PI2127 Datasheet, PDF (5/19 Pages) Vicor Corporation – 60 Volt, 12 Amp Full-Function Active ORing Solution

Functional Description:
The PI2127 integrated Cool-ORing product takes
advantage of two different technologies combining
an 8.5mΩ on-state resistance (R_DS(on)) N-channel
MOSFET with high density control circuitry. This
combination provides superior density, minimizing
PCB space to achieve an ideal ORing diode
function, significantly reducing power dissipation and
eliminating the need for heat sinking, while
minimizing design complexity.
The PI2127’s 8.5mΩ on-state resistance MOSFET
used in the conduction path enables a dramatic
reduction in power dissipation versus the
performance of a diode used in conventional ORing
applications due to its high forward voltage drop.
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 PI2127 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 sensitivity
to fault current. 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. Gate drive is enabled
when SP is 6mV higher than SN. When the SN pin
is 6mV higher than the SP pin, the reverse
comparator will force the gate discharge circuit to
turn off the MOSFET in typically 80ns and assert the
Fault ( FT ) low to report a fault condition.

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.
Figure 3: Reverse comparator hysteresis: V_SP - V_SN
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 Fault ( FT ) low to report a fault condition.
Internal Voltage Regulator:
The PI2127 control circuitry and the gate driver are
biased through the S pin. An internal regulator
clamps the S voltage (V_S-PG ) to 11.7V. The internal
regulator circuit has a comparator to monitor S input
with respect to the PG pin and pulls the MOSFET
GATE low when V_S-PG is lower than the Under-
Voltage Threshold.
Fault Indication: FT
The FT pin is an open collector NPN that will be
pulled low during following fault conditions.
Typical Condition Indication of possible faults
1 Reverse: V_SP-V_SN ≤ -6mV
Input supply shorted
(MOSFET turned OFF)
2 Forward: V_SP-V_SN ≥ +275mV
Open FET, Gate short, Gate
open, or High current
(MOSFET turned ON)
3 Forward V_SP-V_SN ≤ +6mV
Shorted FET on power-up
(MOSFET turned OFF)
4 UVLO
Controller not ready
4.5V < V_S-PG<7.15V _{(MOSFET turned OFF)}
Picor Corporation • picorpower.com
PI2127
Rev 1.3
Page 5 of 19