AAT3169 datasheet(8/14 Pages) AAT

8 / 14 page

AAT3169

High Efficiency 1X/1.5X/2X Charge

Pump for White LED Applications

3169.2006.08.1.2

Functional Description

The AAT3169 is a tri-mode load switch (1X) and

high efficiency (1.5X or 2X) charge pump device

intended for white LED backlight 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 AAT3169

charge pump is enabled when any of the six current

sink inputs near 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 AAT3169

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 six constant current sink inputs (D1 to D6) can

drive six individual LEDs with a maximum current

of 30mA nominal each. Unused sink inputs should

be connected to OUTCP, otherwise the part will

operate only in 2X charge pump mode. The

AS2Cwire serial interface enables the AAT3169 and

sets the current sink magnitudes.

AS2Cwire

addressing allows independent control of two

groups of current sink input: D1~D5 and D6.

Constant Current Output Level Settings

The constant current sink levels for D1 to D6 are

set via the serial interface according to a logarith-

mic scale where each code is approximately 1.8dB

lower than the previous code. In this manner, LED

brightness appears linear with each increasing

code count. Because the inputs D1 to D6 are true

independent constant current sinks, the voltage

observed on any single given input will be deter-

mined by the actual forward voltage (VF) for the

LED being driven.

Functional Block Diagram

D/A

AS2Cwire

Interface

Voltage

Reference

Main

6 x 16 Bit

ROM

Sub

6 x 16 Bit

ROM

1MHz

Oscillator

Soft-Start

Control

1X, 1.5X, 2X

Charge Pump

EN/SET

GND

OUTCP

C1+

C1- C2+

C2-

D/A

AAT3169 датащи(PDF) 8 Page - Advanced Analog Technology, Inc.

AAT3169 датащи(HTML) 8 Page - Advanced Analog Technology, Inc.

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14

датащи скачать

ссылки URL