VN5160S-E
Application Information
3.1.2
Solution 2: a diode (D
) in the ground line
GND
A resistor (R
inductive load.
=1kΩ) should be inserted in parallel to D if the device drives an
GND
GND
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 (≈ 600mV) 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
3.3
Load dump protection
D is necessary (Voltage Transient Suppressor) if the load dump peak voltage exceeds the
ld
V
max DC rating. The same applies if the device is subject to transients on the V line
CC
CC
that are greater than the ones shown in the ISO 7637-2: 2004(E) table.
MCU I/Os protection
If a ground protection network is used and negative transient are present on the V line,
CC
the control pins will be pulled negative. ST suggests to insert a resistor (R ) in line to
prot
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
/I
≤R
≤(V
-V -V
) / I
CCpeak latchup
prot
OHµC IH GND IHmax
Calculation example:
For V
= - 100V and I
≥ 20mA; V
≥ 4.5V
CCpeak
latchup
OHµC
5kΩ ≤R
≤180kΩ.
prot
Recommended R
values is 10kΩ.
prot
3.4
Open load detection in Off state
Off state open load detection requires an external pull-up resistor (R ) connected between
PU
OUTPUT pin and a positive supply voltage (V ) like the +5V line used to supply the
PU
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
V
to be higher than V
; this results in the following condition
OUT
OUT
Olmin
= (V /(R +R ))R <V .
PU
L
PU
L
Olmin
2. no misdetection when load is disconnected: in this case the V has to be higher than
out
V
; this results in the following condition R <(V –V
)/I
.
OLmax
PU
PU OLmax L(off2)
Because I
may significantly increase if V is pulled high (up to several mA), the pull-
out
s(OFF)
up resistor R should be connected to a supply that is switched OFF when the module is in
PU
standby.
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STMICROELECTRONICS [ ST ]
