Application Note (continued)
Input Impedance Recommendations
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.
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., 8 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.
Input Fuse Recommendations
V•I Chips are not internally fused in order to provide flexibility
in power system configuration. However, input line fusing of
V•I Chips must always be incorporated within the power system.
A fast acting fuse, such as NANO2 FUSE 451 Series 7 A 125 V,
is required to meet safety agency Conditions of Acceptability.
The input line fuse should be placed in series with the +IN port.
Application Circuits
VO = 7.6 - 11 V
+Out
-Out
+In
TM
RSV
PC
BCM
48 Vin
(38 - 55 Vdc)
+Out
K
Ro
-In
-Out
NiPOL
1
NiPOL
2
NiPOL
3
NiPOL
4
LOAD
1
LOAD
2
LOAD
3
LOAD
4
Figure 28—The BCM provides an isolated, loosely regulated 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
Vf = PRM Output (Factorized Bus Voltage)
VL = Desired Load Voltage
VS = PRM Output Set Point Voltage
FPA Local Loop
Vo = VL – Io • Ro
VH
SC
SG
CP
RL
VC
PC
TM
IL
+Out
+In
Factorized
Power Bus
L
O
A
D
IM
-Out
PR PRM-AL CD
TM
BCM
RSV
+In
+Out
PC
+Out
48 Vin
(36 - 75 Vdc)
VL
Vf = Vs =
K
K
Ro
-In
–In
–Out
-Out
Vs range = 38 – 55 Vdc
P048K055T24AL
B048K096T24
( k=1/5: Ro=9.5 mΩ)
Figure 29—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.
Vicor Corporation
Tel: 800-735-6200
vicorpower.com
V•I Chip Bus Converter
B048K096T24
Rev. 1.9
Page 14 of 16
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