AUIR3200S_15 Datasheet, PDF (7/19 Pages) International Rectifier – MOSFET DRIVER WITH PROTECTION AND DIAGNOSTIC

AUIR3200S
Over-current protection
The over-current protection is done by monitoring the Vds voltage of the Mosfet. The threshold is adjusted by connecting
the appropriate resistor between Vcc and Vds pin. Below the formula to set the appropriate over-current threshold:
Isd _ threshold = ^{Ivds × Rvds}
RdsOn
The Ivds has a positive temperature coefficient to compensate the positive temperature coefficient of the Rdson of the
Mosfet.
The above formula is only valid when the Mosfet is fully ON. Therefore during the turn on of the MOSFET, the time
‘Tblank on’ disable the vds protection until the Mosfet is fully On.
Over-temperature protection
The temperature protection uses a PTC sensor connected to the tab or the drain of the Mosfet depending on the
mounting. The purpose is to maximize the thermal interface between the sensor and the junction. The PTC sensor, the
Vds threshold and the Mosfet must be chosen in order to not exceed the maximum junction temperature of the Mosfet
during a short circuit.
Protection is evaluated by switching the Mosfet on different currents and by evaluating the junction temperature when the
Mosfet is switched off by the protections. This gives the following drawing. For high impedance short circuit, Vds is smaller
than Vds threshold, so the over-temperature will act. For low impedance short circuit, the Vds protection will switch off the
Mosfet. At the transition current between the 2 protections the junction temperature of the Mosfet is the maximum and
should be lower than the maximum rating.
Over-temperature
protection
Over-current
protection
Short circuit current
Figure 1
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November 02, 2012