Electrical specifications L9823
12/19 DocID7791 Rev 7
2.4 Power outputs characteristics for flyback current, outputs
short circuit protection and diagnostics
For output currents flowing into the circuit the output voltages are limited. The typical value
of this voltage is 50V. This function allows that the flyback current of a inductive load
recirculates into the circuit; the flyback energy is absorbed in the chip.
Output short circuit protection SFPD = Low (dedicated for loads without inrush current):
when the output current exceeds the short circuit threshold, the corresponding output
overload latch is set after a delay time t
dly SCB
and the output is switched off. The delay timer
is started after each rise of CSB and valid datas are transferred to the output control
register. If the short takes place after the delay time has elapsed the shutdown is immediate
(within 15 µs).
Output short circuit protection SFPD = High (dedicated for loads with inrush current, as
lamps): when the load current would exceed the short circuit limit value, the corresponding
output goes in a current regulation mode. The output current is determined by the output
characteristics and the output voltage depends on the load resistance. In this mode high
power is dissipated in the output transistor and its temperature increases rapidly. When the
power transistor temperature exceeds the thermal shutdown threshold, the overload latch is
set and the corresponding output switched off.
For the load diagnostic in output off condition each output features a diagnostic current sink,
of typ 60 µA.
