VNH7040AY datasheet(28/48 Pages) STMICROELECTRONICS

28 / 48 page

Protections

VNH7040AY

28/48

DocID028118 Rev 5

Protections

3.1

Power limitation (high side driver)

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 MultiSense

pin, the output MOSFET switches on and cycles with a thermal hysteresis according to the

maximum instantaneous power. The protection prevents fast thermal transient effects and,

consequently, reduces thermo-mechanical fatigue. When Power Limitation is reached, The

device enters in latch mode and generates the Fault Flag on Multisense=VsenseH when the

faulty leg diagnostic is selected (please refer to Table 13).

3.2

Thermal shutdown (high side and low side)

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 on

MultiSense (please refer to Table 13). The device switches on again as soon as its junction

temperature drops to TR.

3.3

Current limitation and over current detector

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. High side current limitation: in case of short-circuit,

overload or during load power-up, the output current is clamped to a safety level, ILIM_HSD,

by operating the output power MOSFET in the active region.

Low side overcurrent detector: this protection senses the current flowing in the low side. If

the current exceeds a safety level ISD_LS, the device will switch off after a filtering time

tsd_ld.

In case of fault conditions caused by Power Limitation or overtemperature or open

load/short to VCC in OFF state, the fault is indicated by the MultiSense pin being internally

switched to a “current limited” voltage source pulled to level VSENSEH (please refer to

Table 13).

VNH7040AY Datasheet(PDF) 28 Page - STMicroelectronics