Datasheet

VND5T100AJ-E Application information
Doc ID 018513 Rev 2 21/32
3 Application information
Figure 24. Application schematic
3.1 GND protection network against reverse battery
3.1.1 Solution 1: resistor in the ground line (R
GND
only)
This solution can be used with any type of load.
The following is an indication on how to dimension the R
GND
resistor.
1. R
GND
 600 mV / (I
S(on)max
).
2. R
GND
V
CC
) / (-I
GND
)
where -I
GND
is the DC reverse ground pin current and can be found in the absolute
maximum rating section of the device datasheet.
Power dissipation in R
GND
(when V
CC
< 0: during reverse battery situations) is:
P
D
= (-V
CC
)
2
/R
GND
This resistor can be shared amongst several different HSDs. Please note that the value of
this resistor should be calculated with formula (1) where I
S(on)max
becomes the sum of the
maximum on-state currents of the different devices.
Please note that if the microprocessor ground is not shared by the device ground then the
R
GND
produces a shift (I
S(on)max
* R
GND
) in the input thresholds and the status output
values. This shift varies depending on how many devices are ON in the case of several high
side drivers sharing the same R
GND
.
If the calculated power dissipation leads to a large resistor or several devices have to share
the same resistor then ST suggests Solution 2 is used (see below).
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