Operation modes

AN2827

18/30

Doc ID 15047 Rev 1

Hard triggering therefore allows a smooth setting of the flash duration. The resolution is

about 8.8 µs. The minimum flash duration is limited by the ramp-up time of the LED current

and the maximum is limited by the FTIM value. If it is necessary to make a flash pulse longer

then the maximum allowed by FTIM, then it is necessary to reload the COMMAND register

before the internal timer reaches zero (start a new flash before the previous one elapses).

See Section 8.5: Example 5: flash pulse longer than 1.5 s for more details.

Figure 14.

Splitting the flash pulse into several shorter pulses

TRIG pin

100

ms

200

ms

TRIG_EN bit

I²C bus packet

1300 ms

LED current

Time when the

internal flash

timer reaches 0

9

8

7

6

5

4

321

0

Internal Flash timer values

TRIG pin

100

ms

200

ms

TRIG_EN bit

I²C bus packet

1300 ms

LED current

Time when the

internal flash

timer reaches 0

9

8

7

6

5

4

321

0

Internal Flash timer values