BCM48Bx080y240A00
BCM® Bus Converter Rev 1.4 vicorpower.com
Page 1 of 20 08/2016 800 927.9474
BCM® Bus Converter
Isolated Fixed Ratio DC-DC Converter
S
NRTL
CU
S
CUS
®
SW1
enable / disable
switch
F1
VIN
PC
TM
-OUT
+OUT
-IN
+IN
L
O
A
D
BCM®
Bus Converter
Features & Benefits
• 48VDC – 8VDC 240W Bus Converter
• High efficiency (>95%) reduces system
power consumption
• High power density (>817W/in3)
reduces power system footprint by >40%
• Contains built-in protection features:
n Undervoltage
n Overvoltage Lockout
n Overcurrent Protection
n Short circuit Protection
n Overtemperature Protection
• Provides enable/disable control,
internal temperature monitoring
• Can be paralleled to create multi-kW arrays
Typical Applications
• High End Computing Systems
• Automated Test Equipment
• High Density Power Supplies
• Communications Systems
Description
The VI Chip® bus converter is a high efficiency (>95%) Sine
Amplitude Converter™ (SAC™) operating from a 38 to 55VDC
primary bus to deliver an isolated, ratiometric output voltage from
6.3 to 9.2VDC. The Sine Amplitude Converter offers a low AC
impedance beyond the bandwidth of most downstream regulators;
therefore capacitance normally at the load can be located at the
input to the Sine Amplitude Converter. Since the transformation
ratio of the BCM48Bx080y240A00 is 1/6, the capacitance value
can be reduced by a factor of 36x, resulting in savings of board
area, materials and total system cost.
The BCM48BF080y240A00 is provided in a VI Chip package
compatible with standard pick-and-place and surface mount
assembly processes. The co-molded VI Chip package provides
enhanced thermal management due to a large thermal interface
area and superior thermal conductivity. The high conversion
efficiency of the BCM48Bx080y240A00 increases overall
system efficiency and lowers operating costs compared to
conventional approaches.
Typical Application
Product Number Package Style (x) Product Grade (y)
BCM48Bx080y240A00 F = J-Lead T = -40° to 125°C
T = Through hole M = -55° to 125°C
Product Ratings
VIN = 48V (38 – 55V) POUT= up to 240W
VOUT = 8V (6.3 – 9.2V)
(no load)K = 1/6
For Storage and Operating Temperatures see General Characteristics
Part Numbering
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BCM48Bx080y240A00
-IN
PC
RSV
TM
+IN
-OUT
+OUT
-OUT
+OUT
Bottom View
A
B
C
D
E
F
G
H
J
K
L
M
N
P
R
T
43 21
A
B
C
D
E
H
J
K
L
M
N
P
R
T
Pin Configuration
Pin Descriptions
Pin Number Signal Name Type Function
A1-E1, A2-E2 +IN INPUT POWER Positive input power terminal
L1-T1, L2-T2 –IN INPUT POWER
RETURN Negative input power terminal
H1, H2 TM OUTPUT Temperature monitor, input side referenced signal
J1, J2 RSV NC No connect
K1, K2 PC OUTPUT/INPUT Enable and disable control, input side referenced signal
A3-D3, A4-D4,
J3-M3, J4-M4 +OUT OUTPUT POWER Positive output power terminal
E3-H3, E4-H4,
N3-T3, N4-T4 –OUT OUTPUT POWER
RETURN Negative output power terminal
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BCM48Bx080y240A00
Absolute Maximum Ratings
The absolute maximum ratings below are stress ratings only. Operation at or beyond these maximum ratings can cause permanent damage to the device.
Parameter Comments Min Max Unit
+IN to –IN -1 60 V
VIN slew rate Operational -1 1 V/µs
Isolation voltage, input to ouput 2250 V
+OUT to –OUT -1 16 V
Output current transient ≤ 10ms, ≤ 10% DC -3 45 A
Output current average -2 36 A
PC to –IN -0.3 20 V
TM to –IN -0.3 7 V
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BCM48Bx080y240A00
Electrical Specifications
Specifications apply over all line and load conditions, unless otherwise noted; boldface specifications apply over the temperature range of
-40°C ≤ TCASE ≤ 100°C (T-Grade); all other specifications are at TCASE = 25ºC unless otherwise noted.
