GRM21BR71A225KA01 [SKYWORKS]
1.5A Single Flash LED Driver IC;
| 型号： | GRM21BR71A225KA01 |
| 厂家： | 
SKYWORKS SOLUTIONS INC. |
| 描述： | 1.5A Single Flash LED Driver IC |
| 文件： | 总17页 (文件大小：2053K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
DATA SHEET
AAT1274
1.5A Single Flash LED Driver IC
General Description
Features
•
•
•
•
•
•
•
The AAT1274 is a high-efficiency, 1.5A high-current
boost converter for LED photo flash applications. It
maintains output current regulation by switching the
internal high-side and low-side switch transistors, pulse-
width modulated at a fixed frequency of 2MHz. The high
switching frequency allows the use of a small external
inductor and output capacitor, making the AAT1274 ide-
ally suited in all single cell, Li-ion-powered applications.
Input Voltage Range: 2.7V to 5.5V
Single Channel Flash Output
Up to 1.5A Regulated Output Current
Up to 88% Efficiency
2 MHz Switching Frequency
Separate Flash Enable
Single Resistor Sets Flash and Movie Mode Current
AS2Cwire Single Wire Programming:
▪
•
Movie Mode Current
Skyworks' proprietary AS2Cwire™ (Advanced Simple
Serial Control™) serial digital interface is used to enable,
disable, configure, and program the operation of the
AAT1274. Using the AS2Cwire interface, the movie-mode
current level for each LED, and the flash-to-movie-mode
current ratio can be programmed to one of 16 levels. The
AAT1274 includes a separate Flash Enable input to initi-
ate the flash operation and a Flash Inhibit pin which
reduces the flash current to movie-mode levels during
high battery demand.
•
Flash/Movie Mode Current Ratio
•
•
•
True Load Disconnect
Soft-Start and Input Current Limit
Over-Voltage (Open LED, Open Circuit), Short Circuit,
and Over-Temperature Protection
-40°C to +85°C Temperature Range
TDFN33-14 Package
•
•
Applications
•
•
•
•
•
LED Photo Flash / Torch
The maximum flash and movie-mode current is set by
one external resistor where the ratio of flash to movie-
mode current is set at approximately 7.3:1. The AAT1274
can drive one high current LED.
Camera Enabled Mobile Devices
Cellphones/Smartphones
Digital Still Cameras (DSCs)
Multimedia Mobile Phones
The AAT1274 contains a thermal management system to
protect the device in the event of an output short-circuit
condition. Built-in circuitry prevents excessive inrush
current during start-up. The shutdown feature reduces
quiescent current to less than 1.0μA.
The AAT1274 is available in a Pb-free, thermally-enhanced
TDFN33-14 package and operates over the -40°C to 85°C
temperature range.
Typical Application
L1 1μH
SW
VBAT = 2.7V to 5.5V
Enable/Set Input
IN
OUT
COUT
CIN
2.2μF
2.2μF
Flash LED
AAT1274
EN/SET
FL
Flash Enable
Flash Inhibit
FLEN
RSET
RSET
FLINH
PGND AGND FLGND
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DATA SHEET
AAT1274
1.5A Single Flash LED Driver IC
Pin Descriptions
Pin # Symbol Description
1,5
AGND
EN/SET
FL
Analog ground pin. Connect AGND to PGND, and FLGND at a single point as close to the AAT1274 as possible.
Enable and Serial Control input. EN/SET is the AS2Cwire addressing and programming input to: a) adjust the
movie-mode current level; b) select the Flash-to-Movie-mode ratio;
2
3
LED Flash current sink pin. Connect the cathode of Flash LED to FL.
Flash enable pin. A low-to-high transition on the FLEN pin initiates a flash pulse and a high-to-low transition
on the FLEN pin terminates a flash pulse
4
FLEN
Flash output boost converter power input. Connect IN to the input power source. Connect a 2.2μF or larger
ceramic capacitor from IN to PGND and locate as close as possible to the AAT1274 package for optimum per-
formance.
6
IN
7
8
PGND
OUT
Power ground. Connect PGND to the same single point as AGND located as close to the AAT1274 as possible
Power output of the boost converter. Connect a 2.2μF or larger ceramic capacitor from OUT to PGND as close
as possible to the AAT1274. Connect OUT to the anode of the Flash LED.
