General Description
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 cur-
rent from a 2.7V to 5.5V input. A low external parts
count (two 1F flying capacitors and two small 1F
capacitors at V
IN
and V
OUT
) make this part ideally
suited for small battery-powered applications.
AnalogicTech's S
2
CwireTM (Simple Serial ControlTM)
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 V
OUT
short-circuit condition and auto-disable for
load short-circuit condition on any one of the chan-
nels. Built-in soft-start circuitry prevents excessive
inrush current during start-up. A low-current shut-
down feature disconnects the load from V
IN
and
reduces quiescent current to less than 1A.
The AAT3175 is available in a Pb-free, space-saving,
thermally-enhanced 12-pin 3x3mm TDFN package.
Features
V
IN
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 V
F
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
I
Q
<1A in Shutdown
TDFN33-12 Package
Applications
Programmable Current Sinks
White LED Backlighting
White Photo Flash for Mobile Phones
AAT3175
High Efficiency 1X/1.5X/2X Charge Pump
For White LED Flash Applications
Typical Application
C2+
C2-
VOUT
C1+
C1-
VIN
GND
EN/SET
EN/SET
2.7V to 5.5V
D1
D2
D3
AAT3175
D1
D2
D3
D4
C
IN
1
F
C1
1
F
C
OUT
1
F
3175.2006.01.1.2
1
ChargePump
TM
Pin Descriptions
Pin Configuration
TDFN33-12
(Top View)
D4
EN/SET
C1+
1
C1-
VOUT
C2+
D3
D2
D1
GND
VIN
C2-
2
3
4
5
6
12
11
10
9
8
7
Pin #
Symbol
Function
1
D4
Current sink input #4; 100mA max.
2
EN/SET
S
2
Cwire serial interface control pin.
3
C1+
Flying capacitor 1 positive terminal. Connect a 1F capacitor between C1+ and C1-.
4
C1-
Flying capacitor 1 negative terminal.
5
VOUT
Charge pump output to drive load circuit. Requires 1F capacitor connected between
this pin and ground.
6
C2+
Flying capacitor 2 positive terminal. Connect a 1F capacitor between C2+ and C2-.
7
C2-
Flying capacitor 2 negative terminal.
8
VIN
Input power supply. Requires 1F capacitor connected between this pin and ground.
9
GND
Ground.
10
D1
Current sink input #1; 100mA max.
11
D2
Current sink input #2; 50mA max.
12
D3
Current sink input #3; 50mA max.
EP
Exposed paddle (bottom). Connect to GND directly beneath package.
AAT3175
High Efficiency 1X/1.5X/2X Charge Pump
For White LED Flash Applications
2
3175.2006.01.1.2
Absolute Maximum Ratings
1
Thermal Information
3
Symbol
Description
Value
Units
P
D
Maximum Power Dissipation
4
2.0
W
JA
Maximum Thermal Resistance
50
C/W
Symbol
Description
Value
Units
V
IN
Input Voltage
-0.3 to 6
V
V
EN/SET
EN/SET to GND Voltage
-0.3 to V
IN
+ 0.3
V
I
OUT
2
Maximum DC Output Current
300
mA
T
J
Operating Junction Temperature Range
-40 to 150
C
T
LEAD
Maximum Soldering Temperature (at leads, 10 sec)
300
C
AAT3175
High Efficiency 1X/1.5X/2X Charge Pump
For White LED Flash Applications
3175.2006.01.1.2
3
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 25C.
Electrical Characteristics
1
C
IN
= C
OUT
= C
1
= C
2
= 1.0F; T
A
= -40C to +85C, unless otherwise noted. Typical values are T
A
= 25C,
V
IN
= 3.5V.
Symbol
Description
Conditions
Min
Typ
Max
Units
Input Power Supply
V
IN
Operation Range
2.7
5.5
V
1X Mode, 3.0
V
IN
5.5,
0.3
1.0
Active, No Load Current
I
CC
Operating Current
1.5X Mode, 3.0
V
IN
5.5,
1.0
3.0
Active, No Load Current
mA
2X Mode, 3.0
V
IN
5.5,
2.0
3.7
Active, No Load Current
I
SHDN
Shutdown Current
EN/SET = 0
1.0
A
I
DX
I
SINK
Average Current Accuracy
D1, D4 Max Setting
90
100
110
mA
D2, D3 Max Setting
45
50
55
I
(D-Match)
Current Matching
2
V
F
:D1:D4 = 3.6V, D2 and D3
0.5
5.0
%
in Parallel
V
TH
1X to 1.5X or 1.5X to 2X Transition
250
mV
Threshold at Any I
SINK
Pin
Charge Pump Section
T
SS
Soft-Start Time
100
s
F
CLK
Clock Frequency
1000
kHz
EN/SET
V
EN(L)
Enable Threshold Low
V
IN
= 2.7V
0.4
V
V
EN(H)
Enable Threshold High
V
IN
= 5.5V
1.4
V
T
EN/SET LO
EN/SET Low Time
0.3
75
s
T
EN/SET HI MIN
Minimum EN/SET High Time
50
ns
T
EN/SET HI MAX
Maximum EN/SET High Time
75
s
T
OFF
EN/SET Off Timeout
500
s
T
LAT
EN/SET Latch Timeout
500
s
I
EN/SET
EN/SET Input Leakage
-1
1
A
AAT3175
High Efficiency 1X/1.5X/2X Charge Pump
For White LED Flash Applications
4
3175.2006.01.1.2
1. The AAT3175 is guaranteed to meet performance specifications over the -40C to +85C 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.
AAT3175
High Efficiency 1X/1.5X/2X Charge Pump
For White LED Flash Applications
3175.2006.01.1.2
5
Typical Characteristics
C
IN
= C
OUT
= C
1
= C
2
= 1F, T
A
= 25C, V
IN
= 3.5V, unless otherwise noted.
Turn-Off from 1.5X Mode
(V
IN
= 4.0V; 300mA Load)
Time (200
s/div)
I
IN
(200mA/div)
EN
(2V/div)
V
F
(1V/div)
Turn-On to 2X Mode
(V
IN
= 3.8V; 300mA Load)
Time (200
s/div)
V
OUT
(2V/div)
I
IN
(400mA/div)
EN
(2V/div)
V
SINK
(1V/div)
Turn-On to 1.5X Mode
(V
IN
= 4.0V; 300mA Load)
Time (200
s/div)
V
OUT
(2V/div)
I
IN
(400mA/div)
EN
(2V/div)
V
SINK
(1V/div)
Turn-On to 1X Mode
(V
IN
= 4.2V; 300mA Load)
Time (200
s/div)
V
OUT
(2V/div)
I
IN
(400mA/div)
EN
(2V/div)
V
SINK
(1V/div)
300mA LED Pulse
(V
IN
= 3.8V)
Time (100ms/div)
V
OUT
(2V/div)
I
OUT
(200mA/div)
Efficiency vs. Supply Voltage
Supply Voltage (V)
Efficiency (%)
30
40
50
60
70
80
90
100
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
60mA
V
F
= 3.0V
150mA
V
F
= 3.2V
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