Part Number: SN65HVD75
Hello support team,
Regarding SN65HVD75, we received a PCN that the absolute maximum ratings of Supply voltage (VCC) and R pin was changed from 5.5 V to 3.6 V.
Our customer uses the combination of ISOW7821 and SN65HVD75 on his circuit.These devices are already in the design-in state to the customer.In the customer's circuit, the supply voltage of ISOW7821 is 3.3 V.Looking at the specifications of ISOW7821, the maximum value of VISO is 3.58 V when the supply voltage is 3.3 V ± 10%.It seems that there is no margin against this absolute maximum rating of SN65HVD75 of which is 3.6 V.
[Questions]1. Although the absolute maximum rating has been changed, are there any problem if the customer continues to use the combination of these devices?
2. Do you have any experience with this combination?
3. If the supply voltage of the ISOW7821 exceeds 3.3 V + 10%, is there a possibility that the voltage of VISO exceeds 3.6 V?
4. If the supply voltage of the ISOW7821 is limited to the range of 3.3 V ± 5%, will the maximum voltage of VISO be lower than 3.58 V?
We think that we need to give the customer some advice.
We are glad that we were able to resolve this issue, and will now proceed to close this thread.
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In reply to Hao L:
In reply to Manuel Chavez:
In reply to Masanori Tachibana:
Sorry for the delay in answering your question. Please see my answers to your questions below:
3. If the supply voltage of the ISOW7821 exceeds 3.3 V + 10%, is there a possibility that the voltage of VISO exceeds 3.6 V?.
The datasheet max VISO of 3.58 for Vcc of 3.3V +/-10%. If Vcc exceeds that I cannot guarantee that VISO would not also exceed 3.6V. I would expect that if it was slightly higher or lower that it would not exceed it - but you would have to test that in your system across temperature and several different units to ensure it.
The datasheet max VISO is 3.58V for Vcc of 3.3V +/-10%. So for Vcc of 3.3 V ± 5%, VISO would not exceed 3.6 V (guaranteed by the datasheet) and therefore would not damage the SN65HVD75 with an abs max of 3.6V. We cannot guarantee that the maximum would be lower than 3.58V for a Vcc of 3.3 V ± 5%.
Do you have any further questions?
In reply to Dan Kisling:
Thank you for teaching me your view.From described in the datasheet, I understand that your view is correct.
However, the absolute maximum rating of SN65HVD75 is 3.6 V comparing to the maximum VISO value of ISOW7821 which is 3.58 V, and the margin between them is only 20 mV. I think it is too small.If noise or overshoot is superimposed on VCC or RIN even a little, I think there is a possibility of exceeding the absolute maximum rating which is 3.6V.Therefore, I would like to know how to lower the maximum value of VISO of ISOW7821 because I want to get as much margin as possible.If you have any good ideas, please let me know.
In reply to Koteshwar Rao:
In reply to Max Robertson:
Thank you for giving me a lot of advice.I understood that VISO voltage range of ISOW7821 can not be controlled with supply voltage of it.I will consider proposing a circuit to lower the voltage between VISO of ISOW7821 and VCC of SN65HVD75, or will consider proposing another device such as THVD1450 which is pin compatible with SN65HVD75.
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