L6391

Smart shut down function

Doc ID 17892 Rev 1

13/21

7

Smart shut down function

L6391 integrates a comparator committed to the fault sensing function. The comparator

input can be connected to an external shunt resistor in order to implement a simple over-

current detection function.

The output signal of the comparator is fed to an integrated MOSFET with the open drain

output available on pin 2, shared with the SD input. When the comparator triggers, the

device is set in shut down state and both its outputs are set to low level leaving the half-

bridge in tri-state.

Figure 6.

Smart shut down timing waveforms

HIN/LIN

HVG/LVG

SD/OD

open drain gate

(internal)

upper

threshold

lower

threshold

CP-

CP+

PROTECTION

Fast shut down:

the driver outputs are set in SD state

immediately after the comparator

triggering even if the SD signal

has not yet reach

the lower input threshold

real disable time

2

1

1

2

SD/OD

FROM/TO

CONTROLLER

SMART

SD

LOGIC

SHUT DOWN CIRCUIT

TIME CONSTANTS