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BCM® Bus Converter
BCM48Bx120y120B00
®
C
S
US
C
NRTL
US
Isolated Fixed-Ratio DC-DC Converter
Features & Benefits
Product Ratings
• 48VDC – 12VDC 120W Bus Converter
• High efficiency (>95%) reduces system power consumption
• High power density (801W/in ) reduces power system
footprint by >50%
3
VIN = 48V (38 – 55V)
POUT = up to 120W
VOUT = 12V (9.5 – 13.75V)
(no load)
K = 1/4
Description
• “Half Chip” VI Chip® package enables surface mount,
low impedance interconnect to system board
The VI Chip® Bus Converter is a high efficiency (>95%) Sine
Amplitude ConverterTM (SACTM) operating from a 38 to 55VDC
primary bus to deliver an isolated ratiometric output voltage from
9.5 to 13.75VDC. 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 12V regulator
can be located at the input to the SAC. Since the K factor of
the BCM48Bx120y120B00 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.
• Contains built-in protection features against:
Undervoltage
Overvoltage
Overcurrent
Short Circuit
Overtemperature
• Provides enable/disable control, internal temperature
monitoring
The BCM48BH120y120B00 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-toboard thermal resistance. With high conversion efficiency the
BCM48Bx120y120B00 increases overall system efficiency and
lowers operating costs compared to conventional approaches.
• 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
Part Numbering
• Automated Test Equipment
Product Number
Status
BCM48BH120T120B00
Active
• Telecom Base Stations
• High Density Power Supplies
BCM48BH120M120B00 End of Life
• Communication Systems
Package Style
Product Grade
T = -40 to 125°C
H = J-Lead
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
3.15A
C1
POL
BCM®
+IN
+OUT
-IN
-OUT
POL
VOUT
10µF
POL
Note: Product images may not highlight current product markings.
BCM® Bus Converter
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BCM48Bx120y120B00
Pin Configuration
4
3
2
1
A
+OUT
+IN
B
C
D
E
F
G
H
J
-OUT
K
L
M
NC
TM
NC
PC
-IN
Bottom View
Pin Descriptions
Pin Number
Signal Name
Type
Function
A1-B1, A2-B2
+IN
INPUT POWER
Positive input power terminal
L1-M1, L2-M2
–IN
INPUT POWER
RETURN
Negative input power terminal
E1
NC
NC
F2
TM
OUTPUT
G1
NC
NC
H2
PC
OUTPUT/INPUT
A3-D3, A4-D4
+OUT
OUTPUT POWER
Positive output power terminal
J3-M3, J4-M4
–OUT
OUTPUT POWER
RETURN
Negative output power terminal
No connect
Temperature monitor, input side referenced signal
No connect
Enable and disable control, input side referenced signal
Control Pin Specifications
See Using the Control Signals PC, TM for more information.
PC (BCM Primary Control)
TM (BCM Temperature Monitor)
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 60kΩ 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 5V (operating).
The TM pin monitors the internal temperature of the BCM module
within an accuracy of ±5°C. It has a room temperature setpoint of
~3.0V and an approximate gain of 10mV/°C. It can source up to
100µA and may also be used as a “Power Good” flag to verify that
the BCM module is operating.
BCM® Bus Converter
Page 2 of 20
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BCM48Bx120y120B00
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
-1
60
V
-1
1
V/µs
2250
V
-1
16
V
-3
14.2
A
-2
10
A
PC to –IN
-0.3
20
V
TM to –IN
-0.3
7
V
+IN to –IN
VIN slew rate
Operational
Isolation voltage, input to ouput
+OUT to –OUT
Output current transient
≤ 10ms, ≤ 10% DC
Output current average
BCM® Bus Converter
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Rev 1.4
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BCM48Bx120y120B00
Electrical Specifications
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 = 25ºC unless otherwise noted.
