STCF02_07 Datasheet, PDF (13/19 Pages) STMicroelectronics – High power white led driver

STCF02
Detailed operating description
Figure 12. Middle Flash Current (as a percentage of flash current) vs R_MF
6.5 Torch mode
To select this operating mode the Enable pins have to be connected to any one of the follow states:
EN1 = 0, EN2 = 1, EN3 = x
EN1 = 1, EN2 = 1, EN3 = 1.
The STCF02 can continuously provide a torch current adjustable between 25mA and 250mA. The torch
current adjustment is made by resistor R_TORCH (Figure 2). The control loop uses the FB1 pin to sense the
voltage across R_FLASH+R_TORCH. The torch current is then programmed using the following equation:
I_TORCH=160mV/(R_FLASH+R_TORCH).
If the programmed Flash current is 600mA (R_FLASH = 0.27Ω) and a 250mA Torch current is needed, the
R_TORCH resistance is equal to 0.37Ω.
During Torch operation mode the MOS Switch between FB1 and RTBY pins is opened.
The NTC divider for measuring LED temperature is active.
6.6 Shutdown mode
When the device is not used, two shutdown modes are available. They can be selected by the enable
pins:
EN1=0, EN2=0, EN3=X
With this combination the NTC divider for measuring of LED temperature is not active. The quiescent
current is less than 1µA.
EN=1, EN2=0, EN3=1
This combination of enable pins provides shutdown modes with an active NTC divider for sensing LED
temperature. This Mode is useful for measuring the temperature before starting both TORCH and FLASH
MODE operations.
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