STCF05 Datasheet, PDF (21/33 Pages) STMicroelectronics – High power white LED driver with I²C interface

STCF05
9
Registers description
Registers description
9.1
PWR_ON
When set, it activates all analog and power internal blocks including the NTC supporting
circuit, and the device is ready to operate (ready mode). As long as PWR_ON=0, only the
I²C interface is active, minimizing standby mode power consumption.
9.2
TRIG_EN
This bit is and-ed with the TRIG pin to generate the internal signal FL_ON that activates
flash mode. By this way, both soft-triggering and hard-triggering of the flash are possible. If
soft-triggering (through I²C) is chosen, the TRIG pin is not used and must be kept HIGH (VI).
If hard-triggering is chosen, then the TRIG pin has to be connected to a microprocessor I/O
devoted to Flash timing control, and the TRIG_EN bit must be set in advance. Both
triggering modes can benefit of the internal flash time counter, which uses the TRIG_EN bit
and can work either as a safety shut-down timer or as a flash duration timer. Flash mode
can start only if PWR_ON=1. LED current is controlled by the value set by the FDIM_0~3 of
the DIM_REG.
9.3
TCH_ON
When set from ready mode, the STCF05 enters torch mode. The LED current is controlled
by the value set by the TDIM_0~3 of the DIM_REG.
9.4
NTC_ON
Ready mode activates the comparators that monitor the LED temperature. NTC-related
blocks are always active regardless of this bit in the Torch mode and flash mode.
9.5
FTIM_0~3
This 4-bits register defines the maximum flash duration. It is intended to limit the energy
dissipated by the LED to a maximum safe value or to leave to the STCF05 the control of the
flash duration during normal operation. Values from 0~15 correspond to 0~1.5 s (100 ms
steps). The timing accuracy is related to the internal oscillator frequency that clocks the
flash time counter. Entering flash mode (either by soft or hard triggering) activates the flash
time counter, which begins counting down from the value loaded in the F_TIM register.
When the counter reaches zero, flash mode is stopped by resetting TRIG_EN bit, and
simultaneously the ATN pin is set to true (LOW) to alert the microprocessor that the
maximum time has been reached. FTIM value remains unaltered at the end of the count.
9.6
TDIM_0~2
These 3 bits define the LED current in Torch mode in 8 exponential steps. Max current value
in Torch mode is 120 mA.
Doc ID 15257 Rev 4
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