Attribute
Symbol
Conditions / Notes
Min
Typ
Max
Unit
38
48
55
V
1
V/µs
mW
Powertrain
Voltage range
dV / dt
VIN_DC
dVIN / dt
Quiescent power
PQ
No load power dissipation
PNL
PC connected to –IN
68
150
VIN = 48V
2.1
4.1
5
VIN = 38V to 55V
Inrush current peak
IINR_P
VIN = 48V, COUT = 500μF,
IOUT = 10.55A
DC input current
IIN_DC
At POUT = 240W
Transformation ratio
K
Output power (average)
POUT_AVG
Output power (peak)
POUT_PK
Output voltage
Output current (average)
3.5
A
1/4
V/V
VIN = 38 - 55VDC
97
VIN = 46 - 55VDC
120
VIN = 46 - 55VDC , 10ms max, POUT_AVG ≤ 120W
8.5
POUT_AVG ≤ 120W
W
14
V
10
A
92.0
hHOT
VIN = 48V, POUT = 120W; TJ = 100°C
92.6
h20%
24W < POUT < POUT Max
72.0
ROUT_COLD
POUT = 120W, TCASE = -40°C
20.0
28.7
40.0
ROUT_AMB
POUT = 120W, TCASE = 25°C
25.0
38.8
50.0
ROUT_HOT
POUT = 120W, TCASE = 100°C
30.0
47.3
60.0
Efficiency (over load range)
Load capacitance
COUT
Switching frequency
FSW
Output voltage ripple
VOUT_PP
TON1
W
150
VIN = 38V to 55V, POUT = 100W
Efficiency (hot)
BCM® Bus Converter
Page 4 of 20
A
93.5
hAMB
VIN to VOUT (application of VIN)
12
VIN = 48V, POUT = 120W
Efficiency (ambient)
Output resistance
K = VOUT / VIN, at no load
VOUT
IOUT_AVG
5.5
W
94.6
%
93.5
%
%
mΩ
500
µF
1.5
1.6
MHz
COUT = 0µF, IOUT = 10.55A, VIN = 48V,
200
400
mV
VIN = 48V, CPC = 0
570
800
ms
1.4
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BCM48Bx120y120B00
Electrical Specifications (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 = 25ºC unless otherwise noted.
Attribute
Symbol
Conditions / Notes
Min
Typ
Max
Unit
Protection
Input overvoltage lockout threshold
VIN_OVLO+
55.5
58.1
60
V
Input overvoltage recovery threshold
VIN_OVLO-
55.1
58.7
60
V
Input undervoltage recovery
threshold
VIN_UVLO+
30.7
32.9
37.3
V
Input undervoltage lockout
threshold
VIN_UVLO-
29.1
31.5
35.4
V
12
17
24
A
40
A
Output overcurrent trip threshold
IOCP
VIN = 48V, 25ºC
Short circuit protection trip threshold
Short circuit protection response
time
Thermal shutdown threshold
ISCP
24
TSCP
0.8
1.0
1.2
µs
TJ_OTP
125
130
135
°C
POUT (W)
120
97
38
48
VIN (VDC)
Figure 1 — POUT derating vs VIN
BCM® Bus Converter
Page 5 of 20
Rev 1.4
03/2022
55
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BCM48Bx120y120B00
Electrical Specifications (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 = 25ºC unless otherwise noted.
