Datasheet

Application information VND5T050AK-E
22/32 Doc ID 022694 Rev. 3
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).
3.1.2 Solution 2: diode (D
GND
) in the ground line
A resistor (R
GND
=4.7kΩ) should 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 (≈600 mV) 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 to
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 T/R 7637/2 table.
3.3 MCU I/Os protection
If a ground protection network is used and negative transients are present on the V
CC
line,
the control pins will be pulled negative. ST suggests that a resistor (R
prot
) be inserted in line
to prevent the microcontroller I/O pins from latching-up.
The value of these resistors is a compromise between the leakage current of microcontroller
and the current required by the HSD I/Os (Input levels compatibility) with the latch-up limit of
microcontroller I/Os.
-V
CCpeak
/I
latchup
≤ R
prot
≤ (V
OHμC
-V
IH
-V
GND
) / I
IHmax
Calculation example:
For V
CCpeak
= -600 V and I
latchup
≥ 20 mA; V
OHμC
≥ 4.5 V
30 kΩ ≤ R
prot
≤ 180 kΩ.
Recommended R
prot
value is 60 kΩ.