BCM® Bus Converter
BCM352x440y330A00
S
®
US
C
C
NRTL
US
Isolated Fixed Ratio DC-DC Converter
Features & Benefits
Product Ratings
• 352VDC – 44VDC 325W Bus Converter
• High efficiency (>95%) reduces
system power consumption
• High power density (1000W/in3) reduces
power system footprint by >40%
POUT = up to 325W
VOUT = 44V (41.25 – 45.63V)
(no load)
K = 1/8
Description
• “Full Chip” VI Chip® package enables surface mount,
low impedance interconnect to system board
•
VIN = 352V (330 – 365V)
Contains built-in protection features against:
n Undervoltage
n Overvoltage
n Overcurrent
n Short Circuit
n Overtemperature
• Provides enable/disable control,
internal temperature monitoring
• ZVS/ZCS Resonant Sine Amplitude Converter topology
• Can be paralleled to create multi-kW arrays
Typical Application
• High End Computing Systems
The VI Chip® Bus Converter is a high efficiency (>95%) Sine
Amplitude ConverterTM (SACTM) operating from a 330 to 365VDC
primary bus to deliver an isolated ratiometric output voltage from
41.25 to 45.63VDC. 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 regulator
can be located at the input to the SAC. Since the K factor of
the BCM352x440y330A00 is 1/8, that capacitance value can be
reduced by a factor of 64x, resulting in savings of board area,
materials and total system cost.
The BCM352F440y330A00 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
BCM352x440y330A00 increases overall system efficiency and
lowers operating costs compared to conventional approaches.
Part Numbering
• Automated Test Equipment
• Telecom Base Stations
Product Number
Package Style (x)
Product Grade (y)
BCM352x440y330A00
F = J-Lead
T = -40° to 125°C
For Storage and Operating Temperatures see Section 6.0 General Characteristics
Typical Application
Bus Converter
Regulator
PR
enable / disable
switch
PC
TM
SW1
F1
PC
TM
IL
BCM®
+IN
+OUT
-IN
-OUT
F2
Current Multiplier
VC
SG
OS
CD
VC
PC
TM
PRM™
VTM™
+IN
+OUT
+IN
+OUT
-IN
-OUT
-IN
-OUT
VIN
BCM® Bus Converter
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L
O
A
D
BCM352x440y330A00
Pin Configuration
4
3
2
1
A
A
+OUT
B
B
C
C
D
D
E
E
-OUT
F
G
H
H
J
J
+OUT
-OUT
+IN
K
K
L
L
M
M
N
N
P
P
R
R
TM
RSV
PC
-IN
T
T
Bottom View
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
J1, J2
RSV
NC
K1, K2
PC
OUTPUT/INPUT
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
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 50kΩ 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
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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
+IN to –IN
-1.0
Max
Unit
400
V
+IN/-IN TO +OUT/-OUT (hipot)
4242
V
+IN/-IN TO +OUT/-OUT (working)
500
V
-1
60
V
PC to –IN
-0.3
20
V
TM to –IN
-0.3
7
V
245
ºC
+OUT to –OUT
Temperature during reflow
MSL 4 (Datecode 1528 and later)
BCM® Bus Converter
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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
330
352
365
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
395
410
VIN = 352V
6.5
9.5
Inrush current peak
IINR_P
VIN = 365V, COUT = 100μF,
