UG:301 vicorpower.com Applications Engineering: 800 927.9474 Page 2
PI31xx Series Product Description
The PI31xx operates over a wide range input, delivering 50 W or 60 W output power
depending on the individual model number. The PI31xx Series is available in a space
saving surface mountable 0.87” x 0.65” x 0.265” Power –System –in – a – Package (PSiP),
achieving ~50% space reduction versus alternative solutions.
The switching frequency of 900kHz allows for small input and output ﬁlter components
which further reduces the total size and cost of the overall system solution. The output
voltage is sensed and fed back to the internal controller using a proprietary isolated
magnetic feedback scheme which allows for high bandwidth and good common mode
The PI31xx Series requires no external feedback compensation and oers a total
solution with a minimum number of external components. A rich feature set is
oered, including + 10%, -20% output voltage trim capability (depending on the model
number), remote enable, over-voltage protection, adjustable so-start, over-current
protection with auto-restart to protect against both short circuit and overload and over
and under input voltage lockout. A unique temperature monitor and protection circuit
is included that provides an analog voltage proportional to the internal die temperature,
as well as over temperature shutdown, restart and over temperature fault alarm signal.
1. Connect Test Equipment
a. Connect the input DC power supply to the target board as shown in Figure 6.
The negative terminal should be wired to –IN and the positive terminal should
connect to the positive terminal of the DMM wired as a DC Ammeter. Be sure
that the proper sized wires are used to allow minimum voltage drop for a
maximum input current of up to 4 A. Use ring lugs mated to the included
fasteners on the evaluation board. If your input power supply has remote sense
capability, it can be wired to the INN and INP test points if desired. Connect the
positive terminal of the DMM to the +IN lug on the evaluation board.
b. Connect the primary side DMM (for measuring the input voltage) to INN and
c. Connect the oscilloscope as shown in Figure 6 if you are planning to measure
both primary and secondary signals at the same time. If you do not have an
isolated dierential ampliﬁer, it is important to note that simultaneous
measurement of both primary and secondary referenced signals using an
oscilloscope with a grounded chassis is not recommended, as it will short circuit
the primary to secondary isolation barrier. Floating the oscilloscope is also not
recommended due to the large capacitance introduced by this long standing
practice. The best practice is to use an isolated dierential ampliﬁer or use an
oscilloscope with isolated channels. That is, the input returns are isolated from
each other and earth ground.
d. Connect the output DC DMM to the test points OUTN and OUTP. These test
points are done in a Kelvin type manner so that they have no high current
ﬂowing in them.
e. Connect the DC Load to the output lugs OUT+ and OUT-. It is critical for this
connection to be low inductance.