Attribute Symbol Conditions / Notes Min Typ Max Unit
Powertrain
Input voltage range, continuous VIN_DC 38 55 V
Input voltage range, transient VIN_TRANS
Full current or power supported, 50ms max,
10% duty cycle max 38 55 V
Quiescent current IQDisabled, PC Low 1.9 2.8 mA
VIN to VOUT time TON1 VIN = 48V, PC floating 350 500 650 ms
No load power dissipation PNL
VIN = 48V, TCASE = 25ºC 4.0 5.5
W
VIN = 48V 3.0 10.0
VIN = 38V to 55V, TCASE = 25ºC 7.0
VIN = 38V to 55V 11.0
Inrush current peak IINR_P
Worse case of: VIN = 55V, COUT = 2300µF,
RLOAD = 215mΩ13.3 20 A
DC input current IIN_DC At POUT = 240W 0A
Transformation ratio K K = VOUT / VIN, at no load 1/6 V/V
Output power (average) POUT_AVG 240 W
Output power (peak) POUT_PK 10ms max, POUT_AVG ≤ 240W 360 W
Output current (average) IOUT_AVG 36 A
Output current (peak) IOUT_PK 10ms max, IOUT_AVG ≤ 36A 45 A
Efficiency (ambient) hAMB
VIN = 48V, IOUT = 30A; TCASE = 25°C 94.2 95.4
%VIN = 38V to 55V, IOUT = 30A; TCASE = 25°C 92.0
VIN = 48V, IOUT = 15A; TCASE = 25°C 94.0 95.6
Efficiency (hot) hHOT VIN = 48V, IOUT = 30A; TCASE = 100°C 92.8 95.2 %
Efficiency (over load range) h20% 6A < IOUT < 30A 91.0 %
Output resistance
ROUT_COLD IOUT = 30A, TCASE = -40°C 3.0 5.6 8.0
mΩROUT_AMB IOUT = 30A, TCASE = 25°C 5.0 7.4 10.0
ROUT_HOT IOUT = 30A, TCASE = 100°C 5.0 8.2 12.0
Switching frequency FSW 1.49 1.52 1.57 MHz
Output voltage ripple VOUT_PP
COUT = 0F, IOUT = 30A, VIN = 48V,
20MHz BW 160 230 mV
Output inductance (parasitic) LOUT_PAR Frequency up to 30MHz, Simulated J-lead model 600 pH
Output capacitance (internal) COUT_INT Effective value at 8VOUT 45 µF
Output capacitance (external) COUT_EXT 0 2300 µF
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BCM48Bx080y240A00
Electrical Specifications (Cont.)
Specifications apply over all line and load conditions, unless otherwise noted; boldface specifications apply over the temperature range of
-40°C ≤ TCASE ≤ 100°C (T-Grade); all other specifications are at TCASE = 25ºC unless otherwise noted.
Attribute Symbol Conditions / Notes Min Typ Max Unit
Protection
Input overvoltage lockout threshold VIN_OVLO+ 55.1 58.5 60 V
Input overvoltage recovery threshold VIN_OVLO- 55.1 57.2 58 V
Input overvoltage lockout hysteresis VIN_OVLO_HYST 1.2 V
Overvoltage lockout response time TOVLO 8 µs
Fault recovery time TAUTO_RESTART 240 300 380 ms
Input undervoltage lockout
threshold VIN_UVLO- 28.5 31.1 37.4 V
Input undervoltage recovery
threshold VIN_UVLO+ 28.5 33.7 37.4 V
Input undervoltage lockout
hysteresis VIN_UVLO_HYST 1.6 V
Undervoltage lockout response time TUVLO 8 µs
Output overcurrent trip threshold IOCP 42 50 64 A
Output overcurrent response time
constant TOCP Effective internal RC filter 3.8 ms
Short circuit protection trip threshold ISCP 70 A
Short circuit protection response time TSCP 1 µs
Thermal shutdown threshold TJ_OTP 125 °C
Output Voltage (V)
Output Power (W)
P (ave) P (pk), < 10ms I (ave) I (pk), < 10ms
Output Current (A)
0
20
40
60
80
100
120
50
100
150
200
250
300
350
400
6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5
Figure 1 — Safe operating area
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BCM48Bx080y240A00
Signal Characteristics
Specifications apply over all line and load conditions, unless otherwise noted; boldface specifications apply over the temperature range of
-40°C ≤ TCASE ≤ 100°C (T-Grade); all other specifications are at TCASE = 25ºC unless otherwise noted.
Primary Control: PC
• The PC pin enables and disables the BCM. When held low, the BCM is disabled.
• In an array of BCM modules, PC pins should be interconnected to synchronize start up and permit start up into full load conditions.
