Protection features VNS3NV04DP-E
16/21 Doc ID 018529 Rev 2
3 Protection features
During normal operation, the INPUT pin is electrically connected to the gate of the internal
power MOSFET through a low impedance path.
The device then behaves like a standard power MOSFET and can be used as a switch from
DC up to 50 KHz. The only difference from the user’s standpoint is that a small DC current
I
ISS
(typ. 100 µA) flows into the INPUT pin in order to supply the internal circuitry.
The following sections describe the device features.
3.1 Overvoltage clamp protection
Internally set at 45 V, along with the rugged avalanche characteristics of the Power
MOSFET stage give this device unrivalled ruggedness and energy handling capability. This
feature is mainly important when driving inductive loads.
3.2 Linear current limiter circuit
Limits the drain current I
D
to I
lim
whatever the INPUT pin voltages. When the current limiter
is active, the device operates in the linear region, so power dissipation may exceed the
capability of the heatsink. Both case and junction temperatures increase, and if this phase
lasts long enough, junction temperature may reach the overtemperature threshold T
jsh.
3.3 Overtemperature and short circuit protection
These are based on sensing the chip temperature and are not dependent on the input
voltage. The location of the sensing element on the chip in the power stage area ensures
fast, accurate detection of the junction temperature. Overtemperature cutout occurs in the
range 150 to 190 °C, a typical value being 170 °C. The device is automatically restarted
when the chip temperature falls of about 15 °C below shutdown temperature.
3.4 Status feedback
In the case of an overtemperature fault condition (T
j
> T
jsh
), the device tries to sink a
diagnostic current I
gf
through the INPUT pin in order to indicate fault condition. If driven from
a low impedance source, this current may be used in order to warn the control circuit of a
device shutdown. If the drive impedance is high enough so that the INPUT pin driver is not
able to supply the current I
gf
, the INPUT pin falls to 0 V. This however not affects the device
operation: no requirement is put on the current capability of the INPUT pin driver except to
be able to supply the normal operation drive current I
ISS
.
Additional features of this device are ESD protection according to the Human Body model
and the ability to be driven from a TTL Logic circuit.
