LP3954TLSLASHNOPB datasheet(25/60 Pages) TI1

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RFLASH

1.23V

IFLASH

(1.23V)

1 mA

up to 300 mA

1 mA

FLASH

LED

1 mA

LOUT

LP3954

www.ti.com

SNVS340D – JUNE 2005 – REVISED MARCH 2013

CURRENT CONTROL FOR FLASH

To minimize the internal current consumption, the flash function has an enable bit EN_HCFLASH in the

HC_Flash register.

EN_HCFLASH

FLASH disabled, no extra current consumption through RFLASH

FLASH enabled, IFLASH set by HC_SW[1:0] (see below)

HC[1:0] bits in the HC_Flash register control the FLASH current as show in following table.

HC[1:0]

I(FLASH)

0.25 × IMAX(FLASH)

0.50 × IMAX(FLASH)

0.75 × IMAX(FLASH)

1.00 × IMAX(FLASH)

Figure 23 shows the internal structure for the FLASH driver.

Figure 23. Internal Structure of Flash Driver

FLASH TIMING

Flash output is turned on in lower current View finder mode when the EN_HCFLASH bit is written high. The

actual Flash at maximum current starts when the EN_FLASH i/o-pin goes high. The Flash length can be selected

from 3 pre-defined values or EN_FLASH pin pulse length can determine the length. The pulse length is

controlled by the FT_T[1:0] bits as show in the table below.

Current During View

FL_T[1:0]

Flash Duration Typ

Current During FLASH

Finder/Focusing

200ms

Set by HC[1:0]

HC[11] = IMAX(FLASH)

400ms

Set by HC[1:0]

HC[11] = IMAX(FLASH)

600ms

Set by HC[1:0]

HC[11] = IMAX(FLASH)

EN_FLASH on duration

Set by HC[1:0]

HC[11] = IMAX(FLASH)

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