9, 12
10
NC
SW
Not connected
Boost converter switching node. Connect a 1μH inductor between SW and IN.
Flash inhibit pin. FLINH is an active HIGH control input with an internal 200kΩ resistor to AGND. A low-to-
high transition on the FLINH pin reduces FL sink current to the maximum (default) movie-mode current level.
Flash ground pin. Connect FLGND to PGND, and AGND at a single point as close to the AAT1274 as possible.
Flash current set pin. Connect a resistor from RSET to AGND to program the desired flash current for the cur-
11
13
14
EP
FLINH
FLGND
RSET
rent sink FL.
Electrical back contact. Connect to a good thermal ground pad
Pin Configuration
TDFN33-14
(Top View)
14
13
12
11
10
9
1
2
3
4
5
6
7
AGND
EN/SET
FL
RSET
FLGND
N/C
FLEN
AGND
IN
FLINH
SW
N/C
8
OUT
PGND
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DATA SHEET
AAT1274
1.5A Single Flash LED Driver IC
Absolute Maximum Ratings1
TA = 25°C unless otherwise noted.
Symbol
Description
Value
Units
IN, OUT, SW
Maximum Rating
-0.3 to 6.0
V
EN/SET, FLEN,
FLINH, RSET, FL
Maximum Rating
-0.3 to VIN + 0.3
TJ
TS
Operating Junction Temperature Range
Storage Temperature Range
Maximum Soldering Temperature (at Leads, 10 sec)
-40 to 150
-65 to 150
300
C
TLEAD
Thermal Information2
Symbol
Description
Thermal Resistance3
Maximum Power Dissipation
Value
Units
OC/W
W
JA
PD
50
2
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.
2. Mounted on an FR4 board.
3. Derate 20mW/°C above 25°C.
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DATA SHEET
AAT1274
1.5A Single Flash LED Driver IC
Electrical Characteristics
VIN = 3.6V; CIN = COUT = 2.2ꢀF; RSET = 107kΩ; L = 1ꢀH. TA = -40oC to 85°C unless otherwise noted. Typical values are
at TA = 25°C.
Symbol Description
Conditions
Min Typ Max Units
Power Supply – Switching Flash Driver
VIN
VOUT(MAX)
Input Voltage Range
Maximum Output Voltage
2.7
5.5
5.5
1
V
V
mA
EN/SET = FLEN = IN, Set FL Load = 1.5A
EN/SET = IN, FLEN = AGND
EN/SET, FLEN, = AGND
RSET = 107kꢁ
RSET = 107kꢁ = 1.2A
0.67
0.23
IIN(Q)
Supply Current
ISHDN(MAX)
IFL
IFL(ACC)
IMM(LOAD)
FOSC
Input Shutdown Current
Output Current, Flash Mode
Flash Current Accuracy
Total Output Current, Movie Mode
Switching Frequency
Over-Temperature Shutdown Threshold
Over-Temperature Shutdown Hysteresis
1.0
ꢀA
A
%
mA
MHz
°C
1.2
1.5
1.5
±10
206
2.0
140
15
RSET = 107kꢁ, Movie mode current set to 100%
TA = 25°C
2.5
TSD
TSD(HYS)
°C
EN/SET, FLEN
VEN/SET(H)
VFLEN(H)
VEN/SET(L)
VFLEN(L)
,
EN/SET, FLEN Input High Threshold
EN/SET, FLEN Input Low Threshold
1.4
V
V
,
0.4
I
EN/SET, IFLEN EN/SET, FLEN Input Leakage Current
VEN/SET, VFLEN = IN= 5V
-1
1
μA
V
VT(FLINH)
RIN(FLINH)
tEN/SET(LO)
FLINH Input Threshold Voltage
FLINH Input Resistance to AGND
EN/SET Serial Interface Low Time
½ IN
200
kΩ
ꢀs
ns
ꢀs
ꢀs
ꢀs
ꢀs
ꢀs
ꢀs
0.3
75
tEN/SET(HI-MIN) Minimum EN/SET High Time
tEN/SET(HI-MAX) Maximum EN/SET High Time
tEN/SET(OFF)
tENSET(LAT)
tFLEN(ON)
50
