VTM™ Current Multiplier
VTM48EH120 x 010 B00
S
C
NRTL
US
High Efficiency, Sine Amplitude Converter™
FEATURES
• 48 Vdc to 12 Vdc 10 A current multiplier
- Operating from standard 48 V or 24 V PRM modules
• High efficiency (>95%) reduces system power
consumption
• High density (901 W/in3)
• “Half Chip” VI Chip® package enables surface mount,
low impedance interconnect to system board
• Contains built-in protection features against:
-
Overvoltage
Overcurrent
Short Circuit
Overtemperature
• Provides enable / disable control, internal temperature
monitoring, current monitoring
• ZVS / ZCS resonant Sine Amplitude Converter topology
• Less than 50ºC temperature rise at full load
in typical applications
TYPICAL APPLICATIONS
• High End Computing Systems
• Automated Test Equipment
• High Density Power Supplies
• Communications Systems
•0
DESCRIPTION
The VI Chip current multiplier is a high efficiency (>95%)
Sine Amplitude Converter™ (SAC™) operating from a
26 to 55 Vdc primary bus to deliver an isolated output.
The Sine Amplitude Converter offers a low AC impedance
beyond the bandwidth of most downstream regulators, which
means that capacitance normally at the load can be located
at the input to the Sine Amplitude Converter. Since the K factor
of the VTM48EH120T010B00 is 1/4, that capacitance value can
be reduced by a factor of 16, resulting in savings of board area,
materials and total system cost.
The VTM48EH120T010B00 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 large thermal interface
area and superior thermal conductivity. With high conversion
efficiency the VTM48EH120T010B00 increases overall system
efficiency and lowers operating costs compared to conventional
approaches.
The VTM48EH120T010B00 enables the utilization of Factorized
Power Architecture providing efficiency and size benefits by
lowering conversion and distribution losses and promoting high
density point of load conversion.
VIN = 26 to 55 V
IOUT = 10 A (NOM)
VOUT = 6.5 to 13.8 V (NO LOAD)
K= 1/4
PART NUMBERING
PART NUMBER
PRODUCT GRADE
VTM48EH120 x 010 B00
T = -40° to 125°C
M = -55° to 125°C
For Storage and Operating Temperatures see Section 6.0 General Characteristics
Regulator
PR
PC
TM
IL
Current Multiplier
VC
SG
OS
CD
PC
IM
VC
TM
VTM
PRM
™
™
+In
+Out
-In
-Out
+In
+Out
-In
-Out
VIN
Factorized Power Architecture™
VTM™ Current Multiplier
Page 1 of 16
Rev 1.3
01/2021
L
O
A
D
(See Application Note AN:024)
VTM48EH120 x 010 B00
1.0 ABSOLUTE MAXIMUM VOLTAGE RATINGS
The absolute maximum ratings below are stress ratings only. Operation at or beyond these maximum ratings can cause permanent
damage to the device.
MIN
MAX
UNIT
MIN
MAX
UNIT
+ IN to - IN . . . . . . . . . . . . . . . . . . . . . . .
-1.0
60
VDC
IM to - IN.................................................
PC to - IN . . . . . . . . . . . . . . . . . . . . . . . .
-0.3
20
VDC
+ IN / - IN to + OUT / - OUT (hipot)........
TM to -IN . . . . . . . . . . . . . . . . . . . . . . . .
-0.3
7
VDC
+ OUT to - OUT.......................................
VC to - IN . . . . . . . . . . . . . . . . . . . . . . . .
-0.3
20
VDC
0
-1.0
3.15
VDC
2250
VDC
16
VDC
2.0 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 = 25ºC unless otherwise noted.
