BCM48BH120(T,M)120B00

BCM® Bus Converter
BCM48BH120T120B00
S
C
NRTL
US
Fixed Ratio DC-DC Converter
FEATURES
DESCRIPTION
The VI Chip® Bus Converter is a high efficiency (>95%) Sine
Amplitude ConverterTM (SACTM) operating from a 38 to 55 Vdc
primary bus to deliver an isolated ratiometric output from 9.5 to
13.75. The SAC offers a low AC impedance beyond the bandwidth of most downstream regulators, meaning that
input capacitance normally located at the input of a 12 V
regulator can be located at the input to the SAC. Since the
K factor of the BCM48BH120T120B00 is 1/4, that capacitance
value can be reduced by a factor of 16x, resulting in savings of
board area, materials and total system cost.
• 48 Vdc – 12 Vdc 120 W Bus Converter
• High efficiency (>95%) reduces
system power consumption
• High power density (801 W/in3) reduces
power system footprint by >50%
• “Half Chip” VI Chip® package enables surface mount,
low impedance interconnect to system board
• Contains built-in protection features against:
-
The BCM48BH120T120B00 is provided in a VI Chip package
compatible with standard pick-and-place and surface mount
assembly processes. The VI Chip package provides flexible thermal management through its low junction-to-case and junction-to-board thermal resistance. With high conversion
efficiency the BCM48BH120T120B00 increases overall system
efficiency and lowers operating costs compared to
conventional approaches.
Undervoltage
Overvoltage
Overcurrent
Short Circuit
Overtemperature
• Provides enable/disable control,
internal temperature monitoring
• ZVS/ZCS Resonant Sine Amplitude Converter topology
• Less than 50°C temperature rise at full load
in typical applications
TYPICAL APPLICATION
• High End Computing Systems
• Automated Test Equipment
• Telecom Base Stations
• High Density Power Supplies
• Communication Systems
VIN = 38 – 55 V
POUT = 120 W(NOM)
VOUT = 9.5 – 13.75 V (NO LOAD)
K = 1/4
PART NUMBERING
PART NUMBER
BCM48BH120 x 120 B00
PRODUCT GRADE
T = -40° to 125°C
M = -55° to 125°C
For Storage and Operating Temperatures see Section 6.0 General Characteristics
TYPICAL APPLICATION
POL
enable / disable
switch
TM
PC
SW1
F1
VIN
3.15 A
POL
BCM®
BCM™
+In
C1
POL
+Out
10 µF
VOUT
-In
-Out
BCM® Bus Converter
Rev 1.2
vicorpower.com
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07/2015
800 927.9474
POL
BCM48BH120T120B00
ABSOLUTE MAXIMUM RATINGS
CONTROL PIN SPECIFICATIONS
+IN to –IN . . . . . . . . . . . . . . . . . . . . . . . . . -1.0 Vdc – +60 Vdc
PC to –IN . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3 Vdc – +20 Vdc
TM to –IN . . . . . . . . . . . . . . . . . . . . . . . . . -0.3 Vdc – +7.0 Vdc
+IN/-IN to +OUT/-OUT . . . . . . . . . . . . . . . . . . . 2250 V (Hi Pot)
+IN/-IN to +OUT/-OUT . . . . . . . . . . . . . . . . . . . . 60 V (working)
+OUT to –OUT . . . . . . . . . . . . . . . . . . . . . . -1.0 Vdc - +16 Vdc
Temperature during reflow . . . . . . . . . . . . . . . . 245°C (MSL 4)
See section 5.0 for further application details and guidelines.
PACKAGE ORDERING INFORMATION
4
3
2
1
A
+Out
+In
B
C
D
E
F
G
H
J
K
-Out
L
M
NC
TM
NC
PC
-In
Bottom View
Signal
Name
+In
–In
NC
TM
NC
PC
+Out
–Out
PC (BCM® Primary Control)
The PC pin can enable and disable the BCM module. When
held below VPC-DIS the BCM shall be disabled. When allowed
to float with an impedance to –IN of greater than 60 kΩ the
module will start. When connected to another BCM PC pin (either directly, or isolated through a diode), the BCM modules
will start simultaneously when enabled. The PC pin is capable
of being either driven high by an external logic signal or internal pull up to 5 V
(operating).
TM (BCM® Temperature Monitor)
The TM pin monitors the internal temperature of the BCM
module within an accuracy of +5/-5 °C. It has a room temperature setpoint of ~3.0 V and an approximate gain of 10 mV/°C.