75
500
500
EN/SET Off timeout time
EN/SET Latch Timeout Time
FLEN On Delay Time
EN/SET = AGND
EN/SET = AGND
40
10
93
tFLEN(OFF)
tFLINH_ON
FLEN Off Delay Time
FLINH ON Delay Time
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DATA SHEET
AAT1274
1.5A Single Flash LED Driver IC
Typical Characteristics
Flash Mode Efficiency vs. Input Voltage
Movie Mode Efficiency vs. Input Voltage
90
85
80
75
70
65
60
55
50
100
320mA, VF = 2.91V
204mA
104mA
52mA
540mA, VF = 3.00V
90
700mA, VF = 3.04V
900mA, VF = 3.04V
1500mA, VF = 3.15V
1200mA, VF = 3.27V
80
70
60
50
40
2.7
3.1
3.5
3.9
4.3
4.7
5.1
5.5
2.7
3.1
3.5
3.9
4.3
4.7
5.1
5.5
Input Voltage (V)
Input Voltage (V)
Boost Switching Frequency vs. Input Voltage
Shutdown Current vs. Input Voltage
(Movie Mode; L = 1µH)
(VEN/SET = VFLEN = 0V)
3
2.5
2
0.03
0.025
0.02
0.015
0.01
0.005
0
1.5
1
85°C
25°C
0.5
25°C
-40°C
-40°C
0
2.7
3.1
3.5
3.9
4.3
4.7
5.1
5.5
2.7
3.1
3.5
3.9
4.3
4.7
5.1
5.5
Input Voltage (V)
Input Voltage (V)
Supply Current vs. Input Voltage
Movie Mode LED Current vs. Temperature
(VEN = VFLEN = 3.6V)
(IFL = 206mA/Ch; VIN = 3.6V; L = 1µH)
225
220
215
210
205
200
195
190
185
1000
900
800
700
600
500
400
300
200
100
0
85°C
25°C
-40°C
-40
-15
10
35
60
85
2.7
3.1
3.5
3.9
4.3
4.7
5.1
5.5
Input Voltage (V)
Temperature (°C)
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DATA SHEET
AAT1274
1.5A Single Flash LED Driver IC
Typical Characteristics
Movie Mode LED Current Accuracy vs. Input Voltage
(IFL = 206mA; L = 1µH)
Movie Mode Output Ripple
(IFL = 206mA; VIN = 3.6V; L = 1µH)
10
8
VOUT
(AC Coupled)
(50mV/div)
6
4
2
0
VINDUCTOR
(2V/div)
-2
-4
-6
-8
-10
0V
IINDUCTOR
(100mA/div)
100mA
2.7
3.1
3.5
3.9
4.3
4.7
5.1
5.5
Input Voltage (V)
Time (500ns/div)
Flash Mode Output Ripple
Flash LED Current vs. Temperature
(IFL = 1.5A; VIN = 4V; L = 1µH)
(IFL = 1.5A; VIN = 4.2V; L = 1µH)
1580
1560
1540
1520
1500
1480
1460
1440
1420
VOUT
(AC Coupled)
(50mV/div)
VINDUCTOR
(2V/div)
0V
IINDUCTOR
(50mA/div)
1.65A
-40
-15
10
35
60
85
Temperature (°C)
Time (200ns/div)
Flash On Time Delay vs. Input Voltage
Movie Mode Line Transient
(IFL = 1.5A; COUT = 2.2µF; L = 1µH)
(IFL = 206mA; VIN = 4.2V to 3.6V)
80
70
60
50
40
30
20
10
0
4.2V
3.6V
VIN
(500mV/div)
IFL
(AC Coupled)
(50mA/div)
-40°C
25°C
85°C
2.7
3.1
3.5
3.9
4.3
4.7
5.1
5.5
Input Voltage (V)
Time (50µs/div)
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DATA SHEET
AAT1274
1.5A Single Flash LED Driver IC
Typical Characteristics
Flash Turn On Characteristic
Movie Mode to Flash Turn On Characteristic
(IFL = 1.5A; VIN = 3.6V; L = 1µH)
(IFL = 206mA to 1.5A; VIN = 3.6V; L = 1µH)
0V
VFLEN
VFLEN
(5V/div)
(2V/div)
0V
VOUT
(2V/div)
VOUT
(2V/div)
0V
2V
VFL
(2V/div)
VFL
(500mV/div)
0V
0V
IFL
0V
IFLOUTX
(1A/div)
0A
(1A/div)
Time (50µs/div)
Time (50µs/div)
Movie Mode Turn On Characteristic
Movie Mode Transition Characteristic
(IFL = 206mA to 376mA; COUT = 0.22µF;
VIN = 3.6V; L = 1µH)
