Analogic AAT3175 High efficiency 1x/1.5x/2x charge pump for white led flash application Datasheet

AAT3175
High Efficiency 1X/1.5X/2X Charge Pump
For White LED Flash Applications
General Description
Features
The AAT3175 is a low noise, constant frequency
charge pump DC/DC converter that uses a tri-mode
load switch (1X), fractional (1.5X), and doubling
(2X) conversion to maximize efficiency for white
LED flash applications. The AAT3175 is capable of
driving up to three flash LEDs at 300mA total current from a 2.7V to 5.5V input. A low external parts
count (two 1µF flying capacitors and two small 1µF
capacitors at VIN and VOUT) make this part ideally
suited for small battery-powered applications.
•
•
•
•
•
•
•
•
•
•
•
•
AnalogicTech's S2Cwire™ (Simple Serial Control™)
serial digital input is used to enable, disable, and
set current for all LEDs with 16 level settings down
to 0.
The AAT3175 is equipped with built-in protection
for VOUT short-circuit condition and auto-disable for
load short-circuit condition on any one of the channels. Built-in soft-start circuitry prevents excessive
inrush current during start-up. A low-current shutdown feature disconnects the load from VIN and
reduces quiescent current to less than 1µA.
ChargePump™
VIN Range: 2.7V to 5.5V
Up to 300mA Total Flash Current
Fully Programmable Current with Single Wire
— 16 Logarithmic Current Levels
Tri-Mode 1X, 1.5X, and 2X Charge Pump for
Maximum Efficiency and VF Coverage
Drives 3-in-1 or 2-in-1 Flash LEDs
— 0.5% Current Matching
No Inductors, Low Noise Operation
1MHz Constant Switching Frequency
Small Application Circuit
Built-In Thermal Protection
Automatic Soft-Start
IQ <1µA in Shutdown
TDFN33-12 Package
Applications
•
•
•
The AAT3175 is available in a Pb-free, space-saving,
thermally-enhanced 12-pin 3x3mm TDFN package.
Programmable Current Sinks
White LED Backlighting
White Photo Flash for Mobile Phones
Typical Application
C1+
C2+
C1
1µF
2.7V to 5.5V
C1-
C2-
VIN
VOUT
CIN
1µF
D1
AAT3175
GND
D2
D3
COUT
1µF
D1
D2
EN/SET
EN/SET
D3
D4
3175.2006.01.1.2
1
AAT3175
High Efficiency 1X/1.5X/2X Charge Pump
For White LED Flash Applications
Pin Descriptions
Pin #
Symbol
Function
1
2
3
4
5
D4
EN/SET
C1+
C1VOUT
6
7
8
9
10
11
12
EP
C2+
C2VIN
GND
D1
D2
D3
Current sink input #4; 100mA max.
S2Cwire serial interface control pin.
Flying capacitor 1 positive terminal. Connect a 1µF capacitor between C1+ and C1-.
Flying capacitor 1 negative terminal.
Charge pump output to drive load circuit. Requires 1µF capacitor connected between
this pin and ground.
Flying capacitor 2 positive terminal. Connect a 1µF capacitor between C2+ and C2-.
Flying capacitor 2 negative terminal.
Input power supply. Requires 1µF capacitor connected between this pin and ground.
Ground.
Current sink input #1; 100mA max.
Current sink input #2; 50mA max.
Current sink input #3; 50mA max.
Exposed paddle (bottom). Connect to GND directly beneath package.
