ADM8845 データシートの表示（PDF） - Analog Devices

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ADM8845

Charge Pump Driver for LCD White LED Backlights

Analog Devices 

DRIVING FLASH LEDS

The ADM8845 can be operated with any two FBx pins operated

in parallel to double the combined LED current supplied by the

ADM8845. For example, if three flash LEDs need to be driven

with 60 mA/LED, the ADM8845 can be configured as in

Figure 31 (see also Figure 21).

VCC

2.6V–5.5V

CTRL1

CTRL2

RSET

4.27kΩ

VOUT

ADM8845

FB1

FB2

FB3

FB4

GND

FB5

FB6

60mA 60mA 60mA

Figure 31. Driving Three Flash LEDs

ADM8845

DRIVING CAMERA LIGHT, MAIN, AND SUB LEDS

The ADM8845 can also be configured to power a camera light

that is composed of four white LEDs in parallel, packaged into

one package. FB1 to FB4 now power the camera light, and FB5

and FB6 power the main display. The sub display LED is powered

from the ADM8845 by using an external current mirror to

control the current flowing through the sub white LED (see

Figure 32). All white LEDs have 15 mA/LED, therefore total

load on the ADM8845 charge pump is 105 mA, and the maxi-

mum load on the ADM8845 charge pump is 180 mA (see

Figure 21).

C1

C2

1µF

1µF

VCC ADM8845

C4

4.7µF

CHARGE PUMP

1×/1.5×/2× MODE

CTRL1

CTRL2

CONTROL

LOGIC

OSC

VREF

ISET

RSET

9.44kΩ

LED

CURRENT

CONTROL

CIRCUIT

VOUT

C3

2.2µF

FB1

FB2

FB3

FB4

FB5

FB6

CAMERA

15mA/LED

CURRENT CONTROLLED SINKS

 GND

Figure 32. Driving Camera Light, Two Main LEDs, and One Sub LED

MAIN

15mA/LED

SUB

15mA/LED

CURRENT

CONTROL7

R

Rev. 0 | Page 15 of 20

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