF
T LAT
EN/SET
1
2
n-1
0
Data Reg
n ≤ 16
n
0
Figure 1: S2Cwire Interface Timing.
1. The flash LED accuracy is compromised at high DATA settings.
10
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202102A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 25, 2012
DATA SHEET
AAT3176
500mA LED Flash Driver
Application Information
VIN
(5V/div)
Flash and Movie Mode
LED Current Setting
The AAT3176 has two independent LED current setting
pins for LED current in flash and movie mode: RSETF and
RSETM. The MODE pin is designed to select which current
set flows through the LED. When MODE is high, the current set by RSETF is the maximum LED current; when
MODE is low, the maximum current is set by RSETM. The
calculation method of the LED current set resistor value
RSET is the same for either mode and can be calculated
using the following formula:
RSETF = RSETM =
1.22
· 8652
ILED
Table 2 shows some examples of 1% standard metal film
resistor values for different maximum LED currents
(DATA = 1) in movie and flash mode.
RSETM
(kΩ)
Maximum LED
Current (mA)
RSETF
(kΩ)
Maximum LED
Current (mA)
210.0
174.0
150.0
130.0
118.0
105.0
50
60
70
80
90
100
105.0
69.8
52.3
42.2
35.7
30.1
26.1
23.7
21.0
100
150
200
250
300
350
400
450
500
Table 2: Maximum LED Current
RSETM and RSETF Example.
LED current can be set to levels lower than maximum via
S2C DATA transferred through the EN/SET pin, corresponding to percentage of the maximum setting value.
In movie mode, continuous high level of EN/SET lights
the LED light continuously at the programmed current.
In flash mode, EN/SET high level duration controls flash
time; the maximum flash time is 1 second for 500mA
LED current limited by the thermal characteristics of the
package. Figure 2 shows the operating waveform of the
AAT3176 driving an LED for 500ms flash time in flash
mode with 500mA LED current at 3.6V VIN (2x mode).
IIN
(1A/div)
VF
(2V/div)
ILED
(1A/div)
VC1
(5V/div)
VRSETF
(2V/div)
Time (100ms/div)
Figure 2: AAT3176 Operating Waveform
at 500mA LED Current with
500ms Flash Time (RSETF = 21kΩ).
Thermal Considerations
The AAT3176 is designed to deliver continuous LED current in movie mode. The limiting characteristic for maximum safe operating output LED current is package
power dissipation. In order to obtain high operating currents, careful device layout and circuit operating conditions must be taken into account. The following discussions assume that the AAT3176 is mounted on a printed
circuit board utilizing the minimum recommended footprint as stated in the “Printed Circuit Board Layout
Recommendations” section of this datasheet.
At any given ambient temperature (TA), the maximum
package power dissipation can be determined by the following equation:
PD(MAX) =
(TJ(MAX) - TA)
θJA
The AAT3176 is available in the TDFN2.2x2.2-10 package, which has 71.4°C/W of thermal resistance (θJA).
With 125°C TJ(MAX), its PD(MAX) is 1.4W. The maximum
power dissipation occurs when the mode transfers from
1x to 2x. If the die temperature rises above the thermal
limit of 140°C, the internal thermal protection circuit
activates to shut down the charge pump and recovers
when the die temperature drops below 125°C.
To avoid entering thermal protection in flash mode at the
500mA high flash LED current setting, the flash time
should not exceed 1 second at 25°C ambient temperature. Longer flash time causes the junction temperature
to increase quickly, causing thermal shutdown. The LED
current recovers automatically when the junction temperature decreases.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202102A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 25, 2012
11
DATA SHEET
AAT3176
500mA LED Flash Driver
In movie mode, maximum continuous current value is
not limited by the package thermal resistance but by the
integrated metal current density. The maximum value
should not exceed 150mA.
ing forward voltage VF in the range of 4.2V to 1.5V. Low
forward voltage (VF) flash LED may make the 1x/2x
mode automatically transfer voltage point lower and get
higher efficiency at the mode transfer input voltage.
Charge Pump Efficiency
Capacitor Selection
The power conversion efficiency of the AAT3176 depends
on the charge pump mode. By definition, device efficiency is expressed as the output power delivered to the
LED divided by the total input power consumed.
Careful selection of the three external capacitors CIN, C1,
and COUT is important because they will affect turn-on
time, output ripple and transient performance. Optimum
performance is obtained when low ESR ceramic capacitors are used; in general, low ESR may be defined as
less than 100mΩ. A capacitor value of 1μF for all three
capacitors is a good starting point when choosing capacitors; a 2.2μF to 4.7μF value is suitable for input and
output capacitance.
