Data Sheet ADuM260N/ADuM261N/ADuM262N/ADuM263N
Rev. 0 | Page 21 of 23
APPLICATIONS INFORMATION
PCB LAYOUT
The ADuM260N/ADuM261N/ADuM262N/ADuM263N digital
isolators require no external interface circuitry for the logic
interfaces. Power supply bypassing is strongly recommended at
the input and output supply pins (see Figure 22). Bypass
capacitors are connected between Pin 1 and Pin 8 for V
DD1
and
between Pin 9 and Pin 16 for V
DD2
. The recommended bypass
capacitor value is between 0.01 μF and 0.1 μF. The total lead
length between both ends of the capacitor and the input power
supply pin must not exceed 10 mm.
V
DD1
V
IA
V
IB
V
IC
V
ID
, V
OD
V
IE
, V
OE
V
IF
, V
OF
GND
1
V
DD2
V
OA
V
OB
V
OC
V
ID
, V
OD
V
IE
, V
OE
V
IF
, V
OF
GND
2
14998-022
Figure 22. Recommended Printed Circuit Board 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 equally affects all pins on a given component
side. Failure to ensure this can cause voltage differentials between
pins exceeding the Absolute Maximum Ratings of the device,
thereby leading to latch-up or permanent damage.
See the AN-1109 Application Note for board layout guidelines.
PROPAGATION DELAY RELATED PARAMETERS
Propagation delay is a parameter that describes the time it takes
a logic signal to propagate through a component. The propagation
delay to a Logic 0 output may differ from the propagation delay
to a Logic 1 output.
INPUT (V
Ix
)
OUTPUT (V
Ox
)
t
PLH
t
PHL
50%
50%
14998-023
Figure 23. Propagation Delay Parameters
Pulse width distortion is the maximum difference between these
two propagation delay values and is an indication of how
accurately the timing of the input signal is preserved.
Channel matching is the maximum amount the propagation
delay differs between channels within a single ADuM260N/
ADuM261N/ADuM262N/ADuM263N component.
Propagation delay skew is the maximum amount the propagation
delay differs between multiple ADuM260N/ADuM261N/
ADuM262N/ADuM263N components operating under the
same conditions.
JITTER MEASUREMENT
Figure 24 illustrates the eye diagram for the ADuM260N/
ADuM261N/ADuM262N/ADuM263N. The measurement was
taken using an Agilent 81110A pulse pattern generator at 150 Mbps
with pseudorandom bit sequences (PRBS) 2(n − 1), n = 14, for 5 V
supplies. Jitter was measured with the Tektronix Model 5104B
oscilloscope, 1 GHz, 10 GSPS with the DPOJET jitter and eye
diagram analysis tools. The result shows a typical measurement
on the ADuM260N/ADuM261N/ADuM262N/ADuM263N
with 490 ps p-p jitter.
105
0
1
2
3
4
VOLTAGE (V)
5
0
TIME (ns)
–5–10
14998-024
Figure 24. ADuM260N/ADuM261N/ADuM262N/ADuM263N Eye Diagram
INSULATION LIFETIME
All insulation structures eventually break down when subjected
to voltage stress over a sufficiently long period. The rate of
insulation degradation is dependent on the characteristics of the
voltage waveform applied across the insulation as well as on the
materials and material interfaces.
The two types of insulation degradation of primary interest are
breakdown along surfaces exposed to the air and insulation wear
out. Surface breakdown is the phenomenon of surface tracking,
and the primary determinant of surface creepage requirements
in system level standards. Insulation wear out is the phenomenon
where charge injection or displacement currents inside the
insulation material cause long-term insulation degradation.
Surface Tracking
Surface tracking is addressed in electrical safety standards by
setting a minimum surface creepage based on the working voltage,
the environmental conditions, and the properties of the insulation
material. Safety agencies perform characterization testing on the
surface insulation of components that allows the components to be
categorized in different material groups. Lower material group
ratings are more resistant to surface tracking and, therefore, can
provide adequate lifetime with smaller creepage. The minimum
creepage for a given working voltage and material group is in each
system level standard and is based on the total rms voltage across
the isolation, pollution degree, and material group. The material
group and creepage for the ADuM260N/ADuM261N/
ADuM262N/ADuM263N isolators are presented in Table 9.
