Device description

ALED6001

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DocID026965 Rev 2

7.4.5

Thermal shutdown

The ALED6001 implements an autorestarting thermal protection in order to avoid damages

due to excessive die temperature. Once the chip temperature reaches the upper

overtemperature protection (OTP) threshold, the ongoing operation is suddenly stopped,

both the PWMO and XFAULT pins are held low and the 5 V linear regulator (VDR pin) is

turned off. As soon as the die temperature drops below the autorestarting threshold, a new

soft-start sequence takes place if the PWMI pin is still high and a 1 ms (typ.) deglitch delay

has expired.

The XFAULT pin goes low as soon as the OTP threshold is crossed and it is released once

the device temperature drops below a third threshold, lower than the restart one, in order to

provide a stable information to the host system.

Table 7. Faulty conditions management summary

Faulty condition

Detection mechanism

Consequence

1

Output rail/load disconnection

Device turning-off (latched condition).

GATE, PWMO and XFAULT pins are

forced low.

2

Open feedback (VFBP)

3

Open feedback (VFBN)

LED overcurrent

4

Open OVFB path

5

Open PWMO (loss of dimming

MOSFET control)

Output overvoltage

Power switch overcurrent

Ongoing switching cycle terminated

IC overtemperature

Device turning-off (VDR off, LDO3

active).

GATE, PWMO and XFAULT pins are

forced low.

PWMI still high.

XFAULT pin is released

1.

Output-to-ground short-circuit protection can be achieved only if the device can effectively disconnect the output by acting

on the PWMO pin (e.g.: a high-side P-channel MOSFET is used as a dimming switch).