PI2127 Datasheet, PDF (13/19 Pages) Vicor Corporation – 60 Volt, 12 Amp Full-Function Active ORing Solution

happens, the MOSFET is turned on and the FT pin
will be high resistance to indicate that the MOSFET is
in R_DS(on) with no fault conditions existing.
Note that in case of an input fault condition, where the
S pin is at ground and the output (D pin and SN pin)
are at a high voltage there will be two current paths,
one path from D pin to GND and the other path from
SN pin to SP.
The current path from D pin to GND and S pins is due
to the level shift circuit and will draw current from the
output as a function of the voltage between D pin and
GND (V_D-GND) based on the following equation:
I _D−FLT
=
V_D−GND − 0.5V
15kΩ
Where:
I _D−FLT : Maximum D pin current during input short
fault condition
V_D−GND : Voltage difference between the D pin and
ground.
The current path from SN pin to S pin is a function of
the SN voltage based on the following equation:
I _{SN _ FLT}
= ^{VSN −GND −12V}
R_PAR
Where:
I _{SN _ FLT} : SN current during input short fault condition
V_{SN −GND} : Voltage difference between SN pin (or load
voltage) and ground.
R_PAR :
Resistance of the internal path, 10KΩ
typical and 8kΩ minimum

The level shift circuit worst case power dissipation
during input short is:
Pd
=
(V_D−GND − 0.5V ) ²
15kΩ
The thermal resistance and power dissipation of the
level shift circuit will limit the voltage applied at the D
pin during a shorted input condition. When the PCB
temperature exceeds 110°C, the applied voltage must
be derated according to Figure 21. The plot in Figure
21 is calculated using the worst case power
dissipation during an input short with R_θJ-PCB=
100°C/W.
Figure 21: Level shift circuit applied voltage de-rating
(valid during an input short fault condition
as a function of PCB Temperature)
Picor Corporation • picorpower.com
PI2127
Rev 1.3
Page 13 of 19