VN800S / VN800PT Application information
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3 Application information
Figure 21. Application schematic
3.1 GND protection network against reverse battery
3.1.1 Solution 1: resistor in the ground line (R
GND
only)
This can be used with any type of load.
The following is an indication on how to dimension the R
GND
resistor.
1. R
GND
≤ 600mV / (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
will produce a shift (I
S(on)max
* R
GND
) in the input thresholds and the status output
values. This shift will vary 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 to utilize Solution 2 (see below).
V
CC
INPUTn
GND
STATUSn
OUTPUTn
Volt.
Reg
BUS
ASIC
Control & Diagnostic I/O
5V
24VDC
V
CC
DGND
VGND
RGND
Rprot
Rprot
LOAD
R
L
