STLED25 datasheet(18/30 Pages) STMICROELECTRONICS

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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 VOUT

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 VOUT 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 VOUT. 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

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