STCF01 datasheet(8/16 Pages) STMICROELECTRONICS

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6 Detailed Description

STCF01

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Detailed Description

The STCF01 white Led boost converter drives two up to four white LEDs with a constant

current. It needs few external components: two ceramic capacitors (CI=2.2µF CO=4.7µF), one

inductor L=10µH and one schottky diode. The device works with a minimum VI=2.6V, and it has

an Over Voltage Protection on the output guaranteed at minimum value equal to 17V. This

value ensures proper operation with a maximum of four White LEDs in series. In the worst case

of VI=2.6V at VOVP=8V (typical value of two LEDs) it is possible to obtain IO=270mA, while at

VOVP=11V (typical value of three LEDs) it is possible obtain IO=180mA (Figure 4: Maximum

Output Current Vs Input Voltage). The maximum IO current is limited by inductor peak current

internally set at Typ 1.2A. This feature allows saving the battery life from intensive use of the

flash. The SEL pin allows to select high and low current value flowing on the White LEDs.

The two current values are set through external resistors RHC and RLC according the following

formula:

ILED(FLASH) = 2100 * (VI - VHC) / RHC

ILED(TORCH) = 2400 * (VI - VLC) / RLC

An High logic level on SHDN pin puts the device in shutdown mode; if it is hold to Low the flash

or torch mode is activated. When the SHDN pin is LOW the device provides the requested

current in less than 200µs (see TURN ON TIME plot). This fast turn-on time makes the device

suitable for single shoot and multiple shoot operation modes.

STCF01 数据表(PDF) 8 Page - STMicroelectronics