(IFL = 206mA; VIN = 3.6V; L = 1µH)
0V
VEN/SET
VEN/SET
(5V/div)
VOUT
(2V/div)
VOUT
0V
0V
(2V/div)
(2V/div)
0V
VFL
VFL
(500mV/div)
(500mV/div)
0V
0V
0A
IFL
IFL
(200mA/div)
(200mA/div)
0A
Time (100µs/div)
Time (100µs/div)
EN, FLEN High Threshold Voltage
vs. Input Voltage
EN, FLEN Low Threshold Voltage
vs. Input Voltage
1.4
1.3
1.2
1.1
1.0
0.9
0.8
0.7
0.6
0.5
1.4
1.3
1.2
1.1
1.0
0.9
0.8
0.7
85°C
25°C
-40°C
85°C
0.6
25°C
0.5
-40°C
0.4
2.7
0.4
2.7
3.1
3.5
3.9
4.3
4.7
5.1
5.5
3.1
3.5
3.9
4.3
4.7
5.1
5.5
Input Voltage (V)
Input Voltage (V)
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DATA SHEET
AAT1274
1.5A Single Flash LED Driver IC
Typical Characteristics
EN/SET Off Timeout vs. Input Voltage
EN/SET Latch Timeout vs. Input Voltage
300
250
200
300
250
200
150
100
50
85°C
25°C
-40°C
150
85°C
100
25°C
-40°C
50
2.7
3.1
3.5
3.9
4.3
4.7
5.1
5.5
2.7
3.1
3.5
3.9
4.3
4.7
5.1
5.5
Input Voltage (V)
Input Voltage (V)
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DATA SHEET
AAT1274
1.5A Single Flash LED Driver IC
Functional Block Diagram
SW
OUT (to Flash LED)
FL
IN
EN/SET
System Control Enable
2
FLGND
RSET
and AS C Interface
FLEN
FLINH
PGND
AGND
camera flash and PA transmission pulses from occurring
simultaneously. This avoids potential dips to the Li-ion
battery voltage below the system’s undervoltage lockout
threshold (UVLO). During a flash event, strobing the
FLINH pin low-to-high reduces the LED current to the
default movie-mode current level for the duration of
FLINH. Strobing FLINH high-to-low instructs the AAT1274
to revert the flash LED current to its maximum level,
assuming that the FLEN pin is still active (high).
Functional Description
The AAT1274 is a boost converter with a current regu-
lated output designed to drive high current white LED
used in camera flash applications. The AAT1274 has a
constant current sink channel to accurately regulate the
current flow through a high current, high intensity white
flash LED. The AAT1274 has two basic operating modes;
a flash mode controlled by the FLEN pin and the movie/
torch light mode controlled through the AS2Cwire inter-
face.
Movie (Torch) Mode
The movie / torch mode current level, and the flash to
maximum movie mode current ratio are programmed by
the AAT1274 AS2Cwire interface. The movie-mode cur-
rent level can be adjusted to one of 16 steps using a
logarithmic scale where each code level is 1dB below the
previous code. The flash to maximum movie mode cur-
rent ratio can be set from 1:2 to 1:30 with respect to the
maximum programmed flash current as set by the RSET
resistor. The manual FLEN signal has priority over movie-
mode operation.
Flash Mode
A flash pulse may be initiated by pulling the FLEN input
pin from a logic low-to-high state, which initiates a flash
pulse. The maximum flash current in the AAT1274 is set
by an external resistor, RSET, which sets the flash current
and the maximum movie-mode current.