ATTRIBUTE
Input Voltage Range
VIN Slew Rate
SYMBOL
VIN
CONDITIONS / NOTES
No external VC applied
VC applied
No Load power dissipation
PNL
Inrush current peak
IINRP
IIN_DC
K
VOUT
K = VOUT / VIN, IOUT = 0 A
VOUT = VIN • K - IOUT • ROUT, Section 11
DC input current
Transfer ratio
Output voltage
Output current (average)
Output current (peak)
Output power (average)
Efficiency (ambient)
Efficiency (hot)
Efficiency (Over load range)
Output resistance (Cold)
Output resistance (Ambient)
Output resistance (Hot)
Switching frequency
Output ripple frequency
VIN_UV
IOUT_AVG
IOUT_PK
POUT_AVG
hAMB
hHOT
h20%
ROUT_COLD
ROUT_AMB
ROUT_HOT
FSW
FSW_RP
Output voltage ripple
VOUT_PP
Output inductance (parasitic)
LOUT_PAR
Output capacitance (internal)
COUT_INT
Output capacitance (external)
COUT_EXT
PROTECTION
OVLO
Overvoltage lockout
response time
Output overcurrent trip
Short circuit protection trip current
Output overcurrent response
time constant
Short circuit protection response time
Thermal shutdown setpoint
VTM™ Current Multiplier
Page 2 of 16
TYP
26
0
dVIN /dt
Module latched shutdown,
No external VC applied, IOUT = 10A
VIN = 48 V
VIN = 26 V to 55 V
VIN = 48 V, TC = 25ºC
VIN = 26 V to 55 V, TC = 25ºC
VC enable, VIN = 48 V COUT = 500 µF,
RLOAD = 1162 mΩ
VIN UV Turn Off
MIN
TPEAK < 10 ms, IOUT_AVG ≤ 10 A
IOUT_AVG ≤ 10 A
VIN = 48 V, IOUT = 10 A
VIN = 26 V to 55 V, IOUT = 10 A
VIN = 48 V, IOUT = 5 A
VIN = 48 V, TC = 100°C, IOUT = 10 A
2 A < IOUT < 10 A
TC = -40°C, IOUT = 10 A
TC = 25°C, IOUT = 10 A
TC = 100°C, IOUT = 10 A
19.2
0.8
2.0
8
Module latched shutdown
TOVLO
Effective internal RC filter
IOCP
ISCP
55.1
Effective internal RC filter (Integrative).
TSCP
From detection to cessation
of switching (Instantaneous)
TJ_OTP
125
Rev 1.3
01/2021
26.0
V
4.1
5
2.8
4
W
12
A
2.7
A
V/V
V
A
A
W
VDC
94.7
%
94.9
94.1
26.9
38.3
47.1
1.50
3.00
40.0
50.0
60.0
1.60
3.20
%
%
mΩ
mΩ
mΩ
MHz
MHz
200
400
mV
600
pH
20
µF
58.7
500
µF
60
V
2.4
12
24
TOCP
V/µs
10
12.5
135
93.5
90.0
94.0
92.6
72.0
20.0
25
30.0
1.40
2.80
UNIT
55
55
1
1/4
COUT = 0 F, IOUT = 10 A, VIN = 48 V,
20 MHz BW, Section 12
Frequency up to 30 MHz,
Simulated J-lead model
VOUT = 12 V
VTM Standalone Operation
VIN pre-applied, VC enable
VIN_OVLO+
MAX
19
µs
24
A
A
5.3
ms
1
µs
130
135
ºC
VTM48EH120 x 010 B00
3.0 SIGNAL 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 = 25°C unless otherwise noted.
• Used to wake up powertrain circuit.
• A minimum of 11.5 V must be applied indefinitely for VIN < 26 V
to ensure normal operation.
• VC slew rate must be within range for a successful start.
SIGNAL TYPE
STATE
Steady
ATTRIBUTE
VTM CONTROL : VC
• PRM™ VC can be used as valid wake-up signal source.
• VC voltage may be continuously applied;
there will be minimal VC current drawn when VIN > 26 V and VC < 12.
• Internal resistance used in adaptive loop compensation
SYMBOL
External VC voltage
VVC_EXT
VC current draw threshold
VVC_TH
VC current draw
IVC
VC internal resistor
RVC-INT
VC slew rate
dVC/dt
VC inrush current
IINR_VC
CONDITIONS / NOTES
Required for startup, and operation
below 26 V. See Section 7.
Low VC current draw for VIN >26 V
VC = 12 V, VIN = 0 V
VC = 12 V, VIN > 26 V
VC = 16.5 V, VIN > 26 V
TYP
11.5
MAX UNIT
16.5
12
71
21
75
2.05
V
150
mA
kΩ
V/µs
VC = 16.5 V, dVC/dt = 0.25 V/µs
750
VIN pre-applied, PC floating, VC enable
VC output turn-on delay
TON
500
CPC = 0 µF, COUT = 500 µF
Transitional
VC = 11.5 V to PC high, VIN = 0 V,
10
VC to PC delay
TVC_PC
25
dVC/dt = 0.25 V/µs
Internal VC capacitance
CVC_INT
VC = 0 V
2.2
PRIMARY CONTROL : PC
• The PC pin enables and disables the VTM.
• Module will shutdown when pulled low with an impedance
When held below 2 V, the VTM will be disabled.
less than 400 Ω.
