PRM48BF480T400B00 Datasheet, PDF (16/22 Pages) Vicor Corporation – High Efficiency Remote Sense PRM Converter

VTM Control (VC) pin supplies an initial V_CC voltage to
downstream VTMs, enabling them and synchronizing
their startup with the PRM. The V_CC voltage is a pulse,
typically 10 ms duration at 14 V.
If VC is not loaded by a VTM, it must be terminated with
a 1 kΩ resistor to –V_OUT.
Primary Control (PC) is both an input and an output. It
can provide the following features:
• Delayed start: upon application of voltage (>UVLO) to
the module power input and after T_OFF, the PC pin will
source a constant 90 µA current.
• Output disable: PC may be pulled down externally in
order to disable the module. Pull down resistance should
be less than 300 Ω to SG.
• Fault detection flag: The PC 5 V voltage source is
internally turned off when a fault condition is latched.
Note that aside from the Short Circuit fault condition, PC
does not have significant current sinking capability.
Therefore in the case of an array of PRMs with
interconnected PC pins, PC does not in general reflect
the fault state of all PRMs. The common PC line will not
disable neighboring modules when a fault is detected
except for a latched Output Short Circuit fault.
Conversely any unit in the array latching a Short Circuit
fault will disable the array for T_SCR.
Temperature Monitor (TM) pin outputs a voltage
proportional to the absolute temperature of the converter
analog control IC. It can be used to accomplish the
following functions:
• Monitor the control IC temperature: The gain and
setpoint of TM are such that the temperature, in Kelvin,
of the PRM controller IC is equal to the voltage on the
TM pin scaled by 100. (i.e. 3.0 V = 300 K = 27ºC).
• Closed loop thermal management at the system level
(e.g. variable speed fans or coolant flow)
• Fault detection flag: The TM voltage source is turned
off as soon as a fault is detected. For system monitoring
purposes (microcontroller interface) faults are detected
on falling edges of TM.
Reference Enable (RE) pin outputs a regulated 3.3 V,
8 mA voltage source. It is enabled only after successful
startup of the PRM powertrain (see chapters 5.0 and
6.0.) RE is intended to power the output current
transducer and also the voltage reference for the control
loop. Powering the reference generator with RE helps
provide a controlled startup, since the output voltage of
the system is able to track the reference level as it
comes up.
Voltage Source (VS) pin outputs a gated (e.g. mirrors
PC status), non-isolated, regulated 9 V, 5 mA voltage
source. It can be used to power external control circuitry;
it always leads RE.
PRM48BF480T400B00
Signal Ground (SG) pin provides a Kelvin connection to
the PRM’s internal signal ground. It should be used as
the reference for PR, TM, IF, and should return all PC,
VS and RE pin currents. In array configurations with
common ground control circuits, a series resistor (~1 Ω)
is recommended in order to decouple power and signal
current returns.
9.2 Control circuit requirements and design procedure
The PRM48BF480T400B00 is an intelligent powertrain
module designed to fully exploit external output voltage
feedback and current sensing sub-circuits. These two
external circuits are illustrated in Figure 26, which shows
an example of the PRM in a standalone application with
local voltage feedback and high side current sensing.
In general, these circuits include a precision voltage
reference, an operational amplifier which provides
closed loop feedback compensation, and a high side
current sense circuit which includes a shunt and current
sense IC.
The following design procedures refer to the circuit
shown in Figure 26.
9.2.1 Setting the output voltage level
The output voltage setpoint is a function of the voltage
reference and the output voltage sense ratio. With
reference to Fig. 26, R1 and R2 form the output voltage
sensing divider which provides the scaled output voltage
to the negative input of the error amplifier; a dedicated
reference IC provides the reference voltage to the
positive input of the error amplifier. Under normal
operation, the error amplifier will keep the voltages at the
inverting and non-inverting inputs equal, and therefore
the output voltage is defined by:
V
OUT
=V
ref
⋅
R1 + R2
R2
Note that the component R1 will also factor into the
compensation as described in a later section.
It is important to apply proper slew rate to the reference
voltage rise when the control loop is initially enabled.
The recommended range for reference rise time is 1 ms
to 9 ms. The lower rise time limit will ensure optimized
modulator timing performance during startup, and to
allow the current limit feature (through IF pin) to fully
protect the device during power-up. The upper rise time
limit is needed to guarantee a sufficient factorized bus
voltage is provided to any downstream VTM input before
the end of the VC pulse.
PRM® Regulator
Rev 1.1
800 927.9474