202098A.pdf

DATA SHEET
AAT3171
High Current, High Efficiency Charge Pump with Auto-Timer
General Description
Features
The AAT3171 is a high output current, high efficiency,
low noise, low profile charge pump DC/DC converter. The
device is ideal for multi-functional LED photo-flash applications where solution cost, size, and efficiency are
critical.
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The AAT3171 is capable of driving a regulated output
current up to 800mA. Output current levels can be easily programmed in 16 steps through Skyworks' Simple
Serial Control™ (S2Cwire™) interface controlled by a
single microcontroller GPIO line. This allows smooth
transitions and flexible adjustment of brightness in flash
or other lighting modes. The maximum output current
can also be set with an external RSET resistor.
Up to 800mA Output Current
Tri-Mode 1X/1.5X/2X in Current Mode
16 Current Level Steps Set by S2Cwire
External RSET to Set Maximum Current
<1μA of Shutdown
Small Application Circuit
No Inductors
Automatic Soft Start
12-Pin TDFN 3x3mm Package
-40°C to +85°C Temperature Range
Applications
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The tri-mode (1x/1.5x/2x) operation of the internal
charge pump offers excellent power efficiency throughout the output current range for both flash and movie
modes. Combined with a low external parts count (two
1μF flying capacitors and two small bypass capacitors at
VIN and OUT), the AAT3171 is ideally suited for small
battery-powered applications.
Camcorders
Camera Phones
Digital Still Cameras
PDAs and Notebook PCs
Smart Phones
The AAT3171 has a thermal management system to protect the device in the event of a short-circuit condition at
the output pin. Built-in soft-start circuitry prevents
excessive inrush current during start-up. The shutdown
feature disconnects the load from VIN and reduces quiescent current to less than 1μA.
The AAT3171 is available in a Pb-free, thermallyenhanced 12-pin 3x3mm TDFN package and is specified
over the -40°C to +85°C temperature range.
Typical Application
1μF
C1+
2.7V
to 5.5V
1μF
C1-
C2+
OUT
VIN
CIN
4.7μF
EN
C2+
COUT
2.2μF
AAT3171
EN/SET
Flash
LED
FL
CT
RSET
GND
0.1μF
187K
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202098A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 25, 2012
1
DATA SHEET
AAT3171
High Current, High Efficiency Charge Pump with Auto-Timer
Pin Descriptions
Pin #
Symbol
1
VIN
2
3
4
5
6
C1+
C1GND
FL
RSET
7
EN/SET
8
9
10
CT
C2C2+
11
OUT
12
EP
VIN
Function
Input power supply pin. Connect Pin 1 directly to Pin 12 and then to input supply voltage. Connect a 4.7μF or
larger ceramic capacitor to ground.
Flying capacitor C1 positive terminal. Connect a 1μF ceramic capacitor between C1+ and C1-.
Flying capacitor C1 negative terminal.
Ground connection.
Controlled current sink. Connect the flash LED cathode to this pin.
Connect resistor here to set maximum output current.
Charge pump enable / set input control pin. When in the low state, the AAT3171 is powered down and
consumes less than 1μA. When connected to logic high level, the AAT3171 charge pump is active. This pin
should not be left floating.
Flash timeout capacitor. Connect a 0.1μF capacitor between this pin and GND for a flash timeout of 1 second.
Flying capacitor C2 negative terminal.
Flying capacitor C2 positive terminal. Connect a 1μF ceramic capacitor between C2+ and C2-.
Charge pump output. Connect a 2.2μF or larger ceramic capacitor to ground. Connect to flash LED anode to
drive the LED.
Input power supply pin. Connect Pin 12 directly to Pin 1 and then to input supply voltage.
Exposed paddle (bottom). Connect to GND directly beneath package.
Pin Configuration
TDFN33-12
(Top View)
VIN
C1+
C1GND
FL
RSET
2
1
12
2
11
3
10
4
9
5
8
6
7
VIN
OUT
C2+
C2CT
EN/SET
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202098A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 25, 2012
DATA SHEET
AAT3171
High Current, High Efficiency Charge Pump with Auto-Timer
Absolute Maximum Ratings1
TA = 25°C unless otherwise noted.
Symbol
VIN
VEN
VEN(MAX)
IOUT
TJ
TS
TLEAD
Description
Input Voltage
EN to GND Voltage
Maximum EN to Input Voltage
Maximum Output Current
Operating Temperature Range
Storage Temperature Range
Maximum Soldering Temperature (at leads, 10 sec.)
