ADUM3070 AD [Analog Devices], ADUM3070 Datasheet - Page 14

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

ADuM3070
APPLICATIONS INFORMATION
The dc-to-dc converter section of the
side controller architecture with isolated pulse-width modulation
(PWM) feedback. V
that switches current to the primary side of an external power
transformer using internal push-pull switches at the X1 and X2
pins. Power transferred to the secondary side of the transformer
is full-wave rectified with external Schottky diodes (D1 and D2),
filtered with the L1 inductor and C
to the isolated power supply voltage from 3.3 V to 15 V. The
secondary (V
feedback voltage V
creating a PWM control signal that is sent to the primary (V
side by a dedicated iCoupler data channel labeled V
side PWM converter varies the duty cycle of the X1 and X2 switches
to modulate the oscillator circuit and control the power being
sent to the secondary side. This feedback allows for significantly
higher power and efficiency.
The
hysteresis on the V
converter does enter oscillation due to noisy input power or slow
power-on ramp rates.
A minimum load current of 10 mA is recommended to ensure
optimum load regulation. Smaller loads can generate excess noise
on the output because of short or erratic PWM pulses. Excess
noise generated from smaller loads can cause regulation problems,
in some circumstances.
APPLICATION SCHEMATICS
The
in Figure 31 to Figure 33. Figure 31 has a center-tapped secondary
and two Schottky diodes providing full wave rectification for a
single output, typically for power supplies of 3.3 V, 5 V, 12 V, and
15 V. For single supplies when V
note in Figure 31 about connecting together V
Figure 32 is a voltage doubling circuit that can be used for a single
supply whose output exceeds 15 V, which is the largest supply that
can be connected to the regulator input, V
With Figure 32, the output voltage can be as high as 24 V and the
V
Figure 32, to obtain an output voltage lower than 10 V (for
example, V
Figure 33, which also uses a voltage doubling secondary circuit,
is shown as an example of a coarsely regulated, positive power
supply and an unregulated, negative power supply for outputs of
approximately ±5 V, ±12 V, and ±15 V. For any circuit in Figure 31,
Figure 32, or Figure 33, the isolated output voltage (V
set using the voltage dividers, R1 and R2 (values 1 kΩ to 100 kΩ),
using the following equation:
where V
approximately 1.25 V.
REG
ADuM3070
ADuM3070
pin is only about 12 V. When using the circuit shown in
V
ISO
FB
=
is the internal feedback voltage, which is
DD1
V
ISO
FB
= 3.3 V, V
) side controller regulates the output by using a
implements undervoltage lockout (UVLO) with
has three main application schematics, as shown
×
DD1
R1
FB
DD1
R2
from a resistor divider on the output and
+
power input. This feature ensures that the
power is supplied to an oscillating circuit
R2
ISO
= 5 V), connect V
ISO
OUT
= 3.3 V or V
ADuM3070
capacitor, and regulated
REG
(Pin 16), of the part.
REG
REG
to V
, V
ISO
uses a secondary
FB
DD2
. The primary
= 5 V, see the
ISO
, and V
directly.
ISO
) can be
ISO
CC
Rev. 0 | Page 14 of 20
)
.
V
V
V
V
V
DD1
C
V
DD1
DD1
V
C
V
DD1
DD1
C
V
IN
DD1
DD1
IN
DD1
IN
DD1
0.1µF
0.1µF
0.1µF
Figure 33. Positive and Unregulated Negative Supply
FOR V
1 X1
2 GND
3 NC
4 X2
5 TP
6 TP
7 V
8 GND
FOR V
2 GND
8 GND
7 V
1 X1
2 GND
3 NC
4 X2
5 TP
6 TP
7 V
8 GND
DDA
3 NC
5 TP
6 TP
1 X1
4 X2
DDA
DDA
ISO
1
1
V
ISO
1
1
ISO
1
1
= 15V OR LESS, V
Figure 32. Doubling Power Supply
ADuM3070
= 3.3V OR 5V CONNECT V
Figure 31. Single Power Supply
= V
ADuM3070
ADuM3070
FB
V
T1
ISO
V
× (R1 + R2)R2
ISO
T1
T1
= V
= V
D2
D3
D4
D1
FB
D2
D3
D4
D1
FB
D1
D2
× (R1 + R2)/R2
REG
16 V
15 GND
14 VDD2
13 FB
12 NC
11 NC
10 OC
9 GND
× (R1 + R2)/R2
16 V
15 GND
14 V
13 FB
12 NC
11 NC
10 OC
9 GND
16 V
15 GND
14 V
13 FB
12 NC
11 NC
10 OC
9 GND
47µH
47µH
REG
CAN CONNECT TO V
L1
L2
47µH
47µH
REG
DD2
2
2
47µH
L2
L1
REG
DD2
C
47µF
L1
OUT
REG
2
2
100kΩ
2
2
R
OC
, V
100kΩ
C
47µF
C
47µF
100kΩ
0.1µF
R
R
DD2
OUT1
OUT2
OC
OC
+5V
0.1µF
0.1µF
C
47µF
C
47µF
, AND V
Data Sheet
OUT1
OUT2
+5V
+5V
ISO
R1
ISO
V
R2
UNREGULATED
R2
.
UNREGULATED
R1
V
FB
R1
V
R2
REGULATED
FB
COARSELY
–5V TO –15V
.
+5V TO 15V
FB
+12V TO
TO +15V
+6V TO
V
V
V
+24V
+3.3V
ISO
+12V
ISO
ISO
C
FB
C
C
FB
=
=
=
FB