DCM300P280x500A40
Figure 21 shows a scenario where there is no bottom side cooling.
In this case, the heat flow path to the bottom is left open and the
equations now simplify to:
output ripple filtering;
In order to help sensitive signal circuits reject potential noise,
additional components are recommended:
R2_x: 301 Ohm, facilitate noise attenuation for TR pin;
FB1_x, C2_x: FB1 is a ferrite bead with an impedance of at least 10 Ω
at 100MHz. C2_x can be a ceramic capacitor of 0.1uF. Facilitate noise
attenuation for EN pin.
TINT – PD1 • ΦINT-TOP = TCASE_TOP
TINT – PD3 • ΦINT-LEADS = TLEADS
PDTOTAL = PD1 + PD3
VTR VEN
DCM1
R2_1
TR
EN
FT
FB1_1
C2_1
R1_1
L1_1
Thermal Resistance Top
MAX INTERNAL TEMP
L2_1
F1_1
ΦINT-TOP°C / W
+IN
-IN
+OUT
-OUT
+IN
-IN
+OUT
-OUT
C1_1
C3_1
C4
C5
Thermal Resistance Bottom
Thermal Resistance Leads
ΦINT-BOTTOM°C / W
Φ
INT-LEADS°C / W
DCM2
R2_2
TR
EN
FT
+
–
T
CASE_BOTTOM(°C)
TLEADS(°C)
TCASE_TOP(°C)
Power Dissipation (W)
FB1_2
C2_2
R1_2
L1_2
L2_2
F1_2
+IN
-IN
+OUT
-OUT
C1_2
C3_2
≈≈
≈ ≈
≈
R2_8
≈ ≈
Figure 22 — One side cooling thermal model
DCM8
TR
EN
FT
FB1_8
C2_8
R1_8
R3
Figure 22 shows a scenario where there is no bottom side and leads
cooling. In this case, the heat flow path to the bottom is left open and
the equations now simplify to:
L2_8
F1_8
+IN
-IN
+OUT
-OUT
L1_8
R4
D1
C1_8
C3_8
Shared -IN Kelvin
Figure 23 — DCM paralleling configuration circuit 1
TINT – PD1 • ΦINT-TOP = TCASE_TOP
PDTOTAL = PD1
When common mode noise rejection in the input side is needed,
common modes choke can be added in the input side of each DCM.
An example of DCM paralleling circuit is shown below:
Vicor provides a suite of online tools, including a simulator and
thermal estimator which greatly simplify the task of determining
whether or not a DCM thermal configuration is sufficient for a given
condition. These tools can be found at:
www.vicorpower.com/powerbench.
DCM1
R2_1
TR
+
EN
Array Operation
+
FB1_1
C2_1
FT
R1_1
L1_1
R3_1
VTR1
A decoupling network is needed to facilitate paralleling:
n An output inductor should be added to each DCM, before the
outputs are bussed together to provide decoupling.
VEN1
L2_1
F1_1
+IN
-IN
+OUT
-OUT
+IN
+OUT
-OUT
R4_1
D1_1
C1_1
C3_1
_
_
C4
C5
-IN
DCM2
R2_2
n Each DCM needs a separate input filter, even if the multiple DCMs
share the same input voltage source. These filters limit the ripple
current reflected from each DCM, and also help suppress
generation of beat frequency currents that can result when
multiple powertrains input stages are permitted to
direclty interact.
TR
EN
FT
+
FB1_2
C2_2
+
R1_2
L1_2
R3_2
VTR2
VEN2
L2_2
C3_2
F1_2
+IN
-IN
+OUT
-OUT
R4_2
D1_2
C1_2
_
_
≈≈
≈ ≈
DCM8
R2_8
TR
EN
FT
+
If signal pins (TR, EN, FT) are not used, they can be left floating, and
DCM will work in the nominal output condition.
+
FB1_8
C2_8
R1_8
L1_8
R3_8
VTR8
VEN8
L2_8
C3_8
F1_8
+IN
-IN
+OUT
-OUT
R4_8
D1_8
When common mode noise in the input side is not a concern, TR and
EN can be driven and FT received using a single Kelvin connection to
the shared -IN as a reference.
C1_8
_
_
Figure 24 — DCM paralleling configuration circuit 2
An example of DCM paralleling circuit is shown in Figure 23.
Notice that each group of control pins need to be individually driven
and isolated from the other groups control pins. This is because -IN
of each DCM can be at a different voltage due to the common mode
chokes. Attempting to share control pin circuitry could lead to
incorrect behavior of the DCMs.
Recommended values to start with:
L1_x: 1 uH, minimized DCR;
R1_x: 1.0 Ω;
C1_x: Ceramic capacitors in parallel, C1 = 2 µF;
L2_x: L2 ≥ 0.15 uH;
C3_x: electrolytic or tantalum capacitor, 200 uF ≤ C3 ≤2000 uF;
C4, C5: additional ceramic /electrolytic capacitors, if needed for
DCM™ DC-DC Converter
Rev 1.1
vicorpower.com
800 927.9474
Page 21 of 25
10/2015
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