ADM8845 datasheet(15/20 Pages) AD

15 / 20 page

ADM8845

Rev. 0 | Page 15 of 20

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).

VOUT

FB1

FB2

FB3

FB4

FB5

FB6

VCC

2.6V–5.5V

CTRL1

CTRL2

GND

ADM8845

RSET

4.27k

Ω

60mA

Figure 31. Driving Three Flash LEDs

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).

CONTROL

LOGIC

VREF

CHARGE PUMP

×/1.5×/2× MODE

OSC

LED

CURRENT

CONTROL

CIRCUIT

FB1

CURRENT CONTROLLED SINKS

FB2

FB3

FB4

FB5

FB6

VOUT

4.7

µF

VCC

µF

CTRL1

CTRL2

µF

RSET

9.44k

Ω

ISET

GND

2.2

µF

ADM8845

15mA/LED

CURRENT

CONTROL7

CAMERA

MAIN

SUB

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

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