1
out
in
in
in
R1
out
out
PGD
out
in
in
R1
out
PGD
1
2
3
2
(a) (b)
Description
The Multi-Phase Design Guide provides an overview
to paralleling two or three PI33XX-XX devices
together without any change required to the basic
single-phase power stage or compensation design.
Paralleling multiple PI33XX modules increases the
output current capability and reduces the output
voltage ripple. For information on paralleling more
than three regulators, please contact Picor.
Basic Connections
The PI33XX family of Cool-Power products employs a
ZVS topology which operates exclusively in
discontinuous and critical conduction mode.
Therefore, to derive real-time output current
information, each device’s error amplifier output
(EAO) is trimmed to a nominal level (2.2V) when
supporting the maximum rated output load. This will
allow the EAO to track the output load. By trimming
the EAO this way, additional regulators can be
connected in parallel to deliver equal amount of
current to a single regulated point by linking each
regulator’s EAO pin together. The basic pin
connections needed to parallel two or three
regulators are shown in Figure 1. The SYNCO pins are
for phase synchronization, TRK is for soft-start and
fault shutdown tracking. EAO is for current sharing
between phases.
Figure 1 – Basic Connections for Parallel Operation
This method will allow the regulators to remain in
synchronization when the system’s operational
frequency stretches at high output loads. Figure 2
shows the basic synchronization connections and the
phase requiring delays in red.
Two and Three Phases
The PI33XX-2X can be synchronized in a closed loop
configuration to up to three phases by adding an
additional 2.5kΩ (R1) feedback resistor to the design
and incorporating the PGD pin.
vicorpower.com Rev 1.0 Cool-Power®
800 735.6200 11/2012 Page 1 of 4
Figure 2 - SYNCI (In) and SYNCO (Out) Connection for
Two and Three Phase Design
78 1 0 0 1 1 1 1 X 1 1+NC
The required per phase delay and programming code
are presented in the following table.
Table 1 - Phase Programming Codes
Synchronization / Phase Delay
Two regulators connected in parallel operation do not
require any delay programming. As a default setting,
the PI33XX-XX will trigger on the falling edge and will
operate 180⁰ out of phase with the master. For a
three phase operation, a 1/3 phase delay is required
for two of the regulators to ensure proper phase
spacing. Synchronization and phase delay is only
programmable with I
2X).
2CTM
option regulators (PI33XX-
I2C Device Address
The PI33XX-2X supports floating addressing so that
two address lines allows for up to 8 programmable
addresses.
The address is 7 bit with the read/write bit not
included. Table 2 shows the address range that can
be achieved using all possible combinations of ADR0
(pad G1) and ADR1 (pad H1). Bits A[6]-A[3] are fixed
internally and may not be changed. The least
significant 3 bits; A[2]-A[0], will assume the values in
the table based on the decoding of ADR1 and ADR0. A
zero or one indicates the logic strength of the bit and
“NC” indicates that the pin is floating or not
connected. The HEX column indicates the final
address in hexadecimal, while the DEC column is the
decimal address value.
vicorpower.com Rev 1.0 Cool-Power®
800 735.6200 11/2012 Page 2 of 4
Table 2 - PI33XX-2X Device Addressing