POUT = 325W
DC input current
IIN_DC
At POUT = 325W
Transformation ratio
K
Output power (average)
POUT_AVG
Output power (peak)
POUT_PK
Output voltage
VOUT
Output current (average)
IOUT_AVG
12
VIN = 330V to 365V
2
K = VOUT / VIN, at no load
4.5
A
1
A
1/8
V/V
VIN = 352VDC
325
VIN = 330 - 365VDC
305
VIN = 352VDC , 5ms max, POUT_AVG ≤ 325W
495
W
45.63
V
7.7
A
41.25
No load
POUT_AVG ≤ 325W
VIN = 352V, POUT = 325W
94.4
VIN = 330V to 365V, POUT = 325W
94.4
94.3
95.7
Efficiency (ambient)
hAMB
Efficiency (hot)
hHOT
VIN = 352V, POUT = 325W; TJ = 100°C
Efficiency (over load range)
h20%
60W < POUT < 325W
90
ROUT_COLD
TJ = -40°C
60
115
180
ROUT_AMB
TJ = 25°C
100
140
180
ROUT_HOT
TJ = 125°C
150
190
230
Output resistance
Load capacitance
COUT
Switching frequency
FSW
Ripple frequency
FSW_RP
Output voltage ripple
VOUT_PP
VIN to VOUT (application of VIN)
BCM® Bus Converter
Page 4 of 20
TON1
W
1.56
3.12
COUT = 0µF, POUT = 325W, VIN = 352V,
VIN = 352V, CPC = 0
Rev 1.8
08/2016
460
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800 927.9474
W
%
95.3
%
%
mΩ
100
µF
1.65
1.73
MHz
3.3
3.46
MHz
192
400
mV
540
620
ms
BCM352x440y330A00
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+
380
385
400
V
Input overvoltage recovery threshold
VIN_OVLO-
365
380
390
V
Input undervoltage recovery
threshold
VIN_UVLO+
285
300
325
V
Input undervoltage lockout
threshold
VIN_UVLO-
270
285
304
V
10
12
15
A
Output overcurrent trip threshold
IOCP
Short circuit protection trip threshold
ISCP
Short circuit protection response
time
TSCP
Thermal shutdown threshold
VIN = 352V, 25ºC
15
125
TJ_OTP
Output Power (W)
600
500
400
300
200
100
0
40.00
41.00
42.00
43.00
44.00
45.00
Output Voltage (V)
P (ave)
P (pk) < 5ms
Figure 1 — Safe operating area
BCM® Bus Converter
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46.00
A
130
1.2
µs
135
°C
BCM352x440y330A00
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
5.3
V
PC voltage (enable)
VPC_EN
2
2.5
3
V
PC voltage (disable)
VPC_DIS
1.95
V
PC source current (start up)
IPC_EN
50
100
300
µA
PC source current (operating)
IPC_OP
2
3.5
5
mA
50
150
400
kΩ
1000
pF
1000
pF
PC
PC voltage (operating)
PC internal resistance
RPC_SNK
PC capacitance (internal)
CPC_INT
PC capacitance (external)
CPC_EXT
50
TON2
VIN = 352V, pre-applied, CPC = 0, COUT = 0
50
TPC_DIS
VIN = 352V, pre-applied, CPC = 0, COUT = 0
RPC
PC external toggle rate
RPC_TOG
PC to VOUT, disable PC
External capacitance delays PC enable time
Connected to –VIN
External PC resistance
PC to VOUT with PC released
Internal pull down resistor
kΩ
1
Hz
100
150
µs
4
10
µs
+5
ºC
TM
TM accuracy
TM gain
ATM
TM source current
ITM
TM internal resistance
-5
ACTM
10
25
RTM_SNK
External TM capacitance
TM voltage ripple
BCM® Bus Converter
Page 6 of 20
40
CTM
VTM_PP
CTM = 0µF, VIN = 365V, POUT = 325W
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200
400
mV / ºC
100
µA
50
kΩ
50
pF
500
mV
BCM® Bus Converter
Page 7 of 20
NL
5V
2.5 V
5V
3V
PC
VUVLO+
VUVLO–
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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