• PC pin outputs 5V during normal operation. PC pin internal bias level drops to 2.5V during fault mode, provided VIN remains
in the valid range.
SIGNAL TYPE STATE ATTRIBUTE SYMBOL CONDITIONS / NOTES MIN TYP MAX UNIT
ANALOG
OUTPUT
Regular
Operation
PC voltage VPC 4.7 5.0 5.3 V
PC available current IPC_OP 2.0 3.5 5.0 mA
Standby PC source (current) IPC_EN 50 100 µA
PC resistance (internal) RPC_INT Internal pull down resistor 50 150 400 kΩ
Transition PC capacitance (internal) CPC_INT 1000 pF
Start Up PC load resistance RPC_S To permit regular operation 60 kΩ
DIGITAL
INPUT /
OUTPUT
Regular
Operation
PC enable threshold VPC_EN 2.0 2.5 3.0 V
PC disable threshold VPC_DIS 1.95 V
Standby PC disable duration TPC_DIS_T
Minimum time before attempting
re-enable 1s
Transition
PC threshold hysteresis VPC_HYSTER 50 mV
PC enable to VOUT time TON2 VIN = 48V for at least TON1 ms 50 100 150 µs
PC disable to standby time TPC_DIS 410 µs
PC fault response time TFR_PC From fault to PC = 2V 100 µs
Temperature Monitor: TM
• The TM pin monitors the internal temperature of the controller IC within an accuracy of ±5°C.
• Can be used as a “Power Good” flag to verify that the BCM module is operating.
• Is used to drive the internal comparator for Overtemperature Shutdown.
SIGNAL TYPE STATE ATTRIBUTE SYMBOL CONDITIONS / NOTES MIN TYP MAX UNIT
ANALOG
OUTPUT
Regular
Operation
TM voltage range VTM 2.12 4.04 V
TM voltage reference VTM_AMB TJ controller = 27°C 2.95 3.00 3.05 V
TM available current ITM 100 µA
TM gain ATM 10 mV/°C
TM voltage ripple VTM_PP CTM = 0pF, VIN = 48V, IOUT = 30A 120 200 mV
DIGITAL
INPUT /
OUTPUT
Transition TM capacitance (external) CTM_EXT 50 pF
TM fault response time TFR_TM From fault to TM = 1.5V 10 µs
Standby TM voltage VTM_DIS 0 V
TM pull down (internal) RTM_INT Internal pull down resistor 25 40 50 kΩ
Reserved: RSV
Reserved for factory use. No connection should be made to this pin.
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BCM48Bx080y240A00
Timing Diagram
12
34
56
VUVLO+
PC
5 V
3 V
LL • K
A: TON1
B: TOVLO*
C: TAUTO_RESTART
D:TUVLO
E: TON2
F: TOCP
G: TPC–DIS
H: TSCP**
1: Controller start
2: Controller turn o
3: PC release
4: PC pulled low
5: PC released on output SC
6: SC removed
VOUT
TM
3 V @ 27°C
0.4 V
VIN
3 V 5 V
2.5 V
500mS
before retrial
VUVLO–
A
B
E
H
ISSP
IOUT
IOCP
G
F
D
C
VOVLO+
VOVLO–
VOVLO+
NL
Notes:
– Timing and signal amplitudes are not to scale
– Error pulse width is load dependent
*Min value switching o
**From detection of error to power train shut down
C
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BCM48Bx080y240A00
Application Characteristics
The following values, typical of an application environment, are collected at TCASE = 25ºC unless otherwise noted. See associated figures for general trend data.
Input Voltage (V)
Power Dissipation (W
)
-40°C 100°C
TCASE:25°C
0
2
4
6
8
10
12
38 40 42 44 46 47 49 51 53 55
Case Temperature (°C)
Full Load Efficiency (%
)
38V 48V 55V
VIN:
93
94
95
96
-40 -20 020406080100
Load Current (A)
Efficiency (%)
VIN:38V 48V 55V
97
87
82
77
92
72
67
3020
1510 25
50
Figure 2 — No load power dissipation vs. Vin Figure 3 — Full load efficiency vs. temperature; Vin
Figure 4 — Efficiency at TCASE = -40°C
Load Current (A)
Efficiency (%)
VIN:38V 48V 55V
77
79
81
83
85
87
89
91
93
95
97
0 5 10 15 20 25 30
Figure 6 — Efficiency at TCASE = 25°C
Load Current (A)
38V 48V 55V
VIN:
Power Dissipation (W
)
30
20
15
10
25
5
0
3020
1510 25
50
Figure 5 — Power dissipation at TCASE = -40°C
Load Current (A)
38V 48V 55V
VIN:
Power Dissipation (W
)
0
5
10
15
20
25
30
0 5 10 15 20 25 30
Figure 7 — Power dissipation at TCASE = 25°C
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BCM48Bx080y240A00
Application Characteristics (Cont.)
