PRM48BF480T500A00 Datasheet, PDF (27/45 Pages) Vicor Corporation – PRM™ Regulator

PRM48B x 480 y 500A00
DESIGN GUIDELINES
The PRM48B[x]480[y]500A00 regulator is specifically designed
to provide a controlled Factorized Bus distribution voltage for
powering downstream VTM Transformer — fast, efficient,
isolated, low noise Point-of-Load (POL) converters.
The PRM48B[x]480[y]500A00 can be configured for two
operating modes depending on the type of regulation required.
In Adaptive Loop operation the regulation circuitry is enabled
within the device and regulates the voltage at the output
terminals. The PRM48B[x]480[y]500A00 has a programmable
Adaptive Loop load line which can be used to compensate for
downstream VTM output resistance allowing for precise point
of load regulation without the need for remote sensing.
In Remote Sense operation, the internal regulation circuitry is
disabled and the voltage regulation circuitry is provided
externally allowing for remote sensing directly at the point of
load. In certain applications Remote Sense operation can
improve regulation accuracy, and allow for operating with high
amounts of load capacitance and optimizing load transient
response.
Operating Mode Selection
The operating mode is selected through use of the TRIM pin.
When the part is first enabled after V_IN is applied, the TRIM
voltage is sampled. The TRIM pin has an internal pull up
resistor to V_{CC_INT}, so unless external circuitry pulls the pin
voltage lower, it will float up to V_{CC_INT}.
If TRIM is pulled lower than 0.45V during the first startup after
V_IN is applied, the part will be configured for
Remote Sense / Slave operation, where the internal voltage
regulation circuitry is disabled. In this case, for all subsequent
operation the part will output a voltage dependent on the
SHARE / CONTROL NODE voltage provided externally (either
from an external regulation circuit or master PRM).
To configure the part for Remote Sense or Slave operation,
connect the TRIM pin to SGND. It is recommended to make
this connection through a 0Ω jumper for troubleshooting
purposes.
If the sampled TRIM voltage is higher than 0.55V during the
first startup after V_IN is applied, then the part will be configured
for Adaptive Loop operation, and the internal voltage regulation
circuitry is enabled. The PRM will output a voltage dependent
on the TRIM voltage, and will remain in this mode for as long
as V_IN is applied.
To configure the part for Adaptive Loop operation, leave the
TRIM pin disconnected, or apply a voltage/resistance within
the specified range.
The operating mode is detected and latched during the first
start up after V_IN is applied. This selection persists until V_IN is
removed from the part, and is not changed by fault or disable
events. Changing the operating mode can only be done by
removing V_IN.
DESIGN GUIDELINES (Adaptive Loop operation)
In Adaptive Loop operation, the internal voltage control
circuitry is enabled and the voltage at the output terminals is
regulated. The part is nominally set to provide a fixed 48 V
output, and the TRIM pin can be used to adjust the output over
the range of 20 V to 55 V.
When used with a VTM, the AL pin provides ability to program
an Adaptive Loop load line to compensate for the output
resistance (R_OUT) of a downstream VTM, while the VT pin
provides temperature compensation to account for changes in
the VTM R_OUT over temperature.
Trim Mode and Output Trim Control (Adaptive Loop
operation)
In Adaptive Loop operation, during any start up and after
ENABLE transitions high, the TRIM pin voltage is sampled to
determine if trim is active or inactive. If the sampled TRIM
voltage is higher than 3.20V then the PRM will disable trim. In
this case, for all subsequent operation the output voltage will
be programmed to the nominal output of 48V and the TRIM pin
will be ignored during normal operation.
If the sampled TRIM voltage is between
1.0 V and 3.10 V then the PRM will activate trim mode and it
will remain in this mode as long as the PRM is operating.
This selection persists until the PRM is restarted with the
ENABLE pin, or due to fault auto-recovery.
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Rev. 1.0
11/2012