Pin Configuration
TDFN33-12
(Top View)
D4
EN/SET
C1+
C1VOUT
C2+
2
1
12
2
11
3
10
4
9
5
8
6
7
D3
D2
D1
GND
VIN
C2-
3175.2006.01.1.2
AAT3175
High Efficiency 1X/1.5X/2X Charge Pump
For White LED Flash Applications
Absolute Maximum Ratings1
Symbol
VIN
VEN/SET
IOUT2
TJ
TLEAD
Description
Input Voltage
EN/SET to GND Voltage
Maximum DC Output Current
Operating Junction Temperature Range
Maximum Soldering Temperature (at leads, 10 sec)
Value
Units
-0.3 to 6
-0.3 to VIN + 0.3
300
-40 to 150
300
V
V
mA
°C
°C
Value
Units
2.0
50
W
°C/W
Thermal Information3
Symbol
PD
θJA
Description
4
Maximum Power Dissipation
Maximum Thermal Resistance
1. Stresses above those listed in Absolute Maximum Ratings may cause permanent damage to the device. Functional operation at conditions
other than the operating conditions specified is not implied. Only one Absolute Maximum Rating should be applied at any one time.
2. Based on long-term current density limitation.
3. Mounted on an FR4 board.
4. Derate 20mW/°C above 25°C.
3175.2006.01.1.2
3
AAT3175
High Efficiency 1X/1.5X/2X Charge Pump
For White LED Flash Applications
Electrical Characteristics1
CIN = COUT = C1 = C2 = 1.0µF; TA = -40°C to +85°C, unless otherwise noted. Typical values are TA = 25°C,
VIN = 3.5V.
Symbol
Description
Conditions
Input Power Supply
VIN
Operation Range
ICC
ISHDN
IDX
I(D-Match)
Operating Current
Shutdown Current
ISINK Average Current Accuracy
Current Matching2
1X to 1.5X or 1.5X to 2X Transition
Threshold at Any ISINK Pin
Charge Pump Section
TSS
Soft-Start Time
FCLK
Clock Frequency
EN/SET
VEN(L)
Enable Threshold Low
VEN(H)
Enable Threshold High
TEN/SET LO
EN/SET Low Time
TEN/SET HI MIN Minimum EN/SET High Time
TEN/SET HI MAX Maximum EN/SET High Time
TOFF
EN/SET Off Timeout
TLAT
EN/SET Latch Timeout
IEN/SET
EN/SET Input Leakage
Min
Typ
2.7
1X Mode, 3.0 ≤ VIN ≤ 5.5,
Active, No Load Current
1.5X Mode, 3.0 ≤ VIN ≤ 5.5,
Active, No Load Current
2X Mode, 3.0 ≤ VIN ≤ 5.5,
Active, No Load Current
EN/SET = 0
D1, D4 Max Setting
D2, D3 Max Setting
VF:D1:D4 = 3.6V, D2 and D3
in Parallel
90
45
VTH
VIN = 2.7V
VIN = 5.5V
Max
Units
5.5
V
0.3
1.0
1.0
3.0
2.0
3.7
100
50
1.0
110
55
0.5
5.0
µA
mA
%
250
mV
100
1000
µs
kHz
0.4
1.4
0.3
75
50
-1
mA
75
500
500
1
V
V
µs
ns
µs
µs
µs
µA
1. The AAT3175 is guaranteed to meet performance specifications over the -40°C to +85°C operating temperature range and is assured
by design, characterization, and correlation with statistical process controls.
2. Current matching is defined as the deviation of any sink current from the average of all active channels.
4
3175.2006.01.1.2
AAT3175
High Efficiency 1X/1.5X/2X Charge Pump
For White LED Flash Applications
Typical Characteristics
CIN = COUT = C1 = C2 = 1µF, TA = 25°C, VIN = 3.5V, unless otherwise noted.