Load Current (A)
Voltage (mVPK-PK)
0
25
50
75
100
125
150
175
200
225
250
0 5 10 15 20 25 30
VIN:48V
Figure 11 — Vripple vs. Iout: No external Cout, board mounted
module, scope setting : 20MHz analog BW
Load Current (A)
Efficiency (%)
VIN:38V 48V 55V
77
79
81
83
85
87
89
91
93
95
97
0 5 10 15 20 25 30
Figure 8 — Efficiency at TCASE = 100°C
Case Temperature (°C)
ROUT (mΩ)
IOUT:36A
-40 -20 0 20 40 60 80 100
5.0
6.0
7.0
8.0
9.0
Figure 10 — ROUT vs. temperature; nominal input
Load Current (A)
38V 48V 55V
VIN:
Power Dissipation (W
)
0
5
10
15
20
25
30
0 5 10 15 20 25 30
Figure 9 — Power dissipation at TCASE = 100°C
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BCM48Bx080y240A00
Figure 13 — Start up from application of PC;
Vin pre-applied Cout = 2300µF
Figure 12 — Full load ripple, 330µF Cin: No external Cout, Board
mounted module, scope setting : 20MHz analog BW
Figure 15 — 30A – 0A transient response: Cin = 330µF, Iin measured
prior to Cin, no external Cout
Figure 14 — 0A – 30A transient response: Cin = 330µF, Iin measured
prior to Cin , no external Cout
Application Characteristics (Cont.)
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BCM48Bx080y240A00
General Characteristics
Specifications apply over all line and load conditions, unless otherwise noted; boldface specifications apply over the temperature range of
-40°C ≤ TCASE ≤ 100°C (T-Grade); All other specifications are at TCASE = 25ºC unless otherwise noted.
Attribute Symbol Conditions / Notes Min Typ Max Unit
Mechanical
Length L 32.25 / [1.270] 32.50 / [1.280] 32.75 / [1.289] mm / [in]
Width W 21.75 / [0.856] 22.00 / [0.866] 22.25 / [0.876] mm / [in]
Height H 6.48 / [0.255] 6.73 / [0.265] 6.98 / [0.275] mm / [in]
Volume Vol No heat sink 4.81 / [0.294] cm3/ [in3]
Weight W 14.5 / [0.512] g / [oz]
Lead Finish
Nickel 0.51 2.03
µmPalladium 0.02 0.15
Gold 0.003 0.051
Thermal
Operating temperature TJ
BCM48Bx080T240A00 (T-Grade) -40 125 °C
BCM48Bx080M240A00 (M-Grade) -55 125
Thermal resistance fJC
Isothermal heatsink and
isothermal internal PCB 1 °C/W
Thermal capacity 5 Ws/°C
Assembly
Peak compressive force
applied to case (Z-axis) Supported by J-lead only 6 lbs
5.41 lbs/ in2
Storage
Temperature TST
BCM48Bx080T240A00 (T-Grade) -40 125 °C
BCM48Bx080M240A00 (M-Grade) -65 125 °C
ESD Withstand
ESDHBM
Human Body Model,
“JEDEC JESD 22-A114D.01”Class 1D 1000
V
ESDCDM
Charge Device Model,
“JEDEC JESD 22-C101-D” 400
Soldering
Peak temperature during reflow MSL 4 (Datecode 1528 and later) 245 °C
Peak time above 217°C 60 90 s
Peak heating rate during reflow 1.5 3 °C/s
Peak cooling rate post reflow 1.5 6 °C/s
Safety
Working voltage (IN – OUT) VIN_OUT 60 VDC
Isolation voltage (hipot) VHIPOT 2,250 VDC
Isolation capacitance CIN_OUT Unpowered unit 2500 3200 3800 pF
Isolation resistance RIN_OUT At 500VDC 10 MΩ
MTBF
MIL-HDBK-217Plus Parts Count - 25°C
Ground Benign, Stationary, Indoors /
Computer Profile
4.3 MHrs
Telcordia Issue 2 - Method I Case III;
25°C Ground Benign, Controlled 9.5 MHrs
Agency approvals / standards
cTUVus
cURus
CE Marked for Low Voltage Directive and ROHS recast directive, as applicable.