It can source up to 100 uA and may also be used as a “Power
Good” flag to verify that the BCM module is operating.
Designation
A1-B1, A2-B2
L1-M1, L2-M2
E1
F2
G1
H2
A3-D3, A4-D4
J3-M3, J4-M4
BCM® Bus Converter
Rev 1.2
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800 927.9474
BCM48BH120T120B00
1.0 ELECTRICAL CHARACTERISTICS
Specifications apply over all line and load conditions unless otherwise noted; Boldface specifications apply over the
temperature range of -40°C < TJ < 125°C (T-Grade); All other specifications are at TJ = 25º unless otherwise noted
ATTRIBUTE
Voltage range
dV/dt
Quiescent power
No load power dissipation
SYMBOL
VIN
dVIN /dt
PQ
PNL
Inrush current peak
IINR-P
DC input current
IIN-DC
K factor
( )
VOUT
VIN
Output power (average)
CONDITIONS / NOTES
MIN
TYP
MAX
UNIT
38
48
55
1
150
4.1
5
Vdc
V/µs
mW
12
A
3.5
A
VIN = 38 – 55 Vdc; See Figure 14
VIN = 46 – 55 Vdc; See Figure 14
97
120
W
VIN = 46 – 55 Vdc
Average POUT < = 120 W, Tpeak < 10 ms
150
W
14
10.0
V
A
PC connected to -IN
VIN = 48 V
VIN = 38 to 55 V
VIN = 48 V COUT = 500 µF,
IOUT = 10.55 A
68
2.1
5.5
K
POUT
Output power (peak)
POUT-P
Output voltage
Output current (average)
VOUT
IOUT
1/4
Efficiency (ambient)
h
Efficiency (hot)
Minimum efficiency
(over load range)
Output resistance (ambient)
Output resistance (hot)
Output resistance (cold)
Load capacitance
Switching frequency
Ripple frequency
h
Section 3.0
Pout < =120 W
VIN = 48 V, POUT = 120 W
VIN = 38 V to 55 V, POUT = 100 W
VIN = 48 V, TJ = 100°C, POUT = 120 W
h
24 W < POUT < POUT Max
ROUT
ROUT
ROUT
COUT
FSW
FSW-RP
Output voltage ripple
VOUT-PP
VIN to VOUT (application of VIN)
TON1
PC
PC voltage (operating)
PC voltage (enable)
PC voltage (disable)
PC source current (start up)
PC source current (operating)
PC internal resistance
PC capacitance (internal)
PC capacitance (external)
