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ALED6001

Device description

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7.4.4

Output rail disconnection detection or output short-circuit to ground

If the connection between the output rail and the output sensing resistor is lost, the voltage

of both the VFBP and VFBN pins falls down to zero. The ALED6001 detects this faulty

condition by comparing the absolute voltage of both VFBP and VFBN pins with an internal

3.3 V threshold and latches-off as a consequence (the GATE and PWMO pins forced low,

XFAULT pin lowered). Normal operation is resumed by toggling the PWMI pin (PWMI has to

be low for more than 10 ms) after the root cause has been removed.

When the ALED6001 is operating with a boost topology, a similar condition occurs in case of

output-to-ground short-circuit. Of course, because of the inherent path between input and

output, a real protection against this faulty condition can be achieved only if the device is

capable of disconnecting the boost output by means of the dimming switch (e.g.: in case

a P-channel MOSFET is used as a high-side dimming switch).

Figure 12. Load disconnection (1 and 5), open feedback (2 and 3) and open OVFB faulty

conditions