VND830-E
10/20
.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.
OPEN LOAD DETECTION IN OFF STATE
Off state open load detection requires an external pull-up
resistor (R
PU
) connected between OUTPUT pin and a
positive supply voltage (V
PU
) like the +5V line used to
supply the microprocessor.
The external resistor has to be selected according to the
following requirements:
1) no false open load indication when load is connected:
in this case we have to avoid V
OUT
to be higher than
V
Olmin
; this results in the following condition
V
OUT
=(V
PU
/(R
L
+R
PU
))R
L
<V
Olmin.
2) no misdetection when load is disconnected: in this
case the V
OUT
has to be higher than V
OLmax
; this
results in the following condition R
PU
<(V
PU–
V
OLmax
)/
I
L(off2)
.
Because I
s(OFF)
may significantly increase if V
out
is
pulled high (up to several mA), the pull-up resistor R
PU
should be connected to a supply that is switched OFF
when the module is in standby.
The values of V
OLmin
, V
OLmax
and I
L(off2)
are available in
the Electrical Characteristics section.
Figure 8. Open Load detection in off state
V
OL
V batt. V
PU
R
P
R
L
R
DRIVER
+
LOGIC
+
-
INPUT
TATUS
V
CC
OUT
GROUND
I
L(off2)
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