External PC resistance
PC external toggle rate
PC to VOUT with PC released
PC to VOUT, disable PC
VPC
VPC-EN
VPC-DIS
IPC-EN
IPC-OP
RPC-SNK
CPC_INT
CPC_EXT
RPC
FPC-TOG
Ton2
TPC-DIS
W
TJ = 25°C
TJ = 125°C
TJ = -40°C
8.5
93.5
92
92.6
VIN = 48 V, Pre-applied; See Figure 16
VIN = 48 V, Pre-applied; See Figure 16
BCM® Bus Converter
Rev 1.2
vicorpower.com
Page 3 of 16
07/2015
800 927.9474
%
93.5
%
72
%
25.0
30
20
38.8
47.3
28.7
1.5
3.0
50.0
60
40
500
1.6
3.2
mΩ
mΩ
mΩ
uF
MHz
MHz
1.4
2.8
200
400
mV
570
800
ms
4.7
2.0
5.0
2.5
50
100
50
150
5.3
3.0
1.95
300
2
400
588
1000
V
V
V
uA
mA
kΩ
pF
pF
kΩ
Hz
µs
µs
COUT = 0 µF, IOUT = 10.55 A, VIN = 48 V,
Section 8.0
VIN = 48 V, CPC = 0; See Figure 16
Internal pull down resistor
Section 5.0
External capacitance delays PC enable time
Connected to –VIN
94.6
60
60
4
1
100
10
BCM48BH120T120B00
1.0 ELECTRICAL CHARACTERISTICS (CONT.)
Specifications apply over all line and load conditions unless otherwise noted; Boldface specifications apply over the
temperature range of -40°C < TJ < 125°C (T-Grade); All other specifications are at TJ = 25º unless otherwise noted
ATTRIBUTE
TM
TM accuracy
TM gain
TM source current
TM internal resistance
External TM capacitance
TM voltage ripple
PROTECTION
Negative going OVLO
Positive going OVLO
Negative going UVLO
Positive going UVLO
Output overcurrent trip
Short circuit protection
trip current
Short circuit protection
response time
Thermal shutdown
junction setpoint
GENERAL SPECIFICATION
Isolation voltage (Hi-Pot)
Working voltage (IN – OUT)
Isolation vapacitance
Isolation resistance
MTBF
SYMBOL
Actm
ATM
ITM
RTM-SNK
CTM
VTM-PP
VIN OVLOVIN OVLO+
VIN UVLOVIN UVLO+
IOCP
CONDITIONS / NOTES
MIN
TYP
-5
MAX
UNIT
+5
ºC
mV/°C
uA
kΩ
pF
mV
10
CTM = 0 uF, VIN = 55 V, POUT = 120 W
VIN = 48 V, 25°C
25
40
75
180
100
50
50
250
55.1
55.5
29.1
30.7
12
58.7
58.1
31.5
32.9
17
60
60
35.4
37.3
24
V
V
V
V
A
40
A
ISSP
24
TSSP
0.8
1.0
1.2
us
TJ-OTP
125
130
135
°C
VHIPOT
VWORKING
CIN-OUT
RIN-OUT
2250
1750
60
2150
Unpowered unit
1350
10
MIL HDBK 217F, 25°C, GB
cTUVus
CE Mark
Agency approvals / standards
7.1
CE Marked for Low Voltage Directive and ROHS recast directive, as applicable
BCM® Bus Converter
Rev 1.2
vicorpower.com
Page 4 of 16
07/2015
800 927.9474
V
V
pF
MΩ
Mhrs
BCM48BH120T120B00
1.1 APPLICATION CHARACTERISTICS
All specifications are at TJ = 25ºC unless otherwise noted. See associated figures for general trend data.
ATTRIBUTE
SYMBOL
No load power
Inrush current peak
PNL
INR-P
Efficiency (ambient)
η
Efficiency (hot – 100°C)
η
Output resistance (-40°C)
Output resistance (25°C)
Output resistance (100°C)
ROUT_C
ROUT_R
ROUT_H
Output voltage ripple
VOUT-PP
VOUT transient (positive)
VOUT-TRAN+
VOUT transient (negative)
VOUT-TRAN-
Undervoltage lockout
response time
Output overcurrent
response time
Overvoltage lockout
response time
CONDITIONS / NOTES
TYP
UNIT
VIN = 48 V, PC enabled; See Figure 1
COUT = 500 µF, POUT = 120 W
VIN = 48 V, POUT = 120 W
COUT = 500 µF
VIN = 48 V, POUT = 120 W
COUT = 500 µF
VIN = 48 V
VIN = 48 V
VIN= 48 V
COUT = 0uF, POUT = 120 W @ VIN = 48,
VIN = 48 V
IOUT_STEP = 0 TO 10.55 A,
ISLEW >10 A/us; See Figure 12
IOUT_STEP = 10.55 A to 0 A,
ISLEW > 10 A/us; See Figure 11
1.75
6
W
A
95
%
94
%
35
44
56
mΩ
mΩ
mΩ
160
mV
1.4
V
1.3
V
2.4
us
4.4
ms
2.4
µs
TUVLO
TOCP
12 < IOCP < 25 A
TOVLO
BCM® Bus Converter
Rev 1.2
vicorpower.com
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BCM48BH120T120B00
Full Load Efficiency vs. Case Temperature
96
95
2.5
