Datasheet

Description L99MC6
16/32 Doc ID 16523 Rev 2
2.7 Bulb mode (programmable soft start function to drive loads
with higher inrush current)
Loads with start-up currents higher than the overcurrent limits (for example inrush current of
lamps, start current of motors and cold resistance of heaters) can be driven by using the
programmable soft start function (that is overcurrent recovery mode). Each driver has a
corresponding overcurrent recovery bit. If this bit is set, the device automatically switches-
on the outputs again after a fixed recovery time. The PWM modulated current provides
sufficient average current to power up the load (for example heat up the bulb) until the load
reaches operating condition (Figure 6).
The device itself cannot distinguish between a real overload and a non linear load like a light
bulb. A real overload condition can only be qualified by time. As an example the
microcontroller can switch-on light bulbs by setting the overcurrent recovery bit for the first
50 ms. After clearing the recovery bit, the output is automatically disabled if the overload
condition still exits.
Figure 7. Example of programmable soft start function for inductive loads and incandescent
bulbs
Load Current
Unlimited Inrush Current
Limited Inrush Current in
overcurrent recovery
mode with inductive load
t
Load Current
Unlimited Inrush Current
Limited Inrush Current in
overcurrent recovery mode
with incandescent bulb
t