OKDY-T Datasheet, PDF (24/41 Pages) Murata Power Solutions Inc. – 50A Digital PoL DC-DC Converter Series

OKDx-T/50-W12-C
50A Digital PoL DC-DC Converter Series
aligning the output voltage of the slave devices to deliver the same
current as the master device. Artificial droop resistance is added to
the output voltage path to control the slope of the load line curve,
calibrating out the physical parasitic mismatches due to power train
components and PWB layout. Up to 7 devices can be configured in a
given current sharing group.
In order to avoid interference with other algorithms executing
during parallel operation, the dead-time algorithm should be turned
off and fixed dead-times be used.
Phase Adding and Shedding for Parallel Operation
During periods of light loading, it may be beneficial to disable one or
more phases (modules) in order to eliminate the current drain and
switching losses associated with those phases, resulting in higher
efficiency. The product offers the ability to add and drop phases
(modules) using a PMBus command in response to an observed
load current change. All phases (modules) in a current share rail are
considered active prior to the current sharing rail ramp to power-good.
Phases can be dropped after power-good is reached. Any member
of the current sharing rail can be dropped. If the reference module is
dropped, the remaining active module with the lowest member posi-
tion will become the new reference. Additionally, any change to the
number of members of a current sharing rail will precipitate autono-
mous phase distribution within the rail where all active phases realign
their phase position based on their order within the number of active
members. If the members of a current sharing rail are forced to shut
down due to an observed fault, all members of the rail will attempt to
re-start simultaneously after the fault has cleared.
Efficiency Optimized Dead Time Control
The product utilizes a closed loop algorithm to optimize the dead-
time applied between the gate drive signals for the switch and synch
FETs. The algorithm constantly adjusts the deadtime non-overlap to
minimize the duty cycle, thus maximizing efficiency. This algorithm
will null out deadtime differences due to component variation, tem-
perature and loading effects. The algorithm can be configured via the
PMBus interface.
Over Current Protection (OCP)
The product includes current limiting circuitry for protection at con-
tinuous overload. The following OCP response options are available:
1. Initiate a shutdown and attempt to restart an infinite number of
times with a preset delay period between attempts.
2. Initiate a shutdown and attempt to restart a preset number of
times with a preset delay period between attempts.
3. Continue operating for a given delay period, followed by shutdown
if the fault still exists.
4. Continue operating through the fault (this could result in perma-
nent damage to the power supply).
5. Initiate an immediate shutdown.
The default response from an over current fault is an immediate
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shutdown of the device. The device will continuously check for the
presence of the fault condition, and if the fault condition no longer
exists the device will be re-enabled. The load distribution should be
designed for the maximum output short circuit current specified. The
OCP limit and response of the product can be reconfigured using the
PMBus interface.
Initialization Procedure
The product follows a specific internal initialization procedure after
power is applied to the VIN pin:
1. Status of the address and output voltage pin-strap pins are checked
and values associated with the pin settings are loaded to RAM.
2. Values stored in the Murata default non-volatile memory are
loaded to RAM. This overwrites any previously loaded values.
3. Values stored in the user non-volatile memory are loaded to RAM.
This overwrites any previously loaded values.
Once the initialization process is completed, the product is ready
to be enabled using the CTRL pin. The product is also ready to accept
commands via the PMBus interface, which will overwrite any values
loaded during the initialization procedure.
Soft-start Power Up
The soft-start control introduces a time-delay before allowing the
output voltage to rise. Once the initialization time has passed the
device will wait for the configured delay period prior to starting to
ramp its output. After the delay period has expired, the output will
begin to ramp towards its target voltage according to the configured
soft-start ramp time.
The default settings for the soft-start delay period and the soft-
start ramp time is 10 ms. Hence, power-up is completed within 20
ms in default configuration using remote control. When the soft-start
delay time is set to 0 ms, the module will begin its ramp-up after the
internal circuitry has initialized (approximately 2 ms). It is generally
recommended to set the soft-start ramp-up time to a value greater
than 500 μs to prevent inadvertent fault conditions due to excessive
inrush current. The acctual minimum ramp-up time will however
normally be limited by the control loop settings and ramp-up times of
internal interface voltages in the controller circuit to approximately 2
ms. The soft-start power up of the product can be reconfigured using
the PMBus interface.
VIN
CTRL
VOUT
Initialization
time
Delay Ramp
time time
Illustration of Power Up Procedure
MDC_OKDx-T/50-W12-C.A04 Page 24 of 41