NBM3814B60E12A7C00 Datasheet, PDF (19/23 Pages) Vicor Corporation – Non-Isolated, Fixed-Ratio DC-DC Converter

NBM3814x60E12A7yzz
R_JC
+ T_{C_BOT}
s
P_DISS
s
V_HI
+ _DC
Z_{HI_EQ1}
Z_{HI_EQ2}
NBM^™1
R_{0_1}
Z_{LO_EQ1}
V_LO
NBM^™2
R_{0_2}
Z_{LO_EQ2}
Load
Figure 20 — Single-sided cooling VIA thermal model
n Double side cooling: while this option might bring limited
advantage to the module internal components (given the
surface-to-surface coupling provided), it might be appealing
in cases wherethe external thermal system requires allocating
power to two different elements, like for example heatsinks with
independent airflows or a combination of chassis/air cooling.
Current Sharing
The performance of the NBM in a VIA package is based on efficient
transfer of energy through a auto-transformer without the need
of closed loop control. For this reason, the transfer characteristic
can be approximated by an ideal auto-transformer with a positive
temperature coefficient series resistance.
This type of characteristic is close to the impedance characteristic
of a DC power distribution system both in dynamic (AC) behavior
and for steady state (DC) operation.
When multiple NBM modules of a given part number are
connected in an array they will inherently share the load current
according to the equivalent impedance divider that the system
implements from the power source to the point of load.
Some general recommendations to achieve matched array
impedances include:
n Dedicate common copper planes/wires within the PCB/Chassis
to deliver and return the current to the VIA modules.
n Provide as symmetric a PCB/Wiring layout as possible among
VIA™ modules
For further details see AN:016 Using BCM Bus Converters
in High Power Arrays.
Fuse Selection
In order to provide flexibility in configuring power systems, NBM in
a VIA package modules are not internally fused. Input line fusing of
NBM in a VIA package products is recommended at system level to
provide thermal protection in case of catastrophic failure.
Z_{HI_EQn}
NBM^™n
R_{0_n}
Z_{LO_EQn}
Figure 21 — NBM module array
The fuse shall be selected by closely matching system
requirements with the following characteristics:
n Current rating
(usually greater than maximum current of NBM module)
n Maximum voltage rating
(usually greater than the maximum possible input voltage)
n Ambient temperature
n Nominal melting I²t
n Recommend fuse: ≤60A Littelfuse TLS Series or
Littlefuse 456 series rated 40A (HI side)
Startup and Reverse Operation
The NBM3814x60E12A7yzz is capable of startup in forward and
reverse direction once the applied voltage is greater than the
undervoltage lockout threshold.
The non-isolated bus converter modules are capable of reverse
power operation. Once the unit is enabled, energy can be
transferred from low volatge side back to the high voltage side
whenever the low side voltage exceeds V_HI • K. The module will
continue operation in this fashion for as long as no faults occur.
Startup loading could be set to no greater than 20% of rated max
current respectively in forward or reverse direction. A load must
not be present on the +V_HI pin if the powertrain is not actively
switching. Remove +HI load prior to disabling the module using
+LO power or prior to faults. High voltage side MOSEFT body diode
conduction will occur if unit stops switching while a load is present
on the +V_HI and +V_LO voltage is two diodes drop higher than +V_HI.
NBM^™ in a VIA Package
Page 19 of 23
Rev 1.1
05/2016
vicorpower.com
800 927.9474