ANALOGICTECH AAT3194ITP-20-T1

PRODUCT DATASHEET
AAT3194
ChargePump
TM
High Efficiency 1.5X Fractional Charge Pump For White LED Applications
General Description
Features
The AAT3194 is a low noise, constant frequency charge
pump DC/DC converters that use fractional (1.5X) conversion to increase efficiency in white LED applications. The
devices can be used to produce current levels up to 20mA
for each output from a 2.7V to 5.5V input. A low external
parts count (two 1µF flying capacitors and two small
bypass capacitors at IN and OUT) makes these devices
ideally suited for small, battery-powered applications.
• VIN Range: 2.7V to 5.5V
• 20mA Full-Scale Current
• Simple Serial Control (S2Cwire) Interface
▪ 32-Position Logarithmic Scale with Digital Control
• Low Noise Constant Frequency Operation
• 33% Less Input Current Than Doubler Charge Pump
• High Accuracy Brightness Matching
• Small Application Circuit
• Regulated Output Current
• Automatic Soft Start
• No Inductors
• 600kHz Switching Frequency
• IQ <1µA in Shutdown
• Temperature Range: -40°C to 85°C
• 12-Pin TSOPJW Package
AnalogicTech’s Simple Serial Control™ (S2Cwire™) interface is used to enable, disable, and set the LED drive
current for 32-level logarithmic scale LED brightness
control. The AAT3194 has a thermal management system for protection in the event of a short-circuit condition on any of the output pins. Built-in soft-start circuitry
prevents excessive inrush current during start-up. A high
switching frequency enables the use of small external
capacitors. A low-current shutdown feature disconnects
the load from VIN and reduces quiescent current to less
than 1µA. The AAT3194 is available in a Pb-free 12-pin
TSOPJW package.
Applications
• Programmable Current Source
• White LED Backlighting
Typical Application
IN
C1+
C1
1µF
C1C2+
OUT
VBATTERY
CIN
1µF
COUT
1µF
C2
1µF
AAT3194
C2D1
D2
D3
EN/SET
EN/SET
D4
GND
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D4
D3
D2
D1
1
PRODUCT DATASHEET
AAT3194
ChargePump
TM
High Efficiency 1.5X Fractional Charge Pump For White LED Applications
Pin Descriptions
Pin #
Symbol
1
2
3
4
5
6
7
8
9
10
11
12
C2+
OUT
C1C1+
D4
D3
D2
D1
EN/SET
IN
GND
C2-
Function
Flying capacitor 2 positive terminal. Connect a 1µF ceramic capacitor between C2+ and C2-.
Charge pump output. Requires 1µF bypass capacitor to ground.
Flying capacitor 1 negative terminal.
Flying capacitor 1 positive terminal. Connect a 1µF ceramic capacitor between C1+ and C1-.
Current source output 4. If not used, leave pin floating.
Current source output 3. If not used, leave pin floating.
Current source output 2. If not used, leave pin floating.
Current source output 1. Required reference current source. Do not leave pin floating.
Control pin using S2Cwire serial interface.
Input power supply. Requires 1µF or larger ceramic capacitor to ground.
Ground.
Flying capacitor 2 negative terminal.
Pin Configuration
TSOPJW-12
(Top View)
C2+
OUT
C1C1+
D4
D3
2
1
12
2
11
3
10
4
9
5
8
6
7
C2GND
IN
EN/SET
D1
D2
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3194.2008.05.1.1
PRODUCT DATASHEET
AAT3194
ChargePump
TM
High Efficiency 1.5X Fractional Charge Pump For White LED Applications
Absolute Maximum Ratings
TA = 25°C, unless otherwise noted.
