STCF06TBR datasheet(23/33 Pages) STMICROELECTRONICS

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Description of internal registers

STCF06

23/33

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 STCF06 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 (+/- 20 %). 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

and simultaneously the ATN pin is set to true (LOW) to alert the µP that the maximum time

has been reached. FTIM value remains unaltered at the end of the count.

9.6

TDIM_0~3

These 4 bits define the LED current in torch mode with 16 values fitting an exponential law.

Max torch current value is 25% of max flash current. (Figure 12)

9.7

FDIM_0~3

These 4 bits define the LED current in flash mode with 16 values fitting an exponential law.

The Max value of the current is set by the external resistors RFL and RTR. (Figure 12)

Note:

LED current values refer to RFL=0.15 Ω, RTR=1.0 Ω

Table 11. Dimming register

DIM_REG

(write mode)

MSB

LSB

SUB ADD=01

TDIM_3

TDIM_2

TDIM_1

TDIM_0

FDIM_3

FDIM_2

FDIM_1

FDIM_0

Power-ON, SHUTDOWN

MODE

RESET Value

0000

Figure 12.

Flash and torch current vs. dimming value

200

400

600

800

1000

1200

1400

1600

dimming value

Torch current

Flash current

200

400

600

800

1000

1200

1400

1600

dimming value

Torch current

Flash current

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