η=
POUT
PIN
When the input voltage is sufficiently greater than the
LED forward voltage, the device optimizes efficiency by
operating in 1x mode. In 1x mode, the device is working
as a bypass switch and passing the input supply directly
to the output. Due to the very low 1x mode quiescent
current, the input current nearly equals the current
delivered to the LED. Further, the low-impedance bypass
switch introduces negligible voltage drop from input to
output. The power conversion efficiency can be approximated by:
η=
VF · ILED VF
≈
VIN · IIN
VIN
The AAT3176 maintains optimized performance and efficiency by detecting. When the input voltage is not sufficient to sustain LED current, the device automatically
switches to 2x mode. For ideal conversion, the 2x mode
efficiency is given by:
η=
VF
VF · ILED
VF · ILED
=
≈
VIN · IIN
VIN · 2 · ILED
2 · VIN
LED Selection
A good LED lighting application circuit not only determined by the LED driver but also the LED selected. A
higher luminous efficacy LED emits a higher amount of
luminous flux (lumens) for a given power. Most LED
manufacturers' datasheets provide the luminous efficacy
by the luminous flux curve (LED forward current vs luminous flux). From the luminous flux curve, increasing the
LED forward current may increase the LED light;
increased LED forward current also increases LED forward voltage with higher rating.
The AAT3176 is designed to drive high-intensity white
LEDs. It is particularly suitable for LEDs with an operat-
12
Ceramic composition capacitors are highly recommended over all other types of capacitors for use with the
AAT3176. Ceramic capacitors offer many advantages
over their tantalum and aluminum electrolytic counterparts. A ceramic capacitor typically has very low ESR, is
lowest cost, has a smaller PCB footprint and is nonpolarized. Low ESR ceramic capacitors help to maximize
charge pump transient response. Since ceramic capacitors are non-polarized, they are not prone to incorrect
connection damage.
Equivalent Series Resistance (ESR)
ESR is an important characteristic to consider when
selecting a capacitor. ESR is resistance internal to a
capacitor, which is caused by the leads, internal connections, size or area, material composition, and ambient
temperature. Capacitor ESR is typically measured in milliohms for ceramic capacitors and can range to more
than several ohms for tantalum or aluminum electrolytic
capacitors.
Printed Circuit Board
Layout Recommendations
When designing a PCB for the AAT3176, the key requirements are:
1.
Place the flying capacitor CP as close to the chip as
possible; otherwise 2x mode performance will be
compromised.
2. Place input and output decoupling capacitors as
close to the chip as possible to reduce switching
noise and output ripple.
3. Connect the exposed pad to the GND plane to
achieve the best power dissipation.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202102A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 25, 2012
DATA SHEET
AAT3176
500mA LED Flash Driver
Schematic and Layout
J1
CP
1μF U1
AAT3176
1
C1+
2
VOUT
3
FL
4
RSETF
5
RSETM
R7
0
DC+
AAT3176
White LED Driver
VIN
C1GND
EN/SET
MODE
10
9
8
7
6
MODE
MODE
VIN
0
D1
DC-
C OUT
2.2μF
EP
RSETF
21k
RSETM
105K
JP1
C IN
4.7μF
S2Cwire
Microcontroller
EN/SET
R6
20K
S2C
R1
1K
R2
1K
R3
1K
1
2
3
DOWN
4
U2 PIC12F675
VDD
VSS
GP0
GP5
GP4
GP1
GP3
GP2
8
7
MODE
R5
C1
0.1uF 1K
LED2
Red
6
5
R4
1K
UP
LED1
Green
CYCLE
Figure 3: AAT3176 Evaluation Board Schematic.
Figure 4: AAT3176 Evaluation Board
Layout Top Layer.
Figure 5: AAT3176 Evaluation Board
Layout Bottom Layer.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202102A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 25, 2012
13
DATA SHEET
AAT3176
500mA LED Flash Driver
Component
Part Number
Description
Manufacturer
U1
U2
C1
CIN
COUT
CP
CYCLE, UP, DOWN
AAT3176IDH
PIC12F675
GRM188R71C104K
GRM188R60J475K
GRM188R61A225K
GRM188R71C105K
6*6*5
Skyworks
Microchip
D1
FCW401Z4
LED1
LED2
R1 - R5
R6
R7
RSETF
RSETM
0805KGCT
0805KRCT
RC0603FR-071KL
RC0603FR-0720KL
RC0603FR-070RL
RC0603FR-0721KL
RC0603FR-07105KL
500mA LED Flash Driver with Flash and Movie Mode
8-Pin Flash-Based 8-Bit CMOS Microcontrollers
Cap Ceramic 0.1μF 0603 X7R 16V 10%
Cap Ceramic 4.7μF 0603 X5R 6.3V 10%
Cap Ceramic 2.2μF 0603 X5R 10V 10%
Cap Ceramic 1μF 0603 X7R 16V 10%
12V 50mA Pushbutton
Max 300mA Forward Current, Max 1500mA/300ms Peak
Forward Current
Green LED 0805
Red LED 0805
Res 1KΩ 1/10W 1% 0603 SMD
Res 20KΩ 1/10W 1% 0603 SMD
Res 0Ω 1/10W 1% 0603 SMD
Res 21KΩ 1/10W 1% 0603 SMD
Res 105KΩ 1/10W 1% 0603 SMD
Murata
E-LT
Seoul
HB
Yageo
Table 3: AAT3176 Evaluation Board Bill of Materials (BOM).