Efficiency vs. Supply Voltage
300mA LED Pulse
(VIN = 3.8V)
100
Efficiency (%)
90
80
60mA
VF = 3.0V
VOUT
(2V/div)
70
150mA
VF = 3.2V
60
50
IOUT
(200mA/div)
40
30
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 (100ms/div)
Supply Voltage (V)
Turn-On to 1X Mode
Turn-On to 1.5X Mode
(VIN = 4.2V; 300mA Load)
(VIN = 4.0V; 300mA Load)
EN
(2V/div)
EN
(2V/div)
VOUT
(2V/div)
VOUT
(2V/div)
VSINK
(1V/div)
VSINK
(1V/div)
IIN
(400mA/div)
IIN
(400mA/div)
Time (200µ
µs/div)
Time (200µ
µs/div)
Turn-On to 2X Mode
Turn-Off from 1.5X Mode
(VIN = 3.8V; 300mA Load)
(VIN = 4.0V; 300mA Load)
EN
(2V/div)
EN
(2V/div)
VF
(1V/div)
VOUT
(2V/div)
VSINK
(1V/div)
IIN
(200mA/div)
IIN
(400mA/div)
Time (200µ
µs/div)
3175.2006.01.1.2
Time (200µ
µs/div)
5
AAT3175
High Efficiency 1X/1.5X/2X Charge Pump
For White LED Flash Applications
Typical Characteristics
CIN = COUT = C1 = C2 = 1µF, TA = 25°C, VIN = 3.5V, unless otherwise noted.
Line Response
Load Characteristics
(1.5X Mode; 150mA Load)
(VIN = 3.5V; 1.5X Mode; 150mA Load)
4.2V
VIN
(500mV/div)
3.7V
VOUT
(500mV/div)
3.6V
VSINK
(500mV/div)
VIN
(100mV/div)
VOUT
(100mV/div)
VSINK
(100mV/div)
ILED
(10mA/div)
Time (1ms/div)
Time (500ns/div)
Load Characteristics
Input Ripple vs. Input Voltage
(VIN = 3.0V; 2X Mode; 150mA Load)
(150mA Load)
30
Input Ripple (mV)
VIN
(100mV/div)
VOUT
(100mV/div)
VSINK
(100mV/div)
25
20
15
10
5
0
Time (500ns/div)
3.3
3.5
3.8
4.0
4.3
4.5
400
300
-40°C
200
150
25°C
85°C
50
0
EN/SET Off Timeout (µ
µs)
EN/SET Latch Timeout (µ
µs)
6
3.0
EN/SET Off Timeout vs. Input Voltage
350
100
2.8
Input Voltage (V)
EN/SET Latch Timeout vs. Input Voltage
250
2.5
350
300
-40°C
250
200
150
100
25°C
85°C
50
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
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
Input Voltage (V)
Input Voltage (V)
3175.2006.01.1.2
AAT3175
High Efficiency 1X/1.5X/2X Charge Pump
For White LED Flash Applications
Typical Characteristics
CIN = COUT = C1 = C2 = 1µF, TA = 25°C, VIN = 3.5V, unless otherwise noted.
1.2
1.1
1
0.9
-40°C
0.8
0.7
25°C
0.6
85°C
0.5
0.4
0.3
0.2
Enable Threshold Low vs. Input Voltage
Enable Threshold Low (V)
Enable Threshold High (V)
Enable Threshold High vs. Input Voltage
1.2
1.1
1
0.9
-40°C
0.8
0.7
0.6
0.5
25°C
85°C
0.4
0.3
0.2
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
Input Voltage (V)
Input Voltage (V)
3175.2006.01.1.2
7
AAT3175
High Efficiency 1X/1.5X/2X Charge Pump
For White LED Flash Applications
Functional Block Diagram
C1+
C1- C2+
C2-
1X, 1.5X, 2X
Charge Pump
VIN
VOUT
Soft Start
Control
1MHz
Oscillator
D/A
Voltage
Reference
6 x 16 bit
ROM
EN/SET
S2Cwire
Interface
D/A
D1
D/A
D2
D/A
D3
D/A
D4
D/A
GND
Functional Description
The AAT3175 is a tri-mode load switch (1X) and
high efficiency (1.5X or 2X) charge pump device
intended for white LED flash applications. To maximize power conversion efficiency, an internal
sensing circuit monitors the voltage required on
each constant current sink input and sets the load
switch and charge pump modes based on the input
battery voltage and the current sink input voltage.