Symbol
VIN
VOUT
VEN/SET
VEN/SET(MAX)
IOUT
TJ
Description
Input Voltage
Charge Pump Output
EN/SET to GND Voltage
Maximum EN/SET to Input Voltage
Maximum DC Output Current (sum of IOUT and D currents)
Operating Junction Temperature Range
Value
Units
-0.3 to 6
-0.3 to 6
-0.3 to 6
0.3
120
-40 to 150
V
V
V
V
mA
°C
Value
Units
160
625
°C/W
mW
Thermal Information1
Symbol
θJA
PD
Description
Thermal Resistance
Maximum Power Dissipation2
1. Mounted on an FR4 board.
2. Derate 6.25mW/°C above 25°C.
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3
PRODUCT DATASHEET
AAT3194
ChargePump
TM
High Efficiency 1.5X Fractional Charge Pump For White LED Applications
Electrical Characteristics
VIN = 3.5V, TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = 25°C.
Symbol
Description
Input Power Supply
Operation Range
VIN
ICC
Operating Current
ISHDN
Shutdown Current
IDX
Output Current
∆ID/∆VIN Output Current Line Regulation
Current Matching Between Any
I(D-Match)
Two Outputs
η
Efficiency
Charge Pump
tSS
Soft-Start Time
FCLK
Clock Frequency
EN/SET
Enable Threshold Low
VEN(L)
VEN(H)
Enable Threshold High
tLO
EN/SET Low Time
Minimum EN/SET Regulation
tHI
tOFF
EN/SET Off Timeout
Input
EN/SET Input Leakage
Current
4
Conditions
Min
Typ
Max
Units
3
1
24
3
V
mA
µA
mA
%/V
2.7
Active, No Load Current
EN = 0V
3.0V ≤ VIN ≤ 5.5V, TA = 25°C, All Outputs Max Current
3.0V ≤ VIN ≤ 5.5V
16
-3
20
VD1:Dn = 3.6V, VIN = 3.3V
0.3
%
VIN = 3.5V, IOUT(total) = 40mA
93
%
400
µs
kHz
300
VIN = 2.7V to 5.5V
VIN = 2.7V to 5.5V
0.5
1.4
0.3
500
V
V
µs
ns
µs
1
µA
75
50
VIN = 5.5V
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3194.2008.05.1.1
PRODUCT DATASHEET
AAT3194
ChargePump
TM
High Efficiency 1.5X Fractional Charge Pump For White LED Applications
Typical Characteristics
VIN = 3.5V, CIN = COUT = C1 = C2 = 1µF; TA = 25°C, unless otherwise noted.
Efficiency vs. Supply Voltage
Quiescent Current vs. Temperature
100
1.00
Efficiency (%)
0.98
0.96
IQ (mA)
30mA
95
0.94
0.92
0.90
90
85
65
20
40
60
80
3.0
100
3.2
3.4
3.8
4.0
4.2
4.4
Efficiency vs. Load Current
Quiescent Current vs. Supply Voltage
96
1.2
94
Efficiency (%)
1.1
1.0
IQ (mA)
3.6
Supply Voltage (V)
Temperature (°C)
0.9
0.8
92
90
88
86
84
82
0.7
80
0.6
3.0
3.5
4.0
4.5
5.0
0
5.5
20
40
60
80
Load Current (mA)
Supply Voltage (V)
Shutdown Current vs. Temperature
Oscillator Frequency vs. Temperature
1.000
710
700
690
0.100
FOSC (kHz)
Shutdown Current (µA)
60mA
70
60
0
80mA
75
0.86
-20
40mA
80
0.88
-40
20mA
0.010
680
670
660
650
640
630
0.001
-40
620
-20
0
20
40
Temperature (°C)
60
80
100
610
-40
-20
0
20
40
60
80
100
Temperature (°C)
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5
PRODUCT DATASHEET
AAT3194
ChargePump
TM
High Efficiency 1.5X Fractional Charge Pump For White LED Applications
Typical Characteristics
VIN = 3.5V, CIN = COUT = C1 = C2 = 1µF; TA = 25°C, unless otherwise noted.
