STCF02 STMicroelectronics, STCF02 Datasheet - Page 11

• Manufacturer Part Number: STCF02
• Description: HIGH POWER WHITE LED DRIVER
• Manufacturer: STMicroelectronics

Specifications of STCF02

• Drives One Power White Led: up to 600mA between 2.7 to 4.5V
• Torch Mode: up to 250 mA

STCF02
6
6.1
The STCF02 is a buck-boost converter, dedicated to power and control the current of a Power White Led
in a camera cell Phone. The device operates at a constant switching frequency of 1.8MHz typ. It provides
an output voltage down to 2.5V and up to 5.1 V, from a single cell 2.7 V to 5.5 V lithium-ion battery. The
flash current is adjustable from 100mA to 600mA for the input voltage range from 2.7V to 4.5V. Torch
current is adjustable from 25mA to 250mA. The device also includes a medium flash mode with the
current set between the 25% of flash current and flash current. The device contains a pin for connection
of NTC which senses the temperature of the LED.
6.2
Regulation of the PWM controller is made by sensing the current of the led through the R
(see
the operation mode between buck (step down) and boost (step up) mode. Three case can occur:
Boost region (V
I
6.3
To select Flash mode the Enable pins have to be connected as follows: EN1=1, EN2=1, EN3=0.
The STCF02 operates continuously to supply maximum current to the flash LED (up to 600 mA).
The flash current can be adjusted by the R
voltage across R
I
For a flash current programmed at 600mA, the sensing resistor is equal to 0.27Ω .
During this operation mode the MOS Switch between FB1 and RTBY pins is closed.
If the EN3 is forced to High during Flash mode operation, the current is reduced to that of Torch mode.
Such reduction of input power during transition from Flash to Torch mode is achieved within less than
30µs. The NTC divider for measuring LED temperature is active.
LED
FLASH
x R
Figure 2
= 160mV / R
FLASH
Detailed operating description
Introduction
Buck-Boost converter
Flash mode
). Depending on the forward voltage of the Flash LED, the device can automatically change
) is higher than VBAT; Buck region (V
O
FLASH
> VBAT): this configuration is used in most cases, as the output voltage (V
FLASH.
. The flash current is then programmed at:
FLASH
resistor. The control loop uses the FB2 pin to sense the
O
< V
BAT
); Buck / Boost region (V
Detailed operating description
O
~ V
FLASH
I
).
O
= V
resistor
fLED
11/19
+