As the battery discharges over time, the AAT3175
charge pump is enabled when any of the four current sink inputs nears dropout. The charge pump
initially starts in 1.5X mode. If the charge pump
output droops enough for any current source output to become close to dropout, the charge pump
will automatically transition to 2X mode.
The AAT3175 requires only four external components: two 1µF ceramic capacitors for the charge
pump flying capacitors (C1 and C2), one 1µF
ceramic input capacitor (CIN), and one 0.33µF to
1µF ceramic charge pump output capacitor (COUT).
The four constant current sink inputs (D1 to D4) can
drive four individual LEDs with a maximum current
8
of 50mA each for D2 and D3. D1 and D4 are driven
by two parallel current sources, resulting in a maximum of 100mA each. Unused sink inputs are connected to VOUT; otherwise, the part will operate only
in 2X charge pump mode. The S2Cwire serial interface enables the AAT3175 and sets the current sink
magnitudes. The D1~D4 current configuration is
optimized to drive either 2-in-1 LEDs by combining
D1/D2, D3/D4, or 3-in-1 LEDs by combining D2/D3.
Constant Current Output Level Settings
The constant current sink levels for D1 to D4 are set
via the serial interface according to a logarithmic
scale where each code is 1dB lower than the previous code. In this manner, LED brightness appears
linear with each increasing code count. Because
the inputs D1 to D4 are true independent constant
current sinks, the voltage observed on any single
given input will be determined by the actual forward
voltage (VF) for the LED being driven.
Since the input current sinks of the AAT3175 are
programmable, no PWM (pulse width modulation) or
additional control circuitry is needed to control LED
brightness. This feature greatly reduces the burden
3175.2006.01.1.2
AAT3175
High Efficiency 1X/1.5X/2X Charge Pump
For White LED Flash Applications
The S2Cwire serial interface has flexible timing.
Data can be clocked-in at speeds greater than
1MHz, or much slower, such as 15kHz. After data
is submitted, EN/SET is held high to latch the data.
Once EN/SET has been held in the logic high state
for time TLAT, the programmed current becomes
active and the internal data register is reset to zero.
For subsequent current level programming, the
number of rising edges corresponding to the
desired code must be entered on the EN/SET pin.
on a microcontroller or system IC to manage LED or
display brightness, allowing the user to "set it and
forget it." With its high-speed serial interface (1MHz
data rate), the input sink current of the AAT3175 can
be changed successively to brighten or dim LEDs in
smooth transitions (e.g., to fade-out) or in abrupt
steps, giving the user complete programmability and
real-time control of LED brightness.
S2Cwire Serial Interface
When EN/SET is held low for an amount of time
greater than TOFF, the AAT3175 enters into shutdown
mode and draws less than 1µA from VIN. The internal
data register is reset to zero during shutdown.
The current level magnitude is controlled by
AnalogicTech's S2Cwire serial interface. The interface records rising edges of the EN/SET pin and
decodes them into 16 different states. The 16 current level settings available are indicated in Table 1.
Auto-Disable Feature
Data
D2, D3
IOUT (mA)
D1, D4
IOUT (mA)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
50
44
40
36
32
28
25
22
20
17
16
14
13
11
10
0
100
88
80
72
64
56
50
44
40
34
32
28
26
22
20
0
The AAT3175 is equipped with an auto-disable feature for each LED channel. After the IC is enabled
and started up, a test current of 150µA (typical) is
forced through each sink channel. The channel will
be disabled if the voltage of that particular DX pin
does not fall below a certain threshold. This feature
is very convenient for disabling an unused channel
or during an LED fail-short event.
Thermal Protection
The AAT3175 has a built-in thermal protection circuit
that will shut down the charge pump if the die temperature rises above the thermal limit, as is generally the case during a short-circuit of the VOUT pin.
Table 1: Current Level Settings.