Value
Units
-0.3 to 6.0
-0.3 to 6.0
VIN + 0.3
1000
-40 to 150
-65 to 150
300
V
V
V
mA
°C
°C
°C
Value
Units
50
2
°C/W
W
Thermal Information2
Symbol
JA
PD
Description
Thermal Resistance
Maximum Power Dissipation3
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. Derate 20mW/°C above 40°C ambient temperature.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202098A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 25, 2012
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DATA SHEET
AAT3171
High Current, High Efficiency Charge Pump with Auto-Timer
Electrical Characteristics1
CIN = 4.7μF, COUT = 2.2μF, C1 = C2 = 1.0μF; TA = -40°C to +85°C, unless otherwise noted. Typical values are TA = 25°C,
VIN = 3.6V.
Symbol
Power Supply
VIN
ICC
Description
Input Voltage Range
Operating Current
ISHDN(MAX)
IOUT(MAX)
IDX
TSS
VRSET
EN/SET
VEN(L)
VEN(H)
TEN/SET LO
TEN/SET HI
TEN/SET HI MAX
TOFF
TLAT
Input Current
Conditions
VIN Pin Shutdown Current
Maximum Output Current2
Output Current Accuracy
Soft-Start Time
RSET Pin Voltage
Enable Threshold Low
Enable Threshold High
EN/SET Low Time
Minimum EN/SET High Time
Maximum EN/SET High Time
EN/SET Off Timeout
EN/SET Latch Timeout
EN/SET Input Leakage
Min
Typ
2.7
1X, No Load Current
3.0 ≤ VIN ≤ 5.5, 1.5X Mode, No Load Current
3.0 ≤ VIN ≤ 5.5, 2X Mode, No Load Current
EN = 0
VF = 3.6V
Programmed for 600mA; RSET = 187k
300
2.0
3.0
Max
Units
5.5
V
μA
4.0
6.0
1.0
800
540
660
200
0.7
VIN = 2.7V
VIN = 5.5V
0.4
1.4
0.3
75
50
-1
75
500
500
1
mA
μA
mA
mA
μs
V
V
V
μs
ns
μs
μs
μs
μA
1. The AAT3171 is guaranteed to meet performance specifications from 0°C to 70°C. Specification over the -40°C to +85°C operating temperature range is assured by design,
characterization, and correlation with statistical process controls.
2. Mounted on an FR4 board.
4
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202098A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 25, 2012
DATA SHEET
AAT3171
High Current, High Efficiency Charge Pump with Auto-Timer
Typical Characteristics
VIN = 3.6V, CIN = 4.7μF, COUT = 2.2μF, C1 = C2 = 1μF, TA = 25°C, unless otherwise noted.
Efficiency vs. Supply Voltage
Turn-On to 1X Mode
(VIN = 4.2V; ILED = 150mA)
100
90
EN
(2V/div)
Efficiency (%)
80
70
ILED = 300mA
60
ILED = 150mA
50
40
VSINK
(1V/div)
30
20
IIN
(200mA/div)
10
0
VOUT
(2V/div)
2.7 2.8 2.9 3.0 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 3.9 4.0 4.1 4.2
Time (200µs/div)
Supply Voltage (V)
Turn-On to 1.5X Mode
Turn-On to 1X Mode
(VIN = 3.2V; ILED = 150mA)
(VIN = 4.2V; ILED = 600mA)
EN
(2V/div)
EN
(2V/div)
VOUT
(2V/div)
VOUT
(2V/div)
VSINK
(1V/div)
VSINK
(1V/div)
IIN
(200mA/div)
IIN
(500mA/div)
Time (200µs/div)
Time (200µs/div)
Turn-On to 2X Mode
Turn-Off from 1.5X Mode
(VIN = 3.2V; ILED = 600mA)
(VIN = 3.2V; ILED = 150mA)
EN
(2V/div)
EN
(2V/div)
VOUT
(2V/div)
VF
(1V/div)
VSINK
(1V/div)
IIN
(200mA/div)
IIN
(500mA/div)
Time (200µs/div)
Time (200µs/div)
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202098A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 25, 2012
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DATA SHEET
AAT3171
High Current, High Efficiency Charge Pump with Auto-Timer
Typical Characteristics
VIN = 3.6V, CIN = 4.7μF, COUT = 2.2μF, C1 = C2 = 1μF, TA = 25°C, unless otherwise noted.
