Datasheet

Detailed description STLED25
18/30 Doc ID 022323 Rev 3
6.4 Modes of operation
Shutdown mode
The device is in shutdown with minimum current consumption. It goes to PWM_start as
soon as EN13 or EN45 are pulled high.
PWM_start
Once ENxx is asserted, the DC-DC is turned ON with a soft-start procedure until V
OUT
reaches 7 V; this phase takes around 1.2 ms.
If ENxx remains asserted, the device will stay in this condition and wait for 10 ms
(PWM_start_up), then the STLED25 goes to PWM_normal mode. If the next EN is asserted
during the PWM_start_up mode, the device will immediately enable the LED current
sources and continue in PWM_normal mode.
PWM_normal
In this mode of operation the drivers are in the ON state delivering current to the LEDs, and
the DC-DC converter maintains the V
OUT
value with enough headroom to keep the high side
current sources in regulation.
When both EN pins are low, the drivers are turned off and the RUN_HOLD timer starts.
RUN_hold
The RUN_hold time lasts approximately 30 ms. During this time, the DC-DC converter
maintains the last optimum voltage on V
OUT
. If RUN_hold time elapses without EN
reassertion, then the STLED25 goes into shutdown mode. If EN is reasserted, the device
goes to PWM_normaL mode.
Figure 19. Modes of operation