AAT3131 Datasheet, PDF (1/14 Pages) Advanced Analogic Technologies – High Efficiency 1X/1.5X Fractional Charge Pump for White LED Applications

AAT3131
High Efficiency 1X/1.5X Fractional
Charge Pump for White LED Applications
General Description
The AAT3131 is a low noise, constant frequency
charge pump DC/DC converter that uses a dual
mode load switch (1X) and fractional (1.5X) con-
version to maximize efficiency for white LED appli-
cations. The device can be used to produce cur-
rent levels up to 20mA in three of its outputs and
30mA in one of its outputs to drive LEDs from a
2.7V to 5.5V input. Outputs may be operated indi-
vidually or paralleled for driving higher-current
LEDs. A low external parts count (two 1µF flying
capacitors and two small 1µF capacitors at V_IN and
OUT) makes the AAT3131 ideally suited for small
battery-powered applications.
AnalogicTech's Simple Serial Control™ (S²Cwire™)
interface is used to enable, disable, and set the LED
drive current in two groups: the three 20mA outputs
and the single 30mA output with multiple level loga-
rithmic scales. The AAT3131 has a thermal man-
agement 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. A high charge pump switching fre-
quency enables the use of very small external
capacitors. A low-current shutdown feature discon-
nects the load from V_IN and reduces quiescent cur-
rent to less than 1µA. The AAT3131 is available in
a Pb-free 12-pin TSOPJW12 package and is rated
over the -40°C to +85°C temperature range.
Features
ChargePump^™
• V_IN Range: 2.7V to 5.5V
• <1.0µA of Shutdown Current
• 1MHz Switching Frequency
• White LED Backlighting
• Fully Independent Display Lighting
• Dual Mode 1X and 1.5X Charge Pump for
Maximum Efficiency
• Drives Low-V_F and High-V_F Type LEDs
• Up to Three 20mA Outputs
• Single 30mA Output
• Multi-Position Logarithmic Scale with Digital
Control
• Low Noise Constant Frequency Operation
• Regulated Output Current
• Automatic Soft Start
• No Inductors
• Temperature Range: -40°C to +85°C
• 12-Pin TSOPJW Package
Applications
• Color (RGB) Lighting
• Programmable Current Source
• White LED Backlighting
• White Photo Flash for Digital Still Cameras
Typical Application
V_BATTERY
C_IN
C_OUT
1µF
1µF
EN/SET
VIN
C1+
VOUT
C1-
C2+
AAT3131
C2-
D1
D2
D3
D4
EN/SET
GND
C1
1µF
C2
1µF
D5
D4
D3
D2
D1
3131.2005.12.1.2
1