Evaluation Board User Guide
UG-402
Rev. 0 | Page 3 of 12
SINGLE SUPPLY
Two independent and isolated circuits comprise the
ADuM3070
evaluation board. The lower half of the board, shown in Figure 2,
is for a single power supply configuration (see the
ADuM3070
data sheet for applications information about the
ADuM3070
in
this configuration).
10653-
002
Figure 2. Single Supply Configuration
The single supply is configured as a 5 V secondary isolated
supply with a 5 V primary input supply, which can provide up
to 2.5 W of regulated, isolated power. It can be reconfigured for
a 3.3 V secondary isolated supply with a 5 V or 3.3 V primary
input supply (see the Other Input and Isolated Output Supply
Options section). Figure 9 shows the single supply schematic.
TERMINALS
The single supply has terminal blocks on Side 1 (the primary/
power supply input side) and Side 2 (the secondary/power supply
output side). A 4.3 mm isolation barrier separates Side 1 and
Side 2. Figure 3 shows these terminal locations.
Table 1 summarizes the functions of the terminal connections.
They are described in detail in the Input Power Connections
and Output Power Connections sections.
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003
Figure 3. Single Supply Terminals
Input Power Connections
Connect 5 V to P1, l5V IN (or +3.3 V for a
3.3 V primary input supply with a 3.3 V secondary isolated
supply). Connect the negative supply to P2, labeled GND
(GND1 on the schematic). These are the only off-board
connections required for the single supply to function.
V
DD1
supplies the voltage to the transformer primary and to the
ADuM3070
supply voltage, V
DDA
(see the
ADuM3070
data sheet
for additional information about the V
DDA
pin function). V
DD1
and V
DDA
are bypassed by a 47 µF ceramic capacitor (C1) and a
0.1 µF local bypass capacitor (C2) located close to the
ADuM3070
.
R7, R8, C5, and C6 are provided for an optional and unpopulated
snubber, which can be used to reduce radiated emissions.
Power is transferred to Side 2 by a regulated push-pull converter
comprising the
ADuM3070
(U1), an external transformer (T1
or T2), and other components (see the
ADuM3070
data sheet
for an explanation of this circuit functionality).
Output Power Connections
An output load can be connected to P3 (l5V/3.3V on the
silkscreen and not labeled on the schematic), which is the iso-
lated, regulated 5 V output supply. Connect the return of the
load to P4, which is the Side 2 ground reference. P4 is labeled
GND ISO on the silkscreen and GND2 on the schematic. This
supply can provide up to 500 mA in the default 5 V primary
input supply, 5 V secondary isolated supply configuration.
Figure 5 through Figure 8 in this user guide show how the
power supply’s efficiency varies with load current, switching
frequency, and temperature.
Table 1. Single Supply Terminal Function Descriptions
Terminal Pin Label
Description
P1
1
+5V IN
Side 1 5 V primary input supply
P2
1
GND
Side 1 ground reference
P3
1
+5V/3.3V Side 2 5 V secondary isolated supply
P4
1
GND ISO
Side 2 ground reference
Care must be taken to avoid driving the V
DD2
output with an
external voltage because this can result in permanent damage to
the
ADuM3070
.
TRANSFORMER SELECTION
The
EVAL-ADuM3070EBZ
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 a Coilcraft and a Halo
transformer, respectively.
SWITCHING FREQUENCY OPTIONS
The resistor connected from the
ADuM3070
oscillator control
pin (OC) to ground sets the single supply switching frequency.
Figure 4 shows the relationship between this resistance and the
converter switching frequency. The
EVAL-ADuM3070EBZ
can
be configured with 0 Ω, 0805 resistors to four different preset
switching frequencies. Short-circuiting R10 sets R1 (300 kΩ)
and R2 (150 kΩ) in parallel, and short-circuiting R11 sets R1 and
R3 (100 kΩ) in parallel. Table 2 lists the switching frequencies
that can be selected by short- or open-circuiting R10 and R11.
