Protection features VNN7NV04, VNS7NV04, VND7NV04, VND7NV04-1
10/37 Doc ID 7383 Rev 4
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. 100µA) flows into the input pin in order to supply the internal circuitry.
The device integrates:
●
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.
●
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 over temperature threshold T
jsh
.
●
Over temperature 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. Over temperature 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.
●
Status feedback: in the case of an over temperature 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 will fall to 0 V.
This will not however affect 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.