• PC pin outputs 5 V during normal operation. PC pin is equal to 2.5 V
• In an array of VTMs, connect PC pin to synchronize startup.
during fault mode given VIN > 26 V and VC > 11.5 V.
• PC pin cannot sink current and will not disable other module
• After successful start-up and under no fault condition, PC can be used as
during fault mode.
a 5 V regulated voltage source with a 2 mA maximum current.
mA
SIGNAL TYPE
Start Up
STATE
ATTRIBUTE
SYMBOL
CONDITIONS / NOTES
0.02
V
0.25
ANALOG
INPUT
Required for proper startup;
MIN
MIN
TYP
PC voltage
VPC
4.7
5.0
5.3
PC source current
IPC_OP
2
ANALOG
PC resistance (internal)
RPC_INT
Internal pull down resistor
50
150
400
OUTPUT
50
100
300
PC source current
IPC_EN
Start Up
PC capacitance (internal)
CPC_INT
Section 7
588
PC resistance (external)
RPC_EXT
60
PC voltage (enable)
VPC_EN
2
2.5
3
Enable
PC voltage (disable)
VPC_DIS
2
Disable
DIGITAL
PC pull down current
IPC_PD
5.1
INPUT / OUTPUT
PC disable time
TPC_DIS_T
4
Transitional
PC fault response time
TFR_PC
From fault to PC = 2 V
100
TEMPERATURE MONITOR : TM
• The TM pin monitors the internal temperature of the VTM controller IC
• The TM pin has a room temperature setpoint of 3 V (@27°C)
within an accuracy of ±5°C.
and approximate gain of 10 mV/ °C.
• Can be used as a "Power Good" flag to verify that the VTM is operating.
ANALOG
OUTPUT
STATE
Steady
Disable
DIGITAL OUTPUT
(FAULT FLAG)
Transitional
VTM™ Current Multiplier
Page 3 of 16
ATTRIBUTE
TM voltage
TM source current
TM gain
SYMBOL
VTM_AMB
ITM
ATM
TM voltage ripple
VTM_PP
TM voltage
TM resistance (internal)
TM capacitance (external)
TM fault response time
VTM_DIS
RTM_INT
CTM_EXT
TFR_TM
CONDITIONS / NOTES
TJ controller = 27°C
Rev 1.3
01/2021
V
mA
kΩ
µA
pF
kΩ
V
V
mA
µs
µs
TYP
MAX UNIT
2.95
3.00
3.05
100
V
µA
mV/°C
200
mV
50
50
V
kΩ
pF
µs
10
From fault to TM = 1.5 V
µF
MIN
CTM = 0 F, VIN = 48 V,
IOUT = 10 A
Internal pull down resistor
µs
MAX UNIT
Steady
SIGNAL TYPE
µs
120
25
0
40
10
VTM48EH120 x 010 B00
3.0 SIGNAL 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 = 25°C unless otherwise noted.
CURRENT MONITOR : IM
• The nominal IM pin voltage varies between 0.38 V and 2.03 V
representing the output current within ±25% under all operating line
temperature conditions between 50% and 100%.
SIGNAL TYPE
STATE
ANALOG
OUTPUT
ATTRIBUTE
IM voltage (no load)
IM voltage (50%)
IM voltage (full load)
IM gain
IM resistance (external)
Steady
• The IM pin provides a DC analog voltage proportional to
the output current of the VTM.
SYMBOL
CONDITIONS / NOTES
MIN
TYP
MAX
UNIT
VIM_NL
VIM_50%
VIM_FL
A IM
RIM_EXT
TC = 25ºC, VIN = 48 V, IOUT = 0 A
TC = 25ºC, VIN = 48 V, IOUT = 5 A
TC = 25ºC, VIN = 48 V, IOUT = 10 A
TC = 25ºC, VIN = 48 V, IOUT > 5 A
0.06
0.38
1.17
2.03
172
0.5
V
V
V
mV/A
MΩ
2.5
4.0 TIMING DIAGRAM
ISEC
6
7
ISEC
ISEC
1
2 3
VC
4
8
d
5
b
VVC-EXT
a
VOVLO
VPRI
NL
≥ 26 V
c
e
f
VSEC
TM
VTM-AMB
PC
g
5V
3V
a: VC slew rate (dVC/dt)
b: Minimum VC pulse rate
c: TOVLO_PIN
d: TOCP_SEC
e: Secondary turn on delay (TON)
f: PC disable time (TPC_DIS_T)
g: VC to PC delay (TVC_PC)
VTM™ Current Multiplier
Page 4 of 16
1. Initiated VC pulse
2. Controller start
3. VPRI ramp up
4. VPRI = VOVLO
5. VPRI ramp down no VC pulse
6. Overcurrent, Secondary
7. Start up on short circuit
8. PC driven low
Rev 1.3
01/2021
Notes:
– Timing and voltage is not to scale
– Error pulse width is load dependent
VTM48EH120 x 010 B00
5.0 APPLICATION CHARACTERISTICS
The following values, typical of an application environment, are collected at TC = 25ºC unless otherwise noted. See associated figures
for general trend data.
