SN65HVD09: Operating Temperature

Hi Eric,

I did click by error that it is resolved. Regarding your question, thermal image was captured in normal conditions at 30°C ambient temperature.where no signals are present

Hi Eric,

My design have all GND terminal including terminal 1, Is it correct for improved thermal conductivity?

Samuel,

Yes, all GND pins should be connected to the GND net, just for device functionality sake. When you say no signals are present, do you mean that nothing is being transmitted, and the device is idle?

Looking at the ambient temperature and the junction temperature detected by the thermal camera, if we use the following formula:

Tj = Ta + (Θja * Pd)  - where TJ is junction temperature, Ta is ambient temperature, Θja is junction to ambient thermal resistance, and Pd is power dissipated

We get: 53C = 30C + (50 C/W * Pd) 

which gives Pd = 460mW, and if we assume a VCC of 5V, that means 92mA consumed. With 5 ports being drivers, and 4 ports being receivers, and looking at the graph on figure 10, I would expect the current consumption to be ~60mA, which would put Pd at 300mW, and the temperature rise closer to 15C, and the junction temperature at 45C. Given that the thermal resistance is measured on a board that's different than the customer's the parameter is relative to the JEDEC specified PCB, and may be different on your board, slightly higher even, and may account for a few degrees C.

So to answer your question, this does seem like a large rise in temperature when there's no data being transmitted or received, but when you consider all 9 ports being used and enabled at once, it does make sense. Can you try transmitting/receiving data on every port and testing the junction temperature then?

Regards,

Eric Hackett 

Hi Eric,

I'm sorry, I didn´t refresh web page in order to see the last answer.

IC is supplied with 5Vdc and control inputs are configured for 4 drivers and 4 receivers.

About your request, Could all drivers and receivers tie with the same signal and loopback mode?

Samuel,

As long as the signal generator can source the signal for each channel that should be fine. I more just want to see how much the temperature increases if the channels are toggling, as that should increase the power consumption of the transceiver, and thus raise the junction temperature.

Regards,

Eric Hackett

Hi Eric,

1DE/RE–9DE/RE pins are disconected or floatting, Is that correct for my application?

Hi Eric,

I ´m checking my design where driver´s inputs are connected into status LEDs, I think that for this reason IC is warming.

Samuel,

It looks like in the schematic CDE2 is high while the rest of CDE0, CDE1, and BSR are low. This would be the configuration necessary to make ports 1-4 receivers, ports 5-8 drivers, and port 9 a receiver. But if the individual controls are all floating, they are internally pulled up, but since you have the CDE1 and CD2 and BSR controlling the ports, this should be okay.

And if they are connected to LEDs, that would definitely be consuming more current from the driver and raising the power dissipated, and thus the temperature.

Regards,

Eric Hackett 

Hi Eric,

Thanks for your answer. Now I can be sure that 1DE/RE–9DE/RE pins are not necessary to connect.

Can Termination resistors cause overheating? I use 120ohms resistor in each differential port.

Samuel,

No, while the termination resistors will definitely consume current and thus dissipate power, 120 ohms on different buses is the recommended value and should not cause overheating.

Did you get any results with driving data on the bus lines? And did removing the LEDs help at all?

Regards,

Eric Hackett 

Hi Eric,

I´m sorry, sn65hvd09 is damaged, I think it was overheating. I have to purchase some parts and try once again.

Best Regards

SAM

Sam,

Understood, please post back to this thread or make a new one when you get new devices and can run more experiments.

Regards,

Eric Hackett