Datasheet

VND5T035AK-E Application information
Doc ID 018942 Rev 5 21/31
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 produces 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 does 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
maximum 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 transient is present on the V
CC
line, the
control pins are pulled negative. ST suggests that a resistor (R
prot
) have to be inserted in
line to prevent the microcontroller I/Os pins to latch-up.
The value of these resistors is a compromise between the leakage current of the
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.