Attribute
Symbol
Conditions / Notes
Min
Typ
Max
Unit
VPC
4.7
5.0
5.3
V
PC voltage (enable)
VPC_EN
2.0
2.5
3.0
V
PC voltage (disable)
VPC_DIS
1.95
V
PC source current (start up)
IPC_EN
300
µA
PC source current (operating)
IPC_OP
2
mA
400
kΩ
588
pF
1000
pF
PC
PC voltage (operating)
PC internal resistance
RPC_SNK
PC capacitance (internal)
CPC_INT
PC capacitance (external)
CPC_EXT
External PC resistance
RPC
PC external toggle rate
RPC_TOG
PC to VOUT with PC released
PC to VOUT, disable PC
50
Internal pull down resistor
50
100
150
External capacitance delays PC enable time
60
Connected to –VIN
kΩ
1
Hz
TON2
VIN = 48V, pre-applied
60
100
µs
TPC_DIS
VIN = 48V, pre-applied
4
10
µs
+5
ºC
TM
TM accuracy
TM gain
ATM
TM source current
ITM
TM internal resistance
External TM capacitance
TM voltage ripple
BCM® Bus Converter
Page 6 of 20
-5
ACTM
10
25
RTM_SNK
40
CTM
VTM_PP
CTM = 0µF, VIN = 55V, POUT = 120W
Rev 1.4
03/2022
75
180
mV / ºC
100
µA
50
kΩ
50
pF
250
mV
BCM® Bus Converter
Page 7 of 20
NL
5V
2.5 V
5V
3V
PC
VUVLO+
VUVLO–
Rev 1.4
03/2022
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
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BCM48Bx120y120B00
Timing Diagram
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BCM48Bx120y120B00
Application Characteristics
All specifications are at TJ = 25ºC unless otherwise noted. See associated figures for general trend data
Attribute
Symbol
Conditions / Notes
Typ
Unit
1.75
W
No load power
PNL
VIN = 48V, PC enabled
Inrush current peak
INR_P
COUT = 500µF, POUT = 120W
6
A
95
%
Efficiency (ambient)
h
VIN = 48V, POUT = 120W, COUT = 500µF
Efficiency (hot – 100ºC)
h
VIN = 48V, POUT = 120W, COUT = 500µF
94
%
Output resistance (-40ºC)
ROUT_C
VIN = 48V
35
mΩ
Output resistance (25ºC)
ROUT_R
VIN = 48V
44
mΩ
Output resistance (100ºC)
ROUT_H
VIN = 48V
56
mΩ
Output voltage ripple
VOUT_PP
COUT = 0µF, POUT = 120W @ VIN = 48V, VIN = 48V
160
mV
VOUT transient voltage (positive)
VOUT_TRAN+
IOUT_STEP = 0 – 10.55A, ISLEW > 10A/µs
1.4
V
VOUT transient voltage (negative)
VOUT_TRAN-
IOUT_STEP = 10.55 – 0A, ISLEW > 10A/µs
1.3
V
2.4
µs
4.4
ms
2.4
µs
Undervoltage lockout response time
TUVLO
Output overcurrent response time
TOCP
Overvoltage lockout response time
TOVLO
BCM® Bus Converter
Page 8 of 20
12 < IOCP < 25A
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BCM48Bx120y120B00
Application Characteristics
3
96
2.5
95
Efficiency (%)
Power Dissipation (W)
The following values, typical of an application environment, are collected at TCASE = 25ºC unless otherwise noted. See associated figures for general trend data.
2
1.5
94
93
92
1
38
40
42
44
46
47
49
51
53
91
-40
55
-40ºC
25ºC
VIN:
100ºC
16
94
14
Power Dissipation (W)
Efficiency (%)
96
92
90
88
86
84
82
0
2
4
6
8
38V
48V
10
0
2
55V
4
Power Dissipation (W)
Efficiency (%)
8
10
12
48V
55V
Figure 5 — Power dissipation at TCASE = -40°C
88
86
84
82
6
8
10
12
10
8
6
4
2
0
12
0
2
4
Output Load (A)
BCM® Bus Converter
Page 9 of 20
6
38V
VIN:
90
Figure 6 — Efficiency at TCASE = 25°C
55V
Output Load (A)
92
38V
48V
2
14
VIN:
38V
4
16
4
100
6
94
2
80
8
96
0
60
10
0
12
Figure 4 — Efficiency at TCASE = -40°C
80
40
12
Output Load (A)
VIN:
20
Figure 3 — Full load efficiency vs. temperature; Vin
Figure 2 — No load power dissipation vs. Vin
80
0
Case Temperature (C)
Input Voltage (V)
TCASE:
-20
48V
6
8
10
Output Load (A)
55V
VIN:
38V
48V
Figure 7 — Power dissipation at TCASE = 25°C
Rev 1.4
03/2022
55V
12
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BCM48Bx120y120B00
96
16
94
14
Power Dissipation (W)
Efficiency (%)
Application Characteristics (Cont.)
