DCM3414X50M13C2YZZ Datasheet, PDF (17/22 Pages) Vicor Corporation – Regulated DC Converter

prevented from exceeding the current limit threshold by reducing
the output voltage via the internal error amplifier reference. The
current limit threshold at nominal trim and below is typically 115%
of rated output current, but it can vary between 103% to 135%. In
order to preserve the SOA, when the converter is trimmed above the
nominal output voltage, the current limit threshold is automatically
reduced to limit the available output power.
When the output current exceeds the current limit threshold, current
limit action is held off by 1ms, which permits the DCM to
momentarily deliver higher peak output currents to the load. Peak
output power during this time is still constrained by the internal
Power Limit of the module. The fast Power Limit and relatively slow
Current Limit work together to keep the module inside the SOA.
Delaying entry into current limit also permits the DCM to minimize
droop voltage for load steps.
Sustained operation in current limit is permitted, and no derating of
output power is required.
Current limit can reduce the output voltage to as little as the UVP
threshold (V_OUT-UVP). Below this minimum output voltage
compliance level, further loading will cause the module to shut
down due to the output undervoltage fault protection.
Line Impedance, Input Slew rate and Input Stability Requirements
Connect a high-quality, low-noise power supply to the +IN and –IN
terminals. Additional capacitance may have to be added between +IN
and –IN to make up for impedances in the interconnect cables as
well as deficiencies in the source.
Excessive source impedance can bring about system stability issues
for a regulated DC-DC converter, and must either be avoided or
compensated. A 1000 µF input capacitor is the minimum
recommended in case the source impedance is insufficient to satisfy
stability requirements.
Additional information can be found in the filter design application
note:
www.vicorpower.com/documents/application_notes/vichip_appnote23.pdf
Please refer to this input filter design tool to ensure input stability:
http://app2.vicorpower.com/filterDesign/intiFilter.do.
Ensure that the input voltage slew rate is less than 1V/us, otherwise a
pre-charge circuit is required for the DCM input to control the input
voltage slew rate and prevent overstress to input stage components.
Input Fuse Selection
The DCM is not internally fused in order to provide flexibility in
configuring power systems. Input line fusing is recommended at the
system level, in order to provide thermal protection in case of
catastrophic failure. The fuse shall be selected by closely matching
system requirements with the following characteristics:
n Current rating (usually greater than the DCM converter’s
maximum current)
n Maximum voltage rating (usually greater than the maximum
possible input voltage)
n Ambient temperature
n Breaking capacity per application requirements
n Nominal melting I²t
n Recommended fuse: See Agency Approvals for Recommended Fuse
http://www.vicorpower.com
DCM3414x50M13C2yzz
Fault Handling
Input Undervoltage Fault Protection (UVLO)
The converter’s input voltage is monitored to detect an input under
voltage condition. If the converter is not already running, then it will
ignore enable commands until the input voltage is greater than
V_IN-UVLO+. If the converter is running and the input voltage falls
below V_IN-UVLO-, the converter recognizes a fault condition, the
powertrain stops switching, and the output voltage of the unit falls.
Input voltage transients which fall below UVLO for less than t_UVLO
may not be detected by the fault protection logic, in which case the
converter will continue regular operation. No protection is required
in this case.
Once the UVLO fault is detected by the fault protection logic, the
converter shuts down and waits for the input voltage to rise above
V_IN-UVLO+. Provided the converter is still enabled, it will then restart.
Input Overvoltage Fault Protection (OVLO)
The converter’s input voltage is monitored to detect an input over
voltage condition. When the input voltage is more than the
V_IN-OVLO+, a fault is detected, the powertrain stops switching, and the
output voltage of the converter falls.
After an OVLO fault occurs, the converter will wait for the input
voltage to fall below V_IN-OVLO-. Provided the converter is still enabled,
the powertrain will restart.
The powertrain controller itself also monitors the input voltage.
Transient OVLO events which have not yet been detected by the fault
sequence logic may first be detected by the controller if the input
slew rate is sufficiently large. In this case, powertrain switching will
immediately stop. If the input voltage falls back in range before the
fault sequence logic detects the out of range condition, the
powertrain will resume switching and the fault logic will not
interrupt operation. Regardless of whether the powertrain is running
at the time or not, if the input voltage does not recover from OVLO
before t_OVLO, the converter fault logic will detect the fault.
Output Undervoltage Fault Protection (UVP)
The converter determines that an output overload or short circuit
condition exists by measuring its output voltage and the output of
the internal error amplifier. In general, whenever the powertrain is
switching and the output voltage falls below V_OUT-UVP threshold, a
short circuit fault will be registered. Once an output undervoltage
condition is detected, the powertrain immediately stops switching,
and the output voltage of the converter falls. The converter remains
disabled for a time t_FAULT. Once recovered and provided the converter
is still enabled, the powertrain will again enter the soft start
sequence after t_INIT and t_ON.
Temperature Fault Protections (OTP)
The fault logic monitors the internal temperature of the converter. If
the measured temperature exceeds T_INT-OTP, a temperature fault is
registered. As with the under voltage fault protection, once a
temperature fault is registered, the powertrain immediately stops
switching, the output voltage of the converter falls, and the converter
remains disabled for at least time t_FAULT. Then, the converter waits for
the internal temperature to return to below T_INT-OTP before
recovering. Provided the converter is still enabled, the DCM will
restart after t_INIT and t_ON.
DCM^™ in a VIA Package
Page 17 of 22
Rev 1.6
03/2016
vicorpower.com
800 927.9474