ADUM7703 datasheet(20/22 Pages) AD

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ADuM7703

Data Sheet

Rev. 0 | Page 20 of 22

INTERFACING TO ADSP-CM4xx

The ADSP-CM4xx family of mixed-signal control processors

contains an on-chip sinc filter and clock generation modules for

direct connection to the ADuM7703 MCLKIN and MDAT pins.

The ADSP-CM4xx can process bit streams from four ADuM7703

devices using a pair of configurable sinc filters for each bit stream.

The primary sinc filter of each pair produces the filtered and

decimated output for the pair. The output can be decimated to

any integer rate between 8 times and 256 times lower than the

input rate. The four secondary sinc filters are low latency filters

with programmable positive and negative overrange detection

comparators that can detect system fault conditions.

Figure 32 shows the typical interface between the ADuM7703

and the ADSP-CM4xx. Additional information on the

configuration of the sinc filter modules in the ADSP-CM4xx

can be found in the AN-1265 Application Note.

SINC PAIR n

PRIMARY

SECONDARY

LIMIT

CONTROL FOR GROUP n

MODULATOR CLOCK n

ADSP-CM40xF1

ADuM77031

MDAT

MCLKIN

SINC0_CLK0

SINC0_D0

1ADDITIONAL PINS OMITTED FOR CLARITY

Figure 32. Interfacing the ADuM7703 to the ADSP-CM4xx

GROUNDING AND LAYOUT

It is recommended to decouple the VDD1 supply with a 10 μF

capacitor in parallel with a 100 nF capacitor to GND1. Decouple

the VDD2 supply with a 10 μF capacitor in parallel with a 100 nF

capacitor to GND2. In applications involving high common-mode

transients, ensure that board coupling across the isolation barrier

is minimized. Furthermore, design the board layout so that any

coupling that occurs equally affects all pins on a given component

side. Failure to ensure equal coupling can cause voltage differentials

between pins to exceed the absolute maximum ratings of the

device, thereby leading to latch-up or permanent damage. Place

any decoupling as close to the supply pins as possible.

Minimize series resistance in the analog inputs to avoid any

distortion effects, especially at high temperatures. If possible,

equalize the source impedance on each analog input to minimize

offset. Check for mismatch and thermocouple effects on the analog

input PCB tracks to reduce offset drift.

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. In addition to the

testing performed by the regulatory agencies, Analog Devices

carries out an extensive set of evaluations to determine the lifetime

of the insulation structure within the ADuM7703.

Analog Devices performs accelerated life testing using voltage levels

higher than the rated continuous working voltage. Acceleration

factors for several operating conditions are determined. These

factors allow calculation of the time to failure at the actual working

voltage. The values shown in Table 10 summarize the peak voltage

for 37.5 years of (reinforced) service life for a bipolar, ac operating

condition and the maximum VDE approved working voltages.

These tests subjected the ADuM7703 to continuous cross isolation

voltages. To accelerate the occurrence of failures, the selected

test voltages were values exceeding those of normal use. The

time to failure values of these units were recorded and used to

calculate the acceleration factors. These factors were then used

to calculate the time to failure under the normal operating

conditions. The values shown in Table 10 are the lesser of the

following two values:



The value that ensures at least a 37.5 year lifetime of

continuous (reinforced) use.



The maximum VDE approved working voltage.

The lifetime of the ADuM7703 is guaranteed using a bipolar

ac waveform, as shown in Figure 33.

RATED PEAK VOLTAGE

Figure 33. Bipolar AC Waveform, 50 Hz or 60 Hz

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