In mobile GSM systems where the phone remains in
constant contact with the base station by regular com-
munication, a FLINH pin is provided to prevent both the
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DATA SHEET
AAT1274
1.5A Single Flash LED Driver IC
Movie mode operation is controlled entirely by the
AS2Cwire interface via the EN/SET pin. The FLEN signal
will override movie-mode AAT1274 operation when tog-
gled to a logic high level. The part will not reenter movie
mode when FLEN is brought low. To reenter movie mode
after a flash event the part must be cycled off and back
on to reset the movie mode and reprogrammed via the
AS2Cwire interface to the desired movie mode operation.
Application Information
Flash Mode LED Current
Flash sink current can be programmed up to a maximum
of 1.5A. The maximum flash current is set by the RSET
resistor. For the desired flash current, the resistor value
can be calculated using the following equation:
162kΩ × A 162kΩ
Over-Voltage Protection
(Open Flash LED, Open Circuit)
IFL
=
=
= 1.5A
RSET
107kΩ
A flash event is initiated by asserting the FLEN pin. A
flash event is automatically terminated when FLEN is
deasserted. Any time that the FLINH pin is asserted, the
default movie-mode current level will appear at FL chan-
nel. The default movie mode current level will be main-
tained on FL as long as the FLINH and FLEN pins are
asserted. In addition to setting the flash current via RSET,
the flash current can be changed after FLEN is asserted
by programming the movie mode current register with
16 different steps.
The AAT1274 boost converter output is voltage limited by
internal overvoltage protection circuitry to prevent dam-
age to the device in the event an open LED or open circuit
condition occurs. During an open circuit condition, the
output voltage will rise to 5.5V (typical). The OVP circuit
disables the boost converter to prevent the output voltage
from rising above 5.5V. Once the open circuit condition is
removed, normal boost operation will resume.
Short Circuit Protection
The AAT1274 is equipped with an auto-disable feature
for the flash LED channel. After the IC is enabled and
system start up commences, a test current of 2-3mA
(typical) is forced through the sink channel. The channel
will be disabled if the voltage of the SINK pin does not
drop to a predetermined threshold. This feature is very
convenient for disabling the current sink in the event the
flash LED fails to a short circuit. This small test current
is added to the set output current in both Flash and
movie mode conditions.
AS2Cwire Control
of Movie Mode Operation
In the AAT1274 control of the movie mode operation is
managedbytheAdvancedSimpleSerialControl(AS2Cwire)
interface. AS2Cwire relies on the number of rising edges
of the EN/SET pin to address and load internal data reg-
isters. Referring to Table 1:
Address 0 controls the movie mode (MM) current level
as a percentage of the maximum movie mode current
level.
Address 3 sets the maximum possible current for movie
mode operation. The maximum movie mode current is
set as a fraction of the flash current with a peak value
of 1/2 and default value of 1/7.3.
Over-Temperature Protection
The AAT1274 has internal thermal protection circuitry to
disable the device if the internal power dissipation exceeds
a preset thermal limit. The junction over-temperature
threshold is 140°C with 15°C of temperature hysteresis.
During flash or movie-mode operation, if an environmen-
tal condition, flash current sink, or the boost converter
causes the internal die temperature to rise above 140°C,
the boost converter will be shut down. The boost con-
verter output operation will automatically recover when
the over-temperature fault condition is removed.
The last column in Table 1 shows the default values for
each of the address registers.
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DATA SHEET
AAT1274
1.5A Single Flash LED Driver IC
after the AAT1274 has been disabled. When EN/SET is
transitioned from high to low and held low longer than
tOFF (500μs), the device enters a shutdown mode and
draws less than 1uA from the input supply. All data and
address are cleared (reset to 0) during shutdown.
AS2Cwire addressing allows for control of the movie mode
output current, and the ratio of movie-mode current to
flash current. If there are no programmed write instruc-
tions applied to the EN/SET pin prior to the assertion of
the FLEN pin and the device is enabled, then all registers
will be loaded with their default values shown in Table 1.
In the event that the number of rising edges applied at
the EN/SET pin is less than 17, the internal state machine
will interpret instruction to program the output currents
to the desired current level for movie-mode operation.
EN/SET
Rising
Address Edges
Default
Function (No Programming)
Movie Mode
Current
Not Used
Not Used
Flash/Movie
0
17
100%
1
2
3
20
Mode Cur-
rent Ratio
1/7.3
Table 1: AS2Cwire Serial Interface Addressing.