Operating Characteristic
Operating Characteristic
(VIN = 3.3V; 1.5X Mode; ILED = 300mA)
(VIN = 2.9V; 2X Mode; ILED = 300mA)
VIN
(100mV/div)
VIN
(100mV/div)
VOUT
(200mV/div)
VOUT
(200mV/div)
VSINK
(200mV/div)
VSINK
(200mV/div)
Time (2µs/div)
Time (2µs/div)
LED Current vs. RSET
Flash Timer Duration
(Data = 1)
(CT = 0.1µF)
1000
1.8
900
Flash Time (s)
ILED (mA)
700
600
500
400
300
200
0
100
200
300
400
500
600
700
800
900
25°C
1.2
1.0
0.8
0.4
1000
85°C
2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 4.5 4.7 4.9 5.1 5.3 5.5
RSET (kΩ
Ω)
Supply Voltage (V)
EN/SET Latch Timeout vs. Supply Voltage
EN/SET Off Timeout vs. Supply Voltage
350
350
300
250
200
25°C
-40°C
150
100
85°C
50
EN/SET Off Timeout (µs)
EN/SET Latch Timeout (µs)
1.4
0.6
100
300
250
200
150
25°C
-40°C
85°C
100
50
0
0
2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 4.5 4.7 4.9 5.1 5.3 5.5
Supply Voltage (V)
6
-40°C
1.6
800
2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 4.5 4.7 4.9 5.1 5.3 5.5
Supply Voltage (V)
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202098A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 25, 2012
DATA SHEET
AAT3171
High Current, High Efficiency Charge Pump with Auto-Timer
Typical Characteristics
VIN = 3.6V, CIN = 4.7μF, COUT = 2.2μF, C1 = C2 = 1μF, TA = 25°C, unless otherwise noted.
EN/SET High Threshold Voltage
vs. Supply Voltage and Temperature
EN/SET Low Threshold Voltage
vs. Supply Voltage and Temperature
1.0
0.9
0.8
0.7
0.6
25°C
85°C
0.5
VEN(L) (V)
VEN(H) (V)
0.9
1.0
-40°C
-40°C
0.8
0.7
0.6
25°C
85°C
0.5
0.4
0.4
2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 4.5 4.7 4.9 5.1 5.3 5.5
2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 4.5 4.7 4.9 5.1 5.3 5.5
Supply Voltage (V)
Supply Voltage (V)
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202098A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 25, 2012
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DATA SHEET
AAT3171
High Current, High Efficiency Charge Pump with Auto-Timer
Functional Block Diagram
C1+
C1-
C2+
C2-
VIN
Charge Pump
Section 1
Charge Pump
Section 2
OUT
1MHz
Oscillator
Soft-Start
Control
FL
EN/SET
System Control;
S2Cwire;
Timing
RSET
CT
GND
Functional Description
The AAT3171 is a high efficiency, low noise, dual stage
tri-mode 1x/1.5x/2x charge pump device intended for
photo-flash LED applications. The device requires only
four external components: two ceramic capacitors for
the charge pump flying capacitors, one ceramic capacitor
for CIN, and one ceramic capacitor for COUT.
The charge pump is designed to deliver regulated load
currents up to 800mA. The dual stage charge pump section contains soft-start circuitry to prohibit excessive
inrush current during start-up. System efficiency is
maximized with a tri-mode, dual stage charge pump
topology. The internal clock oscillator at 1MHz allows the
use of small external components.
The tri-mode charge pump operation further optimizes
power conversion efficiency. Depending upon the variance of load current (at different modes), input voltage,
and nominal LED forward voltage, the charge pump will
operate in a 1x, 1.5x, or 2x mode to generate the output
voltage required to power the load for a given controlled
constant current. This results in significant power savings over voltage doubling architectures, especially when
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the LEDs are also operated at lower current levels in
movie, viewing, or flashlight modes.
S2Cwire Serial Interface
The AAT3171 utilizes Skyworks' single wire S2Cwire interface to enable/disable the charge pump and adjust the
output current at 16 current levels. Each code defines the
output current to be a percentage of the maximum current set by the resistor at the RSET pin (see Table 1).
