B048K120T30 Datasheet, PDF (13/15 Pages) Vicor Corporation – VI Chip - BCM Bus Converter Module

Application Note (continued)
PRELIMINARY
V•I Chip Voltage Transformation Module
Input Impedance Recommendations
To take full advantage of the BCM capabilities, the impedance presented
to its input terminals must be low from DC to approximately 5 MHz. The
source should exhibit low inductance (less than 100 nH) and should have a
critically damped response. If the interconnect inductance exceeds 100 nH,
the BCM input pins should be bypassed with an RC damper (e.g., 47 µF in
series with 0.3 ohm) to retain low source impedance and stable
operations. Given the wide bandwidth of the BCM, the source response is
generally the limiting factor in the overall system response.
Anomalies in the response of the source will appear at the output of the
BCM multiplied by its K factor. The DC resistance of the source should be
kept as low as possible to minimize voltage deviations. This is especially
important if the BCM is operated near low or high line as the over/under
voltage detection circuitry could be activated.
Input Fuse Recommendations
V•I Chips are not internally fused in order to provide flexibility in
configuring power systems. However, input line fusing of V•I Chips must
always be incorporated within the power system. A fast acting fuse should
be placed in series with the +IN port.
Application Circuits
48 Vin
(38 - 55 Vdc)
+Out
+In
-Out
TM
RSV
BCM
PC
+Out
K
Ro -In
-Out
Vo = 9.5 - 13.7 V
NiPOL
1
NiPOL
2
NiPOL
3
NiPOL
4
LOAD
1
LOAD
2
LOAD
3
LOAD
4
Figure 27—The BCM provides an isolated output from a narrow range input ideal for driving non-isolated point of load converters (niPOLs)
In the following figure;
K = BCM Transformation Ratio
RO = BCM Output Resistance
VO = BCM Output
FPA Local Loop
Vf = PRM Output (Factorized Bus Voltage)
VL = Desired Load Voltage
VS = PRM Output Set Point Voltage
Vo = VL – IO • RO
48 Vin
(36 - 75 Vdc)
VC
VH
PC
SC
TM
IL
SG
OS
ROS
NC
NC
PR _PRM-AL CD
+In
+Out
–In
–Out
Factorized
Power Bus
V_f
=
VL
K
VS range = 38 - 55 Vdc
+Out
+In
L
-Out
TM
RSV
BCM
O
PC
+Out
A
K
D
Ro -In
-Out
B048K120T30
(K = 1/4 : RO = 11.7 mΩ)
Figure 28—The PRM regulates its output to provide a constant factorized bus voltage. The output voltage is the nominal load voltage, Vo, at no
load and decreases with load at a constant rate equal to the BCM output resistance Ro.
vicorpower.com 800-735-6200
V•I Chip Bus Converter Module
B048K120T30
Rev. 1.0
Page 13 of 16