Only For Training And Service Purposes - LG GM200 Service Manual

3. TECHNICAL BRIEF
The AAT3157 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
applications. The AAT3157 is capable of driving six LEDs for a total of 180mA from a 2.7V to 5.5V input.
The current sinks may be operated individually or in parallel for driving higher current LEDs. A low
external parts count (two 1μF flying capacitors and two small 1μF capacitors at IN and OUTCP) make this
part ideally suited for small, battery-powered applications.
AnalogicTech's AS2Cwire™ (Advanced Simple Serial Control™) serial digital input is used to enable,
disable, and set current for each LED with a 16 setting down to 50 μA. The low- current mode supply
current can be as low as 50 μA to save power.
Each output of the AAT3157 is equipped with built in protection for output short-circuit and auto-
disable for load short-circuit conditions. Built-in softstart circuitry prevents excessive inrush current
during start-up. A low-current shutdown feature disconnects the load from the input and reduces
quiescent current to less than 1μA. The AAT3157 is available in a Pb-free, space-saving 2.85x3.0mm 12-
pin TSOPJW package.
The current level magnitude is controlled by AnalogicTech's Simple Serial Control(S
interface. The interface records rising edges of the EN/SET pin and decodes them into 16 different states.
The 16 current level setting available are indicated table in below.
LGE Internal Use Only
LGE Internal Use Only
Figure 3-6-3 AAT3157 current level setting
- 50 -
2
C wire) Serial
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Only for training and service purposes