ATTRIBUTE
SYMBOL
No load power dissipation
Efficiency (ambient)
Efficiency (hot)
Output resistance (ambient)
Output resistance (hot)
Output resistance (cold)
PNL
hAMB
hHOT
ROUT_AMB
ROUT_HOT
ROUT_COLD
Output voltage ripple
VOUT_PP
VOUT Transient (positive)
VOUT_TRAN+
VOUT Transient (negative)
VOUT_TRAN-
CONDITIONS / NOTES
TYP
UNIT
VIN = 48 V
VIN = 48 V, IOUT = 10 A
VIN = 48 V, IOUT = 10 A, TC = 100ºC
VIN = 48 V, IOUT = 10 A
VIN = 48 V, IOUT = 10 A, TC = 100ºC
VIN = 48 V, IOUT = 10 A, TC = -40ºC
COUT = 0 F, IOUT = 10 A, VIN = 48 V,
20 MHz BW, Section 12
IOUT_STEP = 0 A TO 10A, VIN = 48 V,
ISLEW > 10 A /us
IOUT_STEP = 10 A to 0 A, VIN = 48 V
ISLEW > 10 A /us
2.1
94.5
94.0
50.1
57.4
40.7
W
%
%
mΩ
mΩ
mΩ
261
mV
100
mV
100
mV
Full Load Efficiency vs. TCASE
96
3.5
95
Full Load Efficiency (%)
3
2.5
2
1.5
1
0.5
94
93
92
91
90
89
26
29
32
36
39
42
45
49
52
55
-40
-20
0
Input Voltage (V)
TCASE:
-40ºC
25ºC
VIN:
100ºC
10
88
8
PD
6
80
4
76
2
Efficiency (%)
92
Power Dissipation (W)
Efficiency (%)
12
2
3
4
5
6
7
26 V
26 V
48 V
55 V
26 V
8
9
48 V
55 V
12
92
10
88
8
84
6
PD
80
4
2
72
0
0
10
1
2
3
4
5
6
7
8
9
10
Load Current (A)
48 V
Figure 3 — Efficiency and power dissipation at –40°C
VTM™ Current Multiplier
Page 5 of 16
100
96
Load Current (A)
VIN:
80
76
0
72
1
60
Efficiency and Power Dissipation 25ºC Case
Efficiency & Power Dissipation -40°C Case
96
0
40
Figure 2 — Full load efficiency vs. temperature
Figure 1 — No load power dissipation vs. VIN
84
20
Case Temperature (C)
Power Dissipation (W)
No Load Power Dissipation (W)
No Load Power Dissipation vs. Line
4
55 V
VIN:
26 V
48 V
55 V
26 V
48 V
Figure 4 — Efficiency and power dissipation at 25°C
Rev 1.3
01/2021
55 V
VTM48EH120 x 010 B00
92
10
88
8
84
6
PD
80
4
76
2
ROUT vs. TCASE at VIN = 48 V
60
55
50
Rout (m )
12
Power Dissipation (W)
Efficiency (%)
Efficiency & Power Dissipation 100°C Case
96
45
40
35
30
72
0
0
1
2
3
4
5
6
7
8
9
25
10
-40
-20
0
26 V
VIN:
48 V
55 V
26 V
48 V
40
I OUT :
55 V
60
80
100
10 A
Figure 6 — ROUT vs. temperature
Figure 5 — Efficiency and power dissipation at 100°C
IM Voltage vs. Load at VIN = 48 V
Output voltage Ripple vs. Load
300
2.5
275
2.25
250
2
225
1.75
200
IM (V)
Ripple (mV pk-pk)
20
Case Temperature (C)
Load Current (A)
175
150
125
1.5
1.25
1
0.75
100
0.5
75
0.25
50
0
0
1
2
3
4
5
6
7
8
9
10
0
1
2
3
VIN:
48 V
4
5
6
7
8
9
10
Load Current (A)
Load Current (A)
26 V
TCASE:
55 V
Figure 7 — VRIPPLE vs. IOUT ; No external COUT. Board mounted
module, scope setting: 20 MHz analog BW
-40ºC
25ºC
100ºC
Figure 8 — IM voltage vs. load
IM Voltage vs. Load 25°C Case
IM Voltage vs. TCASE & Line
2.2
2
1.75
2
1.5
1.8
IM (V)
IM (V)
1.25
1
0.75
1.6
1.4
0.5
1.2
0.25
1
-40
0
0
1
2
3
4
5
6
7
8
9
10
-20
0
20
TCASE:
26ºC
Figure 9 — IM voltage vs. load
VTM™ Current Multiplier
Page 6 of 16
48ºC
40
60
80
TCASE (°C)
Load Current (A)
55ºC
VIN
26 V
48 V
Figure 10 — Full load IM voltage vs. TCASE
