VNQ7140AJ Datasheet, PDF (26/46 Pages) STMicroelectronics – Quad channel high-side driver with MultiSense analog feedback

Protections
VNQ7140AJ
3
Protections
3.1
Power limitation
The basic working principle of this protection consists of an indirect measurement of the
junction temperature swing ΔTj through the direct measurement of the spatial temperature
gradient on the device surface in order to automatically shut off the output MOSFET as
soon as ΔTj exceeds the safety level of ΔTj_SD. According to the voltage level on the
FaultRST pin, the output MOSFET switches on and cycles with a thermal hysteresis
according to the maximum instantaneous power which can be handled (FaultRST = Low)
or remains off (FaultRST = High). The protection prevents fast thermal transient effects
and, consequently, reduces thermo-mechanical fatigue.
3.2
Thermal shutdown
In case the junction temperature of the device exceeds the maximum allowed threshold
(typically 175°C), it automatically switches off and the diagnostic indication is triggered.
According to the voltage level on the FaultRST pin, the device switches on again as soon
as its junction temperature drops to TR (FaultRST = Low) or remains off (FaultRST = High).
3.3
Current limitation
The device is equipped with an output current limiter in order to protect the silicon as well
as the other components of the system (e.g. bonding wires, wiring harness, connectors,
loads, etc.) from excessive current flow. Consequently, in case of short circuit, overload or
during load power-up, the output current is clamped to a safety level, ILIMH, by operating the
output power MOSFET in the active region.
3.4
Negative voltage clamp
In case the device drives inductive load, the output voltage reaches a negative value during
turn off. A negative voltage clamp structure limits the maximum negative voltage to a
certain value, VDEMAG, allowing the inductor energy to be dissipated without damaging the
device.
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