Analog Devices EVAL-ADuM3070EBZ, Руководство пользователя

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UG-402 Evaluation Board User Guide
Rev. 0 | Page 4 of 12
The user can select a different switching frequency by removing
R10 and R11 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 installed. Figure 6
shows how the efficiency curve varies over temperature with a
500 kHz switching frequency.
Table 2. Switching Frequency Selection
R10 R11 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
f
S
W
(k
H
z)
R
OC
(
Ω)
10653-
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 resistor to R9 sets the
output supply for 3.3 V. The voltage at the feedback node (the
FB pin of the
ADuM3070 ) should be the desired output voltage
divided to approximately 1.25 V. Having R9 open-circuited sets
the secondary isolated supply to 5 V, and having it short-circuited
sets the supply to 3.3 V. See the
ADuM3070 data sheet for more
details on setting the secondary isolated output supply voltage.
Figure 8 shows how the single supply efficiency curve changes
when it is reconfigured for either of these supply options.
90
80
70
60
50
40
30
20
10
0
0 500 450 400 350 300 250 200 150 100 50
E
FF
IC
IE
NC
Y
(%
)
LOAD CURRENT (mA)
f
SW
= 1MHz
f
SW
= 700kHz
f
SW
= 500kHz
f
SW
= 200kHz
10653-
005
Figure 5. 5 V In to 5 V Out Efficiency with 1:2 Coilcraft Transformer at Various
Switching Frequencies
90
80
70
60
50
40
30
20
10
0
0 500 450 400 350 300 250 200 150 100 50
E
FF
IC
IE
NC
Y
(%
)
LOAD CURRENT (mA)
T
A
= –40°C
T
A
= +25°C
T
A
= +105°C
10653-
006
Figure 6. 5 V In to 5 V Out Efficiency with 1:2 Coilcraft Transformer at 500 kHz
over Temperature
90
80
70
60
50
40
30
20
10
0
0 500 450 400 350 300 250 200 150 100 50
E
FF
IC
IE
NC
Y
(%
)
LOAD CURRENT (mA)
f
SW
= 1MHz
f
SW
= 700kHz
f
SW
= 500kHz
f
SW
= 200kHz
10653-
007
Figure 7. 5 V In to 5 V Out Efficiency with 1:2 Halo Transformer at Various
Switching Frequencies