Rev 1.3
01/2021
55 V
100
VTM48EH120 x 010 B00
Safe Operating Area
20
Output Current (A)
18
16
14
10 ms Max
12
10
Continuous
8
6
4
2
0
0
2
4
6
8
10
12
14
Output Voltage (V)
Figure 11 — Safe operating area
Figure 12 — Full load ripple, 100 µF CIN; No external COUT. Board
mounted module, scope setting : 20 MHz analog BW
Figure 13 — Start up from application of VIN ; VC pre-applied
COUT = 500 µF
Figure 14 — Start up from application of VC; VIN pre-applied
COUT = 500 µF
Figure 15 — 0 A – 10 A transient response:
CIN = 100 µF, no external COUT
Figure 16 — 10 A – 0 A transient response:
CIN = 100 µF, no external COUT
VTM™ Current Multiplier
Page 7 of 16
Rev 1.3
01/2021
VTM48EH120 x 010 B00
6.0 GENERAL CHARACTERISTICS
Specifications apply over all line and load conditions unless otherwise noted; Boldface specifications apply over the temperature
range of -40ºC < TJ < 125ºC (T-Grade); All Other specifications are at TJ = 25°C unless otherwise noted.
ATTRIBUTE
MECHANICAL
Length
Width
Height
Volume
Weight
SYMBOL
L
W
H
Vol
W
CONDITIONS / NOTES
TYP
MAX
UNIT
21.7 / [0.85]
16.4 / [0.64]
6.48 / [0.255]
22.0 / [0.87]
16.5 / [0.65]
6.73 / [0.265]
2.44 / [0.150]
8.0 / 0.28
22.3 / [0.88]
16.6 / [0.66]
6.98 / [0.275]
mm/[in]
mm/[in]
mm/[in]
cm3/[in3]
g/[oz]
No heat sink
Nickel
Palladium
Gold
Lead finish
MIN
0.51
0.02
0.003
2.03
0.15
0.051
-40
-55
125
125
°C
°C
Ws/°C
3
lbs
125
125
°C
°C
µm
THERMAL
Operating temperature
TJ
VTM48EH120T010B00 (T-Grade)
VTM48EH120M010B00 (M-Grade)
Thermal capacity
5
ASSEMBLY
Peak compressive force
Applied to case (Z-axis)
Storage temperature
Supported by J-lead only
TST
ESDHBM
ESD withstand
ESDMM
VTM48EH120T010B00 (T-Grade)
VTM48EH120M010B00 (M-Grade)
Human Body Model,
"JEDEC JESD 22-A114C.01"
Machine Model,
"JEDEC JESD 22-A115-A"
2.5
-40
-65
1500
VDC
400
SOLDERING
Peak temperature during reflow
Peak time above Liquidus
Peak heating rate during reflow
Peak cooling rate post reflow
SAFETY
Isolation voltage (hipot)
Isolation capacitance
Isolation resistance
MTBF
Agency approvals / standards
VTM™ Current Multiplier
Page 8 of 16
RoHS
245
Non-RoHS
225
Requires AN:009 compliance
Requires AN:009 compliance
Requires AN:009 compliance
VHIPOT
CIN_OUT
RIN_OUT
60
1
1
2250
1350
10
Unpowered Unit
1.5
1.5
90
3
6
s
°C/s
°C/s
1750
2150
VDC
pF
MΩ
MIL HDBK 217, 25ºC,
5.0
Ground Benign
cTÜVus
cURus
CE Marked for low voltage directive and RoHS recast directive, as applicable
Rev 1.3
01/2021
°C
MHrs
VTM48EH120 x 010 B00
7.0 USING THE CONTROL SIGNALS VC, PC, TM, IM
The VTM Control (VC) pin is an input pin which powers the
internal VCC circuitry when within the specified voltage range
of 11.5 V to 16.5 V. This voltage is required in order for the
VTM module to start, and must be applied as long as the input
is below 26 V. In order to ensure a proper start, the slew rate of
the applied voltage must be within the specified range.
