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ADUM2250 Working Voltage & Regulation Questions

Question asked by ProgrammerAndy on Jun 19, 2012
Latest reply on Aug 3, 2012 by MSCantrell

I'm very new to insulation standards, so I have a few questions.

 

What I'm pretty sure on is our box will need double or reinforced insulation.  We will most likely be using I2C and probably will insulate the rest of the circuit from our high voltage inputs going into an ADE7878.  The plan is to use the ADUM2250 and some other unidirectional iCouplers for the HSDC (high-speed data capture lines) going between the ADE7878 and a microcontroller (and the rest of the circuit).  We'll need a DC-DC converter to get isolated power over to the ADE7878, of course.

 

Our box will measure up voltages up to 345 V line-to-neutral (600 V line-to-line) on the voltage inputs to the ADE7878.  Readings can be read over Ethernet too.  So it appears our box falls under the IEC 61010-1 standard for test-and-measurement equipment as well as IEC 60950-1 for information technology equipment.

 

I have a copy of 61010-1 that's about a year old, but from it it seems for basic insulation we need 3,320 VACrms and a clearance/creepage of 5.5 mm. 

 

# 1. One question I have, do these voltages and clearances differ between 61010-1 and 60950-1?

 

Looking over the ADUM2250 spec sheet, I see that it has a minimum 7.7mm creepage and 8.0mm clearance.  Since it provides isolation of 5kVACrms too, it appears to meet the needs for basic insulation regarding IEC 61010-1.

# 2. Am I interpreting that correctly?

 

This FAQ question says that all iCoupler meet at least 400 VACrms but I'm a bit confused because the table seems to imply even for the ADUM225x series that it only supports 400 VACrms working voltage for a bipolar AC waveform, contradicting the spec sheet.  That page doesn't specify which standard that is met either.

 

# 3. So in order to achieve double insulation, one solution is to put two ADUM2250's back-to-back with isolated supplies from DC-DC converters?

 

# 4. I'm a little unclear about section 6.5.3 of IEC 61010-1 regarding protective impedances.  Would a pair of resistors in series with the voltage input line count (such as in the voltage divider)?  So you would only need one ADUM2250 along with the resistors?

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