BCM352x440y330A00
Timing Diagram
BCM352x440y330A00
Application Characteristics
All specifications are at TJ = 25ºC unless otherwise noted. See associated figures for general trend data
Attribute
No load power
Symbol
PNL
Conditions / Notes
VIN = 352V, PC enabled
COUT = 100µF, POUT = 325W
Typ
Unit
6.5
W
Inrush current peak
IINR_P
2
A
Efficiency (ambient)
h
VIN = 352V, POUT = 325W
95.7
%
Efficiency (hot – 100ºC)
h
VIN = 352V, POUT = 325W
95.3
%
Output resistance (-40ºC)
ROUT_C
VIN = 352V
115
mΩ
Output resistance (25ºC)
ROUT_R
VIN = 352V
140
mΩ
Output resistance (100ºC)
ROUT_H
VIN = 352V
190
mΩ
Output voltage ripple
VOUT_PP
COUT = 0µF, POUT = 325W @ VIN = 352V, VIN = 352V
192
mV
VOUT transient voltage (positive)
VOUT_TRAN+
IOUT_STEP = 0 – 7.7A, ISLEW > 10A/µs
3.2
mV
VOUT transient voltage (negative)
VOUT_TRAN-
IOUT_STEP = 7.7 – 0A, ISLEW > 10A/µs
2.8
mV
150
µs
7.5
ms
120
µs
3
V
Undervoltage lockout response time
TUVLO
Output overcurrent response time
TOCP
Overvoltage lockout response time
TOVLO
TM voltage (ambient)
BCM® Bus Converter
Page 8 of 20
VTM_AMB
Rev 1.8
08/2016
10 < IOCP < 15A
TJ @ 27ºC
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Application Characteristics
12
97
10
96.5
Efficiency (%)
No Load 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.
8
6
4
2
0
96
95.5
95
94.5
325
330
335
340
345
350
355
360
365
94
-60
370
-40
-20
-40°C
TCASE:
25°C
100°C
V IN:
100
60
80
100
120
360V
352V
8
9
8
9
365V
22
Power Dissipation (W)
95
Efficiency (%)
40
Figure 3 — Full load efficiency vs. temperature; Vin
Figure 2 — No load power dissipation vs. Vin
90
85
80
75
70
65
20
18
16
14
12
10
8
60
0
1
2
3
4
5
6
7
8
0
9
1
2
352V
3
4
330V
VIN:
365V
Figure 4 — Efficiency at TCASE = -40°C
5
6
7
Output Load (A)
Output Load (A)
330V
VIN:
352V
365V
Figure 5 — Power dissipation at TCASE = -40°C
98
17
Power Dissipation (W)
96
94
Efficiency (%)
20
0
Case Temperature (C)
Input Voltage (V)
92
90
88
86
84
82
15
13
11
9
7
5
80
0
1
2
VIN:
3
4
5
6
Output Current (A)
330V
352V
7
9
0
1
2
VIN:
365V
Figure 6 — Efficiency at TCASE = 25°C
BCM® Bus Converter
Page 9 of 20
8
3
4
5
6
Output Current (A)
330V
352V
Figure 7 — Power dissipation at TCASE = 25°C
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7
365V
BCM352x440y330A00
Application Characteristics (Cont.)
98
20
Power Dissipation (W)
96
Efficiency (%)
94
92
90
88
86
84
82
80
18
16
14
12
10
8
6
4
0
1
2
VIN:
3
4
5
6
Output Current (A)
330V
352V
7
8
0
9
1
2
3
Figure 8 — Efficiency at TCASE = 100°C
5
330V
VIN:
365V
4
6
Output Current (A)
352V
7
8
9
365V
Figure 9 — Power dissipation at TCASE = 100°C
200
250
190
Ripple (mV pk-pk)
ROUT (mΩ)
180
170
160
150
140
130
120
200
150
100
50
110
100
-60
-40
-20
0
20
40
60
80
100
120
0
0
IOUT:
0.7A
BCM® Bus Converter
Page 10 of 20
Rev 1.8
08/2016
4
VIN:
7.7A
Figure 10 — ROUT vs. temperature; nominal input
2
6
8
Load Current (A)
Case Temperature (°C)
352V
Figure 11 — Vripple vs. Iout: No external Cout, board mounted
module, scope setting : 20MHz analog BW
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Application Characteristics (Cont.)
