ISOW7841: Ground shifting

RAJEESH R

Part Number: ISOW7841

In our application we are going to connect 30V battery module in series configuration to get 1000V battery pack. Each battery pack has AFE(Analog front end) and microcontroller inside.So we need to establish isolated SPI communication between the AFE and microcontroller . That means each module has AFE, Microcontroller and Isolated SPI IC. So we chosen ISOW7841.Please let's know is this ic capable of working with the ground shift .That means when battery module are connected in series ground shift is going to happen,and AFE ic is capable of seeing that ground shift. But i don't know about ISOW7841. Please tell me this ic is capable or not.

over 5 years ago

0 Clemens Ladisch over 5 years ago

Guru 318700 points

While one of the primary purposes of isolators is to protect against transients, they also work with DC or AC ground shifts. This is called "working voltage" in the datasheet:

>100-Year projected lifetime at 1 kV_RMS working voltage

Increasing the working voltage reduces the lifetime, as discussed in section 10.2.3.1 of the datasheet. Your application will be fine.

0 Koteshwar Rao over 5 years ago

TI__Guru 55885 points

Hi Rajeesh,

The max ground shift from one device to another device in your application is going to be about 970V DC. Since this is under device DC working spec of 1414V DC, ISOW7841 will be able to withstand and support these ground shifts.

Let me know if you have any other questions, thank you.

Regards,
Koteshwar Rao

0 RAJEESH R over 5 years ago in reply to Clemens Ladisch

Prodigy 40 points

I didn't get the concept of working voltage. Could you please explain?

0 Clemens Ladisch over 5 years ago in reply to RAJEESH R

Guru 318700 points

The ground shift (i.e., the difference between the grounds) is the working voltage.

0 Koteshwar Rao over 5 years ago in reply to RAJEESH R

TI__Guru 55885 points

Hi Rajeesh,

Working voltage of isolator is the continuous voltage that the isolator can withstand across its isolation barrier for its life. This for ISOW7841 means that the voltage between GND1 and GND2 can be upto 1414V DC continuously applied for its life. Hence, the DC working voltage for ISOW7841 is 1414V DC.

For more details on high voltage isolation terms, please refer to the white paper at the link below. Thanks.

Regards,
Koteshwar Rao

0 RAJEESH R over 5 years ago in reply to Koteshwar Rao

Prodigy 40 points

Thanks for your reply and sharing the document. I read and understood. So I am going to use ISOW7841 in our application.

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ISOW7841: Ground shifting