Efficiency (%)
2
1.5
94
93
92
91
1
-40
38
40
42
44
46
47
49
51
53
-20
55
-40ºC
25ºC
96
94
14
94
92
12
10
90
8
PD
6
4
84
82
2
80
0
38 V
VIN :
4
6
8
Output Load (A)
48 V
55 V
10
η
88
8
86
38 V
48 V
55 V
84
4
82
2
0
2
38 V
VIN:
55
86
6
PD
4
82
2
80
0
48 V
48 V
55 V
10
12
8
10
55 V
38 V
12
48 V
55 V
40
35
30
25
20
-40
-20
0
20
40
Temperature (°C)
38 V
48 V
45
Output Load (A)
38 V
8
50
ROUT (mW)
8
Power Dissipation (W)
Efficiency (%)
14
88
VIN :
6
ROUT vs. TCASE at VIN = 48 V
60
12
6
4
Figure 4 — Efficiency and power dissipation at 25°C (case); VIN
16
10
4
6
PD
0
90
2
12
Output Load (A)
η
0
14
10
Efficiency & Power Dissipation 100°C Case
84
55 V
90
12
96
92
48 V
80
Figure 3 — Efficiency and power dissipation at -40°C (case); VIN
94
100
16
92
Efficiency (%)
Efficiency (%)
Power Dissipation (W)
16
2
80
Efficiency & Power Dissipation 25°C Case
Efficiency & Power Dissipation -40°C Case
0
60
Figure 2 — Full load efficiency vs. temperature; VIN
96
86
40
38 V
VIN :
100ºC
Figure 1 — No load power dissipation vs. VIN ; TCASE
88
20
Case Temperature (C)
Input Voltage (V)
TCASE:
0
Power Dissipation (W)
No Load Power Dissipation (W)
No Load Power Dissipation vs. Line
3
55 V
Figure 5 — Efficiency and power dissipation at 100°C (case); VIN
I OUT :
10.0 A
Figure 6 — ROUT vs. temperature vs. IOUT
BCM® Bus Converter
Rev 1.2
vicorpower.com
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60
80
100
BCM48BH120T120B00
Output Voltage Ripple vs. Load
Ripple (mV pk-pk)
200
175
150
125
100
75
50
0
1
2
3
4
5
6
7
8
9
10
Load Current (A)
VIN:
48 V
Figure 7 — Vripple vs. IOUT ; 48 VIN , no external capacitance
Figure 8 — PC to VOUT start up waveform
Figure 9 — VIN to VOUT start up waveform
Figure 10 — Output voltage and input current ripple,
48 VIN ,120 W no COUT
Figure 11 — Positive load transient (0 – 11.3 A)
Figure 12 — Negative load transient (11.3 A – 0 A)
BCM® Bus Converter
Rev 1.2
vicorpower.com
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07/2015
800 927.9474
BCM48BH120T120B00
POUT (W)
q
120
q
97
38
Figure 13 — PC disable waveform, 48 VIN , 500 µF COUT full load
48
VIN (VDC)
55
Figure 14 — POUT derating vs. VIN
2.0 PACKAGE/MECHANICAL SPECIFICATIONS
All specifications are at TJ = 25ºC unless otherwise noted. See associated figures for general trend data.
ATTRIBUTE
SYMBOL
CONDITIONS / NOTES
Length
Width
Height
Volume
Footprint
L
W
H
Vol
F
No heat sink
No heat sink
Power density
PD
No heat sink
Weight
W
ESD rating
Peak temperature during reflow
Peak time above 217°C
Peak heating rate during reflow
Peak cooling rate post reflow
[a]
[b]
TYP
MAX
UNIT
21.7 / 0.854 22.0 / 0.866 22.3 / 0.878 mm/in
16.37 / 0.644 16.50 / 0.650 16.63 / 0.655 mm/in
6.48 / 0.255 6.73 / 0.265 6.98 / 0.275 mm/in
2.44 / 0.150
cm3/in3
3.6 / 0.56
cm2/in2
801
W/in3
W/cm3
49
0.28/8
oz/g
Nickel (0.51-2.03 µm)
Palladium (0.02-0.15 µm)
Gold (0.003-0.05 µm)
Lead finish
Operating temperature
Storage temperature
Thermal impedance
Thermal capacity
Peak compressive force
Applied to case (Z-axis)
MIN
TJ
TST
ØJC
-40
-40
Junction to case
125
125
2.7
°C
°C
°C/W
Ws/°C
3.0
lbs
245
150
3
6
VDC
VDC
°C
s
°C/s
°C/s
5
Supported by J-leads only
ESDHBM
ESDMM
Human Body Model[a]
Machine Model[b]
MSL 4 (Datecode 1528 and later)
2.5
1500
400
1.5
1.5
JEDEC JESD 22-A114C.01
JEDED JESD 22-A115-A
BCM® Bus Converter
Rev 1.2
vicorpower.com
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BCM48BH120T120B00
2.1 MECHANICAL DRAWING
BOTTOM VIEW
TOP VIEW ( COMPONENT SIDE )
mm
(inch)
NOTES:
