adum6200 Analog Devices, Inc., adum6200 Datasheet - Page 18

• Manufacturer Part Number: adum6200
• Description: Dual-channel, 5 Kv Isolators With Integrated Dc-to-dc Converter Adum6200/adum6201/adum6202
• Manufacturer: Analog Devices, Inc.

ADuM6200/ADuM6201/ADuM6202
APPLICATIONS INFORMATION
The dc-to-dc converter section of the ADuM620x 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 ADuM620x implements undervoltage lockout (UVLO)
with hysteresis on the V
that the converter does not enter oscillation due to noisy input
power or slow power-on ramp rates.
The ADuM620x can accept an external regulation control
signal (RC
This feature allows a single regulator to control multiple power
modules without contention. When accepting control from a
master power module, the V
adding their power. Because there is only one feedback control
path, the supplies work together seamlessly. The ADuM620x
can only regulate itself or accept regulation (slave device) from
another device in this product line; it cannot provide a
regulation signal to other devices.
PCB LAYOUT
The ADuM620x digital isolators with 0.4 W isoPower integrated
dc-to-dc converter require no external interface circuitry for the
logic interfaces. Power supply bypassing is required at the input
and output supply pins (see Figure 23). Note that low ESR bypass
capacitors are required between Pin 1 and Pin 2 and between
Pin 15 and Pin 16, as close to the chip pads as possible.
The power supply section of the ADuM620x 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 induc-
tance, 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
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 for V
capacitor must have a low ESR; for example, use of a ceramic
capacitor is advised.
DD1
ISO
, and between Pin 15 and Pin 16 for V
) side controller regulates the output by creating a PWM
IN
) that can be connected to other isoPower devices.
DD1
power input. This feature ensures
ISO
pins can be connected together,
DD1
and V
DD1
DD1
power is supplied to
ISO
ISO
) side by a dedicated
. The smaller
.
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The total lead length between the ends of the low ESR capacitor
and the input power supply pin must not exceed 2 mm. Installing
the bypass capacitor with traces more than 2 mm in length may
result in data corruption. 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 19, thereby leading to latch-up and/or
permanent damage.
The ADuM620x is a power device that dissipates approximately
1 W of power when fully loaded and running at maximum speed.
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 23
shows enlarged pads for Pin 8 (GND
Multiple vias should be implemented 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 ADuM620x devices do 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
With a fast V
up to 100 mA/V of V
the output can turn on, so the peak current is proportional to
the maximum input voltage.
BYPASS < 2mm
V
V
V
IA
IB
RC
DD1
E1
GND
GND
V
/V
RC
/V
/NC
DD1
SEL
OA
OB
IN
slew rate.
1
1
DD1
slew rate (200 μs or less), the peak current draws
Figure 23. Recommended PCB Layout
DD1
. The input voltage goes high faster than
DD1
, the input switching circuit begins
1
) and Pin 9 (GND
V
GND
V
V
NC
V
V
GND
ISO
OA
OB
SEL
E2
/NC
ISO
/V
/V
ISO
ISO
IA
IB
).