Datasheet

VN751S Reverse polarity protection
Doc ID 12320 Rev 7 11/17
7 Reverse polarity protection
A schematic solution to protect the IC against a reverse polarity condition is proposed.
This schematic is effective with any type of load connected to the outputs of the IC.
The RGND resistor value can be selected according to the following conditions to be met:
R
GND
≤ 600 mV / (I
S
in ON state max).
R
GND
≥ (-V
CC
) / (-I
GND
)
where -IGND is the DC reverse ground pin current and can be found in the absolute
maximum rating section of the device datasheet.
The power dissipation associated to R
GND
during reverse polarity condition is:
PD = (-V
CC
)
2
/R
GND
This resistor can be shared by several different ICs. In such case I
S
value on formula (1) is
the sum of the maximum ON-state currents of the different devices.
Please note that if the microprocessor ground and the device ground are separated then the
voltage drop across the R
GND
(given by I
S
in ON state max * R
GND
) produce a difference
between the generated input level and the IC input signal level. This voltage drop will vary
depending on how many devices are ON in the case of several high side switches sharing
the same R
GND
.
Figure 9. Reverse polarity protection
Status
i
Input
i
GND
Output
i
+ Vcc
R
GND
(Optional)
Load
Status
i
Input
i
GND
Output
i
+ Vcc
R
GND
(Optional)
Load