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Technical Document


UG:301 vicorpower.com Applications Engineering: 800 927.9474 Page 1
PI31xx-xx-EVAL1 Cool-Power
®
ZVS Isolated
DC-DC Converter Evaluation Board
Chris Swartz
Principal Applications Engineer
May 2013
Introduction
The PI31xx-xx-EVAL1 evaluation board allows the user to test the basic operating
principles of the PI31xx series of high density DC-DC power converters and experience
the performance and value of this solution compared to alternate conventional
solutions. Each evaluation board is populated with the components that could be used
in a final design. It is not designed or intended to be used in end product applications.
Please read this document prior to the connection of test equipment and refer to the
product datasheet for device specifications, descriptions and characteristics. Remember
to follow good lab safety practices and use safety glasses at all times.
The PI31xx-xx-EVAL1 is configured to support one single input and one single output.
Each board oers pin strap options for trimming the output voltage up and down,
turning the converter on and o and adding EMI system “Y” capacitors. Additional
parts are included to compensate for line impedance associated with long leads from
the bench power supply to the converter. Additional component footprints are made
available to allow the user to test dierent design configurations that may be required
to meet their end needs. Kelvin type test points are included to allow for easy and
convenient connections of testing instruments for evaluation of eciency, line/load
regulation and transient response. A low impedance oscilloscope connection using a
Johnson jack is included for ripple measurement and evaluation of the output voltage
during transient events. Each demo board is equipped with a heatsink to allow high
power operation with a small amount of air flow and to allow operation of the board
over various temperature extremes.
Contents Page
Introduction 1
Product Description 2
Board Connections 2
Thermal Considerations 3
Max I/O Ratings 5
Schematic
BOMs 6
Test Setup 11
PCB Artwork 12
Mechanical Outline 14
Ordering Information 14
USER GUIDE | UG:301
Figure 1.
PI31xx-xx-EVAL1
Evaluation Board
UG:301 vicorpower.com Applications Engineering: 800 927.9474 Page 2
Cool-Power
®
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
noise immunity.
The PI31xx Series requires no external feedback compensation and oers a total
solution with a minimum number of external components. A rich feature set is
oered, 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.
Board Connections
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
INP respectively.
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 dierential 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 dierential 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.
UG:301 vicorpower.com Applications Engineering: 800 927.9474 Page 3
2. Default Pin Strap Configuration
a. Ensure the pin straps are in the following default locations before proceeding:
nENABLE = Not Used (enabled)
nTRIM_UP = Not Used
nTRIM_DN = Not Used
nOPT1 = Not Used
nOPT2 = Not Used
3. Pin Strap Functions
a. ENABLE – adding a strap on this pin will cause the converter to shut down.
b. TRIM_UP – Adding a strap in this location will adjust the output voltage
up by 10%.
c. TRIM_DN – Adding a strap in this location will adjust the output voltage down
by 10%. Only one strap can be connected at a time. If both trim straps are out,
the output voltage should be set to the model’s nominal output.
4. Trimming And Soft Start
a. For those customers who wish to trim to another voltage by changing the preset
trim resistors to another value, the trim equation shown in Figure 2 can be used:
R
low
=
(
–V
)
R
INT
(
–Vout
nom
)
+ V
desired
desired
R
high
=
(
–RSS
)
(
–Vout
nom
)
V
ERO
+ V
V
ref
V
ref
[
(
–Vout
nom
) +
V
]
desired
desired
Where: R1 = Rlow R3 = Rhigh VERO = 4.9 and Vref can be found in the appropriate
model datasheet.
Figure 3 shows an equation for so start configuration where C7 = C
REF
C
REF
=
T
ssdesired
– 230 10
−6
23000
ENABLE
TRIM/SS
SGND
RSS
Rhigh
Rlow
VERO
Vref
PI31xx
10k
Figure 4.
PI31xx Trimming Equivalent
Circuit
Figure 2.
PI31xx Trim Equation
Figure 3.
PI31xx Soft Start Equation
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