VND5012AK-E
Figure 7. Application Schematic
+5V
V
CC
R
prot
CS_DIS
D
ld
µC
R
prot
R
prot
CURRENT SENSE
GND
R
SENSE
R
GND
V
GND
D
GND
INPUT
OUTPUT
Note: Channel 2 has the same internal circuit as channel 1.
GND PROTECTION
REVERSE BATTERY
NETWORK
AGAINST
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 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
HSDs. 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
shared by 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 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 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 (j600mV) 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.
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 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
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
5kΩ
≤
R
prot
≤
65kΩ.
Recommended R
prot
value is 10kΩ.
8/13
STMICROELECTRONICS [ STMICROELECTRONICS ]