mm
2. DIMENSIONS ARE inch .
UNLESS OTHERWISE SPECIFIED, TOLERANCES ARE:
3. .X / [.XX] = +/-0.25 / [.01]; .XX / [.XXX] = +/-0.13 / [.005]
4. PRODUCT MARKING ON TOP SURFACE
DXF and PDF files are available on vicorpower.com
2.2 RECOMMENDED LAND PATTERN
4
RECOMMENDED LAND PATTERN
3
2
1
A
+Out
( COMPONENT SIDE SH OWN )
+In
B
C
D
E
F
G
H
J
K
-Out
L
M
Bottom View
NOTES:
3. .X / [.XX] = +/-0.25 / [.01]; .XX / [.XXX] = +/-0.13 / [.005]
mm
2. DIMENSIONS ARE inch .
UNLESS OTHERWISE SPECIFIED, TOLERANCES ARE:
4. PRODUCT MARKING ON TOP SURFACE
DXF and PDF files are available on vicorpower.com
Signal
Name
+In
–In
NC
TM
NC
PC
+Out
–Out
Designation
A1-B1, A2-B2
L1-M1, L2-M2
E1
F2
G1
H2
A3-D3, A4-D4
J3-M3, J4-M4
2.3 RECOMMENDED LAND PATTERN FOR PUSH PIN HEAT SINK
Notes:
1. Maintain 3.50 (0.138) Dia. keep-out zone
free of copper, all PCB layers.
2. (A) minimum recommended pitch is 24.00 (0.945)
this provides 7.50 (0.295) component
edge–to–edge spacing, and 0.50 (0.020)
clearance between Vicor heat sinks.
(B) Minimum recommended pitch is 25.50 (1.004).
This provides 9.00 (0.354) component
edge–to–edge spacing, and 2.00 (0.079)
clearance between Vicor heat sinks.
3. V•I Chip™ module land pattern shown
for reference only, actual land pattern may differ.
Dimensions from edges of land pattern
to push–pin holes will be the same for
all half size V•I Chip products.
4. RoHS compliant per CST–0001 latest revision.
5. Unless otherwise specified:
Dimensions are mm (inches)
tolerances are:
x.x (x.xx) = ±0.3 (0.01)
x.xx (x.xxx) = ±0.13 (0.005)
6. Plated through holes for grounding clips (33855)
shown for reference. Heat sink orientation and
device pitch will dictate final grounding solution.
(NO GROUNDING CLIPS)
BCM® Bus Converter
Rev 1.2
vicorpower.com
Page 9 of 16
07/2015
800 927.9474
(WITH GROUNDING CLIPS)
NC
TM
NC
PC
-In
BCM48BH120T120B00
3.0 POWER, VOLTAGE, EFFICIENCY RELATIONSHIPS
Because of the high frequency, fully resonant SAC topology,
power dissipation and overall conversion efficiency of BCM®
converters can be estimated as shown below.
OUTPUT
POWER
INPUT
POWER
Key relationships to be considered are the following:
1. Transfer Function
P R OUT
a. No load condition
P NL
VOUT = VIN • K
Eq. 1
Figure 15 — Power transfer diagram
Where K (transformer turns ratio) is constant
for each part number
b. Loaded condition
VOUT = Vin • K – IOUT • ROUT
Eq. 2
2. Dissipated Power
The two main terms of power losses in the
BCM module are:
- No load power dissipation (PNL ) defined as the power
used to power up the module with an enabled power
train at no load.
- Resistive loss (ROUT) refers to the power loss across
the BCM module modeled as pure resistive impedance.
~ PNL + PR
PDISSIPATED ~
OUT
Eq. 3
Therefore, with reference to the diagram shown in Figure 15
POUT = PIN – PDISSIPATED = PIN – PNL – PROUT
Eq. 4
Notice that ROUT is temperature and input voltage dependent
and PNL is temperature dependent (See Figure 15).
