PI2003-00-QEIG Ver la hoja de datos (PDF) - Vicor
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PI2003-00-QEIG Datasheet PDF : 16 Pages
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Application Information:
The PI2003 is designed to replace ORing diodes in
high current redundant power architectures.
Replacing a traditional diode with a PI2003
controller IC and a low on-state resistance N-
channel MOSFET will result in significant power
dissipation reduction as well as board space
reduction, efficiency improvement and additional
protection features. This section describes in detail
the procedure to follow when designing with the
PI2003 Active ORing controller and N-Channel
MOSFETs. The following is a low side Active ORing
design example.
Fault Indication:
FT output pin is an open collector output and
should be pulled up to the logic voltage or to the
controller VC via a resistor (10KΩ). Also the FT
output can be pulled with a current limiting resistor
directly to an unregulated voltage source, such as
the return of a -48V bus. In this condition connect
the FT pin to the FC pin for clamping.
Also the FT pin can be used to drive an LED or
opto-coupler device. The circuit in figure 12a shows
a PI2003 configuration for an LED/opto-coupler that
will turn on during a fault condition. The FC
connection protects the FT pin if the LED is open.
Use the circuit in figure 12b to turn on the LED/opto-
coupler when there is no fault and to turn off during
a fault condition.
Figure 12a: Fault circuit where the LED turns on
during a fault.
enhance the MOSFET. The maximum gate to VC
voltage loss (headroom), VHDVC-G is 0.5V.
VHDVC-G specification is the Gate Voltage High (VG)
in the Gate Driver section under the
Electrical Specification.
If the bus voltage is higher than 11V then a bias
resistor (Rbias) is required, and should be
connected between the PI2003 VC pin and supply.
The resistor is selected based on the input voltage
range.
Rbias = Vbusmin −VCclamp
IC max
Rbias maximum power dissipation:
Pd Rbias
=
(Vbusmax −VCclamp ) 2
Rbias
Rbias maximum power dissipation is at maximum
input voltage and minimum clamp voltage (11V).
Where:
Vbusmin : V(bus) minimum voltage
Vbusmax : V(bus) maximum voltage
VCClamp : Controller clamp voltage, 11V
ICmax : Controller maximum bias current (2.0mA)
Note: If the FT pin is connected to the VC pin via a
resistor (RFT), the FT sink current ( I FT )
during a fault condition should be added to
the maximum bias current ICmax in the
above equations.
The FT pin sink current during a fault can
be calculated using the following
approximate equation:
I FT
= VCclampMax
RFT
Figure 12b: Fault circuit where the LED turns off
during a fault.
VC Power Source:
The PI2003 VC input voltage should be higher than
the required gate-to-source voltage (Vgs) to fully
N-Channel MOSFET Selection:
There are several factors that affect the MOSFET
selection including cost, on-state resistance
(Rds(on)), current rating, power dissipation, thermal
conductivity, drain-to-source breakdown voltage
(BVdss), gate-to-source voltage rating (Vgs), and
gate threshold voltage (Vgs(TH)).
The first step is to select suitable MOSFETs based
on the BVdss requirement for the application. The
BVdss voltage rating should be higher than the
applied Vin voltage plus expected transient voltages.
Stray parasitic inductance in the circuit can also
contribute to significant transient voltage conditions,
particularly during MOSFET turn-off after a reverse
Picor Corporation • picorpower.com
PI2003
Rev 1.0
Page 10 of 16
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