FUNCTIONAL DESCRIPTION
The device has a diagnostic output which
indicates open load conditions in off state as well
as in on state, output shorted to V
CC
and
overtemperature. The truth table shows input,
diagnostic and output voltage level in normal
operation and in fault conditions. The output
signals are processed by internal logic. The
open load diagnostic output has a 5 ms filtering.
The filter gives a continuous signal for the fault
condition after an initial delay of about 5 ms. This
means that a disconnection during normal
operation, with a duration of less than 5 ms does
not affect the status output. Equally, any
re-connection of less than 5 ms during a
disconnection duration does not affect the status
output. No delay occur for the status to go low in
case of overtemperature conditions. From the
falling edge of the input signal the status output
initially low in fault condition (over temperature or
open load) will go back with a delay (t
povl
)in case
of overtemperature condition and a delay (t
pol
) in
case of open load. These feature fully comply
with International Standard Office (I.S.O.)
requirement for automotive High Side Driver.
To protect the device against short circuit and
over current conditions, the thermal protection
turns the integrated Power MOS off at a
minimum junction temperature of 140
o
C.
When the temperature returns to 125
o
C the
switch is automatically turned on again. In short
circuit the protection reacts with virtually no
delay, the sensor being located in the region of
the die where the heat is generated. Driving
inductive loads, an internal function of the
device ensures the fast demagnetization with a
typical voltage (V
demag
) of -18V.
This function allows to greatly reduce the power
dissipation according to the formula:
P
dem
= 0.5 • L
load
• (I
load
)
2
• [(V
CC
+V
demag
)/V
demag
]
•f
where f = switching frequency and
V
demag
= demagnetization voltage
Based on this formula it is possible to know
the value of inductance and/or current to avoid
a thermal shut-down. The maximum inductance
which causes the chip temperature to reach the
shut down temperature in a specific thermal
environment, is infact a function of the load
current for a fixed V
CC
, V
demag
and f.
PROTECTING THE DEVICE AGAIST LOAD
DUMP - TEST PULSE 5
The device is able to withstand the test pulse
No. 5 at level II (V
s
= 46.5V) according to the
ISO T/R 7637/1 without any external
component. This means that all functions of the
device are performed as designed after
exposure to disturbance at level II. The VN06SP
is able to withstand the test pulse No.5 at level
III adding an external resistor of 150 ohm
between GND pin and ground plus a filter
capacitor of 1000 µF between V
CC
pin and
ground (if R
LOAD
≤ 20 Ω).
PROTECTING THE DEVICE AGAINST
REVERSE BATTERY
The simplest way to protect the device against a
continuous reverse battery voltage (-26V) is to
insert a Schottky diode between GND pin and
ground, as shown in the typical application circuit
(fig.3).
The consequences of the voltage drop across
this diode are as follows:
If the input is pulled to power GND, a negative
voltage of -V
f
is seen by the device. (Vil, Vih
thresholds and Vstat are increased by Vf with
respect to power GND).
The undervoltage shutdown level is increa- sed
by Vf.
If there is no need for the control unit to handle
external analog signals referred to the power
GND, the best approach is to connect the
reference potential of the control unit to node [6]
(see application circuit in fig. 4), which becomes
the common signal GND for the whole control
board avoiding shift of V
ih
, V
il
and V
stat
. This
solution allows the use of a standard diode.
Switching Time Waveforms
VN31SP
5/9
