ANALOGICTECH AAT3171IWP-T1

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
AnalogicTech's 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.
ChargePump™
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
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.
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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+
CIN
4.7µF
EN
3171.2007.03.1.1
COUT
2.2µF
AAT3171
EN/SET
Flash
LED
FL
CT
0.1µF
C2+
OUT
VIN
RSET
GND
187K
1
AAT3171
High Current, High Efficiency
Charge Pump with Auto-Timer
Pin Descriptions
Pin #
Symbol
1
VIN
2
C1+
3
4
5
6
7
C1GND
FL
RSET
EN/SET
8
CT
9
10
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
3171.2007.03.1.1
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
θJA
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.
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3
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)2
VIN Pin Shutdown Current
Maximum Output Current
IDX
Output Current Accuracy
TSS
VRSET
EN/SET
VEN(L)
VEN(H)
TEN/SET LO
TEN/SET HI
TEN/SET HI MAX
TOFF
TLAT
Input Current
Conditions
Min
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 = 187kΩ
Max
Units
5.5
V
µA
300
2.0
4.0
3.0
6.0
mA
1.0
µA
mA
660
mA
800
540
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
Typ
200
0.7
VIN = 2.7V
VIN = 5.5V
µs
V
0.4
1.4
0.3
75
50
-1
75
500
500
1
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
3171.2007.03.1.1
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
Supply Voltage (V)
Time (200µs/div)
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)
3171.2007.03.1.1
Time (200µs/div)
5
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)
700
ILED (mA)
-40°C
1.6
800
600
500
400
300
200
1.4
25°C
1.2
1.0
0.8
85°C
0.6
100
0
100
200
300
400
500
600
700
800
900
0.4
1000
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)
350
350
300
250
200
25°C
-40°C
150
100
85°C
50
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
EN/SET Off Timeout vs. Supply Voltage
EN/SET Off Timeout (µs)
EN/SET Latch Timeout (µs)
EN/SET Latch Timeout vs. Supply Voltage
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)
3171.2007.03.1.1
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
25°C
0.6
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)
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7
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.
8
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 the LEDs are also operated at lower current
levels in movie, viewing, or flashlight modes.
S2Cwire Serial Interface
The AAT3171 utilizes Analogic Tech's 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).
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AAT3171
High Current, High Efficiency
Charge Pump with Auto-Timer
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
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.
Table 1: Current Level Settings.
THI
TLO
TOFF
T LAT
EN/SET
1
Data Reg
2
n-1
0
n ≤ 16
n-1
0
Figure 1: S2Cwire Serial Interface Timing.
3171.2007.03.1.1
9
AAT3171
High Current, High Efficiency
Charge Pump with Auto-Timer
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 achieve flash and torch mode control, the autotimer 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 autotimer 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.
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.
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.
10
Real-Time Control of the CT Pin
AAT3171
EN/SET
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.
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
single-wire interface. By using any typical digital
I/O port, an additional enable can be created (see
Figure 3).
The I/O port output configuration can be any one of
open-drain 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).
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AAT3171
High Current, High Efficiency
Charge Pump with Auto-Timer
EN
ENFL
Mode
0
0
1
1
0
1
0
1
Off
Off
Flash
Torch
R1 =
600mA · 187kΩ
ILED (torch)
Next, choose R2 based on the desired flash level
LED current:
Table 2: Flash/Torch Control Modes.
R2 =
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:
The current and resistance values used in the equations come from the conditions placed on the IDX
parameter of the Electrical Characteristics table.
C1
1µF
C1+
R1 · 600mA · 187kΩ
R1 · ILED (flash) - 600mA · 187kΩ
C2
1µF
C1-
C2+
2.7V
to 5.5V
C2+
VOUT
CIN
4.7µF
EN
EN/SET
CT
Flash
LED
F1
R2
CT
ENCT
C OUT
2.2µF
AAT3171
RSET
ENFL
GND
R1
Figure 3: Flash/Torch Control Using the RSET Pin.
3171.2007.03.1.1
11
AAT3171
High Current, High Efficiency
Charge Pump with Auto-Timer
For examples of standard 1% values where the
LED flash current level is targeted for 700mA, see
Table 3.
R1
Ω)
(kΩ
R2
Ω)
(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.
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 to use 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.