S2Cwire Serial Interface Timing
THI
TLO
TOFF
T LAT
EN/SET
1
Data Reg
3175.2006.01.1.2
2
n-1
0
n ≤ 16
n-1
0
9
AAT3175
High Efficiency 1X/1.5X/2X Charge Pump
For White LED Flash Applications
Applications Information
LED Selection
Although the AAT3175 is specifically intended for
driving white LEDs, the device can also be used to
drive most types of LEDs with forward voltage
specifications ranging from 2.0V to 4.1V. LED
applications may include display backlighting, camera photo-flash applications, color (RGB) LEDs,
infrared (IR) diodes for remotes, and other loads
benefiting from a controlled output current generated from a varying input voltage. Since the D1 to D4
input current sinks are matched with negligible voltage dependence, the LED brightness will be
matched regardless of the specific LED forward
voltage (VF) levels. In some instances (e.g., in high
luminous output applications such as photo flash),
it may be necessary to drive high-VF type LEDs.
The low dropout current sinks in the AAT3175
make it capable of driving LEDs with forward voltages as high as 4.1V at full current from an input
supply as low as 3.5V. Outputs can be paralleled to
drive high-current LEDs without complication.
Device Switching Noise Performance
The AAT3175 operates at a fixed frequency of
approximately 1MHz to control noise and limit harmonics that can interfere with the RF operation of
cellular telephone handsets or other communication devices. Back-injected noise appearing on the
input pin of the charge pump is 20mV peak-topeak, typically ten times less than inductor-based
DC/DC boost converter white LED backlight solutions. The AAT3175 soft-start feature prevents
noise transient effects associated with inrush currents during start-up of the charge pump circuit.
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; generally, low ESR
may be defined as less than 100mΩ. A value of
1µF for all four capacitors is a good starting point
10
when choosing capacitors. If the LED current
sources are only programmed for light current levels, then the capacitor size may be decreased.
Capacitor Characteristics
Ceramic composition capacitors are highly recommended over all other types of capacitors for use
with the AAT3175. 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
(i.e., greater than 2.2µF) are often available in lowcost Y5V and Z5U dielectrics, but capacitors
greater than 1µF are not typically required for
AAT3175 applications.
Capacitor area is another contributor to ESR.
Capacitors that are physically large will have a
lower ESR when compared to an smaller capacitor
made of equivalent material. These larger devices
can improve circuit transient response when compared to an equal value capacitor in a smaller
package size.
3175.2006.01.1.2
AAT3175
High Efficiency 1X/1.5X/2X Charge Pump
For White LED Flash Applications
Ordering Information
Package
Marking1
Part Number (Tape and Reel)2
TDFN33-12
QAXYY
AAT3175IWP-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 Information
TDFN33-12
2.40 ± 0.05
Detail "B"
3.00 ± 0.05
Index Area
(D/2 x E/2)
0.3 ± 0.10 0.16 0.375 ± 0.125
0.075 ± 0.075
3.00 ± 0.05
1.70 ± 0.05
Top View
Bottom View
Pin 1 Indicator
(optional)
0.23 ± 0.05
Detail "A"
0.45 ± 0.05
0.1 REF
0.05 ± 0.05
0.229 ± 0.051
+ 0.05
0.8 -0.20
7.5° ± 7.5°
Detail "B"
Option A:
C0.30 (4x) max
Chamfered corner
Side View
Option B:
R0.30 (4x) max
Round corner
Detail "A"
All dimensions in millimeters.
1. XYY = assembly and date code.
2. Sample stock is generally held on part numbers listed in BOLD.
3175.2006.01.1.2
11
AAT3175
High Efficiency 1X/1.5X/2X Charge Pump
For White LED Flash Applications
© 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.
Advanced Analogic Technologies, Inc.
830 E. Arques Avenue, Sunnyvale, CA 94085
Phone (408) 737-4600
Fax (408) 737-4611
12
3175.2006.01.1.2
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