92
90
88
86
84
82
80
0
2
4
6
8
10
12
10
8
6
4
2
0
12
0
2
4
Output Load (A)
38V
VIN:
48V
55V
8
10
12
48V
55V
Figure 9 — Power dissipation at TCASE = 100°C
200
60
Ripple (mV pk-pk)
55
50
ROUT (mΩ)
38V
VIN:
Figure 8 — Efficiency at TCASE = 100°C
45
40
35
30
175
150
125
100
75
25
20
-40
6
Output Load (A)
50
-20
0
20
40
60
80
100
IOUT:
0
1
2
3
4
5
6
7
8
9
10
Load Current (A)
Temperature (°C)
10A
VIN:
48V
Figure 10 — ROUT vs. temperature; nominal input
Figure 11 — Vripple vs. Iout: No external Cout, board mounted
module, scope setting : 20MHz analog BW
Figure 12 — PC to VOUT start up wave form
Figure 13 — VIN to VOUT start up wave form
BCM® Bus Converter
Rev 1.4
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BCM48Bx120y120B00
Application Characteristics (Cont.)
Figure 14 — Output voltage and input current ripple;
VIN = 48V, 120W, no COUT
Figure 15 — 0A – 11.3A transient response: Cin = 330µF,
Iin measured prior to Cin , no external Cout
Figure 16 — 11.3A – 0A transient response: Cin = 330µF,
Iin measured prior to Cin , no external Cout
Figure 17 — PC disable wave form; VIN = 48V, COUT = 500µF,
full load
BCM® Bus Converter
Rev 1.4
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BCM48Bx120y120B00
General Characteristics
All specifications are at TJ = 25ºC unless otherwise noted. See associated figures for general trend data.
Attribute
Symbol
Conditions / Notes
Min
Typ
Max
Unit
Mechanical
Length
L
21.7 / [0.854]
22.0 / [0.866] 22.3 / [0.878]
mm / [in]
Width
W
16.37 / [0.644] 16.50 / [0.650] 16.63 / [0.655] mm / [in]
Height
H
6.48 / [0.255]
Volume
Vol
Footprint
6.73 / [0.265] 6.98 / [0.275]
mm / [in]
No heat sink
2.44 / [0.150]
cm3/ [in3]
F
No heat sink
3.6 / [0.56]
cm3/ [in3]
Power density
PD
No heat sink
801
W/in3
49
W/cm3
Weight
W
8 / [0.28]
g / [oz]
Nickel
Lead Finish
0.51
2.03
Palladium
0.02
0.15
Gold
0.003
0.051
µm
Thermal
Operating temperature
TJ
-40
125
°C
Storage temperature
TST
-40
125
°C
Thermal impedance
øJC
2.7
°C/W
Junction to case
Thermal capacity
5
Ws/°C
Assembly
Peak compressive force
applied to case (Z-axis)
Supported by J-lead only
2.5
ESDHBM
Human Body Model,
JEDEC JESD 22-A114C.01
1500
ESDMM
Machine Model,
JEDEC JESD 22-A115-A
400
ESD Withstand
3.0
lbs
VDC
Soldering
Peak temperature during reflow
MSL 4 (Datecode 1528 and later)
245
Peak time above 217°C
°C
150
s
Peak heating rate during reflow
1.5
3
°C/s
Peak cooling rate post reflow
1.5
6
°C/s
60
VDC
Safety
Working voltage (IN – OUT)
VIN_OUT
Isolation voltage (hipot)
VHIPOT
Isolation capacitance
CIN_OUT
Isolation resistance
RIN_OUT
MTBF
2250
Unpowered unit
1350
VDC
1750
10
MIL-HDBK-217Plus Parts Count - 25°C
Ground Benign
7.1
cTÜVus
UKCA, electrical equipment (safety) regulations
CE Marked for Low Voltage Directive and RoHS Recast Directive, as applicable
BCM® Bus Converter
Rev 1.4
Page 12 of 20 03/2022
pF
MΩ
cURus
Agency approvals / standards
2150
MHrs
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Using the Control Signals PC, TM
Primary Control (PC) pin can be used to accomplish the
following functions:
n Delayed start: At start up, PC pin will source a constant
100µA current to the internal RC network. Adding an external
capacitor will allow further delay in reaching the 2.5V threshold
for module start.