The S2Cwire interface records rising edges of the EN/SET
pin and decodes them into 16 individual current level
settings with Code 1 reserved for maximum current.
Once EN/SET has been held in the logic high state for
time TLAT (500μs), the programmed current is seen at the
current source outputs and the internal data register is
reset to 0. For subsequent current level programming,
the number of rising edges corresponding to the desired
code must be applied on the EN/SET pin.
When EN/SET is held low for an amount of time longer
than TOFF (500μs), the AAT3171 enters into shutdown
mode and draws less than 1μA from VIN. Data and
address registers are reset to 0 during shutdown.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
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DATA SHEET
AAT3171
High Current, High Efficiency Charge Pump with Auto-Timer
THI
TLO
TOFF
T LAT
EN/SET
1
2
n-1
n ≤ 16
0
Data Reg
n
0
Figure 1: S2Cwire Serial 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
0.0
Table 1: Current Level Settings.
Application Information
Selecting a Timer Capacitor for CT
The CT pin must be configured according to the desired
flash function. There are two options: connect a small
valued capacitor or connect the pin to GND.
Configure the timer feature for the AAT3171 by connecting a small valued capacitor between the CT pin and
GND. The value of the capacitor will determine the timeout duration according to the following formula:
T = CT · 10
To disable the auto-timer feature, connect the CT pin to
ground. The result will be a small bias current of approximately 3μA. A large valued pull-down resistor should not
be used for connecting the CT pin to GND. The CT pin can
be connected directly to GND. If a pull-down resistor is
preferred, it should be of low value (i.e., less than 10K).
The primary considerations for selecting the capacitor
type are leakage current and tolerance of the capacitor
value. The auto-timer duration is determined by charging
and discharging the timing capacitor with a small charging/discharging current of approximately 3μA. Avoid leaky
capacitor types as they will distort the time-out duration.
Select the capacitor value’s tolerance according to the
desired time-out tolerance.
Real-Time Control of the CT Pin
To achieve flash and torch mode control, the auto-timer
can be enabled or disabled in real-time. This can be done
by connecting a microcontroller or microprocessor GPIO
port to the CT pin.
To set up flash mode in real-time, enable the auto-timer
by tri-stating the GPIO port. Do not drive the port high. It
can only be set to high-impedance so that the CT capacitor can be charged and discharged by the AAT3171.
To set up torch mode in real-time, disable the autotimer by driving the GPIO port low so that the CT pin will
be pulled to GND through the GPIO port.
AAT3171
EN/SET
s
µF
As an example, the result of connecting a 0.1μF capacitor between the CT pin and GND will be a 1 second timeout duration. Operationally, when the AAT3171 is
enabled, it will automatically disable itself after 1 second. When using the auto-timer feature, select a CT
capacitor value according to the formula above.
Tri-state = TMR ON
Low = TMR OFF
CT
0.1μF = 1 sec
Figure 2: Enable or Disable the Auto-Timer in
Real-Time for Flash/Torch Control.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202098A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 25, 2012
9
DATA SHEET
AAT3171
High Current, High Efficiency Charge Pump with Auto-Timer
Flash/Torch Control Using the RSET Pin
An alternative method can be used for flash/torch control that eliminates the need to use the S2Cwire singlewire interface. By using any typical digital I/O port, an
additional enable can be created (see Figure 3).
C1
1μF
C1+
C2
1μF
C1-
C2+
2.7V
to 5.5V
C2+
VOUT
CIN
4.7μF
COUT
2.2μF
AAT3171
Flash
LED
The current and resistance values used in the equations
come from the conditions placed on the IDX parameter of
the Electrical Characteristics table. For examples of standard 1% values where the LED flash current level is
targeted for 700mA, see Table 3.
R1 (kΩ)
R2 (kΩ)
ILED Torch
(mA)
ILED Flash
(mA)
920
732
649
562
193
205
210
223
122
153
173
200
703
701
707
703
Table 3: Open-Drain I/O Example Resistor Values.
EN
EN/SET
F1
R2
CT
ENCT
RSET
ENFL
GND
CT
R1
Figure 3: Flash/Torch Control Using the RSET Pin.
The I/O port output configuration can be any one of opendrain NMOS, open-drain PMOS, or push-pull type. The
control will always act as an active-low flash enable or,
equivalently, an active-high torch enable (see Table 2).