The above relations can be combined to calculate the overall module efficiency:
h =
POUT
PIN
=
PIN – PNL – PROUT
PIN
=
VIN • IIN – PNL – (IOUT)2 • ROUT
VIN • IIN
=1–
BCM® Bus Converter
Rev 1.2
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800 927.9474
(
PNL + (IOUT)2 • ROUT
VIN • IIN
)
Eq. 5
NL
5V
2.5 V
5V
3V
PC
VUVLO+
VUVLO–
Figure 16 — Timing diagram
BCM® Bus Converter
Rev 1.2
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1
A
E: TON2
F: TOCP
G: TPC–DIS
H: TSSP**
B
D
1: Controller start
2: Controller turn off
3: PC release
C
*Min value switching off
**From detection of error to power train shutdown
A: TON1
B: TOVLO*
C: Max recovery time
D:TUVLO
0.4 V
3 V @ 27°C
TM
LL • K
Vout
C
500mS
before retrial
3V
VIN
VOVLO+
VOVLO–
2
F
4: PC pulled low
5: PC released on output SC
6: SC removed
IOCP
ISSP
IOUT
E
3
G
4
Notes:
H
5
– Timing and voltage is not to scale
– Error pulse width is load dependent
6
BCM48BH120T120B00
4.0 OPERATING
BCM48BH120T120B00
5.0 USING THE CONTROL SIGNALS TM AND PC
The PC control pin can be used to accomplish the following
functions:
• Delayed start: At start up, PC pin will source a constant
100 uA current to the internal RC network. Adding an
external capacitor will allow further delay in reaching the
2.5 V threshold for module start.
• Synchronized start up: In a parallel module array, PC pins
shall be connected in order to ensure synchronous start of all
the units. While every controller has a calibrated 2.5 V
reference on PC comparator, many factors might cause
different timing in turning on the 100 uA current source on
each module, i.e.:
– Different VIN slew rate
– Statistical component value distribution
By connecting all PC pins, the charging transient will be
shared and all the modules will be enabled synchronously.
• Auxiliary voltage source: Once enabled in regular
operational conditions (no fault), each BCM® module PC
provides a regulated 5 V, 2 mA voltage source.
• Output disable: PC pin can be actively pulled down in order
to disable module operations. Pull down impedance shall be
lower than 1 kΩ and toggle rate lower than 1 Hz.
• Fault detection flag: The PC 5 V voltage source is internally
turned off as soon as a fault is detected. After a minimum
disable time, the module tries to re-start, and PC voltage is
re-enabled. For system monitoring purposes (microcontroller
interface) faults are detected on falling edges of PC signal.
It is important to notice that PC doesn’t have current sink
capability (only 150 kΩ typical pull down is present),
therefore, in an array, PC line will not be capable of disabling
all the modules if a fault occurs on one of them.
6.0 FUSE SELECTION
VI Chip productss are not internally fused in order to provide
flexibility in configuring power systems. Input line fusing of
VI Chip modules is recommended at system level, in order to
provide thermal
protection in case of catastrophic failure.
The fuse shall be selected by closely matching system
requirements with the following characteristics:
• Current rating (usually greater than maximum
BCM converter current)
• Maximum voltage rating (usually greater than the
maximum possible input voltage)
• Ambient temperature
• Nominal melting I2t
• Recommended fuse: 3.15 A Little Fuse Nano2 Fuse
The temperature monitor (TM) pin provides a voltage proportional to the absolute temperature of the converter control IC.
It can be used to accomplish the following functions:
• Monitor the control IC temperature: The temperature in
Kelvin is equal to the voltage on the TM pin scaled
by x100. (i.e. 3.0 V = 300 K = 27ºC). It is important to
remember that VI Chip® products are multi-chip modules,
whose temperature distribution greatly vary for each part
number as well with input/output conditions, thermal
management and environmental conditions. Therefore, TM
cannot be used to thermally protect the system.
• Fault detection flag: The TM voltage source is internally
turned off as soon as a fault is detected. After a minimum
disable time, the module tries to re-start, and TM voltage is
re-enabled.
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BCM48BH120T120B00
7.0 CURRENT SHARING
The SAC™ topology bases its performance on efficient transfer
of energy through a transformer, without the need of closed
loop control. For this reason, the transfer characteristic can be
approximated by an ideal transformer with some resistive drop
and positive temperature coefficient.
This type of characteristic is close to the impedance characteristic
of a DC power distribution system, both in behavior
(AC dynamic) and absolute value (DC dynamic).
When connected in an array (with same K factor), the BCM®
module will inherently share the load current with parallel
units, according to the equivalent impedance divider that the
system implements from the power source to the point of load.
It is important to notice that, when successfully started, BCM
converters are capable of bidirectional operations (reverse
power transfer is enabled if the BCM converter input falls
within its operating range and the BCM converter is otherwise
enabled). In parallel arrays, because of the resistive behavior, circulating currents are never experienced, because of energy conservation law.