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:
12
R2 =
RSET · R1
R1 - RSET
ILED (torch) = 600mA · 187kΩ ·
VIO ⎞
⎛ R 2 - R1
⎝ R1 · R2 0.7V · R2 ⎠
Once again, the current and resistance values used
in 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.
Example standard 1% values are provided in Table 4.
R1
Ω)
(kΩ
R2
Ω)
(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.
Device Power Efficiency
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.
η=
POUT
PIN
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AAT3171
High Current, High Efficiency
Charge Pump with Auto-Timer
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:
V
V ·I
η = F LED ≈ F
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 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.
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:
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
LED Selection
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.
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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 100mΩ. 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 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 non-polarized. 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.
13
AAT3171
High Current, High Efficiency
Charge Pump with Auto-Timer
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 short-circuit of the OUT pin.
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.
Figure 4 illustrates an example of an adequate
PCB layout. 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 (θJA) 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.
14
Figure 4: Example PCB Layout.
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.
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.
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+).
3171.2007.03.1.1
AAT3171
High Current, High Efficiency
Charge Pump with Auto-Timer
Button(s) Pushed1, 2
DATA
MOVIE+DATA
FLASH
MOVIE
DATA+FLASH+MOVIE
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.
3171.2007.03.1.1
15
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
R2
1K
R1
1K
U2
1
VDD
2
GP5
3
GP4
4
GP3
FLASH
SW2
MOVIE
SW1
8
VSS 7
GP0 6
GP1
GP2 5
VR4
POT10K
C6
1uF
R5
330
LED7
RED
PIC12F675
Figure 7: AAT3171 Evaluation Board Schematic.
16
3171.2007.03.1.1
AAT3171
High Current, High Efficiency
Charge Pump with Auto-Timer
Evaluation Board Component Listing
Component
Part Number
Description
Manufacturer
U1
AAT3171
AnalogicTech
U2
PIC12F675
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
D1
R1-R3
C1-C2
C3
C4
C5
C6
R5
R6
R7
R8
VR4
LED7
J1-J2
SW1-SW3
3171.2007.03.1.1
LW C9SP
Chip Resistor
GRM18x
GRM18x
GRM18x
GRM18x
GRM31x
Chip Resistor
Chip Resistor
Chip Resistor
Chip Resistor
EVN-5ESX50B14
CMD15-21SRC/TR8
PRPN401PAEN
PTS645TL50
Microchip
OSRAM OPTO
Vishay
Murata
Murata
Murata
Murata
Murata
Vishay
Vishay
Vishay
Vishay
Panasonic-ECG
Chicago Miniature Lamp
Sullins Electronics
ITT Industries
17
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
All AnalogicTech products are offered in Pb-free packaging. The term “Pb-free” means
semiconductor products that are in compliance with current RoHS standards, including
the requirement that lead not exceed 0.1% by weight in homogeneous materials. For more
information, please visit our website at http://www.analogictech.com/pbfree.
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.
18
3171.2007.03.1.1
AAT3171
High Current, High Efficiency
Charge Pump with Auto-Timer
© Advanced Analogic Technologies, Inc.
AnalogicTech cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in an AnalogicTech product. No circuit patent licenses, copyrights, mask work rights,
or other intellectual property rights are implied. AnalogicTech reserves the right to make changes to their products or specifications or to discontinue any product or service without notice.
Customers are advised to obtain the latest version of relevant information to verify, before placing orders, that information being relied on is current and complete. All products are sold subject to the terms and conditions of sale supplied at the time of order acknowledgement, including those pertaining to warranty, patent infringement, and limitation of liability. AnalogicTech
warrants performance of its semiconductor products to the specifications applicable at the time of sale in accordance with AnalogicTech’s standard warranty. Testing and other quality control techniques are utilized to the extent AnalogicTech deems necessary to support this warranty. Specific testing of all parameters of each device is not necessarily performed.
AnalogicTech and the AnalogicTech logo are trademarks of Advanced Analogic Technologies Incorporated. All other brand and product names appearing in this document are registered trademarks or trademarks of their respective holders.
Advanced Analogic Technologies, Inc.
830 E. Arques Avenue, Sunnyvale, CA 94085
Phone (408) 737- 4600
Fax (408) 737- 4611
3171.2007.03.1.1
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