EN
ENFL
Mode
0
0
1
1
0
1
0
1
Off
Off
Flash
Torch
Table 2: Flash/Torch Control Modes.
According to I/O port type, the following equations can
be used to calculate appropriate resistor values.
For an open-drain NMOS I/O port output configuration,
the line is pulled low to GND or left floating, according to
state. To calculate the appropriate R1 and R2 resistor
values, first calculate the R1 resistor value needed for the
desired torch level LED current:
R1 =
600mA · 187kΩ
ILED (torch)
Next, choose R2 based on the desired flash level LED current:
R2 =
R1 · 600mA · 187kΩ
R1 · ILED (flash) - 600mA · 187kΩ
If the I/O port must be configured as an open-drain PMOS
type output, the appropriate equations can be generated
from these same concepts. As done in the previous example, the necessary values can then be calculated.
As a reference, the equations applicable to the PMOS
case are:
R1 =
600mA · 187kΩ
ILED (flash)
VIO
-1
0.7
R2 =
ILED (torch)
1
R1 600mA · 187kΩ
The value for VIO must come from the I/O supply voltage
used in the system. 0.7V is the typical value of the VRSET
parameter found in the Electrical Characteristics table.
For a push-pull I/O port output configuration, first calculate the overall RSET value needed for the desired flash
level LED current:
RSET =
600mA · 187kΩ
ILED (flash)
Next, choose a reasonable value for R1. A value that is
slightly larger than RSET, calculated from above, is appropriate. Calculate R2 and then calculate the torch mode
current level that results:
R2 =
RSET · R1
R1 - RSET
ILED (torch) = 600mA · 187kΩ ·
VIO
R2 + R 1
R1 · R2 0.7V · R2
Once again, the current and resistance values used in
10
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202098A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 25, 2012
DATA SHEET
AAT3171
High Current, High Efficiency Charge Pump with Auto-Timer
the equations come from the conditions placed on the IDX
parameter of the Electrical Characteristics table. 0.7V is
the typical value for the VRSET parameter. The value to
use for VIO must come from the I/O supply voltage used
in the system.
The AAT3171 further maintains optimized performance
and efficiency by detecting when the input voltage is not
sufficient to sustain LED current. The device automatically switches to 1.5x mode when the input voltage
drops too low in relation to the LED forward voltage.
Example standard 1% values are provided in Table 4.
In 1.5x mode, the output voltage can be boosted to 3/2
the input voltage. The 3/2 conversion ratio introduces a
corresponding 1/2 increase in input current. For ideal
conversion, the 1.5x mode efficiency is given by:
R1 (kΩ)
R2 (kΩ)
ILED Torch
(mA)
ILED Flash
(mA)
169
165
162
160
1000
1000
1000
1000
95
111
124
132
776
792
805
813
Table 4: Push-Pull I/O Example Resistor Values.
In all of the approaches mentioned, the open-drain
NMOS or PMOS type configurations offer the most flexibility for current level selection.
When configured as an output, if the I/O port is only
push-pull type, then the equivalent open-drain NMOS
can also be realized. To realize this, activate the port as
output only when driving the line low. Otherwise, to
release the line, set the port to be tri-stated.
η=
VF
VF · ILED
=
VIN · 1.5IIN 1.5 · VIN
Similarly, when the input falls further, such that 1.5X
mode can no longer sustain LED current, the device will
automatically switch to 2x mode. In 2x mode, the output
voltage can be boosted to twice the input voltage. The
doubling conversion ratio introduces a corresponding
doubling of the input current. For ideal conversion, the
2x mode efficiency is given by:
η=
VF
VF · ILED
=
VIN · 2IIN
2 · VIN
Device Power Efficiency
LED Selection
The AAT3171 power conversion efficiency 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.
The AAT3171 is designed to drive high-intensity white
LEDs. It is particularly suitable for LEDs with an operating forward voltage in the range of 4.2V to 1.5V.
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. The power conversion efficiency can be
approximated by:
η=
VF · ILED VF
≈
VIN · IIN
VIN
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 charge pump device can also drive other loads that
have similar characteristics to white LEDs. For various
load types, the AAT3171 provides a high-current, programmable ideal constant current source.