AS2Cwire Serial Interface
AS2Cwire latches data or address after the EN/SET pin
has been held high for longer than tLAT (500μs). Address
or data are differentiated by the number of EN/SET rising
edges. Since the data registers are 4 bits each, the dif-
ferentiating number of pulses is 24 or 16, so that Address
0 is signified by 17 rising edges, and Address 3 by 20
rising edges. Data is inclusively applied to any number of
rising edges between 1 and 16. A typical write protocol is
a burst of EN/SET rising edges which signify a particular
address that is followed by a pause with EN/SET held
high for the prescribed tLAT timeout period, then a burst
of rising edges signifying data, and a tLAT timeout for the
data registers. Once an address is set, then multiple
writes to the corresponding data register are allowed.
Address 0 is the default address on the first rising edge
Movie Mode Current – Address 0
The AAT1274 movie mode current settings are controlled
using the AS2Cwire interface. The default ratio between
the flash current level and maximum movie mode cur-
rent level is 1:7.3.
For example, if an RSET value of 107kΩ is chosen, then
the flash current is set to 1500mA. For movie mode
operation, the maximum current available is then:
IFL(MAX)
7.3
1500mA
7.3
=
= 206mA
IMOVIE MODE
=
Address
Data
THI
TLAT
TLO
TLAT
EN/SET
1
2
16
17
1
2 . . .
n ≤ 16
Address
0
1
0
n
Data Reg 1
Figure 1: AS2Cwire Serial Interface Timing Diagram.
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DATA SHEET
AAT1274
1.5A Single Flash LED Driver IC
Address 0 controls precise movie mode current levels.
The movie mode current can be adjusted in a logarithmic
fashion to one of 16 steps represented as a fraction of
the maximum movie mode current in Table 2. On initial
EN, the movie-mode output immediately supplies 100%
of the set movie-mode current.
The maximum movie mode current level can be calcu-
lated using the following equation:
107kΩ × A
1
IMOVIE MODE
=
=
= Max Movie Mode Current
RSET
FL to MM Ratio
Data
Flash to Movie Mode Ratio
1
2
3
4*
5
6
7
8
9
10
11
12
13
14
15
16
½
Data
Percentage of Maximum MM Current
1/3.8
1/5.5
1/7.3
1/8.9
1/10.5
1/12.2
1/13.8
1/14.9
1/16.5
1/18
1*
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
100%
89%
79%
71%
63%
56%
50%
45%
40%
36%
32%
28%
25%
22%
20%
0%
1/19.6
1/21.1
1/22.6
1/24
OFF
Table 3: Address 3, Flash/
Movie Mode Current Ratio.
Table 2: Address 0, Movie Mode (MM)
Current Programming.
Shutdown
Flash to Maximum Movie Mode
Current Ratio – Address 3
Since the flash current sink is the only power returns for
the flash LED loads, there is no leakage current to load
if all the sink switches are disabled. When the EN/SET
pin is held low for an amount of time greater than tOFF
(500μs), the AAT1274 flash boost converter section
enters shutdown mode and draws less than 1μA from the
input power source. All data and address registers for
the flash and/or movie mode are cleared (reset to 0)
during shutdown.
The maximum movie mode current is a fixed ratio of the
flash current controlled by Address 3. The ratio may be
varied from 1:2 to OFF in 16 linear steps as shown in
Table 3. The default value for Address 3 is Data = 4 and
represents a flash to maximum movie mode current level
of 1 to 7.3. The default maximum movie mode current
can be calculated:
Selecting the Boost Inductor
IFL(MAX)
7.3
IMOVIE MODE
=
The AAT1274 controller utilizes PWM control and the
switching frequency is fixed. To maintain 2MHz maximum
switching frequency and stable operation, a 1μH inductor
is recommended. Manufacturer’s specifications list both
the inductor DC current rating, which is a thermal limita-
tion, and peak inductor current rating, which is deter-
mined by the saturation characteristics. Measurements at
full load and high ambient temperature should be per-
formed to ensure that the inductor does not saturate or
exhibit excessive temperature rise.
