l6391n STMicroelectronics, l6391n Datasheet - Page 14

• Manufacturer Part Number: l6391n
• Description: High-voltage High And Low Side Driver
• Manufacturer: STMicroelectronics

Smart shut down function
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In common over-current protection architectures the comparator output is usually connected
to the SD input and an RC network is connected to this SD/OD line in order to provide a
mono-stable circuit, which implements a protection time that follows the fault condition.
Differently from the common fault detection systems, L6391 Smart shut down architecture
allows to immediately turn-off the outputs gate driver in case of fault, by minimizing the
propagation delay between the fault detection event and the actual outputs switch-off. In fact
the time delay between the fault and the outputs turn off is no more dependent on the RC
value of the external network connected to the pin. In the smart shut down circuitry, the fault
signal has a preferential path which directly switches off the outputs after the comparator
triggering. At the same time the internal logic turns on the open drain output and holds it on
until the SD voltage goes below the SD logic input lower threshold. The Smart shut down
system provides the possibility to increase the time constant of the external RC network
(that is the disable time after the fault event) up to very large values without increasing the
delay time of the protection. Any external signal provided to the SD pin is not latched and
can be used as control signal in order to perform, for instance, PWM chopping through this
pin. In fact when a PWM signal is applied to the SD input and the logic inputs of the gate
driver are stable, the outputs switch from the low level to the state defined by the logic inputs
and vice versa.
Doc ID 17892 Rev 1
L6391