IR5001S & (PbF)
conducting and Vout of the IR5001S is high (FET
current flows from source to drain), the current must
reverse the direction before the IR5001S will switch
the FET off.
The asymmetrical offset voltage
prevents potential oscillations at light load that could
otherwise occur if the offset voltage was centered
Vout is the output pin of the IR5001S, and connects
directly to the gate of the external Active ORing N-
FET. The voltage level at the Vout pin is typically a
diode drop lower than the Vcc voltage.
FETst and FETch
FETch and FETst pins are diagnostic pins that can
be used to determine the status of the Active ORing
FETst is an open-drain output pin. When the voltage
difference between VINP - VINN is less than 0.3V,
the FETst pin will be logic high. This is normally the
case when Active ORing is operating properly (VINP
- VINN is less than ~100mV). If the Active ORing
FET is not turned on while the IR5001S is properly
biased, the output of the FETst pin will be logic low
(only the body diode of the N-FET is conducting, and
VINP - VINN is ~700mV).
FETch pin. In traditional systems with diode ORing,
it is not possible to determine if the diode is
functioning properly unless external circuitry is used.
For example, the diode could be failed short, and the
system would not be aware of it until the source fails
and the whole system gets powered down due to
lost redundancy (shorted diode failed to isolate the
source failure). With the FETch pin it is possible to
perform a periodic check of the status of the Active
ORing circuit to assure that system redundancy is
In the IR5001S, the FETch pin is an input pin that
can be used to turn off the output of the IR5001S:
logic high signal on FETch will pull the Vout pin low,
and turn-off the channel of the Active ORing N-FET.
This will force the current to flow through the body
diode, resulting in VINP – VINN voltage increase
from less than ~100mV, to ~700mV. This voltage
increase will be reported at FETst pin, which will
switch from logic high to logic low, and indicate that
the Active ORing circuit is working properly. Failure
of the FETst pin output to change from logic high to
logic low would indicate that the Active ORing circuit
may not be operating as designed, and the system
may no longer have power redundancy. For details
on how to use this feature consult IR5001S
Evaluation Kit, P/N IRDC5001-LS48V.
If the FETch pin is not used, it should be tied to
ground (for noise immunity purposes). FETst pin
should be left open if unused.
In typical target applications, the ground pin (Gnd) of
IR5001S is connected to the source of the Active