Datasheet > AAT3194_08

AAT3194_08

更新时间： 2022-04-23 23:00:11

品牌	Logo	应用领域
ANALOGICTECH		泵
页数	文件大小	规格书
12页	1265K
描述
High Efficiency 1.5X Fractional Charge Pump For White LED Applications

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AAT3194_08 数据手册

PRODUCT DATASHEET

AAT3194

ChargePump

High Efficiency 1.5X Fractional Charge Pump For White LED Applications

Functional Block Diagram

Soft Start

C1+

C1-

1.5X

Charge

Pump

600kHz

Oscillator

C2+

C2-

Voltage

Reference

OUT

Current

Mode

DAC

S²Cwire

Interface

32x8 bit

ROM

EN/SET

GND

vidual current level settings each 1dB apart (see Table 1,

Current Level Settings). Code 32 is full scale, and Code 1

is full scale attenuated by 31dB. The modulo 32 interface

wraps states back to state 1 after the 32nd clock. With

each EN/SET pulse, the output current increases by 1dB.

To decrease the output current by 1dB, 31 EN/SET clock

pulses are required. The counter can be clocked at speeds

up to 1MHz, so intermediate states are not visible. The

first rising edge of EN/SET enables the IC and initially sets

the output LED current to -31dB, the lowest setting equal

to 525µA. Once the final clock cycle is input for the

desired brightness level, the EN/SET pin is held high to

maintain the device output current at the programmed

level. The device is disabled 500µs after the EN/SET pin

transitions to a logic low state.

Functional Description

The AAT3194 is a high efficiency 1.5X fractional charge

pumps intended for white LED backlight applications. The

fractional charge pump consists of a linear regulator fol-

lowed by a 1.5X charge pump. The AAT3194 requires only

four external components: two 1µF ceramic capacitors for

the charge pump flying capacitors (C1 and C2), one 1µF

ceramic capacitor for C_IN, and one 0.33µF to 1µF ceramic

capacitor for C_OUT. The charge pump output is converted

into four constant current outputs (D1 to D4) to drive four

individual LEDs with a maximum of 20mA each. The cur-

rent source output magnitude is controlled by the EN/SET

serial data S²Cwire interface. The interface records rising

edges of the EN/SET pin and decodes them into 32 indi-

w w w . a n a l o g i c t e c h . c o m

3194.2008.05.1.1

1...5 6 789 10 11 12

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