Capacitor Selection
Careful selection of the four external capacitors CIN, C1,
C2, and COUT is important because they will affect turn-on
time, output ripple, and transient performance. Optimum
performance will be obtained when low equivalent series
resistance (ESR) ceramic capacitors are used. In general, low ESR may be defined as less than 100m. A
value of 1μF for the flying capacitors is a good starting
point when choosing capacitors. If the LED current sinks
are only programmed for light current levels, then the
capacitor size may be decreased.
Ceramic composition capacitors are highly recommended over all other types of capacitors for use with the
AAT3171. Ceramic capacitors offer many advantages
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11
DATA SHEET
AAT3171
High Current, High Efficiency Charge Pump with Auto-Timer
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 maximize
charge pump transient response. Since ceramic capacitors are non-polarized, they are not prone to incorrect
connection damage.
Equivalent Series Resistance
ESR is an important characteristic to consider when
selecting a capacitor. ESR is a resistance internal to a
capacitor that 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.
Ceramic Capacitor Materials
Ceramic capacitors less than 0.1μF are typically made
from NPO or C0G materials. NPO and C0G materials generally have tight tolerance and are very stable over temperature. Larger capacitor values are usually composed
of X7R, X5R, Z5U, or Y5V dielectric materials. Large
ceramic capacitors are often available in lower-cost
dielectrics, but capacitors greater than 4.7μF are not
typically required for AAT3171 applications.
out. The bottom of the package features an exposed
metal paddle. The exposed paddle acts, thermally, to
transfer heat from the chip and, electrically, as a ground
connection.
The junction-to-ambient thermal resistance (JA) for the
package can be significantly reduced by following a
couple of important PCB design guidelines.
The PCB area directly underneath the package should be
plated so that the exposed paddle can be mated to the
top layer PCB copper during the re-flow process. This
area should also be connected to the top layer ground
pour when available. Further, multiple copper plated
thru-holes should be used to electrically and thermally
connect the top surface paddle area to additional ground
plane(s) and/or the bottom layer ground pour.
The chip ground is internally connected to both the
paddle and the GND pin. The GND pin conducts large
currents and it is important to minimize any differences
in potential that can result between the GND pin and
exposed paddle. It is good practice to connect the GND
pin to the exposed paddle area using a trace as shown
in Figure 4.
Capacitor area is another contributor to ESR. Capacitors
that are physically large will have a lower ESR when
compared to an equivalent material smaller capacitor.
These larger devices can improve circuit transient
response when compared to an equal value capacitor in
a smaller package size.
Thermal Protection
The AAT3171 has a thermal protection circuit that will
shut down the charge pump if the die temperature rises
above the thermal limit, as is the case during a shortcircuit of the OUT pin.
Figure 4: Example PCB Layout.
PCB Layout
To achieve adequate electrical and thermal performance,
careful attention must be given to the PCB layout. In the
worst-case operating condition, the chip must dissipate
considerable power at full load. Adequate heat-sinking
must be achieved to ensure intended operation.
The flying capacitors C1 and C2 should be connected
close to the chip. Trace length should be kept short to
minimize path resistance and potential coupling. The
input and output capacitors should also be placed as
close to the chip as possible.
Figure 4 illustrates an example of an adequate PCB lay-
12
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
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DATA SHEET
AAT3171
High Current, High Efficiency Charge Pump with Auto-Timer
Evaluation Board User Interface
The user interface for the AAT3171 evaluation board is
provided by 3 buttons and a couple of connection terminals. The board is operated by supplying external power
and pressing individual buttons or button combinations.
The table below indicates the function of each button or
button combination.
To power-on the evaluation board, connect a power supply or battery to the DC- and DC+ terminals. Make the
board’s supply connection by positioning the J1 jumper
to the ON position. A red LED indicates that power is
applied.
Button(s) Pushed1, 2
DATA
MOVIE+DATA
FLASH
MOVIE
DATA+FLASH+MOVIE
The evaluation board is made flexible so that the user
can disconnect the enable line from the microcontroller
and apply an external enable signal. By removing the
jumper from J2, an external enable signal can be applied
to the board. Apply the external enable signal to the ON
pin of the J2 terminal.
When applying an external enable signal, consideration
must be given to the voltage level. The externally
applied voltage cannot exceed the supply voltage that is
applied to the VIN pins of the device (i.e., DC+).
Description
Increments through the 16 data settings. Hold-down to auto-cycle.
Decrement the data setting. Hold-down to auto-cycle.
Generate a flash pulse. Current level determined by the DATA setting (defaults to DATA 1).
Trim-pot VR4 sets timeout duration.