Figure 12 — PC to VOUT start up wave form
Figure 13 — VIN to VOUT start up wave form
Figure 14 — Output voltage and input current ripple;
VIN = 352V, 325W, no COUT
Figure 15 — 0A – 7.7A transient response: Cin = 330µF,
Iin measured prior to Cin, no external Cout
Figure 14 — 7.7A – 0A transient response: Cin = 330µF,
Iin measured prior to Cin, no external Cout
Figure 15 — PC disable waveform, VIN = 352V, COUT = 100µF,
full load
BCM® Bus Converter
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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
32.4 / [1.27]
32.5 / [1.28]
32.6 / [1.29]
mm / [in]
Width
W
21.7 / [0.85]
22.0 / [0.87]
22.3 / [0.89]
mm / [in]
6.48 / [0.255]
Height
H
6.73 / [0.265] 6.98 / [0.275]
mm / [in]
Volume
Vol
No heat sink
4.81 / [0.295]
cm3/ [in3]
Footprint
F
No heat sink
7.3 / [1.1]
cm3/ [in3]
Power density
PD
No heat sink
1017
W/in3
62
W/cm3
Weight
W
14 / [0.5]
Nickel
Lead Finish
g / [oz]
0.51
2.03
Palladium
0.02
0.15
Gold
0.003
0.05
µm
Thermal
Operating temperature
TJ
-40
125
°C
Storage temperature
TST
-40
125
°C
Thermal impedance
øJC
1.5
°C/W
Min board heat sinking
1.1
Thermal capacity
9
Ws/°C
Assembly
Peak compressive force
applied to case (Z-axis)
No J-lead support
5
ESDHBM
Human Body Model,
JEDEC JESD 22-A114C.01
1500
ESDMM
Machine Model,
JEDEC JESD 22-A115-A
400
ESD Withstand
6
lbs
VDC
Soldering
Peak temperature during reflow
MSL 4 (Datecode 1528 and later)
245
Peak time above 217°C
ºC
150
s
Peak heating rate during reflow
1.5
3
°C/s
Peak cooling rate post reflow
1.5
6
°C/s
500
VDC
Safety
Working voltage (IN – OUT)
VIN_OUT
Isolation voltage (hipot)
VHIPOT
Isolation capacitance
CIN_OUT
Isolation resistance
RIN_OUT
MTBF
4242
Unpowered unit
500
VDC
660
10
MIL HDBK 217F, 25°C, GB
4.2
cURus
CE Marked for Low Voltage Directive and ROHS recast directive, as applicable.
BCM® Bus Converter
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800 927.9474
pF
MΩ
cTUVus
Agency approvals / standards
800
MHrs
BCM352x440y330A00
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 400Ω 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
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Sine Amplitude Converter™ Point of Load Conversion
IIN
IOUT
ROUT
+
+
V•I
K • IOUT
VIN
+
+
IQ
–
K
K • VIN
VOUT
–
–
–
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 BCM352x440y330A00 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:
R
VOUT = VIN • K
(1)
VVin
in
+
–
SAC™
SAC
1/8
KK==1/32
Vout
V
out
K represents the “turns ratio” of the SAC.
Rearranging Eq (1):
VOUT (2)
K =
VIN
Figure 19 — K = 1/8 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
Page 14 of 20
Rev 1.8
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BCM352x440y330A00
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 15.6mΩ, with K = 1/8.
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.
S
VVin
in
+
–
C
SAC™
SAC
K = 1/8
K = 1/32
VVout
out
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.
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
(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:
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
IOUT = C • dVOUT
K2 dt
(9)
=
1
–
(PNL + (IOUT)2 • ROUT)
VIN • IIN
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 = 1/8 as shown in Figure 20, C = 1µF would appear as C = 64µF
when viewed from the output.
BCM® Bus Converter
Page 15 of 20
Rev 1.8
08/2016
vicorpower.com
800 927.9474
(12)
BCM352x440y330A00
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:
COUT = CIN
K2
This enables a reduction in the size and number of capacitors used
in a typical system.
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 15 and 16.
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 BCM352x440y330A00 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.
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
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