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BCM48Bx080y240A00
Using the Control Signals PC, TM
Primary Control (PC) pin can be used to accomplish the
following functions:
n
Logic enable and disable for module: Once T
ON1
time has
been satisfied, a PC voltage greater than V
PC_EN
will cause
the module to start. Bringing PC lower than V
PC_DIS
will
cause the module to enter standby.
n
Auxiliary voltage source: Once enabled in regular
operational conditions (no fault), each BCM module
PC provides a regulated 5V, 3.5mA voltage source.
n
Synchronized start up: In an array of parallel modules, PC
pins should be connected to synchronize start up across
units. This permits the maximum load and capacitance
to scale by the number of paralleled modules.
n
Output disable: PC pin can be actively pulled down in order
to disable the module. Pull down impedance shall be lower
than 60Ω.
n
Fault detection flag: The PC 5V voltage source is internally
turned off as soon as a fault is detected.
n
Note that PC can not sink significant current during a fault
condition. The PC pin of a faulted module will not cause
interconnected PC pins of other modules to be disabled.
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:
n
Monitor the control IC temperature: The temperature in
Kelvin is equal to the voltage on the TM pin scaled
by 100. (i.e. 3.0V = 300K = 27ºC). If a heat sink is applied,
TM can be used to protect the system thermally.
n
Fault detection flag: The TM voltage source is internally
turned off as soon as a fault is detected. For system
monitoring purposes microcontroller interface faults are
detected on falling edges of TM signal.
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BCM48Bx080y240A00
Sine Amplitude Converter™ Point of Load Conversion
The Sine Amplitude Converter (SAC™) uses a high frequency
resonant tank to move energy from input to output. The resonant
LC tank, operated at high frequency, is amplitude modulated as
a function of input voltage and output current. A small amount
of capacitance embedded in the input and output stages of the
module is sufficient for full functionality and is key to achieving
power density.
The BCM48Bx080y240A00 SAC can be simplified into the
preceeding model.
At no load:
VOUT = VIN • K (1)
K represents the “turns ratio” of the SAC.
Rearranging Eq (1):
K = VOUT (2)
VIN
In the presence of load, VOUT is represented by:
VOUT = VIN • K – IOUT • ROUT (3)
and IOUT is represented by:
IOUT = IIN – IQ (4)
K
ROUT represents the impedance of the SAC, and is a function of the
RDSON of the input and output MOSFETs and the winding resistance
of the power transformer. IQ represents the quiescent current of
the SAC control, gate drive circuitry, and core losses.
The use of DC voltage transformation provides additional
interesting attributes. Assuming that ROUT = 0Ω and IQ = 0A, Eq. (3)
now becomes Eq. (1) and is essentially load independent, resistor R
is now placed in series with VIN.
The relationship between VIN and VOUT becomes:
VOUT = (VIN – IIN • R) • K (5)
Substituting the simplified version of Eq. (4)
(IQ is assumed = 0A) into Eq. (5) yields:
VOUT = VIN • K – IOUT • R • K2 (6)
R
SAC
K = 1/32
Vin
Vout
+
–
Vin Vout
R
SAC™
K = 1/6
Figure 17 — K = 1/6 Sine Amplitude Converter
with series input resistor
Figure 16 — VI Chip® module AC model
+
–
+
–
VOUT
COUT
VIN
V•I
K
+
–
+
–
CIN
IOUT
RCOUT
IQ
ROUT
RCIN
88mA
1/6 • Iout 1/6 • Vin
Rcin
0.57mΩ
470pH
0.5ΩRcout
400µΩ
Lout = 600pH
2µF IQ
Lin = 5.7nH Iout
Rout
Vin Vout
Cout
CIN
7.4mΩ
45µF
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BCM48Bx080y240A00
This is similar in form to Eq. (3), where ROUT is used to represent
the characteristic impedance of the SAC™. However, in this case a
real R on the input side of the SAC is effectively scaled by K2 with
respect to the output.
Assuming that R = 1Ω, the effective R as seen from the secondary
side is 28mΩ, with K = 1/6.
A similar exercise should be performed with the additon of a
capacitor or shunt impedance at the input to the SAC. A switch in
series with VIN is added to the circuit. This is depicted in Figure 18.
A change in VIN with the switch closed would result in a change in
capacitor current according to the following equation:
IC(t) = C dVIN (7)
dt
Assume that with the capacitor charged to VIN, the switch is
opened and the capacitor is discharged through the idealized SAC.
