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AAT3120
3-Channel Charge Pump For White LED Applications General Description
The AAT3120 is a low noise, constant frequency charge pump DC/DC converter that uses fractional (1.5X) conversion to improve efficiency for white LED applications. The device can be used to produce eight current levels up to 20mA per channel for up to three channels. 1X load switch mode is also built-in to improve efficiency at low current settings. Low external parts count (two 1µF flying capacitors and two small 1µF capacitors at VIN and OUT) makes the AAT3120 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 each LED at eight different levels.
Features
• • • •
ChargePump™
• • • • • • •
VIN Range: 2.7V to 5.5V Fractional Charge Pump Mode Drives Low-VF and High-VF Type LEDs Up to Three LED Outputs — Single Wire Programming — Eight Regulated Current Settings — Max 20mA per Channel Low Noise Constant Frequency Operation No Inductors 1MHz Switching Frequency Small Application Circuit Automatic Soft-Start IQ <1µA in Shutdown 12-Pin TSOPJW Package
The AAT3120 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 circuitApplications ry prevents excessive inrush current during startup. A high charge pump switching frequency • Color (RGB) Lighting enables the use of very small external capacitors. • Programmable Current Source A low current shutdown feature disconnects www.DataSheet4U.com the • White LED Backlighting load from VIN and reduces quiescent current to less • White Photo Flash for DSCs than 1µA. The AAT3120 is available in the very small Pb-free 12-pin TSOPJW package.
Typical Application
VIN C1+ C1 1 µF VOUT VBATTERY CIN 1µF C OUT 1µF C1C2+ C2 1 µF
AAT3120
C2D1 D2 D3
EN/SET
EN/SET GND
D3
D2
D1
3120.2005.11.1.1
1
AAT3120
3-Channel Charge Pump For White LED Applications Pin Descriptions
Pin #
1 2 3 4 5 6 7 8 9 10 11 12
Symbol
C2+ OUT C1C1+ N/C D3 D2 D1 EN/SET IN GND C2-
Function
Flying capacitor 2 positive terminal. Connect a 1µF capacitor between C2+ and C2-. Charge pump output. Requires 1µF capacitor connected between this pin and ground. Flying capacitor 1 negative terminal. Flying capacitor 1 positive terminal. Connect a 1µF capacitor between C1+ and C1-. No connection. Current source output #3. Current source output #2. Current source output #1. Control pin. Input power supply. Requires 1µF capacitor connected between this pin and ground. Ground. Flying capacitor 2 negative terminal.
Pin Configuration
TSOPJW-12 (Top View) C2+ OUT C1C1+ N/C D3 C2GND IN EN/SET D1 D2
1 2 3 4 5 6
12 11 10 9 8 7
2
3120.2005.11.1.1
AAT3120
3-Channel Charge Pump For White LED Applications Absolute Maximum Ratings1
TA = 25°C, unless otherwise noted. Symbol
VIN VOUT VEN/SET VEN/SET(MAX) IOUT2 TJ TLEAD
Description
Input Voltage Charge Pump Output FB or EN/SET to GND .