STMicroelectronics STEVAL-TLL009V1 Camera flash based on the STCF07 STEVAL-TLL009V1 STEVAL-TLL009V1 Datenbogen
Produktcode
STEVAL-TLL009V1
External component selection
STCF07
20/26
Doc ID 16757 Rev 3
11
External component selection
11.1
Input and output capacitor selection
For input and output capacitors it is recommended to use ceramic capacitors with low ESR.
For good device stability when supplied by a low input voltage of 2.7 V at maximum ratings,
it is recommended to use 10 µF / 6.3 V as a minimum value for the input capacitor, and 4.7
µF / 6.3 V as a minimum value for the output capacitor.
For good device stability when supplied by a low input voltage of 2.7 V at maximum ratings,
it is recommended to use 10 µF / 6.3 V as a minimum value for the input capacitor, and 4.7
µF / 6.3 V as a minimum value for the output capacitor.
Note:
See recommended components in
11.2 Inductor
selection
A thick, shielded inductor with low DC series wiring resistance is recommended for this
application. For good efficiency, it is recommended to use an inductor with a series DC
resistance of R
application. For good efficiency, it is recommended to use an inductor with a series DC
resistance of R
DCL
< R
D
/ 10, where R
D
is the dynamic resistance of the LED.
For nominal operation, the peak inductor current can be calculated using the formula:
I
PEAK
= {(I
OUT
/
η) + [(V
OUT
- V
IN
) x V
IN
²) / (2 x L x F x V
OUT
²)]} x V
OUT
/ V
IN
where:
I
PEAK
= peak inductor current
I
OUT
= current sourced at pin V
OUT
η = efficiency of the STCF07
V
OUT
= output voltage at pin V
OUT
V
IN
= input voltage at pin V
IN
L = inductance value of the inductor
F = switching frequency
Note:
See recommended components in
11.3 LED
selection
All LEDs with forward voltages from 2.7 V to 5 V are suitable for use with STCF07 device.
The LED forward voltage must include the voltage spread of this value. It is possible to set
the LED current in the two different operating modes (high current mode and low current
mode) through two external sensing resistors.
The LED forward voltage must include the voltage spread of this value. It is possible to set
the LED current in the two different operating modes (high current mode and low current
mode) through two external sensing resistors.
Note:
See recommended components in
11.4 R
HC
selection
The R
HC
resistor value can be calculated using equations R
HC
= 160 mV / I
HC
and P
RHC
=
R
HC
* I
HC
2
, where P
RHC
is the dissipated power on the R
HC
resistor. It is recommended to
use a 1206 package size thin metal film resistor with 1% or 5% maximum tolerance. The
maximum high LED current for the STCF07 device is 800 mA with a battery voltage range
2.7 V to 5.5 V.
maximum high LED current for the STCF07 device is 800 mA with a battery voltage range
2.7 V to 5.5 V.