UG-197
Evaluation Board User Guide
Rev. 0 | Page 4 of 16
ADuM3471 is equipped. C8, C10, C11, and C12 are 0603 pads
for optional and unpopulated loads for the data outputs.
Table 1: Single Supply Terminal Function Descriptions
Terminal
Pin
Label
Description
J1
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
J2
N/A N/A
SMA connector to J1, I/O1 (V
IA
)
J3
1
+5V/3.3V
Side 2 +5 V secondary isolated
supply
2
I/O1
V
OA
Logic Output A
3
I/O2
V
OB
Logic Output B
4
I/O3
V
OC
Logic Output C
5
I/O4
V
ID
Logic Input D
6
GND ISO
Side 2 ground reference
The PCB was designed for compatibility with the entire
ADuM347x family. If another ADuM347x replaces the
ADuM3471, 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 with an
external voltage because this can result in permanent damage to
the ADuM347x.
TRANSFORMER SELECTION
The EVAL-ADuM3471 supports multiple transformer options.
The single supply is equipped with a Halo TGSAD-260V6LF
(T1) or a Coilcraft JA4631-BL(T2) 1:2 turns ratio transformer.
The Coilcraft footprint is offset to the left of the Halo footprint.
Figure 5 and Figure 7 show the efficiency curves for the single
supply operating with either transformer.
SWITCHING FREQUENCY OPTIONS
The resistor connected from the ADuM3471 OC/oscillator
control pin to ground sets the single 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 R30 sets R1 (300 kΩ) and R2
(150 kΩ) in parallel, and short-circuiting R31 sets R1 and R3
(100 kΩ) in parallel. Table 2 lists the switching frequencies that
can be selected by short- or open-circuiting R30 and R31.
The user can select a different switching frequency by removing
R30 and R31 and then choosing R1 based on Figure 4. The
board is configured for the 500 kHz setting by default. Figure 5
and Figure 7 show how the switching frequency affects the
supply’s efficiency with either transformer equipped. Figure 6
shows how the efficiency curve varies over temperature with a
500 kHz switching frequency.
Table 2. Switching Frequency Selection
R30
R31
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
1500
1400
1300
1200
1100
1000
900
800
700
600
500
400
300
200
100
0
0
50
100
150
200
250
300
350
400
450
500
S
W
IT
CHI
NG
F
RE
Q
UE
NCY
(
kHz
)
R
OC
(k
Ω)
09417-
004
Figure 4. Switching Frequency vs. R
OC
Resistance
OTHER INPUT AND ISOLATED OUTPUT SUPPLY
OPTIONS
The single supply can be configured to have a 3.3 V secondary
isolated supply with a 3.3 V or 5 V primary input supply. Short-
circuiting R4 by soldering a 0 Ω 0805 to R32 sets the output
supply for 3.3 V. The voltage at the feedback node (the FB pin of
the ADuM3471) should be the desired output voltage divided to
approximately 1.25 V. Having R32 open-circuited sets the
secondary isolated supply to 5 V, and having it short-circuited
sets the supply to 3.3 V. See the ADuM347x data sheet for more
details on setting the secondary isolated output supply voltage.
Figure 8 shows how the single supply’s efficiency curve changes
when it is reconfigured for either of these supply options.