n Synchronized start up: In an array of parallel modules, PC
pins should be connected to synchronize start up across
units. While every controller has a calibrated 2.5V reference
on PC comparator, many factors might cause different timing in
turning on the 100µA 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.
n Auxiliary voltage source: Once enabled in regular
operational conditions (no fault), each BCM module
PC provides a regulated 5V, 2mA voltage source.
n Output disable: PC pin can be actively pulled down in order
to disable the module. Pull down impedance shall be lower
than 1kΩ and toggle rate lower than 1Hz.
n Fault detection flag: The PC 5V 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.
n Note that PC doesn’t have current sink capability (only 150kΩ
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.
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). 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.
n 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.
BCM® Bus Converter
Rev 1.4
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BCM48Bx120y120B00
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BCM48Bx120y120B00
Sine Amplitude Converter™ Point of Load Conversion
IIN
IOUT
ROUT
+
+
V•I
K • IOUT
VIN
+
+
IQ
–
K • VIN
VOUT
–
K
–
–
Figure 18 — VI Chip® module DC model
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 BCM48Bx120y120B00 SAC can be simplified into the
preceeding model.
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.
At no load:
RRIN
VOUT = VIN • K
(1)
Vin
VIN
+
–
SAC™
SAC™
K = 1/4
K = 1/32
VV
out
OUT
K represents the “turns ratio” of the SAC.
Rearranging Eq (1):
VOUT (2)
K =
VIN
Figure 19 — K = 1/4 Sine Amplitude Converter
with series input resistor
The relationship between VIN and VOUT becomes:
In the presence of load, VOUT is represented by:
VOUT = VIN • K – IOUT • ROUT (3)
VOUT = (VIN – IIN • R) • K
(5)
and IOUT is represented by:
Substituting the simplified version of Eq. (4)
(IQ is assumed = 0A) into Eq. (5) yields:
VOUT = VIN • K – IOUT • R • K2 (6)
IIN – IQ (4)
IOUT =
K
BCM® Bus Converter
Rev 1.4
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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 K 2 with
respect to the output.
Assuming that R = 1Ω, the effective R as seen from the secondary
side is 62.5mΩ, with K = 1/4.
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 20.
SAC™
IN
+
–
CC
SAC™
K = 1/4
K = 1/32
Vout
V
Low impedance is a key requirement for powering a highcurrent, 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.
S
VVin
BCM48Bx120y120B00
OUT
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.
Figure 20 — Sine Amplitude Converter™ with input capacitor
A change in VIN with the switch closed would result in a change in
capacitor current according to the following equation:
n Resistive loss (PR
): refers to the power loss across
OUT
the BCM module modeled as pure resistive impedance.
PDISSIPATED = PNL + PR (10)
OUT
Therefore,
IC(t) = C
dVIN
dt
(7)
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
K2 dt
POUT = PIN – PDISSIPATED = PIN – PNL – PR (11)
OUT
The above relations can be combined to calculate the overall
module efficiency:
POUT PIN – PNL – PROUT
h =
=
P
P
IN
IN
= VIN • IIN – PNL – (IOUT)2 • ROUT
VIN • IIN
(9)
=
1
The equation in terms of the output has yielded a K 2 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 = 1/4 as shown in Figure 20, C = 1µF would appear as C = 16µF
when viewed from the output.
BCM® Bus Converter
Rev 1.4
Page 15 of 20 03/2022
–
(PNL + (IOUT)2 • ROUT)
VIN • IIN
(12)
Select Devices are End of Life
Refer to page 1
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 47µF 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:
BCM48Bx120y120B00
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
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