9/18
VND600-E
Figure 8. Application Schematic
GND PROTECTION NETWORK AGAINST
REVERSE BATTERY
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’s 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
HSD. 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
common with 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 the ST suggests to utilize Solution 2 (see
below).
Solution 2:
A diode (D
GND
) in the ground line.
A resistor (R
GND
=1kΩ) should be inserted in parallel to
D
GND
if the device will be driving an inductive load.
This small signal diode can be safely shared amongst
several different HSDs.
Also in this case, the presence of the ground network will
produce a shift ( 600mV) in the input thresholds and the
status output values if the microprocessor ground is not
common with the device ground. This shift will not vary if
more than one HSD shares the same diode/resistor
network.
Series resistor in INPUT and STATUS lines are also
required to prevent that, during battery voltage transient,
the current exceeds the Absolute Maximum Rating.
Safest configuration for unused INPUT and STATUS pin
is to leave them unconnected.
LOAD DUMP PROTECTION
D
ld
is necessary (Voltage Transient Suppressor) if the
load dump peak voltage exceeds V
CC
max DC rating.
The same applies if the device will be subject to
transients on the V
CC
line that are greater than the ones
shown in the ISO T/R 7637/1 table.
.
µC I/Os PROTECTION:
If a ground protection network is used and negative
transient are present on the V
CC
line, the control pins will
be pulled negative. ST suggests to insert a resistor (R
prot
)
in line to prevent the µC I/Os pins to latch-up.
The value of these resistors is a compromise between
the leakage current of µC and the current required by the
HSD I/Os (Input levels compatibility) with the latch-up lim-
it of µC I/Os.
-V
CCpeak
/I
latchup
≤ R
prot
≤ (V
OHµC
-V
IH
-V
GND
) / I
IHmax
Calculation example:
For V
CCpeak
= - 100V and I
latchup
≥ 20mA; V
OHµC
≥ 4.5V
5kΩ ≤ R
prot
≤ 65kΩ.
Recommended R
prot
value is 10kΩ.
V
CC
GND
OUTPUT2
CURRENT SENSE1
D
ld
+5V
R
prot
R
SENSE2
OUTPUT1
R
SENSE1
INPUT1
D
GND
R
GND
V
GND
CURRENT SENSE2
INPUT2
µ
C
R
prot
R
prot
R
prot
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