PRELIMINARY
Application Note
(continued)
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.
V•I Chip Bus Converter Module
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.
Applying the BCM
BCM
Vin = 38-55 Vdc
N
P
N
S
K=N
S
/ N
P
BCM
N
P
N
S
Vout = (Vin•K) – (Iout•Rout)
= 38.0-55.0 Vdc @ No load
= 36.8-53.9 Vdc @ Full load
K=N
S
/ N
P
BCM
N
P
N
S
B048K480T30
K =1
Iout = 6.3 A
Rout = 188.0 mΩ
Paralleling
BCM automatically current share
when connected in parallel.
No interconnections required.
K=N
S
/ N
P
Isolation Barrier
Standoff Voltage=2.250 Vdc
Figure 27—The
BCM provides an isolated output proportional to its input. It is easily parallelable to create high power arrays and/or N+M redundancy.
In the following figure;
K = BCM Transformation Ratio
R
O
= BCM Output Resistance
V
O
= BCM Output
V
f
= PRM Output (Factorized Bus Voltage)
V
L
= Desired Load Voltage
V
S
= PRM Output Set Point Voltage
FPA Local Loop
Vo = V
L
– I
O
• R
O
VC
PC
TM
IL
NC
PR
VH
SC
SG
OS
NC
CD
R
OS
+In
PRM-AL
Factorized
Power Bus
V
f
=
V
L
K
+In
+Out
+Out
TM
RSV
PC
BCM
K
Ro
-Out
48 Vin
(36 - 75 Vdc)
–In
–Out
+Out
-In
L
O
A
D
-Out
V
S
range = 38 - 55 Vdc
(K =1
B048K480T30
: R
O
= 188.0 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
B048K480T30
Rev. 1.5
Page 13 of 15
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