Some additional notes on the using the VC pin:
• In most applications, the VTM module will be powered
by an upstream PRM™ which provides a 10 ms VC pulse
during startup. In these applications the VC pins of the PRM
and VTM should be tied together.
• The VC voltage can be applied indefinitely allowing for
continuous operation down to 0 VIN.
• The fault response of the VTM module is latching.
A positive edge on VC is required in order to restart the unit.
If VC is continuously applied the PC pin may be toggled
to restart the module.
Primary Control (PC) pin can be used to accomplish the
following functions:
• Delayed start: Upon the application of VC, the PC pin will
source a constant 100 µA current to the internal RC
network. Adding an external capacitor will allow further
delay in reaching the 2.5 V threshold for module start.
• Auxiliary voltage source: Once enabled in regular
operational conditions (no fault), each VTM PC provides a
regulated 5 V, 2 mA voltage source.
• Output disable: PC pin can be actively pulled down in order
to disable the module. Pull down impedance shall be lower
than 400 Ω.
• Fault detection flag: The PC 5 V voltage source is internally
turned off as soon as a fault is detected. It is important to
notice that PC doesn’t have current sink capability. Therefore,
in an array, PC line will not be capable of disabling
neighboring modules if a fault is detected.
• Fault reset: PC may be toggled to restart the unit if VC
is continuously applied.
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 100. (i.e. 3.0 V = 300 K = 27ºC). If a heat sink is applied,
TM can 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. For system
monitoring purposes (microcontroller interface) faults are
detected on falling edges of TM signal.
VTM™ Current Multiplier
Page 9 of 16
Current Monitor (IM) pin provides a voltage proportional to
the output current of the VTM module. The nominal voltage
will vary between 0.38 V and 2.03 V over the output current
range of the module (See Figures 8–10). The accuracy of the
IM pin will be within 25% under all line and temperature
conditions between 50% and 100% load.
8.0 STARTUP BEHAVIOR
Depending on the sequencing of the VC with respect to the
input voltage, the behavior during startup will vary as follows:
• Normal Operation (VC applied prior to VIN): In this case the
controller is active prior to ramping the input. When the
input voltage is applied, the VTM output voltage will track
the input (See Figure 13). The inrush current is determined by
the input voltage rate of rise and output capacitance. If the
VC voltage is removed prior to the input reaching 26 V, the
VTM module may shut down.
• Stand Alone Operation (VC applied after VIN ): In this case the
module output will begin to rise upon the application of the
VC voltage (See Figure 14). The Adaptive Soft Start circuit
(See Section 10) may vary the ouput rate of rise in order to
limit the inrush current to it’s maximum level. When starting
into high capacitance, or a short, the output current will be
limited for a maximum of 900 µsec. After this period, the
adaptive soft start circuit will time out and the module
may shut down. No restart will be attempted until VC is
re-applied, or PC is toggled. The maximum output
capacitance is limited to 500 µF in this mode of operation
to ensure a sucessful start.
9.0 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
VTM48EH120T010B00 case to less than 100ºC will keep all
junctions within the VI Chip 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 board 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.
Rev 1.3
01/2021
VTM48EH120 x 010 B00
11.0 SINE AMPLITUDE CONVERTER™ POINT OF LOAD CONVERSION
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 VTM48EH120T010B00 SAC can be simplified into the
following model:
The Sine Amplitude Converter (SAC™) uses a high frequency
resonant tank to move energy from input to output. (The
resonant tank is formed by Cr and leakage inductance Lr in the
power transformer windings as shown in the VTM™ Module
Block Diagram. See Section 10). The resonant LC tank,
operated at high frequency, is amplitude modulated as
1040 pH
IOUT
IOUT
LIN = 3.7 nH
LOUT = 600 pH
38.3 mΩ
+
VIN
V
IN
OUT
RROUT
R
RCIN
CIN
6.3 mΩ
CCININ
V•I
1/4 • IOUT
900 nF
IIQQ
0.042 A
RRCOUT
COUT
3125 mΩ
+
+
–
–
+
650 µΩ
1/4 • VIN
COUT
COUT
20 µF
VVOUT
OUT
K
–
–
Figure 17 — VI Chip® module AC model
ROUT = 0 Ω and IQ = 0 A, Eq. (3) now becomes Eq. (1) and is
essentially load independent. A resistor R is now placed in
series with VIN as shown in Figure 18.