General recommendations to achieve matched array impedances
are (see also AN016 for further details):
• to dedicate common copper planes within the PCB to
deliver and return the current to the modules
• to make the PCB layout as symmetric as possible
• to apply same input/output filters (if present) to each unit
Figure 17 — BCM® module array
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8.0 INPUT AND OUTPUT FILTER DESIGN
A major advantage of SAC™ systems versus conventional
PWM converters is that the transformers do not require large
functional filters. The resonant LC tank, operated at extreme
high frequency, is amplitude modulated as a function of input
voltage and output current, and efficiently transfers charge
through the isolation transformer. A small amount of
capacitance, embedded in the input and output stages of the
module, is sufficient for full functionality and is key to achieve
power density.
This paradigm shift requires system design to carefully evaluate
external filters in order to:
1.Guarantee low source impedance:
To take full advantage of the BCM® module dynamic
response, the impedance presented to its input terminals
must be low from DC to approximately 5 MHz. The
connection of the module to its power source should be
implemented with minimal distribution inductance. If the
interconnect inductance exceeds 100 nH, the input should
be bypassed with a RC damper to retain low source
impedance and stable operation. With an interconnect
inductance of 200 nH, the RC damper may be as high as
47 µF in series with 0.3 Ω. A single electrolytic or
equivalent low-Q capacitor may be used in place of the
series RC bypass.
Total load capacitance at the output of the module shall not
exceed the specified maximum. Owing to the wide bandwidth
and low output impedance of the module, low frequency
bypass capacitance and significant energy storage may be
more densely and efficiently provided by adding capacitance at
the input of the module. At frequencies <500 kHz the module
appears as an impedance of ROUT between the source and load.
Within this frequency range capacitance at the input appears
as effective capacitance on the output per the relationship
defined in Eq. 6.
COUT =
CIN
K2
Eq. 6
This enables a reduction in the size and number of capacitors
used in a typical system.
2.Further reduce input and/or output voltage ripple without
sacrificing dynamic response:
Given the wide bandwidth of the module, 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 module multiplied by its
K factor. This is illustrated in Figures 11 and 12.
3.Protect the module from overvoltage transients imposed
by the system that would exceed maximum ratings and
cause failures:
The BCM module input/output voltage ranges shall not
be exceeded. An internal overvoltage lockout function
prevents operation outside of the normal operating input
range. Even during this condition, the powertrain is exposed
to the applied voltage and power MOSFETs must withstand
it. A criterion for protection is the maximum amount of
energy that the input or output switches can tolerate if
avalanched.
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Figure 18 – BCM® module behavioral block diagram
BCM® Bus Converter
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TM
PC
-Vin
+Vin
560 pF
2.5 V
40 K
5V
Voltage dependent
temperature sensor
2.5 V
One shot
delay
320/540 ms
2 mA
PC Pull-Up
& Source
150 K
1.5 k
100 uA
UVLO
OVLO
18.5 V
Wake-Up Power
and Logic
Vref
(125°C)
Primary
Gate
Drive
supply
Min. off
time and
restart
Enable
Modulator
Vref
Over-Current
Protection
Slow
current
limit
Fast
current
limit
Differential primary
current sensing
Primary Stage &
Resonant Tank
-Vout
+Vout
BCM48BH120T120B00
BCM48BH120T120B00
Vicor’s comprehensive line of power solutions includes high density AC-DC and DC-DC modules and accessory components, fully configurable AC-DC and DC-DC power supplies, and complete custom power
systems.
Information furnished by Vicor is believed to be accurate and reliable. However, no responsibility is assumed by Vicor for its use. Vicor makes no
representations or warranties with respect to the accuracy or completeness of the contents of this publication. Vicor reserves the right to make
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Specifications are subject to change without notice.
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when properly used in accordance with instructions for use provided in the labeling can be reasonably expected to result in a significant injury to the
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Vicor and its subsidiaries own Intellectual Property (including issued U.S. and Foreign Patents and pending patent applications) relating to the products described in this data sheet. No license, whether express, implied, or arising by estoppel or otherwise, to any intellectual property rights is
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The products described on this data sheet are protected by the following U.S. Patents Numbers:
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Andover, MA, USA 01810
Tel: 800-735-6200
Fax: 978-475-6715
email
Customer Service: [email protected]
Technical Support: [email protected]corpower.com
BCM® Bus Converter
Rev 1.2
vicorpower.com
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