ADUM3070 AD [Analog Devices], ADUM3070 Datasheet - Page 16

• Manufacturer Part Number: ADUM3070
• Description: Isolated Switching Regulator
• Manufacturer: AD [Analog Devices]

ADuM3070
Table 13. Transformer Reference Designs
Part No.
JA4631-BL
JA4650-BL
KA4976-AL
TGSAD-260V6LF
TGSAD-290V6LF
TGSAD-292V6LF
TGAD-260NARL
TGAD-290NARL
TGAD-292NARL
TRANSFORMER ISOLATION VOLTAGE
Isolation voltage and isolation type should be determined for
the requirements of the application and then specified. The
transformers in Table 13 have been specified for 2500 V rms for
supplemental or basic isolation and for 1500 V rms for functional
isolation. Other isolation levels and isolation voltages can be
specified and requested from the manufacturers that are listed
in Table 13 or from other manufacturers.
SWITCHING FREQUENCY
The
200 kHz to 1 MHz by changing the value of the R
shown in Figure 31, Figure 32, and Figure 33. The value of the
R
determined from the switching frequency vs. R
curve shown in Figure 4. The output filter inductor value and
output capacitor value for the
have been designed to be stable over the switching frequency
range from 500 kHz to 1 MHz, when loaded from 10% to 90%
of the maximum load.
The
voltage is not regulated and is dependent on the transformer
turns ratio, N
output load current and the losses in the dc-to-dc converter
circuit. This open-loop mode is selected when the OC pin is
connected high to the V
switching frequency is 318 kHz.
TRANSIENT RESPONSE
The load transient response of the output voltage of the
for 10% to 90% of the full load is shown in Figure 19 to Figure 26
for the application schematics in Figure 31 and Figure 32. The
response shown is slow but stable and can have more output
change than desired for some applications. The output voltage
change with load transient has been reduced, and the output has
been shown to remain stable by adding more inductance to the
output circuits, as shown in the second V
Figure 19 to Figure 26.
OC
ADuM3070
resistor needed for the desired switching frequency can be
ADuM3070
S
/N
switching frequency can be adjusted from
also has an open-loop mode where the output
P
Manufacturer
Coilcraft
Coilcraft
Coilcraft
Halo Electronics
Halo Electronics
Halo Electronics
Halo Electronics
Halo Electronics
Halo Electronics
, and the conditions of the output including
DD2
pin. In open-loop mode, the
ADuM3070
Turns Ratio,
PRI:SEC
1CT:2CT
1CT:3CT
1CT:5CT
1CT:2CT
1CT:3CT
1CT:5CT
1CT:2CT
1CT:3CT
1CT:5CT
application schematics
ISO
output waveform in
OC
ET Constant
(V × µs Min)
18
18
18
14
14
14
14
14
14
OC
resistance
ADuM3070
resistor
Rev. 0 | Page 16 of 20
Total Primary
Inductance (µH)
255
255
255
389
389
389
389
389
389
For additional improvement in transient response, add a 0.1 µF
ceramic capacitor (C
As shown in Figure 19 to Figure 26, this value helps reduce the
overshoot and undershoot during load transients.
COMPONENT SELECTION
Power supply bypassing is required at the input and output supply
pins. Note that a low ESR ceramic bypass capacitor of 0.1 µF is
required on Side 1 between Pin 7 and Pin 8, and on Side 2 between
Pin 14 and Pin 15, as close to the chip pads as possible.
The power supply section of the
frequency to efficiently pass power through the external power
transformer. Bypass capacitors are required for several operating
frequencies. Noise suppression requires a low inductance, high
frequency capacitor; ripple suppression and proper regulation
require a large value capacitor. To suppress noise and reduce ripple,
large valued ceramic capacitors of X5R or X7R dielectric type are
recommended. The recommended capacitor value is 10 µF for
V
available in moderate 1206 or 1210 sizes for voltages up to 10 V. For
output voltages larger than 10 V, two 22 µF ceramic capacitors can
be used in parallel. See Table 14 for recommended components.
Inductors must be selected based on the value and supply current
needed. Most applications with switching frequencies between
500 kHz and 1 MHz and load transients between 10% and 90%
of full load are stable with the 47 µH inductor value listed in Table 14.
Values as large as 200 µH can be used for power supply applications
with a switching frequency as low as 200 kHz to help stabilize the
output voltage or for improved load transient response (see Figure 19
to Figure 26). Inductors in a small 1212 or 1210 size are listed in
Table 14 with a 47 µH value and a 0.41 A current rating to handle the
majority of applications below a 400 mA load, and with a 100 µH
value and a 0.34 A current rating to handle a load to 300 mA.
Schottky diodes are recommended for their low forward voltage
to reduce losses and their high reverse voltage of up to 40 V to
withstand the peak voltages available in the doubling circuit
shown in Figure 32 and Figure 33.
DD1
and 47 µF for V
Total Primary
Resistance (Ω)
0.2
0.2
0.2
0.8
0.8
0.8
0.8
0.8
0.8
FB
ISO
) in parallel with the high feedback resistor.
. These capacitors have a low ESR and are
Isolation
Voltage (rms)
2500
2500
2500
2500
2500
2500
1500
1500
1500
ADuM3070
Isolation
Type
Basic
Basic
Basic
Supplemental
Supplemental
Supplemental
Functional
Functional
Functional
uses a high oscillator
Data Sheet
Reference
Figure 31
Figure 32
Figure 33
Figure 31
Figure 32
Figure 33
Figure 31
Figure 32
Figure 33