ISO7741: layout questions

Kailyn Chen

Part Number: ISO7741

Hello,

About our isolators PCB layout, one customer need to confirm how to decide the groove width, because by carving / cutting grooves on PCB we can increase the creepage of PCB .

So what is the groove width? Could you please give me some advice?

Best regards

Kailyn

over 3 years ago

+1 Darrah Merillat over 3 years ago

TI__Mastermind 29430 points

Hello Kailyn,

Thank you for your question. Cutting grooves into the PCB can help increase creepage however we do not specify any particular widths for our isolators as this is largely system dependent. The minimum creepage required for any system is defined by the relevant industry standards, so the amount of additional creepage required would depend on how the isolator's creepage compares to the standard requirement. However, for a groove greater than 1mm wide, the existing creepage distance plus the width of the groove and twice the depth of the groove must equal or exceed the required creepage distance. The groove should also not be large enough to weaken or compromise the PCB substrate potentially resulting in mechanical test failures.

Regards,
Darrah

0 Kailyn Chen over 3 years ago in reply to Darrah Merillat

TI__Genius 9560 points

Hi Darrah，

Thank you very much for your reply.

The customer also need to confirm about the below test, VTEST = VIOTM,t=60s, how much about the threshold leakage current ?

Best regards

kailyn

+1 Darrah Merillat over 3 years ago in reply to Kailyn Chen

TI__Mastermind 29430 points

Hello Kailyn,

During the VIOTM test we use a threshold leakage current of 100μA.

Regards,
Darrah

0 Kailyn Chen over 3 years ago in reply to Darrah Merillat

TI__Genius 9560 points

Hi Darrah，

Thank you very much for your reply, about the threshold leakage current of 100μA, the customer wants to confirm how to decide the 100uA is the threshold leakage current?

Best regards

kailyn

+1 Darrah Merillat over 3 years ago in reply to Kailyn Chen

TI__Mastermind 29430 points

Hi Kailyn,

The standards typically defines the value of this current threshold and we believe that 10mA is the typical threshold that the industry uses, while at TI we use 100μA.

Regards,
Darrah

0 Kailyn Chen over 3 years ago in reply to Darrah Merillat

TI__Genius 9560 points

Hi Darrah，

Sorry to interrupt you again.

The customer gave the feedback that he tested the threshold leakage current much less than 100uA, I confirmed with him how to test it .

He put the 2 sides of the ISO7741 are shorted so that the device is a 2-terminal network, applying 1 minute of power AC power to the 2 sides. Could you please help to analyze?

Best regards

Kailyn

0 Darrah Merillat over 3 years ago in reply to Kailyn Chen

TI__Mastermind 29430 points

Hi Kailyn,

Can you confirm what is the voltage being tested for 1 minute and what is the leakage current observed?

Isolation

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ISO7741: layout questions