PQ60280HZX22 Datasheet, PDF (14/16 Pages) SynQor Worldwide Headquarters – High efficiency, 94% at full rated load current

Applications Section
Input: 35-75V
Output: 28V
Current: 21.5A
Package: Half-brick
Automatic Configuration: The micro-controller inside each power
converter unit is programmed at the factory with a unique chip number.
In every other respect, each shared unit is identical and has the same
orderable part number.
On initial startup (or after the master is disabled or shuts down),
each unit determines the chip number of every other unit currently
connected to the shared serial bus formed by the SHARE(+) and
SHARE(-) pins. The unit with the highest chip number dynamically
reconfigures itself from slave to master. The rest of the units (that do
not have the highest chip number) become slaves.
The master unit then broadcasts its control state over the shared serial
bus on a cycle-by-cycle basis. The slave units interpret and implement
the control commands sent by the master, mirroring every action of
the master unit.
If the master is disabled or encounters a fault condition, all units will
immediately shut down, and if the master unit is unable to restart,
then the unit with the next highest chip number will become master. If
a slave unit is disabled or encounters a fault condition, all other units
continue to run, and the slave unit can restart seamlessly.
Automatic Interleaving: The slave units automatically lock
frequency with the master, and interleave the phase of their switching
transitions for improved EMI performance. To obtain the phase angle
relative to the master, each slave divides 360 degrees by the total
number of connected units, and multiples the result by its rank among
chip numbers of connected units.
ORing Diodes placed in series with the converter outputs must also
have a resistor smaller than 500 Ω placed in parallel. This resistor
keeps the output voltage of a temporarily disabled slave unit consistent
with the active master unit. If the output voltage of the slave unit
were allowed to totally discharge, and the slave unit tried to restart, it
would fail because the slave reproduces the duty cycle of the master
unit, which is running in steady state and cannot repeat an output
voltage soft-start.
Common-Mode Filtering must be either a single primary side choke
handling the inputs from all the paralleled units, or multiple chokes
placed on the secondary side. This ensures that a solid Vin(-) plane
is maintained between units. Adding a common-mode choke at the
output eliminates the need for the 470 nH indcutor at the output of
shared units when Vout > 18 V. If an output common-mode choke
is used, sense connections must be made on the module-side of the
choke.
Resonance Between Output Capacitors is Possible: When
multiple higher-voltage modules are paralleled, it is possible to
excite a series resonance between the output capacitors internal to
the module and the parasitic inductance of the module output pins.
This is especially likely at higher output voltages where the module
internal capacitance is relatively small. This problem is independent
of external output capacitance. For modules with an output voltage
greater than 18 V, to ensure that this resonant frequency is below the
switching frequency it is recommended to add a nominal 470 nH of
inductance, located close to the module, in series with each converter
output. There must be at least 10 ¼F of capacitance per converter,
located on the load-side of that inductor. The inductance could be from
the leakage inductance of a secondary-side common-mode choke; in
which case the output capacitor should be appropriately sized for the
chosen choke. When using an output common-mode choke, the Sense
lines must be connected on the module-side of the common-mode
choke (see Figure G).
RS-485 Physical Layer: The internal RS-485 transceiver includes
many advanced protection features for enhanced reliability:
• Current Limiting and Thermal Shutdown for
Driver Overload Protection
• IEC61000 ESD Protection to +/- 16.5 kV
• Hot Plug Circuitry – SHARE(+) and SHARE(-)
Outputs Remain Tri-State During Power-up/Power-down
Internal Schottky Diode Termination: Despite signaling at high
speed with fast edges, external termination resistors are not necessary.
Each receiver has four Schottky diodes built in, two for each line in the
differential pair. These diodes clamp any ringing caused by transmission
line reflections, preventing the voltage from going above about 5.5 V
or below about -0.5 V. Any subsequent ringing then inherently takes
place between 4.5 and 5.5 V or between -0.5 and 0.5 V. Since each
receiver on the bus contains a set of clamping diodes to clamp any
possible transmission line reflection, the bus does not necessarily need
to be routed as a daisy-chain.
Pins SHARE(+) and SHARE(-) are referenced to Vin(-), and therefore
should be routed as a differential pair near the Vin(-) plane for optimal
signal integrity. The maximum difference in voltage between Vin(-
) pins of all units on the share-bus should be kept within 0.3 V to
prevent steady-state conduction of the termination diodes. Therefore,
the Vin(-) connections to each unit must be common, preferably
connected by a single copper plane.
Share Accuracy: Inside each converter micro-controller, the duty
cycle is generated digitally, making for excellent duty cycle matching
between connected units. Some small duty cycle mismatch is caused
by (well controlled) process variations in the MOSFET gate drivers.
However, the voltage difference induced by this duty cycle mismatch
appears across the impedance of the entire power converter, from
input to output, multiplied by two, since the differential current flows
out of one converter and into another. So, a small duty cycle mismatch
yields very small differential currents, which remain small even when
100 units are placed in parallel.
In other current-sharing schemes, it is common to have a current-
sharing control loop in each unit. However, due to the limited bandwidth
of this loop, units do not necessarily share current on startup or during
transients before this loop has a chance to respond. In contrast, the
current-sharing scheme used in this product has no control dynamics:
control signals are transmitted fast enough that the slave units can
mirror the control state of the master unit on a cycle-by-cycle basis,
and the current simply shares properly, from the first switching cycle
to the last.
Product # PQ60280HZx22
Phone [phone]
www.synqor.com
Doc.# 005-0005788 Rev. D
12/26/13
Page 14