Data Sheet

ADuM5000

Rev. B | Page 11 of 16

APPLICATIONS INFORMATION

The dc-to-dc converter section of the ADuM5000 works on

principles that are common to most switching power supplies.

It has a secondary side controller architecture with isolated pulse-

an oscillating circuit that switches current into a chip scale air

core transformer. Power transferred to the secondary side is

side controller regulates the output by creating a PWM control

i

Coupler 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.

signal that can be connected to other isoPower devices. This feature

allows a single regulator to control multiple power modules without

pins can be connected together to work as a single supply. Because

there is only one feedback control path, the supplies work together

seamlessly. The ADuM5000 can be a source of regulation control,

as well as being controlled by another isoPower device.

There is an undervoltage lockout (UVLO) with hysteresis in the

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, such

as ensuring that the system supply rises to a minimum level

before the ADuM5000 demands current. It also prevents any

voltage drop due to converter current from turning the supply

off and possibly oscillating.

PCB LAYOUT

The ADuM5000 digital isolator is a 0.5 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 ADuM5000 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

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.

NC

NC

NC

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Figure 14. Recommended PCB Layout

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 ADuM5000 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

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 ADuM5000 does not contain a soft start circuit. Take the

start-up current and voltage behavior into account when designing

with this device.

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 time this