Normalized I DIODE vs. Temperature
IDIODE Response
(-31dB to 0dB)
1.02
1.01
ENSET
(2V/div)
IDIODE
1.00
0.99
0dB
0.98
0.97
0.96
IDIODE
0.95
-40
-20
0
20
40
60
80
-31dB
100
Time (10µs/div)
Temperature (°C)
IDIODE vs. VIN
IDIODE Response
(-9dB to -10dB)
100
IDIODE (mA)
80
ENSET
(2V/div)
60
40
0dB
-10dB
20
IDIODE
0
3.0
3.5
4.0
-9dB
4.5
-31dB
VIN (V)
Time (10µs/div)
VIH and VIL vs. VIN
100
1.000
80
0.975
0.950
VIH and VIL (V)
IDIODE (mA)
IDIODE vs. VDIODE
60
40
0.850
0.825
VIL
0.750
3.0
3.2
3.4
3.6
3.8
4.0
V DIODE (V)
6
VIH
0.875
0.800
0.775
20
0
0.925
0.900
2.5
3.0
3.5
4.0
4.5
5.0
5.5
VIN (V)
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3194.2008.05.1.1
PRODUCT DATASHEET
AAT3194
ChargePump
TM
High Efficiency 1.5X Fractional Charge Pump For White LED Applications
Typical Characteristics
VIN = 3.5V, CIN = COUT = C1 = C2 = 1µF; TA = 25°C, unless otherwise noted.
Turn-On
Turn-Off
ENSET
(2V/div)
ENSET
(2V/div)
OUT
(5V/div)
OUT
(5V/div)
VDIODE
(5V/div)
VDIODE
(2V/div)
IIN
(50mA/div)
IIN
(50mA/div)
Time (100µs/div)
Time (200µs/div)
40mA Load Characteristics
60mA Load Characteristics
IN
OUT
20mV/div
OUT
10mV/div
IN
VDIODE
VDIODE
Time (1µs/div)
Time (1µs/div)
80mA Load Characteristics
OUT
20mV/div
IN
VDIODE
Time (1µs/div)
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7
PRODUCT DATASHEET
AAT3194
ChargePump
TM
High Efficiency 1.5X Fractional Charge Pump For White LED Applications
Functional Block Diagram
IN
Soft Start
1.5X
Charge
Pump
600kHz
Oscillator
Voltage
Reference
EN/SET
5
S2Cwire
Interface
32x8 bit
ROM
C1+
C1C2+
C2OUT
8
Current
Mode
DAC
D1
D2
D3
D4
GND
Functional Description
The AAT3194 is a high efficiency 1.5X fractional charge
pumps intended for white LED backlight applications. The
fractional charge pump consists of a linear regulator followed by a 1.5X charge pump. The AAT3194 requires only
four external components: two 1µF ceramic capacitors for
the charge pump flying capacitors (C1 and C2), one 1µF
ceramic capacitor for CIN, and one 0.33µF to 1µF ceramic
capacitor for COUT. The charge pump output is converted
into four constant current outputs (D1 to D4) to drive four
individual LEDs with a maximum of 20mA each. The current source output magnitude is controlled by the EN/SET
serial data S2Cwire interface. The interface records rising
edges of the EN/SET pin and decodes them into 32 indi-
8
vidual current level settings each 1dB apart (see Table 1,
Current Level Settings). Code 32 is full scale, and Code 1
is full scale attenuated by 31dB. The modulo 32 interface
wraps states back to state 1 after the 32nd clock. With
each EN/SET pulse, the output current increases by 1dB.
To decrease the output current by 1dB, 31 EN/SET clock
pulses are required. The counter can be clocked at speeds
up to 1MHz, so intermediate states are not visible. The
first rising edge of EN/SET enables the IC and initially sets
the output LED current to -31dB, the lowest setting equal
to 525µA. Once the final clock cycle is input for the
desired brightness level, the EN/SET pin is held high to
maintain the device output current at the programmed
level. The device is disabled 500µs after the EN/SET pin
transitions to a logic low state.
