PI2007 Datasheet, PDF (5/19 Pages) Vicor Corporation – Universal High Side Active ORing Controller IC

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Functional Description:
The PI2007 Cool-ORing controller IC is designed to
drive single or parallel N-channel MOSFETs in high
side Active ORing applications. The PI2007 used
with an external MOSFET can function as an ideal
ORing diode in the high side of a redundant power
system, significantly reducing power dissipation and
eliminating the need for heatsinking.
An N-channel MOSFET in the conduction path offers
extremely low on-resistance resulting in a dramatic
reduction of power dissipation versus the
performance of a diode used in conventional ORing
applications due to its high forward voltage drop.
This can allow for the elimination of complex heat
sinking and other thermal management
requirements.
Due to the inherent characteristics of the MOSFET,
current will flow in the forward and reverse directions
while the gate remains above the gate threshold
voltage. Ideal ORing applications should not allow
reverse current flow, so the controller has to be
capable of very fast and accurate detection of
reverse current caused by input power source
failures, and very fast turn off of the gate of the
MOSFET. Once the gate voltage falls below the gate
threshold, the MOSFET is off and the body diode will
be reverse biased preventing reverse current flow
and subsequent excessive voltage droop on the
redundant bus.
Differential Amplifier:
The PI2007 integrates a high-speed low offset
voltage differential amplifier to sense the difference
between the Sense Positive (SP) pin voltage and
Sense Negative (SN) pin voltage with high accuracy.
The amplifier output is connected to the Reverse
and Forward comparators.
Reverse Current Comparator: RVS
The reverse current comparator provides the critical
function in the controller, detecting negative voltage
caused by reverse current. When the SN pin is 6mV
higher than the SP pin, the reverse comparator will
force the gate discharge circuit to turn off the
MOSFETs in typically 80ns.
The reverse comparator will hold the gate low until
the SP pin is 6mV higher than the SN pin. The
reverse comparator hysteresis is shown in Figure 3.
There is a bias current path from SN to SP during
the reverse fault condition. The bias current is
proportional to the voltage between SN and SP.
The maximum SN pin bias current is 9mA when
V_SN=80V and V_SP=0V and assumes that the
MOSFET is in the off condition. Refer to Figure 15
in the Application Information section for more
details.
Forward Voltage Comparator: FWD
The FWD comparator detects when a forward
voltage condition exists and SP is above 275mV
(typical) positive with respect to SN. When SP-SN is
more than 275mV, the FWD comparator will assert
the Gate Status low to report a fault condition.
VC and Internal Voltage Regulator:
The PI2007 has a separate input VC that provides
power to the control circuitry, charge pump and gate
driver. An internal regulator clamps the VC voltage
(V_VC-SGND) to 11.7V.
The internal regulator circuit has a comparator to
monitor the VC voltage and pulls the GATE pin low
when the VC is lower than the VC Under-Voltage
Threshold.
In 12V Bus applications (10V to 14V) the VR input
pin can be connected to the input voltage eliminating
the need for an external limiter. An internal 420Ω
resistor is connected between the VR pin and the
internal regulator VC pin.
Charge Pump:
The PI2007 has an integrated charge pump that
approximately doubles the VC voltage with
reference to the SGND pin, to drive the N-Channel
MOSFET gate to a voltage higher than the input
voltage at 15µA minimum source current.
Gate Driver:
The gate driver (GATE) output is configured to drive
an external N-channel MOSFET. In the high state,
the gate driver applies a 20µA typical current source
to the MOSFET gate from the integrated charge
pump. The Charge Pump voltage is limited to
2*(V_VC –V_SGND -1V).
When a reverse current fault is initiated, the gate
driver pulls the GATE pin low to the PGND pin and
discharges the MOSFET gate with 4A typical peak
capability.
Fault Indication: FT
Figure 3: Reverse comparator hysteresis: V_SP - V_SN
The FT pin is an open collector NPN that will be
pulled low when the Gate pin is low. The FT pin is
also pulled low when V_VC-SGND is below UVLO or
during the following fault conditions as indicated in
the table below:
Picor Corporation • picorpower.com
PI2007
Rev 1.3
Page 5 of 19