Functions description

L6520, L6521

12/19

Doc ID 16998 Rev 3

5.6.4

Choke saturation control (CSC) during ignition and run mode

The same thresholds used to detect OCPH and OCPL are active.

The control is still based on the time between two consecutive thresholds but its behavior is

different with respect to the OCPH/OCPL detection to take into account the increase of dI/dt

when the inductor is saturating. When either the two lower thresholds are crossed in a time

shorter than 255 ns or the higher threshold is crossed, the LS driver is immediately turned

off and the time between the LS turn on and the instant when the second threshold (THM or

TLM) is crossed is used to calculate the new (higher) frequency.

If this new frequency is higher than 100 kHz then the new frequency will be set at 100 kHz.

frequency at which the first threshold was crossed is reached. Then, the decreasing ratio

ratio is maintained until run frequency is reached.

If the run frequency has not been reached after 200 ms from when the lower threshold was

crossed the first time, the IC is turned off (latched).

A leading edge blanking of 255 ns is active.

5.7

End of life (EOL)

An embedded window comparator can be used to detect the end of life (EOL) when the

lamp is directly connected to ground (lamp to ground configuration).

After the ignition sequence, the EOL window comparator becomes active. When the voltage

at EOL pin goes outside the limits of this comparator a 1.5 s timer is started. If the EOL pin

voltage does not return inside the allowed range before the end of the timer, the IC is shut

down (latched).

The EOL pin is biased to the center of the window comparator by means of an OTA (2.5 V

typ. with +/- 1.5 V typ. window), having a current capability equal to 9.1 µA (typ.).