At no load:
VOUT = VIN • K
(1)
K represents the “turns ratio” of the SAC.
Rearranging Eq (1):
K=
VOUT
VIN
R
R
(2)
VVin
IN
+
–
SAC™
SAC
= 1/32
1/32
KK =
Vout
V
OUT
In the presence of load, VOUT is represented by:
VOUT = VIN • K – IOUT • ROUT
Figure 18 — K = 1/32 Sine Amplitude Converter™
with series input resistor
(3)
The relationship between VIN and VOUT becomes:
and IOUT is represented by:
IOUT =
IIN – IQ
K
VOUT = (VIN – IIN • R) • K
(4)
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 and gate drive circuitry.
The use of DC voltage transformation provides additional
interesting attributes. Assuming for the moment that
VTM™ Current Multiplier
Page 10 of 16
(5)
Substituting the simplified version of Eq. (4)
(IQ is assumed = 0 A) into Eq. (5) yields:
VOUT = VIN • K – IOUT • R • K2
Rev 1.3
01/2021
(6)
VTM48EH120 x 010 B00
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 = 1 Ω, the effective R as seen from the secondary
side is 0.98 mΩ, with K = 1/32 as shown in Figure 18.
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 19.
SS
VVin
IN
+
–
C
C
SAC™
SAC
K = 1/32
K = 1/32
VVout
OUT
Figure 19 — 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:
IC(t) = C
dVIN
dt
PDISSIPATED = PNL + PROUT
(10)
Therefore,
(7)
POUT = PIN – PDISSIPATED = PIN – PNL – PROUT
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
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, 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, these benefits are not useful if the series impedance
of the SAC is too high. The impedance of the SAC must be low
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 magnetic
components to be small since magnetizing currents remain
low. Small magnetics mean small path lengths for turns. Use of
low loss core material at high frequencies reduces core losses
as well.
The two main terms of power loss in the VTM™ 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
VTM current multiplier modeled as pure resistive impedance.
The above relations can be combined to calculate the overall
module efficiency:
(8)
h =
(9)
=
POUT = PIN – PNL – PROUT
PIN
PIN
Substituting Eq. (1) and (8) into Eq. (7) reveals:
IOUT =
C
K2
•
dVOUT
dt
Writing the equation in terms of the output has yielded a K2
scaling factor for C, this time in the denominator of the
equation. For a K factor less than unity, this results in an
effectively larger capacitance on the output when expressed in
terms of the input. With a K=1/32 as shown in Figure 19,
C=1 µF would effectively appear as C=1024 µF when viewed
from the output.
VTM™ Current Multiplier
Page 11 of 16
(11)
Rev 1.3
01/2021
VIN • IIN – PNL – (IOUT)2 • ROUT
VIN • IIN
= 1–
(
)
PNL + (IOUT)2 • ROUT
VIN • IIN
(12)
VTM48EH120 x 010 B00
12.0 INPUT AND OUTPUT FILTER DESIGN
A major advantage of a SAC™ system versus a conventional
PWM converter is that the former does 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 achieving
high 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 VTM module dynamic
response, the impedance presented to its input terminals
must be low from DC to approximately 5 MHz. Input
capacitance may be added to improve transient
performance or compensate for high source impedance.
2.Further reduce input and /or output voltage ripple without
sacrificing dynamic response.
Given the wide bandwidth of the VTM 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.
3.Protect the module from overvoltage transients imposed
by the system that would exceed maximum ratings and
cause failures.
The VI Chip® module input/output voltage ranges must
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.
VTM™ Current Multiplier
Page 12 of 16
13.0 CAPACITIVE FILTERING CONSIDERATIONS
FOR A SINE AMPLITUDE CONVERTER
It is important to consider the impact of adding input and
output capacitance to a Sine Amplitude Converter™ on the
system as a whole. Both the capacitance value, and the
effective impedance of the capacitor must be considered.
A Sine Amplitude Converter has a DC ROUT value which has
already been discussed in section 11. The AC ROUT of the SAC
contains several terms:
• Resonant tank impedance
• Input lead inductance and internal capacitance
• Output lead inductance and internal capacitance
The values of these terms are shown in the behavioral model in
section 11. It is important to note on which side of the
transformer these impedances appear and how they reflect
across the transformer given the K factor.