For example, if an RSET value of 107kΩ is chosen, then
the flash current is set to 1500mA. For movie mode
operation, the maximum current available is then:
1500mA
IMOVIE MODE
=
= 206mA
7.3
* Denotes the default value.
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DATA SHEET
AAT1274
1.5A Single Flash LED Driver IC
current is less than the output ripple and, as a result, less
input capacitance is required.
Selecting the Boost Capacitors
In general, it is a good design practice to place a decou-
pling capacitor (input capacitor) between the IN and
ground. An input capacitor in the range of 2.2μF to 10μF
is recommended. A larger input capacitor in this applica-
tion may be required for stability, transient response,
and/or ripple performance. The high output ripple inher-
ent in the boost converter necessitates the use of low
impedance output filtering. 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 with the AAT1274 boost regulator. MLC capacitors of
type X7R or X5R are recommended to ensure good
capacitance stability over the full operating temperature
range. The output capacitor is selected to maintain the
output load without significant voltage droop (∆VOUT) dur-
ing the power switch ON interval. A 2.2μF ceramic output
capacitor is recommended (see Table TBD). Typically,
6.3V or 10V rated capacitors are required for this flash
LED boost output application. Ceramic capacitors selected
as small as 0603 are available which meet these require-
ments. MLC capacitors exhibit significant capacitance
reduction with applied voltage. Output ripple measure-
ments should confirm that output voltage droop and
operating stability are within acceptable limits. Voltage
de-rating can minimize this factor, but results may vary
with package size among specific manufacturers. To
maintain stable operation at full load, the output capaci-
tor should be selected to maintain ∆VOUT between 100mV
and 200mV. The boost converter input current flows dur-
ing both ON and OFF switching intervals. The input ripple
PCB Layout Guidelines
Boost converter performance can be adversely affected
by poor layout. Possible impact includes high input and
output voltage ripple, poor EMI performance, and
reduced operating efficiency. Every attempt should be
made to optimize the layout in order to minimize para-
sitic PCB effects (stray resistance, capacitance, and
inductance) and EMI coupling from the high frequency
SW node. A suggested PCB layout for the AAT1274 1.5A
step-up regulator is shown in Figures 3 and 4. The fol-
lowing PCB layout guidelines should be considered:
1. Minimize the distance from capacitor CIN and COUT’s
negative terminals to the PGND pins. This is espe-
cially true with output capacitor COUT, which conducts
high ripple current from the output to the PGND pins.
2. Minimize the distance under the inductor between IN
and switching pin SW; minimize the size of the PCB
area connected to the SW pin.
3. Maintain a ground plane and connect to the IC PGND
pin(s) as well as the PGND connections of CIN and
COUT
.
4. Consider additional PCB exposed area for the flash
LED to maximize heatsinking capability. This may be
necessary when using high current application and
long flash duration application.
5. Connect the exposed paddle (bottom of the die) to
PGND or GND. Connect AGND, FLGND to GND as
close as possible to the package.
Inductance
Saturated Rated
DCR
(mΩ)
Size (mm)
LxWxH
Manufacturer
Part Number
(μH)
Current (A)
Type
Cooper Bussmann
Cooper Bussmann SDH3812-1R0-R
Cooper Bussmann
Sumida
SD3812-1R0-R
1
1
1
1
1
2.69
3
2.25
2.69
2.5
48
45
44.8
48
4.0 x 4.0 x 1.2
3.8 x 3.8 x 1.2
5.2 x 5.2 x 1.0
4.0 x 4.0 x 1.2
4.1 x 4.1 x 1.2
shielded drum core
shielded drum core
shielded drum core
shielded drum core
shielded drum core
SD10-1R0-R
CDH38D11/S
LPS4012-102NLC
Coilcraft
60
Table 4: Typical Suggested Surface Mount Inductors.
Manufacturer
Part Number
Capacitance (ꢀF)
Voltage Rating (V)
Temp Co.
Case Size
Murata
Murata
Murata
Murata
Murata
Murata
GRM185R60J225KE26
GRM188R71A225KE15
GRM21BR70J225KA01
GRM21BR71A225KA01
GRM219R61A475KE19
GRM21BR71A106KE51
2.2
2.2
2.2
2.2
4.7
10
6.3
10
6.3
10
10
10
X5R
X7R
X7R
X7R
X5R
X7R
0603
0603
0805
0805
0805
0805
Table 5: Typical Suggested Surface Mount Capacitors.
