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Analog Devices isoPower devices (ADuM524x)

S

Steve

Jan 1, 1970
0
We have developed an isolated thermocouple product for industrial
applications that uses these isoPower devices. The parts work well for
our purposes but the power supply is horribly inefficient and produces
severe radiated emissions at 300mHz (integrated PS switching
frequency) and higher harmonics. We've tried everything from PWB
layout changes, multi layer boards, ferrites/caps/filters, etc. but
still have not been able to reduce the emissions to meet the CE
requirments for industrial environments.

Anyone have any experience with this part?

Thanks,
Steve
 
J

John Larkin

Jan 1, 1970
0
We have developed an isolated thermocouple product for industrial
applications that uses these isoPower devices. The parts work well for
our purposes but the power supply is horribly inefficient and produces
severe radiated emissions at 300mHz (integrated PS switching
frequency) and higher harmonics. We've tried everything from PWB
layout changes, multi layer boards, ferrites/caps/filters, etc. but
still have not been able to reduce the emissions to meet the CE
requirments for industrial environments.

Anyone have any experience with this part?

Thanks,
Steve


We used transformer coupled supplies, at 60 KHz with deliberately
slowed edges, to avoid problems like that:

http://www.highlandtechnology.com/DSS/V450DS.html

Probably cheaper, too.

We do use their logic isolators, which seem fine, but not the
self-powered ones.

John
 
R

Robert Adsett

Jan 1, 1970
0
We have developed an isolated thermocouple product for industrial
applications that uses these isoPower devices. The parts work well for
our purposes but the power supply is horribly inefficient and produces
severe radiated emissions at 300mHz (integrated PS switching

MHz Presumably ;)
frequency) and higher harmonics. We've tried everything from PWB
layout changes, multi layer boards, ferrites/caps/filters, etc. but
still have not been able to reduce the emissions to meet the CE
requirments for industrial environments.

All the switching currents are within the chip (other than maybe
transient input) so there may not be much you can do externally to
reduce EMI. Have you tried shielding it?

Robert
 
D

D from BC

Jan 1, 1970
0
We have developed an isolated thermocouple product for industrial
applications that uses these isoPower devices. The parts work well for
our purposes but the power supply is horribly inefficient and produces
severe radiated emissions at 300mHz (integrated PS switching
frequency) and higher harmonics. We've tried everything from PWB
layout changes, multi layer boards, ferrites/caps/filters, etc. but
still have not been able to reduce the emissions to meet the CE
requirments for industrial environments.

Anyone have any experience with this part?

Thanks,
Steve

Switch to alternative ?

Maybe check out the various isolators at NVE
http://www.nve.com/IsolatorApplications.php
"
NVE’s IL700 family of high-speed digital isolators are CMOS
devices manufactured with NVE’s patented* IsoLoop® spintronic
Giant Magnetoresistive (GMR) technology. The IL710S is the
world’s fastest isolator of its type, with a 150 Mbps typical data
rate.
"

Not opto nor RF.


D from BC
British Columbia
Canada.
 
R

Robert Adsett

Jan 1, 1970
0
MHz Presumably ;)


All the switching currents are within the chip (other than maybe
transient input) so there may not be much you can do externally to
reduce EMI. Have you tried shielding it?

Apparently I wasn't thinking clearly. A conductive shield across the
isolation gap might not be very good for the isolation.

I take it you've implemented there suggestion about providing 100Ohms
or so of impedance at 300MHz and adding caps to slow down the
transition edges?

Robert
 
R

Robert Adsett

Jan 1, 1970
0
Switch to alternative ?

Maybe check out the various isolators at NVEhttp://www.nve.com/IsolatorApplications.php
"
NVE's IL700 family of high-speed digital isolators are CMOS
devices manufactured with NVE's patented* IsoLoop(R) spintronic
Giant Magnetoresistive (GMR) technology. The IL710S is the
world's fastest isolator of its type, with a 150 Mbps typical data
rate.
"

Not opto nor RF.

Similar technology to the AD part. I think the problem he is seeing
is coming from the isolated power supply portion of the chip, I don't
recall any of the NVE parts providing that. It would be rather nice
not to have to add a transformer or an Isolated DC-DC but not if you
can't get past the EMI requirements of course.

Robert
 
J

John Larkin

Jan 1, 1970
0
Switch to alternative ?

Maybe check out the various isolators at NVE
http://www.nve.com/IsolatorApplications.php
"
NVE’s IL700 family of high-speed digital isolators are CMOS
devices manufactured with NVE’s patented* IsoLoop® spintronic
Giant Magnetoresistive (GMR) technology. The IL710S is the
world’s fastest isolator of its type, with a 150 Mbps typical data
rate.
"

Not opto nor RF.


D from BC
British Columbia
Canada.

Some interested party, ADI or TI, published a paper showing that the
NVE parts are buggy and can get confused about output states.

I think Steve's problem is with the power isolation stuff, not the
logic isolator.

John
 
Q

qrk

Jan 1, 1970
0
We have developed an isolated thermocouple product for industrial
applications that uses these isoPower devices. The parts work well for
our purposes but the power supply is horribly inefficient and produces
severe radiated emissions at 300mHz (integrated PS switching
frequency) and higher harmonics. We've tried everything from PWB
layout changes, multi layer boards, ferrites/caps/filters, etc. but
still have not been able to reduce the emissions to meet the CE
requirments for industrial environments.

Anyone have any experience with this part?

Thanks,
Steve

Can you show us a schematic how you tried filtering the noise
problems?

Did your filters have any effect on the noise problem?
 
A

asanazi

Jan 1, 1970
0
We have developed an isolated thermocouple product for industrial
applications that uses these isoPower devices. The parts work well for
our purposes but the power supply is horribly inefficient and produces
severe radiated emissions at 300mHz (integrated PS switching
frequency) and higher harmonics. We've tried everything from PWB
layout changes, multi layer boards, ferrites/caps/filters, etc. but
still have not been able to reduce the emissions to meet the CE
requirments for industrial environments.

Anyone have any experience with this part?

Thanks,
Steve

Maybe you should forgot about the integrated power converter and build
external one (or use off-shelve from power-one, Synqor, Tyco, etc.).
We used ADUM1200 for isolated DC/DC converters as separation of
synchronisation pulses for rectification; however we also notice that
sometime, during power-up, outputs doesn't reflect input state. ADuM
use inductore as isolation barier. Later we replaced with capacitor
isolators (ISO from TI). Performance is better and there is no more
"strange" behavior during strat-up. Also MTBF is much better for ISO
than for ADuM.

Janusz
 
D

D from BC

Jan 1, 1970
0
Some interested party, ADI or TI, published a paper showing that the
NVE parts are buggy and can get confused about output states.

I think Steve's problem is with the power isolation stuff, not the
logic isolator.

John

I was thinkn:
Some isolator + clean power = possible solution

Isn't an onboard 300Mhz converter like trying to have a quiet meeting
in one room with fire crackers going off in the adjacent room.. :p


D from BC
British Columbia
Canada.
 
J

Joerg

Jan 1, 1970
0
John said:
We used transformer coupled supplies, at 60 KHz with deliberately
slowed edges, to avoid problems like that:

http://www.highlandtechnology.com/DSS/V450DS.html

Probably cheaper, too.

That's the way to do it.

We do use their logic isolators, which seem fine, but not the
self-powered ones.

I mostly use a modulation scheme, essentially a clock and then a DC
restore (clamping) on the system side. That way there are no
single-sourced parts in the machine.
 
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