The overall AC impedance varies from model to model but for
most models it is dominated by DC ROUT value from DC to
beyond 500 KHz. The behavioral model in section 11 should be
used to approximate the AC impedance of the specific model.
Any capacitors placed at the output of the VTM module reflect
back to the input of the module by the square of the K factor
(Eq. 9) with the impedance of the module appearing in series.
It is very important to keep this in mind when using a PRM™
regulator to power the VTM. Most PRM™ regulators have a limit
on the maximum amount of capacitance that can be applied to
the output. This capacitance includes both the regulator output
capacitance and the current multiplier output capacitance
reflected back to the input. In PRM regulator remote sense
applications, it is important to consider the reflected value of
VTM current multiplier output capacitance when designing and
compensating the PRM regulator control loop.
Capacitance placed at the input of the VTM module appear to
the load reflected by the K factor, with the impedance of the
VTM module in series. In step-down VTM ratios, the effective
capacitance is increased by the K factor. The effective ESR of
the capacitor is decreased by the square of the K factor, but
the impedance of the VTM module appears in series. Still, in
most step-down VTM modules an electrolytic capacitor placed
at the input of the module will have a lower effective
impedance compared to an electrolytic capacitor placed at the
output. This is important to consider when placing capacitors
at the output of the current multiplier. Even though the
capacitor may be placed at the output, the majority of the AC
current will be sourced from the lower impedance, which in
most cases will be the VTM current multiplier. This should be
studied carefully in any system design using a VTM current
multiplier. In most cases, it should be clear that electrolytic
output capacitors are not necessary to design a stable, wellbypassed system.
Rev 1.3
01/2021
VTM48EH120 x 010 B00
14.0 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 the same K factor, the VTM
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.
Some general recommendations to achieve matched array
impedances:
• Dedicate common copper planes within the PCB
to deliver and return the current to the modules.
• Provide the PCB layout as symmetric as possible.
• Apply same input / output filters (if present) to each unit.
16.0 REVERSE OPERATION
The VTM48EH120T010B00 is capable of reverse operation.
If a voltage is present at the output which satisfies the
condition VOUT > VIN • K at the time the VC voltage is applied,
or after the unit has started, then energy will be transferred
from secondary to primary. The input to output ratio will be
maintained. The VTM48EH120T010B00 will continue to
operate in reverse as long as the input and output are within
the specified limits. The VTM48EH120T010B00 has not been
qualified for continuous operation (>10 ms) in the reverse
direction.
For further details see AN:016 Using BCM® Bus Converters
in High Power Arrays.
VIN
ZIN_EQ1
VTM™1
ZOUT_EQ1
VOUT
RO_1
ZIN_EQ2
+
–
VTM™2
ZOUT_EQ2
RO_2
DC
Load
ZIN_EQn
VTM™n
ZOUT_EQn
RO_n
Figure 20 — VTM module array
15.0 FUSE SELECTION
In order to provide flexibility in configuring power systems
VI Chip® products 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:
• Current rating (usually greater than maximum
VTM module current)
• Maximum voltage rating (usually greater than the maximum
possible input voltage)
• Ambient temperature
• Nominal melting I2t
VTM™ Current Multiplier
Page 13 of 16
Rev 1.3
01/2021
VTM48EH120 x 010 B00
17.1 MECHANICAL DRAWING
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
17.2 RECOMMENDED LAND PATTERN
4
3
2
1
A
+Out
+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
Designation
+In
–In
IM
TM
VC
PC
+Out
–Out
A1-B1, A2-B2
L1-M1, L2-M2
E1
F2
G1
H2
A3-D3, A4-D4
J3-M3, J4-M4
17.3 RECOMMENDED HEAT SINK PUSH PIN LOCATION
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) = ±0.13 (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.
VTM™ Current Multiplier
Page 14 of 16
(NO GROUNDING CLIPS)
Rev 1.3
01/2021
(WITH GROUNDING CLIPS)
IM
TM
VC
PC
-In
VTM48EH120 x 010 B00
Revision History
Revision
Date
1.3
01/05/21
VTM™ Current Multiplier
Page 15 of 16
Description
Provided additional information to soldering guidelines
Rev 1.3
01/2021
Page Number(s)
10
VTM48EH120 x 010 B00
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Vi
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VTM™ Current Multiplier
Page 16 of 16
Rev 1.3
01/2021
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