VN920 / VN920-B5 / VN920SO
APPLICATION SCHEMATIC
+5V
V
CC
R
prot
INPUT
D
ld
R
prot
µC
OUTPUT
CURRENT SENSE
R
SENSE
GND
R
GND
V
GND
D
GND
This small signal diode can be safely shared amongst
several different HSD. Also in this case, the presence of
the ground network will produce a shift ( 600mV) in the
input threshold 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.
GND PROTECTION NETWORK AGAINST
REVERSE BATTERY
Solution 1: Resistor in the ground line (R
can be used with any type of load.
only). This
GND
The following is an indication on how to dimension the
R
resistor.
GND
1) R
2) R
where -I
≤ 600mV / (I
).
S(on)max
LOAD DUMP PROTECTION
GND
GND
≥ (−V ) / (-I
)
CC
GND
D
is necessary (Voltage Transient Suppressor) if the
ld
is the DC reverse ground pin current and can
load dump peak voltage exceeds V max DC rating. The
GND
CC
be found in the absolute maximum rating section of the
device’s datasheet.
Power Dissipation in R
battery situations) is:
same applies if the device will be subject to transients on
the V
line that are greater than the ones shown in the
CC
ISO T/R 7637/1 table.
(when V <0: during reverse
CC
GND
µC I/Os PROTECTION:
2
P = (-V ) /R
D
CC
GND
If a ground protection network is used and negative
This resistor can be shared amongst several different
HSD. Please note that the value of this resistor should be
transients are present on the V line, the control pins will
CC
be pulled negative. ST suggests to insert a resistor (R
)
prot
calculated with formula (1) where I
becomes the
in line to prevent the µC I/Os pins to latch-up.
S(on)max
sum of the maximum on-state currents of the different
devices.
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.
Please note that if the microprocessor ground is not
common with the device ground then the R
will
GND
produce a shift (I
* R
) in the input thresholds
S(on)max
GND
-V
/I
≤ R
≤ (V
-V -V
) / I
CCpeak latchup
prot
OHµC IH GND
IHmax
and the status output values. This shift will vary
depending on how many devices are ON in the case of
Calculation example:
several high side drivers sharing the same R
.
For V
= - 100V and I
≥ 20mA; V
≥ 4.5V
CCpeak
latchup
OHµC
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).
5kΩ ≤ R
≤ 65kΩ.
prot
Recommended R
value is 10kΩ.
prot
Solution 2: A diode (D
) in the ground line.
GND
A resistor (R
GND
=1kΩ) should be inserted in parallel to
GND
D
if the device will be driving an inductive load.
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