ISO1212EVM: Changing 100V input to 300V

we need protection at the input for your chip.  what kind of protection we have to use.  Also we need your circuit Evaluation Board to work form min 100V to max 300V  with threshold  60V.

what should I do with enable pin????? connected  to VCC1 ???

Hi Abraham and Dan,

The ISO1212 and its EVM can be protected using Zener or TVS diodes, fuses, and other typical protection elements. When selecting a protection component, for example a Zener diode, choose its safety voltage such that it is high enough to not interfere with normal operation, but low enough to protect the system. In this example, a Zener diode with Zener voltage of 315V - 360V is sufficient, like 330V.

To enable the output on side 1, tie the EN pin to Vcc1 or you may leave it floating. Connecting EN to Vcc1 with a 4.7kΩ resistor will keep the output reliably enabled. On the EVM, the output can be enable by connecting Pins 1 and 2 with jumper J3, as shown in the EVM User's Guide.

Regarding the input voltage scaling from 100V - 300V with a set 60V threshold, please await a response from the Isolation team next week. Dan Kisling is out of the office and will return early next week.


Thank you for your time,
Manuel Chavez

HI Manuel... Attached is the  modification fro my application 100V...300V,, let tour team check it

Hi Abraham,

Sorry for the delay in responding. 

Those values look pretty good. One concern I have is for how much current will be seen at the module input. Using the calculator from the document I linked we can see the following:

The current is on the order of 10’s of milliamps. This will mean we will have to size the resistors appropriately. Just looking at the threshold resistor: it will have to be able dissipate ~3.3W of power.

If possible, it would be best if the threshold voltage is about half of the input voltage.

For example, if we wanted 300V inputs and 150V thresholds, we could choose the following values:

If we wanted 110V inputs with 60V thresholds we could use the following values:

Note how the current at the input module has significantly reduced.

Best regards,

Dan

How about protection at the input...CHIP has max  60V......so zener or TVS has to be rated to 60V???

Hi Abraham,

Yes. The Zener diode in parallel with Cin (D1, D2, D3...) should be rated to protect from >60V levels. Following the method I mentioned earlier, diodes with Zener voltages of 62V - 66V can be used. The 315V Zener diodes should be placed on the high side (right of the schematic) towards the inputs to the system.


Thank you,
Manuel Chavez

HI Manuel,

please check my diagram....

is this correct >>  where I have to put 315X zener as you said in your previous note.. 

Hi Abraham,

The image is cropped such that the 315V diode cannot be seen, but the resistors and 60V diode do appear in the right place. I do encourage you to chose a Zener diode of >60V Zener voltage and to choose power resistors capable of dissipating multiple Watts for Rth and Rshunt. If necessary, Rth may be found in an SMD package, like the SMF518KJT.

Would you like for me to review the larger schematic showing the 315V Zener diode?


Thank you,
Manuel Chavez

HI  Manuel

As shown in the diagram. I don't know where to put 315V zener...

can you tell me where to put it

Hi Abraham,

I apologize for the confusion. The 315V Zener diode may be placed as a protective element to the device on each channel as shown below.


I hope this is helpful! Please let me know your thoughts.


Thank you for your time,
Manuel Chavez

PSA: In a following post, it is clarified that the ~60V Zener diode to be placed near the ISO1212 input pins is more effective at protecting the IC from over-voltages than the 315V Zener diode placed near the board inputs

Hi Manuel

but you need protection for your input  ...spec max 60V..

so I will use zener at the input of your chip as shown

Hi Abraham, all,

Because the resistor values are a non-trivial change, I am posting an updated system schematic shared on this thread:


The resistor divider is similar in terms of ratio, but I will need to confirm that this will maintain the high voltage compatibility and 60V threshold as we expect it to. Removing the ~60V Zener diode is not recommended to protect the ISO1212. In fact, the 60V Zener is preferred over the 315V Zener since it is closest to the device and can provide dedicated protection.

Since I do not believe we have specified this, is a specific transient or overvoltage condition expected in this test?


Thank you for posting to E2E!
Manuel Chavez

It seems good

Thanks for your help

Abraham,

You're welcome!


Best wishes,
Manuel Chavez