AN3223 datasheet(21/29 Pages) STMICROELECTRONICS

Part #	AN3223

Description	Driver for double flash LED with I²C interface

PDF	29 Pages

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Manufacturer	STMICROELECTRONICS [STMicroelectronics]

Direct Link	http://www.st.com

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21 / 29 page

AN3223

The light sensor

Doc ID 17553 Rev 2

21/29

The light sensor

The light sensor is an optional feature which optimizes the FLASH duration according to the

light conditions in the flashed scene. This feature requires three external components to be

connected to the STCF04 according to

Figure 12. It is recommended to connect the

collector of the phototransistor to VREF = 1.8 V. The integrating capacitor CINT is discharged

before every FLASH pulse. This reset takes approximately 200 µs. During the FLASH the

voltage on this capacitor increases according to the amount of light in the scene and TFOTO,

RLIGHT, and CINT parameters. The values of these components must be selected according

to the final application purpose.

Figure 12.

Optional light sensor feature

AM07806v1

AN3223 Datasheet(PDF) 21 Page - STMicroelectronics