Detailed description

STCF06

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by setting the PWR_ON bit; from flash operation by resetting the TRIG pin or the TRIG_EN

bit or automatically from flash operation when the time counter reaches zero; from torch

operation by resetting the TCH_ON bit. The device automatically enters this mode also

when an overload or an abnormal condition has been detected during flash or torch

operation (Table 16: Status register details:).

7.7

Single or multiple flash using external (µP) temporization

To avoid the I²C bus time latency, it is recommended to use the dedicated TRIG pin to define

the flash duration (hard-triggering). The TRIG_EN bit of CMD_REG should be set before

starting each flash operation, because it could have been reset automatically in the previous

flash operation. The flash duration is determined by the pulse length that drives the TRIG

pin. As soon as the flash is activated, the system needs typically 1.2 ms to ramp up the

output current on the Power LED. The internal time counter will time-out flash operation and

keep the LED dissipated energy within safe limits in case of Software deadlock; FTIM

register has to be set first, either in Stand-by or in ready mode. Multiple flashes are possible

by strobing the TRIG pin. Time out counter will cumulate every flash on-time until the

defined time out is reached unless it is reloaded by updating the CMD_REG. After a single

or multiple flash operations are timed-out, the device automatically goes into Ready mode

by resetting the TRIG_EN bit, and also resets the F_RUN bit. The ATN pin is pulled down to

inform the µP that the STAT_REG has been updated.

7.8

External (µP) temporization using TRIG_EN bit

Even if it is possible, it is not recommended to use the TRIG_EN bit to start and stop the

flash operation, because of I²C bus latencies: this would result in inaccurate flash timing.

Nevertheless, if this operation mode is chosen, the TRIG pin has to be kept High (logic level

the Time Counter will Time-out flash operation and keep the energy dissipated by the LED

within safe limits in case of SW deadlock.

7.9

Single flash using internal temporization

Flash triggering can be obtained either by TRIG pin (hard-triggering) or by I²C commands

(soft-triggering). The first solution is recommended for an accurate start time, while the

second is less accurate because of the I²C bus time latency. Stop time is defined by the

STCF06 internal temporization and its accuracy is determined by the internal oscillator. For

hard-triggering, it is necessary to set the TRIG_EN bit in advance. For soft-triggering, the

setting the FTIM and the TRIG_EN through I²C (both are located in the CMD REG). There is

a delay time between the moment the flash is triggered and when it appears. This delay is

caused by the time necessary to charge up the output capacitor, which is around 1.2 ms

depending on battery voltage and output current value. Once triggered, the flash operation

will be stopped when the time counter reaches zero. As soon as the flash is finished, the

F_RUN bit is reset, the ATN pin is pulled down for 11 µs to inform the µP that the STAT_REG

has been updated and the device goes back to Ready mode. If it is necessary to make a

flash longer than the internal timer allows or a continuous flash, then the FTIM must be

reloaded through I²C bus every time, before the internal timer reaches zero. For example: To

get a continuous flash, set FTIM to 1.5 s and every 1 s reload the CMD_REG.