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3194.2008.05.1.1
PRODUCT DATASHEET
AAT3194
ChargePump
High Efficiency 1.5X Fractional Charge Pump For White LED Applications
TM
Applications Information
EN/SET Serial Interface
The current source output magnitude is controlled by the
EN/SET pin using AnalogicTech’s Simple Serial Control
(S2Cwire) interface. The interface records rising edges of
the EN/SET pin and decodes them into 32 individual current level settings each 1dB apart. Code 32 is full scale,
and Code 1 is full scale attenuated by 31dB. The modulo
32 interface wraps states back to state 1 after the 32nd
clock, so 1dB of attenuation is achieved by clocking the
EN/SET pin 31 times (see graph titled, “IDIODE Response
-9dB to -10dB”). The counter can be clocked at speeds
up to 1MHz, so intermediate states are not visible. The
first rising edge of EN/SET enables the IC and initially
sets the output LED current to -31dB, the lowest setting
equal to 525µA. Once the final clock cycle is input for the
desired brightness level, the EN/SET pin is held high to
maintain the device output current at the programmed
level. The device is disabled 500µs after the EN/SET pin
transitions to a logic low state.
Current Level Settings
LED current level is set via the serial interface according
to a logarithmic scale where each code is 1dB greater
than the previous code. In this manner, the LED brightness appears linear with each increasing code.
Code
20mA max
Code
20mA max
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
0.549
0.627
0.706
0.784
0.863
1.020
1.098
1.255
1.412
1.569
1.804
1.961
2.275
2.510
2.824
3.137
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
3.529
4.000
4.471
5.020
5.647
6.353
7.059
7.922
8.941
10.039
11.216
12.627
14.118
15.843
17.804
20.000
The EN/SET timing is designed to accommodate a wide
range of data rates. After the first rising edge of EN/SET,
the charge pump is enabled and reaches full capacity
after the soft-start time (TSS). During the soft-start time,
multiple clock pulses may be entered on the EN/SET pin
to set the final output current level with a single burst of
clocks. Alternatively, the EN/SET clock pulses may be
entered one at a time to gradually increase the LED
brightness over any desired time period. A constant current is sourced as long as EN/SET remains in a logic high
state. The current source outputs are switched off after
EN/SET has remained in a low state for at least the tOFF
timeout period (see Figure 2).
Table 1: Current Level Settings.
Normalized Current to Full Scale
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
1
2
3
4
5
6
7
8
9
10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32
Code
Figure 1: Normalized Current Level Settings.
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PRODUCT DATASHEET
AAT3194
ChargePump
TM
High Efficiency 1.5X Fractional Charge Pump For White LED Applications
tLO
tHI
tOFF
EN/SET
Code
2
1
OFF
3
OFF
Figure 2: EN/SET Timing Diagram.
THI > 50ns
ON/1
2
300ns < TLO < 75µs
3
4
5
50ns minimum to enable
n
(n < =32)
6
OFF
Figure 3: Enable / Disable / LED Brightness Level Set Data Input.
LED Selection
The AAT3194 is designed to drive white LEDs with forward voltages to 4.2V. Since the D1:D4 output current
sources are matched with negligible voltage dependence, the LED brightness will be matched regardless of
their forward voltage matching.
Charge Pump Efficiency
The AAT3194 uses a fractional charge pump. The efficiency (η) can be simply defined as a linear voltage
regulator with an effective output voltage that is equal to
one and one half times the input voltage. Efficiency (η)
for an ideal 1.5X charge pump can typically be expressed
as the output power divided by the input power:
η=
POUT
PIN
In addition, with an ideal 1.5X charge pump, the output
current may be expressed as 2/3 of the input current.
The expression to define the ideal efficiency (η) can be
rewritten as:
η=
POUT
VOUT · IOUT
V
=
= OUT
PIN
VIN · 1.5IOUT 1.5VIN
-or-
η(%) = 100
⎛ VOUT ⎞
⎝ 1.5VIN⎠
For a charge pump with an output of 5V and a nominal
input of 3.5V, the theoretical efficiency is 95%. Due to
10
internal switching losses and IC quiescent current consumption, the actual efficiency can be measured at
93%. These figures are in close agreement for output
load conditions from 1mA to 100mA. Efficiency will
decrease as load current drops below 0.05mA or when
the level of the power supply of IN approaches OUT.
Refer to the Typical Characteristics section of this
datasheet for measured plots of efficiency versus input
voltage and output load current for the given charge
pump output voltage options.
