Operation modes

AN3223

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Doc ID 17553 Rev 2

Note:

Monitoring mode can be also entered from Idle mode, but the device has a greater power

consumption in this case.

5.3

Idle mode

Idle mode allows accessing of all the internal registers. The NTC feature can be activated in

this mode and the temperature of the LED can be sensed by the A/D converter of the

microcontroller. The following data must be written to the COMMAND register to enter Idle

mode.

5.4

NTC feature

The NTC feature can be used in all modes. The NTC is activated automatically in the Flash

and Torch mode regardless of the value of the NTC_ON bit. NTC must be activated

manually in all the other modes.

The NTC feature is activated by setting the NTC_ON bit in the COMMAND register to 1.

As soon as the NTC feature is activated, the internal switch connects the NTC resistor to the

monitored by the A/D converter of the microcontroller. An external voltage reference must be

connected to the NTC to use this feature. The bits NTC_W and NTC_H of the STATUS

register are not properly set if there is no external reference voltage connected to the NTC.

If the NTC feature is not going to be used, neither the negative thermistor nor the external

reference needs to be connected. In this case, it is recommended to ground the RX pin. As

the NTC feature is automatically activated during Flash and Torch mode, leaving the RX pin

floating could lead to unwanted interruptions of the light due to non-defined voltage on the

RX pin.

If the NTC feature is activated and the PWR_ON bit in the COMMAND register is zero, the

bits NTC_W and NTC_H in the STATUS register are not set properly, because the

comparators which determine their values are not enabled in this case. But it is still possible

to measure the voltage on the NTC pin through the A/D converter.

Table 8 summarizes the NTC feature possibilities.

Table 6.

COMMAND register data for entering Idle mode

CMD_REG

PWR_ON FLASH_ON

TCH_ON

NTC_ON

TCHV_H

CHRG

MONTR

N/A

100

x

x

0

0

0

MSB

LSB

Table 7.

COMMAND register data for activation of the NTC feature

CMD_REG

PWR_ON FLASH_ON

TCH_ON

NTC_ON

TCHV_H

CHRG

MONTR

N/A

xxx

1

x

x

x

0

MSB

LSB