In this case,
IC = IOUT • K (8)
substituting Eq. (1) and (8) into Eq. (7) reveals:
IOUT = C
• dVOUT (9)
K2 dt
The equation in terms of the output has yielded a K2 scaling factor
for C, specified in the denominator of the equation.
A K factor less than unity results in an effectively larger capacitance
on the output when expressed in terms of the input. With a
K = 1/6 as shown in Figure 18, C = 1µF would appear as C = 36µF
when viewed from the output.
Low impedance is a key requirement for powering a high-
current, low-voltage load efficiently. A switching regulation stage
should have minimal impedance while simultaneously providing
appropriate filtering for any switched current. The use of a SAC
between the regulation stage and the point of load provides a
dual benefit of scaling down series impedance leading back to
the source and scaling up shunt capacitance or energy storage
as a function of its K factor squared. However, the benefits are
not useful if the series impedance of the SAC is too high. The
impedance of the SAC must be low, i.e. well beyond the crossover
frequency of the system.
A solution for keeping the impedance of the SAC low involves
switching at a high frequency. This enables small magnetic
components because magnetizing currents remain low. Small
magnetics mean small path lengths for turns. Use of low loss core
material at high frequencies also reduces core losses.
The two main terms of power loss in the BCM module are:
n No load power dissipation (PNL): defined as the power
used to power up the module with an enabled powertrain
at no load.
n Resistive loss (PROUT): refers to the power loss across
the BCM module modeled as pure resistive impedance.
PDISSIPATED = PNL + PROUT (10)
Therefore,
POUT = PIN – PDISSIPATED = PIN – PNL – PROUT (11)
The above relations can be combined to calculate the overall
module efficiency:
h = POUT = PIN – PNL – PROUT (12)
PIN PIN
= VIN • IIN – PNL – (IOUT)2 • ROUT
VIN • IIN
= 1 – (PNL + (IOUT)2 • ROUT)
VIN • IIN
C
S
SAC
K = 1/32
Vin
Vout
+
–
Figure 18 — Sine Amplitude Converter™ with input capacitor
C
SAC™
K = 1/6
S
Vin
Vout
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BCM48Bx080y240A00
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’s dynamic
response, the impedance presented to its input terminals
must be low from DC to approximately 5MHz. The
connection of the bus converter module to its power
source should be implemented with minimal distribution
inductance. If the interconnect inductance exceeds
100nH, the input should be bypassed with a RC damper
to retain low source impedance and stable operation.
With an interconnect inductance of 200nH, the RC damper
may be as high as 1µF in series with 0.3Ω. A single
electrolytic or equivalent low-Q capacitor may be used in
place of the series RC bypass.
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 14 and 15.
3. Protect the module from overvoltage transients imposed
by the system that would exceed maximum ratings and
cause failures:
The 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.
Total load capacitance at the output of the BCM 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 <500kHz 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. 13.
COUT = CIN (13)
K2
This enables a reduction in the size and number of capacitors used
in a typical system.
Thermal Considerations
VI Chip® products are multi-chip modules whose temperature
distribution varies greatly for each part number as well as with the
input / output conditions, thermal management and environmental
conditions. Maintaining the top of the BCM48Bx080y240A00 case
to less than 100ºC will keep all junctions within the VI Chip module
below 125ºC for most applications.
The percent of total heat dissipated through the top surface
versus through the J-lead is entirely dependent on the particular
mechanical and thermal environment. The heat dissipated through
the top surface is typically 60%. The heat dissipated through the
J-lead onto the PCB surface is typically 40%. Use 100% top surface
dissipation when designing for a conservative cooling solution.
It is not recommended to use a VI Chip module for an extended
period of time at full load without proper heat sinking.
BCM® Bus Converter Rev 1.4 vicorpower.com
Page 16 of 20 08/2016 800 927.9474
BCM48Bx080y240A00
BCM®1
R0_1
ZIN_EQ1 ZOUT_EQ1
ZOUT_EQ2
VOUT
ZOUT_EQn
ZIN_EQ2
ZIN_EQn
R0_2
R0_n
BCM®2
BCM®n
Load
DC
VIN
+
Figure 19 — BCM module array
Current Sharing
The performance of the SAC™ topology is based 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 a positive
temperature coefficient series resistance.
This type of characteristic is close to the impedance characteristic
of a DC power distribution system both in dynamic (AC) behavior
and for steady state (DC) operation.
When multiple BCM modules of a given part number are
connected in an array they will inherently share the load current
according to the equivalent impedance divider that the system
implements from the power source to the point of load.