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DATA SHEET
AAT1274
1.5A Single Flash LED Driver IC
DC-
DC+
FLINH
JP2
0
R3
JP3
SW4
0
MCU
2 1
4 3
5
10k
R5 R6 R7
10K 10K 10K
C3
JP4
1μF
U2
1
2
3
4
8
7
6
5
VDD
GP5
GP4
GP3
VSS
R4
SW1
2 1
R10
GP0
GP1
GP2
100k
0
0
0
R8
100k
Movie Mode Control
Flash Movie Mode
4 3
(opt)
330
5
R9
330
SW2
PIC12F675
VOUT
LED1
RED
2 1
4 3
5
D1
LED2
GRN
JP1
SW3
FLEN
0
2 1
4 3
5
U1
1
2
3
4
5
6
7
14
13
12
11
10
9
AGND
EN/SET
FL
RSET
FLGND
N/C
JP5
L1
R2
100K
FLEN
AGND
IN
FLINH
SW
EN/SET
1uH
N/C
8
PGND
OUT
C4
220μF
AAT1274 TDFN33-14
C2
2.2μF
R1
133k
C1
2.2μF
L1
C1, C2 Murata GRM188R71A225KE15 2.2μF, 0603, X7R, 10V
D1 Lumiled LXCL-PWF4 or equivalent
CooperBussmann SD3812-1R0-R, 1μH, 2.69A, 48mΩ
Figure 2: AAT1274 Evaluation Board Schematic.
Figure 3: AAT1274 Evaluation Board
Top Side Layout.
Figure 4: AAT1274 Evaluation Board
Bottom Side Layout.
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DATA SHEET
AAT1274
1.5A Single Flash LED Driver IC
Component
Part Number
Description
Manufacturer
1.5A Step-Up Current Regulator for Flash LED;
TDFN33-14 package
U1
AAT1274IWO
Skyworks
U2
SW1 – SW4
R1
R2, R4, R10
R3, R5, R6, R7
R8, R9
JP1, JP2
C1, C2
C3
PIC12F675
PTS645TL50
Chip Resistor
Chip Resistor
Chip Resistor
8-bit CMOS, FLASH-based μC; 8-pin SOIC package
Switch Tact, SPST, 5mm
133kꢁ, 1%, 1/4W; 0402
100kꢁ, 1%, 1/4W; 0603
10kꢁ, 5%, 1/4W; 0603
330ꢁ, 5%, 1/4W; 0603
0Ω, 5%
Microchip
ITT Industries
Vishay
Vishay
Vishay
Vishay
Vishay
MuRata
MuRata
Chip Resistor
Chip Resistor
GRM188R71A225KE15
GRM216R61A105KA01
SD3812-1R0-R
FCW401Z4
CMD15-21SRC/TR8
CMD15-21VGC/TR8
PRPN401PAEN
2.2ꢀF, 10V, X7R, 0603
1ꢀF, 10V, X5R, 0805
Drum Core, 1ꢀH, 2.69A, 48mꢁ
White Flash LED
L1
D1
LED1
LED2
Cooper Bussmann
Seoul Semiconductor
Chicago Miniature Lamp
Chicago Miniature Lamp
Sullins Electronics
Red LED; 1206
Green LED; 1206
Conn. Header, 2mm zip
JP3, JP4, JP5
Table 6: AAT1274 Evaluation Board Bill of Materials.
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DATA SHEET
AAT1274
1.5A Single Flash LED Driver IC
Ordering Information
Package
Marking1
Part Number(Tape and Reel)2
AAT1274IWO-T1
TDFN33-14
B1XYY
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
TDFN33-14
Detail "A"
Index Area
1.650 0.050
3.000 0.050
Top View
Bottom View
0.425 0.050
+ 0.100
0.000
- 0.000
Pin 1 Indicator
(Optional)
Side View
Detail "A"
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.
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DATA SHEET
AAT1274
1.5A Single Flash LED Driver IC
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. Sky-
works 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 here-
under, 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, IN-
CLUDING 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 en-
vironmental 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
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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 pub-
lished 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.
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