IC-DC IC-Haus, IC-DC Datasheet - Page 16

• Manufacturer Part Number: IC-DC
• Description: 2-CHANNEL BUCK/BOOST DC/DC CONVERTER
• Manufacturer: IC-Haus

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Selecting the coil
The coil should be designed for a maximum cut-off
current of 1 A. A small internal resistor in the coil re-
duces loss and increases converter efficiency. At a low
supply voltage this internal resistor can determine the
maximum available output current.
The EMI caused by the coil should be taken into con-
sideration. Toroidal core coils have little noise radia-
tion yet are expensive and difficult to install. Bar core
coils are reasonably priced and easier to use yet have
a higher noise emittance. For modest EMI require-
ments inexpensive radio interference suppression coils
of several tens of µH are suitable .
Selecting the capacitors
Selecting back-up capacitors C
unproblematic. As the residual ripple of intermediate
voltages VH1 and VH2 does not affect output volt-
ages VCC1 and VCC2 thanks to the back-end linear
regulators, a small capacitor is sufficient without any
specific demands being made of the internal resis-
tor. A combination of electrolytic and ceramic capaci-
tors (e.g. 3.3 µF || 100 nF) is recommended. Before us-
ing tantalum capacitors, the user must verify whether
these are suitable for the residual AC amplitude (resid-
ual ripple) at pins VH1 and VH2.
Stability of the linear regulators across the entire load
area is guaranteed if the values given in the electrical
characteristics are selected for CVCC1 and CVCC2.
The suppression of interference voltage is improved
by using small capacitor series resistors. A combina-
tion of tantalum and ceramic capacitors is also recom-
mended in this case. If one of the two outputs remains
open, this capacitor can be omitted.
To avoid feedback of interference from supply voltage
VB onto output voltages VCC1 and VCC2, blocking
should be provided directly at pin VB. A combination
of tantalum and ceramic capacitors (e.g. 1 µF || 100 nF)
is also recommended in this case.
DESCRIPTION OF THE APPLICATION
iC-DC
2-CHANNEL BUCK/BOOST DC/DC CONVERTER
e.g.: Siemens Matsushita B78108-S1224-J (22 µH/1 A, axial), TDK series NLC565050T-. . . (SMD), TOKO series 10RF459-. . . (SMD
shielded)
VH
, C
VH1
and C
VH2
is
Printed circuit board layout
The GND path from the switching converter and from
each linear regulator should be strictly separated to
avoid cross couplings. The neutral point of all GND
paths is the GND connection at iC-DC. It is possible
and not critical, however, to route GND from supply VB
and the base point of capacitors C
together to the neutral point. The capacitors should be
very close to their relevant pins, however.
Blocking capacitors for supply VB should be arranged
as close as possible to pins VB and GND. The capaci-
tors for outputs VCC1 and VCC2 should be placed di-
rectly at the load and not at the IC to also block inter-
ferences which are coupled via the wiring to the load.
The ground planes underneath the wiring of output
voltages VCC1, VCC2, POE1, and POE2 should be
kept separate from the ground planes of switching con-
verters VH, VH1, and VH2. The ground planes must
be connected up at a neutral point (see Figure 8).
The thermal pad should be connected to the PCB by
an appropriate ground plane. The resulting power dis-
sipation can be transferred to a different wiring layer,
e.g. a ground plane, by vias directly underneath the
IC.
Figure 8: Example layout: evaluation board DC1D
Rev A3, Page 16/19
VH
, C
VH1
and C
VH2
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