BCM4414xG0F4440yzz
Filtering
The BCM in a VIA package has built-in single stage EMI filtering
located on the high voltage side. The integrated EMI filtering
consists of a common mode choke and differential mode
capacitors. However, it does not include Y2 capacitors for
common mode filtering. Y2 common mode capacitors can be
added externally on the high voltage side between +HI and PE
(Case), and –HI and PE (Case) to meet certain EMI requirements.
A typical test set-up block diagram for conducted emissions is
shown in Figure 27.
EMI
Receiver
LISN
LISN
+HI
+LO
Single
DC
Power
Supply
Screen
Room /
Filters
VIA BCM
(DUT)
Load
–HI
–LO
The integrated filtering reduces the voltage ripple on the high
voltage side. External LO side filtering can be added as needed,
with ceramic capacitance used as a LO side bypass for this purpose.
VIA HI side and LO side voltage ranges shall not be exceeded. An
internal overvoltage function prevents operation outside of the
normal operating HI side range. However, the VIA is exposed to
the applied voltage even when disabled, and must withstand it.
External transient protection circuitry may be required to protect
the VIA from overvoltage transients imposed by a system that
would exceed maximum ratings.
Figure 27 — Typical test set up block diagram for
Conducted Emissions
The source response is generally the limiting factor in the
overall system response, given the wide bandwidth of the BCM.
Anomalies in the response of the source will appear at the LO side
of the module multiplied by its K factor.
Total load capacitance at the LO side of the BCM shall not exceed
the specified maximum to ensure correct operation in start up.
Due to the wide bandwidth and small LO side impedance of the
BCM, low frequency bypass capacitance and significant energy
storage may be more densely and efficiently provided by adding
capacitance at the HI side of the BCM.
At frequencies less than 500kHz, the BCM appears as an
impedance of RLO between the source and load. Within this
frequency range, capacitance connected at the HI side appears as
an effective scaled capacitance on the LO side per the relationship
defined in Equation 14.
CHI
CLO
=
(14)
K2
This enables a reduction in the size and number of capacitors used
in a typical system.
BCM® in a VIA™ Package
Page 23 of 43
Rev 1.2
01/2018
VICOR [ VICOR CORPORATION ]
