VN5016AJ-E Application Information
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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).
3.1.2 Solution 2 : diode (D
GND
) in the ground line
A resistor (R
GND
=1kshould be inserted in parallel to D
GND
if the device drives 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
threshold and in the status output values if the microprocessor ground is not common to the
device ground. This shift will not vary if more than one HSD shares the same diode/resistor
network.
3.2 Load dump protection
D
ld
is necessary (Voltage Transient Suppressor) if the load dump peak voltage exceeds the
V
CC
max DC rating. The same applies if the device is subject to transients on the V
CC
line
that are greater than the ones shown in the ISO 7637-2: 2004(E) table.
3.3 MCU 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 limit 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
5k R
prot
180k.
Recommended values: R
prot
=10kC
EXT
=10nF.