Toggle on/off movie mode illumination. Current level determined by the DATA setting. Leave on
to see effects of changing DATA.
Reset, shutdown.
Table 5: Evaluation Board User Interface.
Figure 5: AAT3171 Evaluation Board
Top Side Layout.
Figure 6: AAT3171 Evaluation Board
Bottom Side Layout.
1. The ‘+’ sign indicates that these buttons are all pressed and released together.
2. Flash timeout duration is adjustable from 10ms to 2 seconds. Rotate trim pot VR4 clockwise to reduce the duration. When the timeout duration determined by the value of CT
is set to be less than the VR4 setting, it will supersede.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
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13
DATA SHEET
AAT3171
High Current, High Efficiency Charge Pump with Auto-Timer
Evaluation Board Schematic
DC-
DC+
J1
VIN
C4
4.7μF
C1
1μF
OSRAM OPTO
Ceramos Flash LED
LW C9SP
D1
R8
187K
U1
AAT3171
1
2
3
4
5
6
VIN
VIN
C1+
VOUT
C1C2+
GND
C2F1
CT
RSET EN/SET
12
11
10
9
8
7
C2
1μF
R8 = 187K
for 600mA
C3
2.2μF
C5
Insert C5 for
0.1μF AAT3171 only.
No C5 for
AAT3174.
R6
100K
J2
DC+
R7
220
R3
1K
DATA
SW3
FLASH
SW2
MOVIE
SW1
R2
1K
R1
1K
U2
1
VDD
2
GP5
3
GP4
4
GP3
VSS
GP0
GP1
GP2
8
7
6
5
VR4
POT10K
C6
1uF
R5
330
LED7
RED
PIC12F675
Figure 7: AAT3171 Evaluation Board Schematic.
Evaluation Board Component Listing
Component
Part Number
Description
Manufacturer
U1
U2
D1
R1 - R3
C1 - C2
C3
C4
C5
C6
R5
R6
R7
R8
VR4
LED7
J1 - J2
SW1 - SW3
AAT3171
PIC12F675
LW C9SP
Chip Resistor
GRM18x
GRM18x
GRM18x
GRM18x
GRM31x
Chip Resistor
Chip Resistor
Chip Resistor
Chip Resistor
EVN-5ESX50B14
CMD15-21SRC/TR8
PRPN401PAEN
PTS645TL50
Tri-Mode High Eff. CP for White LED Flash; DFN33-12 Package
8-bit CMOS, FLASH-based μC; 8-pin PDIP Package
Ceramos TopLooker, High Brightness Flash LED
1K, 5%, 1/4W; 1206
1.0μF, 10V, X5R, 0603, Ceramic
2.2μF, 10V, X5R, 0603, Ceramic
4.7μF, 6.3V, X5R, 0603, Ceramic
0.1μF, 16V, X7R, 0603, Ceramic
1.0μF, 10V, X5R, 1206, Ceramic
330, 5%, 1/4W; 1206
100K, 5%, 1/4W; 1206
220, 5%, 1/4W; 1206
187K, 1%, 1/10W; 0603
10K POT; 3mm Squared SMD
Red LED; 1206
Conn. Header, 2mm
Switch Tact, SPST, 5mm
Skyworks
Microchip
OSRAM OPTO
Vishay
Murata
Murata
Murata
Murata
Murata
Vishay
Vishay
Vishay
Vishay
Panasonic-ECG
Chicago Miniature Lamp
Sullins Electronics
ITT Industries
14
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
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DATA SHEET
AAT3171
High Current, High Efficiency Charge Pump with Auto-Timer
Ordering Information
Package
Marking1
Part Number (Tape and Reel)2
TDFN33-12
TAXYY
AAT3171IWP-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 Information3
TDFN33-12
Index Area
0.43 ± 0.05
Detail "A"
C0.3
0.45 ± 0.05
2.40 ± 0.05
3.00 ± 0.05
0.1 REF
3.00 ± 0.05
1.70 ± 0.05
Top View
Bottom View
0.23 ± 0.05
Pin 1 Indicator
(optional)
0.05 ± 0.05
0.23 ± 0.05
0.75 ± 0.05
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.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202098A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 25, 2012
15
DATA SHEET
AAT3171
High Current, High Efficiency Charge Pump with Auto-Timer
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
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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 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
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16
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202098A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 25, 2012