Some general recommendations to achieve matched array
impedances include:
n Dedicate common copper planes within the PCB
to deliver and return the current to the modules.
n Provide as symmetric a PCB layout as possible among modules
n Apply same input / output filters (if present) to each unit.
For further details see AN:016 Using BCM Bus Converters
in High Power Arrays.
Fuse Selection
In order to provide flexibility in configuring power systems
VI Chip® modules are not internally fused. Input line fusing
of VI Chip products is recommended at system level to provide
thermal protection in case of catastrophic failure.
The fuse shall be selected by closely matching system
requirements with the following characteristics:
n Current rating (usually greater than maximum current
of BCM module)
n Maximum voltage rating (usually greater than the maximum
possible input voltage)
n Ambient temperature
n Nominal melting I2t
n Recommend fuse: ≤ 10A Littlefuse Nano2 Fuse.
Reverse Operation
BCM modules are capable of reverse power operation. Once the
unit is started, energy will be transferred from secondary back to
the primary whenever the secondary voltage exceeds VIN • K. The
module will continue operation in this fashion for as long as no
faults occur.
The BCM48Bx080y240A00 has not been qualified for continuous
operation in a reverse power condition. Furthermore fault
protections which help protect the module in forward operation
will not fully protect the module in reverse operation.
Transient operation in reverse is expected in cases where there is
significant energy storage on the output and transient voltages
appear on the input. Transient reverse power operation of less than
10ms, 10% duty cycle is permitted and has been qualified to cover
these cases.
BCM® Bus Converter Rev 1.4 vicorpower.com
Page 17 of 20 08/2016 800 927.9474
BCM48Bx080y240A00
inch
mm
NOTES:
1. DIMENSIONS ARE .
2. UNLESS OTHERWISE SPECIFIED, TOLERANCES ARE:
.X / [.XX] = +/-0.25 / [.01]; .XX / [.XXX] = +/-0.13 / [.005]
3. PRODUCT MARKING ON TOP SURFACE
DXF and PDF files are available on vicorpower.com
inch
mm
NOTES:
1. DIMENSIONS ARE .
2. UNLESS OTHERWISE SPECIFIED, TOLERANCES ARE:
.X / [.XX] = +/-0.25 / [.01]; .XX / [.XXX] = +/-0.13 / [.005]
3. PRODUCT MARKING ON TOP SURFACE
DXF and PDF files are available on vicorpower.com
inch
mm
NOTES:
1. DIMENSIONS ARE .
2. UNLESS OTHERWISE SPECIFIED, TOLERANCES ARE:
.X / [.XX] = +/-0.25 / [.01]; .XX / [.XXX] = +/-0.13 / [.005]
3. PRODUCT MARKING ON TOP SURFACE
DXF and PDF files are available on vicorpower.com
inch
mm
NOTES:
1. DIMENSIONS ARE .
2. UNLESS OTHERWISE SPECIFIED, TOLERANCES ARE:
.X / [.XX] = +/-0.25 / [.01]; .XX / [.XXX] = +/-0.13 / [.005]
3. PRODUCT MARKING ON TOP SURFACE
DXF and PDF files are available on vicorpower.com
J-Lead Package Recommended Land Pattern
mm
(inch)
J-Lead Package Mechanical Drawing
BCM® Bus Converter Rev 1.4 vicorpower.com
Page 18 of 20 08/2016 800 927.9474
BCM48Bx080y240A00
TOP VIEW ( COMPONENT SIDE )
BOTTOM VIEW
NOTES:
1. DIMENSIONS ARE
2. UNLESS OTHERWISE SPECIFIED TOLERANCES ARE:
X.X [X.XX] = ±0.25 [0.01]; X.XX [X.XXX] = ±0.13 [0.005]
3. RoHS COMPLIANT PER CST-0001 LATEST REVISION
DXF and PDF files are available on vicorpower.com
inch
(mm).
NOTES:
1. DIMENSIONS ARE
2. UNLESS OTHERWISE SPECIFIED TOLERANCES ARE:
X.X [X.XX] = ±0.25 [0.01]; X.XX [X.XXX] = ±0.13 [0.005]
3. RoHS COMPLIANT PER CST-0001 LATEST REVISION
DXF and PDF files are available on vicorpower.com
inch
(mm).
RECOMMENDED HOLE PATTERN
( COMPONENT SIDE SHOWN )
TOP VIEW ( COMPONENT SIDE )
BOTTOM VIEW
NOTES:
1. DIMENSIONS ARE
2. UNLESS OTHERWISE SPECIFIED TOLERANCES ARE:
X.X [X.XX] = ±0.25 [0.01]; X.XX [X.XXX] = ±0.13 [0.005]
3. RoHS COMPLIANT PER CST-0001 LATEST REVISION
DXF and PDF files are available on vicorpower.com
inch
(mm).
