adum6000 Analog Devices, Inc., adum6000 Datasheet - Page 11

• Manufacturer Part Number: adum6000
• Description: Isolated, 5 Kv, Dc-to-dc Converter Adum6000
• Manufacturer: Analog Devices, Inc.

APPLICATIONS INFORMATION
The dc-to-dc converter section of the ADuM6000 works on
principles that are common to most switching power supplies. It
has a secondary side controller architecture with isolated pulse-
width modulation (PWM) feedback. V
an oscillating circuit that switches current into a chip scale air
core transformer. Power transferred to the secondary side is
rectified and regulated to either 3.3 V or 5 V. The secondary
(V
control signal that is sent to the primary (V
iCoupler data channel. The PWM modulates the oscillator
circuit to control the power being sent to the secondary side.
Feedback allows for significantly higher power and efficiency.
The ADuM6000 provides a regulation control output (RC
signal that can be connected to other isoPower devices. This
feature allows a single regulator to control multiple power mod-
ules without contention. When auxiliary power modules are
present, the V
single supply. Because there is only one feedback control path,
the supplies work together seamlessly. The ADuM6000 can be
a source of regulation control (master mode), and it can also be
controlled by another isoPower device (slave mode).
The ADuM6000 implements undervoltage lockout (UVLO)
with hysteresis in the V
input voltage rises above the UVLO threshold, the dc-to-dc
converter becomes active. The input voltage must be decreased
below the turn-on threshold by the hysteresis value to disable
the converter. This feature has many benefits in the power-up
sequence of the converter. For example, UVLO ensures that the
system supply rises to a minimum level before the ADuM6000
demands current. Also, it prevents any voltage drop due to
converter current from turning the supply off and causing
oscillation.
PCB LAYOUT
The ADuM6000 digital isolator is a 0.4 W isoPower integrated
dc-to-dc converter that requires no external interface circuitry
for the logic interfaces. Power supply bypassing is required at
the input and output supply pins (see Figure 14).
The power supply section of the ADuM6000 uses a 180 MHz
oscillator frequency to pass power efficiently through its chip
scale transformers. In addition, the normal operation of the
data section of the iCoupler introduces switching transients
on the power supply pins. Bypass capacitors are required for
several operating frequencies. Noise suppression requires a low
inductance, high frequency capacitor, whereas ripple suppression
and proper regulation require a large value capacitor. These
capacitors are most conveniently connected between Pin 1 and
Pin 2 for V
ISO
) side controller regulates the output by creating a PWM
DD1
, and between Pin 15 and Pin 16 for V
ISO
pins can be connected together to work as a
DD1
input protection circuitry. When the
DD1
DD1
power is supplied to
) side by a dedicated
ISO
.
OUT
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)
To suppress noise and reduce ripple, a parallel combination of
at least two capacitors is required. The recommended capacitor
values are 0.1 μF and 10 μF. Best practice recommends using a
very low inductance ceramic capacitor, or its equivalent, for the
smaller value. The total lead length between both ends of the
capacitor and the input power supply pin should not exceed
10 mm. Consider bypassing between Pin 1 and Pin 8 and
between Pin 9 and Pin 16 unless both common ground pins
are connected together close to the package.
In applications involving high common-mode transients, ensure
that board coupling across the isolation barrier is minimized.
Furthermore, design the board layout such that any coupling that
does occur affects all pins equally on a given component side.
Failure to ensure this can cause voltage differentials between
pins exceeding the absolute maximum ratings for the device
as specified in Table 10, thereby leading to latch-up and/or
permanent damage.
The ADuM6000 is a power device that dissipates approximately
1 W of power when fully loaded. Because it is not possible to apply
a heat sink to an isolation device, the device primarily depends
on heat dissipation into the PCB through the GND pins. If the
device is used at high ambient temperatures, provide a thermal
path from the GND pins to the PCB ground plane. The board
layout in Figure 14 shows enlarged pads for Pin 2 and Pin 8
(GND
vias from the pad to the ground plane to significantly reduce the
temperature inside the chip. The dimensions of the expanded
pads are at the discretion of the designer and depend on the
available board space.
START-UP BEHAVIOR
The ADuM6000 device does not contain a soft start circuit.
Therefore, the start-up current and voltage behavior must be
taken into account when designing with this device.
When power is applied to V
to operate and draw current when the UVLO minimum voltage
is reached. The switching circuit drives the maximum available
power to the output until it reaches the regulation voltage where
PWM control begins. The amount of current and the time
required to reach regulation voltage depends on the load and
the V
RC
RC
GND
GND
DD1
V
RC
V
1
DD1
OUT
DD1
SEL
) and for Pin 9 and Pin 15 (GND
IN
1
1
slew rate.
NC
Figure 14. Recommended PCB Layout
DD1
, the input switching circuit begins
ISO
NC
NC
). Implement multiple
NC
ADuM6000
V
GND
V
V
GND
ISO
SEL
ISO
ISO
ISO