UG-197
Evaluation Board User Guide
Rev. 0 | Page 8 of 16
Data I/O Connection
The EVAL-ADuM3471 supports a variety of I/O configurations.
The user has access to all four of the ADuM3471 isolated data
channels via the terminals. With an ADuM3471 populated,
I/O1 through I/O3 are inputs on Side 1 and outputs on Side 2.
I/O4 is an output on Side 1 and an input on Side 2. Table 3
identifies the ADuM3471 pins to which the I/Ox are connected.
Populating J5 allows the user to connect the ADuM3471 V
IA
input directly to a 50 Ω signal source. R37 must be shorted with
a 0 Ω resistor to connect the SMA to V
IA
. R38, R39, and R40
allow the user to implement various I/O interconnection
schemes. For example, soldering 0 Ω 0805s to R40 and R39 ties
V
IA
, V
IB
, and V
IC
together.
Note that R38 must not be populated if an external signal
source is applied to I/O3. This can cause permanent damage to
the ADuM3471 because an output pin is being driven. R38 can
be used to connect V
IC
to V
OD
so that V
OD
drives V
IC
. C14
through C16 and C22 should not be populated. C17, C23, C24,
and C25 are 0603 pads provided for optional and unpopulated
loads for the data outputs. Though the I/Ox for the single and
double supplies share names on the silkscreen, they are not
connected.
The PCB is designed for compatibility with the entire
ADuM347x family. If the ADuM3471 is replaced by another
ADuM347x, other I/O interconnection schemes are possible
(see the ADuM347x data sheet for the pin descriptions of these
configurations). These changes are at the discretion of the user.
Care must be taken to avoid driving an output pin because this
can result in permanent damage to the ADuM347x.
Table 3. Double Supply Terminal Function Descriptions
Terminal
Pin
Label
Description
J4
1
+5V IN
Side 1 +5 V primary input
supply
2
I/O1
V
IA
Logic Input A
3
I/O2
V
IB
Logic Input B
4
I/O3
V
IC
Logic Input C
5
I/O4
V
OD
Logic Output D
6
GND
Side 1 ground reference
J5
N/A
N/A
SMA connector to J4, I/O1 (V
IA
)
J6
1
+15V/12V Side 2 +15 V secondary
isolated supply (regulated)
2
+7.5V/6V
Side 2 +7.5 V secondary
isolated supply (unregulated)
3
I/O1
V
OA
Logic Output A
4
I/O2
V
OB
Logic Output B
5
I/O3
V
OC
Logic Output C
6
I/O4
V
ID
Logic Input D
7
GND ISO
Side 2 ground reference
TRANSFORMER SELECTION
The EVAL-ADuM3471 supports multiple transformer options.
The double supply is equipped with a Halo TGSAD-290V6LF
(T3) or a Coilcraft JA4650-BL (T4) 1:3 turns ratio transformer.
The Coilcraft footprint is directly to the left of the Halo foot-
print (see the ADuM347x data sheet for a detailed discussion of
transformer selection with the ADuM347x). Figure 12 and
Figure 14 show the supply’s efficiency with either transformer at
different switching frequencies. Figure 13 shows how temper-
ature affects efficiency.
SWITCHING FREQUENCY OPTIONS
The resistor connected from the ADuM3471 OC/oscillator
control pin to ground sets the double supply switching frequency.
Figure 4 shows the relationship between this resistance and the
converter switching frequency. The EVAL-ADuM347x can be
configured with 0 Ω 0805s to four different preset switching
frequencies. Short-circuiting R26 sets R9 (300 kΩ) and R10
(150 kΩ) in parallel, and short-circuiting R27 sets R9 and R11
(100 kΩ) in parallel. Table 4 lists the switching frequencies that
can be selected by short- or open-circuiting R26 and R27. The
user can select a different switching frequency by removing R26
and R27 and then choosing R9 based on Figure 4. The board is
configured for the 500 kHz setting by default. Figure 12 and
Figure 14 show how the switching frequency affects the
efficiency with either transformer.
Table 4. Switching Frequency Selection
R26
R27
R
OC
Switching Frequency
Open
Open
300 kΩ
200 kHz
0 Ω
Open
100 kΩ
500 kHz
Open
0 Ω
75 kΩ
700 kHz
0 Ω
0 Ω
50 kΩ
1 MHz
