About the difference in the voltage between GND1 and GND2 of ISO7640FM

Hello Jason,

Thank you very much for your answer.
I will inform the customer of them.

Best regards,
Takishin

Hello Jason,

should I read into your answer that ISO764x capacitive couplers are not suited for applications with permanent DC working voltage, e.g. HV battery managment systems?

I think it would be appropriate to give at least orientating information about behaviour with DC working voltage in the datasheet. I also wonder if the voltage ratings according to EN and UL standards must have a formal reservation about reduced DC voltage strength?

To ask a simple question, is ISO764x suited for 1 kV DC working voltage, Cat. I, basic insulation? What are possible restrictions?

Best regards,

Frank

Hi Frank,

Jason has switched roles, and no longer supports these products. I have notified the engineer that covers the isolators and you should get a response shortly.

Thanks,

John

Hi Frank,

We initially observed that ISO7640FM was sensitive to large DC offset voltages between GND1 and GND2. We have now rectified this problem.

Hi Saleem,

that's good news.

Can we expect a datasheet update or other document stating the component dc rating?

Thanks!

Hi Frank,

We're still working on cleaning up the old die stock and inventory. Once we do that, I'll update the datasheet.

Hi Saleem,

I just noticed that the recent ISO741FC datasheet (25 MBPS version of the digital isolator) doesn't have a reservation about DC working voltage. Does this mean that presently shipped ISO741FC can be used with DC offsets up to the rated working voltage?

Best regards,

Frank  

Hi Frank,

For DC offsets, we're recommending our new digital isolator family, ISO734x. ISO7342C and ISO7341C/FC are planned to be released in 4Q14.  Preview datasheet is attached.

0160.ISO7342C_Datasheet.pdf

ISO7641FC isn't recommended for DC offset applications.

Hi Saleem!

So if I were to buy a ISO7640FM right now, it would have the DC offset fix?  I plan on using an ISO734x, but it's not available yet, and I have a prototype to build.  The to appear to be pin/package compatible, so I figure on just making the switch when it does become available, but I don't want to do something dangerous in the meantime.

Justin

Hi Justin,

You can use ISO7640FM for your prototype.  The DC charge spread issue doesn't impact the integrity of the isolation barrier, so it's not going to create a hazard. The issue may temporarily show up as functionality problem if exposed to high voltage DC for long period, but most devices will recover if the conditions are removed.

Awesome- thanks Saleem!!

I found another difference that may be problematic- the ISO7640FM is rated as 5000V reinforced isolation under UL 61010-1, and the ISO 7342C is rated as 3000V single isolation, but to UL1577.  The data sheet indicates CSA and IEC 61010 ratings to include reinforced, but it doesn't seem to say at what voltage.  Am I reading this correctly?  Will ISO7342C have a reinforced isolation rating under UL 61010-1, or just the CSA and IEC equivalents?

Justin

Yes, ISO7342 will have reinforced isolation rating under CSA and IEC equivalents of 61010-1; there is currently no plan to certify to UL 61010-1. What's the reinforced working voltage requirement of your application?

We're also releasing ISO7842 next month; ISO7842 has very high isolation rating of 8000Vpk / 5.7kVrms.

Saleem Marwat said:

You can use ISO7640FM for your prototype.  The DC charge spread issue doesn't impact the integrity of the isolation barrier, so it's not going to create a hazard. The issue may temporarily show up as functionality problem if exposed to high voltage DC for long period, but most devices will recover if the conditions are removed.

Hi Saleem,

thanks for giving details about the failure mechanism. Can you also comment the expectable time scale? If DC HV is applied across the isolation barrier, will we likely see a function loss after minutes, hours, days or months?

Best regards,

Frank

Frank,

It'll depend on the DC voltage and temperature. The higher the voltage and temperature, the higher the likelihood of functional loss. You may not experience any issues at all if you are applying 200 or 300 V at room temperature.

Hi Saleem!

Thanks for the information- that new part looks great!!

My application has an 1800V reinforced working voltage isolation requirement.  I was going to use two chips, but if it looks like I may be able to get away with one with the ISO7842.

Justin

Hi Justin,

Yes, ISO7842 has very strong isolation specs / performance. Good luck!

Saleem, there doesn't appear to be any information on ISO7842 yet.

Robert

Hi Robert,

For more details on ISO7842, please contact iso_bdm@list.ti.com directly.

Thanks Saleem

Robert