Power Efficiency and Device Evaluation
The charge pump efficiency discussion in the previous
section only accounts for efficiency of the charge pump
section itself. Due to the unique circuit architecture and
design of the AAT3194, it is very difficult to measure
efficiency in terms of a percent value comparing input
power over output power. Since the device outputs are
pure constant current sources, it is difficult to measure
the output voltage for a given output (D1 to D4) to
derive an output power measurement. For any given
application, white LED forward voltage levels can differ,
yet the output drive current will be maintained as a constant. This makes quantifying output power a difficult
task when taken in the context of comparing to other
white LED driver circuit topologies. A better way to
quantify total device efficiency is to observe the total
input power to the device for a given LED current drive
level. The best white LED driver for a given application
should be based on trade-offs of size, external components count, reliability, operating range, and total energy
usage...not just “% efficiency.”
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3194.2008.05.1.1
PRODUCT DATASHEET
AAT3194
ChargePump
TM
High Efficiency 1.5X Fractional Charge Pump For White LED Applications
Equivalent Series Resistance
700
VIN = 3.6V
Input Power (mW)
600
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.
500
400
300
200
100
0
0
20
40
60
80
100
Output (LED) Current (mA)
Figure 3: Input Power vs. LED Current.
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 all four capacitors is a good starting point
when choosing capacitors. If the LED current sources are
only programmed for minimal current levels, then the
capacitor size may be decreased.
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 low-cost Y5V and Z5U dielectrics, but capacitors greater than 1µF are not typically required for
AAT3194 applications.
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.
Test Current/Channel Disable
Capacitor Characteristics
Ceramic composition capacitors are highly recommended
over all other types of capacitors for use with the
AAT3194. Ceramic capacitors offer many advantages
over their tantalum and aluminum electrolytic counterparts. A ceramic capacitor typically has very low ESR, is
lowest cost, has a smaller PCB footprint, and is nonpolarized. Low ESR ceramic capacitors help maximize
charge pump transient response. Since ceramic capacitors are non-polarized, they are not prone to incorrect
connection damage.
3194.2008.05.1.1
Ceramic Capacitor Materials
Each channel of the output is equipped with a test current function. The AAT3194 uses a small (~2µA) current
source injected into each output pin to detect the presence of an LED. Unused channels other than channel 1
should be left open and will be automatically disabled
instead of wasting the programmed output current.
Thermal Protection
The AAT3194 has a thermal protection circuit that will
shut down the charge pump and current outputs if the
die temperature rises above the thermal limit.
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PRODUCT DATASHEET
AAT3194
ChargePump
TM
High Efficiency 1.5X Fractional Charge Pump For White LED Applications
Ordering Information
Package
Marking1
Part Number (Tape and Reel)2
TSOPJW-12
UUXYY
AAT3194ITP-20-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/about/quality.aspx.
Package Information
TSOPJW-12
2.85 ± 0.20
2.40 ± 0.10
0.20 + 0.10
- 0.05
0.50 BSC 0.50 BSC 0.50 BSC 0.50 BSC 0.50 BSC
7° NOM
0.055 ± 0.045
0.04 REF
0.15 ± 0.05
+ 0.10
1.00 - 0.065
0.9625 ± 0.0375
3.00 ± 0.10
4° ± 4°
0.45 ± 0.15
0.010
2.75 ± 0.25
All dimensions in millimeters.
1. XYY = assembly and date code.
2. Sample stock is generally held on part numbers listed in BOLD.
Advanced Analogic Technologies, Inc.
3230 Scott Boulevard, Santa Clara, CA 95054
Phone (408) 737-4600
Fax (408) 737-4611
© 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. Except as provided in AnalogicTech’s terms and
conditions of sale, AnalogicTech assumes no liability whatsoever, and AnalogicTech disclaims any express or implied warranty relating to the sale and/or use of AnalogicTech products including liability or warranties
relating to fitness for a particular purpose, merchantability, or infringement of any patent, copyright or other intellectual property right. In order to minimize risks associated with the customer’s applications, adequate
design and operating safeguards must be provided by the customer to minimize inherent or procedural hazards. 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
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12
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