ISOW7840: Circuit getting heated

Hi Frank,

Thank you for posting to E2E! Please let us know the following information for our understanding:

• Are the signals or power supplies connected to ISOW7840F exceeding its recommended or absolute maximum operating conditions?
• Does the ISOW7840 heat up immediately after powering up, or after a certain event or test?
• Confirm which temperature the ISOW7840F device reaches if possible

Thank you,
Manuel Chavez

Hi Frank,

Could you please share the information that Manuel has requested to be able to help customer debug the issue?
Additionally, I have the following questions.

1. I understand that customer PCB includes a line receiver (SN55LVDS32) which is connected to ISOW7840 and then the outputs of ISOW are connected to the data acquisition system containing an MPU or FPGA maybe.
2. To provide a differential signal to line receiver, you are using a line driver IC (SN55LVDS31) output to be applied to customer PCB. SN55LVDS31 is not part of customer PCB is only used for testing.
3. Please confirm if the above two points are accurate. Please do also help us with the schematic showing devices on both sides of ISOW7840, i.e., both line receiver and data acquisition system.
4. I also need to know the load on VISO output of ISOW. I am also assuming the VISO pins of two ISOW devices are not connected together.
5. Please mention what is the ambient temperature at which ISOW is being tested and what temperature does customer see on ISOW device.

Regards,
Koteshwar Rao

Hi Manuel,

Thank you. my response is below.

1.Power supply is in recommended voltage level and it is 3.3V
2.IC Heating only while doing loop back test.
3. It is bit difficult to measure.

Regards,

Hi Frank,

Thanks for your inputs to the questions posted by Manuel.

FRANK1 said:

2.IC Heating only while doing loop back test.

Could you please elaborate what exactly did you mean by loop back mode? Since the device has all 4 channels in one direction, I am not too sure what loop back mode meant here.

Koteshwar Rao said:

• I understand that customer PCB includes a line receiver (SN55LVDS32) which is connected to ISOW7840 and then the outputs of ISOW are connected to the data acquisition system containing an MPU or FPGA maybe.
• To provide a differential signal to line receiver, you are using a line driver IC (SN55LVDS31) output to be applied to customer PCB. SN55LVDS31 is not part of customer PCB is only used for testing.
• Please confirm if the above two points are accurate. Please do also help us with the schematic showing devices on both sides of ISOW7840, i.e., both line receiver and data acquisition system.
• I also need to know the load on VISO output of ISOW. I am also assuming the VISO pins of two ISOW devices are not connected together.
• Please mention what is the ambient temperature at which ISOW is being tested and what temperature does customer see on ISOW device.

Please do also help answer above questions and share requested information for better understanding and quicker resolution to the issue. Thanks.

Regards,
Koteshwar Rao

Hi Koteshwar ,

Thank you.

I can not get response from customer now.

You can close this ticket at first.

Thank you for your support.

Hi Koteshwar ，

I got the response from customer yesterday.

Can you help me to check it again?

or I create a new ticket?

I have attached line driver and receiver connection details how it has looped.
While testing only the isolator ic for the receiver is getting heated.
Both receiver and driver is in same system,
and the test is to confirm whether the receiver ic working properly before start the actual test.
The receiver will connect to UUT once the loop back test passed.

Thanks.Line driver and reciever Loop back.pdf

Hi Frank,

Thank you for following up and providing the connection details; we can continue the conversation on this thread or you may post any additional questions using the yellow "Ask a related question" button in the top right corner of this window.

In the schematic, what is Viso for both of the digital isolators connected to? The loading of Viso and signal pins is important for us to understand -- can our customer share waveforms of the Viso pins and signal lines being used when the device is overheating?

Ensure the input power supplies are stable for both isolator and line driver devices and that there are no short-circuits between PCBs besides the signal and GND connections. Please also provide the ambient temperature level at which these devices are being tested and the change in temperature of both ISOW7840 devices during this heating if possible.


Thank you,
Manuel Chavez