Detailed description

STCF05

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Doc ID 15257 Rev 4

10

Detailed description

10.1

Power ON reset

This mode is initiated by applying a supply voltage above the VPW_ON RESET threshold

value. An internal timing (~ 1 µs) defines the duration of this status. The logic blocks are

powered, but the device doesn't respond to any input. The registers are reset to their default

values, the ATN and SDA pins are in high impedance, the I²C slave address is internally set

by reading the ADD pin configuration. After the internally defined time has elapsed, the

STCF05 automatically enters the shutdown mode.

10.2

Shutdown, shutdown with NTC

In this mode only the I²C interface is alive, accepting I²C commands and register settings.

The device enters this mode: automatically from Power ON reset status or by resetting the

PWR_ON bit from other operation modes. Power consumption is at the minimum (1 µA typ)

if NTC is not activated (NTC_ON=0). If PWR_ON and NTC_ON is set, the T1 is switched

ON (see the block diagram), allowing the microprocessor to measure the LED temperature

through its A/D converter.

10.3

Ready mode

In this mode all internal blocks are turned ON, but the DC-DC converter is disabled and the

White LED is disconnected. The NTC circuit can be activated to monitor the temperature of

the LED and I²C commands and register settings are allowed to be executed immediately.

Only in this mode the auxiliary LED is operational and can be turned ON and set at the

desired brightness using the AUX REGISTER.

The device enters this mode:

●

from standby 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).

10.4

Single or multiple flash using external (microprocessor)

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 standby or in ready mode. Multiple flashes are possible