NOTES:
1. DIMENSIONS ARE
2. UNLESS OTHERWISE SPECIFIED TOLERANCES ARE:
X.X [X.XX] = ±0.25 [0.01]; X.XX [X.XXX] = ±0.13 [0.005]
3. RoHS COMPLIANT PER CST-0001 LATEST REVISION
DXF and PDF files are available on vicorpower.com
inch
(mm).
RECOMMENDED HOLE PATTERN
( COMPONENT SIDE SHOWN )
Through Hole Package Recommended Land Pattern
mm
(inch)
Through Hole Package Mechanical Drawing
BCM® Bus Converter Rev 1.4 vicorpower.com
Page 19 of 20 08/2016 800 927.9474
BCM48Bx080y240A00
Notes:
1. Maintain 3.50 (0.138) Dia. keep-out zone
free of copper, all PCB layers.
2. (A) Minimum recommended pitch is 39.50 (1.555).
This provides 7.00 (0.275) component
edge-to-edge spacing, and 0.50 (0.020)
clearance between Vicor heat sinks.
(B) Minimum recommended pitch is 41.00 (1.614).
This provides 8.50 (0.334) component
edge-to-edge spacing, and 2.00 (0.079)
clearance between Vicor heat sinks.
3. VI 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 full-size VI Chip® products.
4. RoHS compliant per CST–0001 latest revision.
(NO GROUNDING CLIPS) (WITH GROUNDING CLIPS)
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.
Recommended Heat Sink Push Pin Location
BCM® Bus Converter Rev 1.4 vicorpower.com
Page 20 of 20 08/2016 800 927.9474
BCM48Bx080y240A00
Vicor’s comprehensive line of power solutions includes high density AC-DC and DC-DC modules and ac-
cessory 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
changes to any products, specifications, and product descriptions at any time without notice. Information published by Vicor has been checked and
is believed to be accurate at the time it was printed; however, Vicor assumes no responsibility for inaccuracies. Testing and other quality controls
are used to the extent Vicor deems necessary to support Vicor’s product warranty. Except where mandated by government requirements, testing of
all parameters of each product is not necessarily performed.
Specifications are subject to change without notice.
Vicor’s Standard Terms and Conditions
All sales are subject to Vicor’s Standard Terms and Conditions of Sale, which are available on Vicor’s webpage or upon request.
Product Warranty
In Vicor’s standard terms and conditions of sale, Vicor warrants that its products are free from non-conformity to its Standard Specifications (the
“Express Limited Warranty”). This warranty is extended only to the original Buyer for the period expiring two (2) years after the date of shipment
and is not transferable.
UNLESS OTHERWISE EXPRESSLY STATED IN A WRITTEN SALES AGREEMENT SIGNED BY A DULY AUTHORIZED VICOR SIGNATORY, VICOR DIS-
CLAIMS ALL REPRESENTATIONS, LIABILITIES, AND WARRANTIES OF ANY KIND (WHETHER ARISING BY IMPLICATION OR BY OPERATION OF LAW)
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ing safeguards.
Vicor will repair or replace defective products in accordance with its own best judgment. For service under this warranty, the buyer must contact
Vicor to obtain a Return Material Authorization (RMA) number and shipping instructions. Products returned without prior authorization will be
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Life Support Policy
VICOR’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS WITHOUT THE EXPRESS
PRIOR WRITTEN APPROVAL OF THE CHIEF EXECUTIVE OFFICER AND GENERAL COUNSEL OF VICOR CORPORATION. As used herein, life support
devices or systems are devices which (a) are intended for surgical implant into the body, or (b) support or sustain life and whose failure to perform
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
user. A critical component is any component in a life support device or system whose failure to perform can be reasonably expected to cause the
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and components in life support applications assumes all risks of such use and indemnifies Vicor against all liability and damages.
Intellectual Property Notice
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
granted by this document. Interested parties should contact Vicor’s Intellectual Property Department.
The products described on this data sheet are protected by the following U.S. Patents Numbers:
5,945,130; 6,403,009; 6,710,257; 6,911,848; 6,930,893; 6,934,166; 6,940,013; 6,969,909; 7,038,917; 7,145,186; 7,166,898; 7,187,263;
7,202,646; 7,361,844; D496,906; D505,114; D506,438; D509,472; and for use under 6,975,098 and 6,984,965.
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