14
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202102A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 25, 2012
DATA SHEET
AAT3176
500mA LED Flash Driver
Ordering Information
Package
Part Marking1
Part Number (Tape and Reel)2
TDFN2.2x2.2-10
8HXXY
AAT3176IDH-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
TDFN2.2x2.2-10
2.200 ± 0.050
Detail "A"
0.400 ± 0.050
0.180 ± 0.050
1.700 ± 0.050
2.200 ± 0.050
Index Area
0.900 ± 0.050
Top View
0.400 BSC
Bottom View
0.500 ± 0.050
0.203 REF
0.750 ± 0.050
Pin 1 Indicator
(optional)
Detail "A"
Side View
All dimensions in millimeters.
1. XYY = assembly and date code.
2. Sample stock is generally held on part numbers listed in BOLD.
3. The leadless package family, which includes QFN, TQFN, DFN, TDFN and STDFN, has exposed copper (unplated) at the end of the lead terminals due to the manufacturing
process. A solder fillet at the exposed copper edge cannot be guaranteed and is not required to ensure a proper bottom solder connection.
Copyright © 2012 Skyworks Solutions, Inc. All Rights Reserved.
Information in this document is provided in connection with Skyworks Solutions, Inc. (“Skyworks”) products or services. These materials, including the information contained herein, are provided by Skyworks as a
service to its customers and may be used for informational purposes only by the customer. Skyworks assumes no responsibility for errors or omissions in these materials or the information contained herein. Skyworks may change its documentation, products, services, specifications or product descriptions at any time, without notice. Skyworks makes no commitment to update the materials or information and shall have no
responsibility whatsoever for conflicts, incompatibilities, or other difficulties arising from any future changes.
No license, whether express, implied, by estoppel or otherwise, is granted to any intellectual property rights by this document. Skyworks assumes no liability for any materials, products or information provided hereunder, including the sale, distribution, reproduction or use of Skyworks products, information or materials, except as may be provided in Skyworks Terms and Conditions of Sale.
THE MATERIALS, PRODUCTS AND INFORMATION ARE PROVIDED “AS IS” WITHOUT WARRANTY OF ANY KIND, WHETHER EXPRESS, IMPLIED, STATUTORY, OR OTHERWISE, INCLUDING FITNESS FOR A PARTICULAR
PURPOSE OR USE, MERCHANTABILITY, PERFORMANCE, QUALITY OR NON-INFRINGEMENT OF ANY INTELLECTUAL PROPERTY RIGHT; ALL SUCH WARRANTIES ARE HEREBY EXPRESSLY DISCLAIMED. SKYWORKS DOES
NOT WARRANT THE ACCURACY OR COMPLETENESS OF THE INFORMATION, TEXT, GRAPHICS OR OTHER ITEMS CONTAINED WITHIN THESE MATERIALS. SKYWORKS SHALL NOT BE LIABLE FOR ANY DAMAGES, INCLUDING BUT NOT LIMITED TO ANY SPECIAL, INDIRECT, INCIDENTAL, STATUTORY, OR CONSEQUENTIAL DAMAGES, INCLUDING WITHOUT LIMITATION, LOST REVENUES OR LOST PROFITS THAT MAY RESULT FROM
THE USE OF THE MATERIALS OR INFORMATION, WHETHER OR NOT THE RECIPIENT OF MATERIALS HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
Skyworks products are not intended for use in medical, lifesaving or life-sustaining applications, or other equipment in which the failure of the Skyworks products could lead to personal injury, death, physical or environmental damage. Skyworks customers using or selling Skyworks products for use in such applications do so at their own risk and agree to fully indemnify Skyworks for any damages resulting from such improper
use or sale.
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
design, or damage to any equipment resulting from the use of Skyworks products outside of stated published specifications or parameters.
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
identification purposes only, and are the property of their respective owners. Additional information, including relevant terms and conditions, posted at www.skyworksinc.com, are incorporated by reference.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202102A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 25, 2012
15