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Hi,
In our project, we are going to use this TCA6424ARGJR IO expander part. We need some clarification for the below mentioned points.
1. What is the maximum power dissipated by this part?
2. What is the maximum junction temperature for this part?
3. We are going to use all the IO pins in which each pins sinks a current of about 10mA. Is the part suitable for this kind of applications?
Thanks & Regards,
Shahul
Hello Shahul,
1) The maximum power dissipated in the part is the power dissipation due to IOs and the ICC.
You will need to add some resistance in series with the diode or you will you could damage the part and it will help with power dissipation within the part. The max I_OH (High-level output current) is 10mA max. I have drawn a diagram explaining the problem and how to fix it. See below:
There are some other added benefits of putting the series resistor, 1) Less of the power dissipation is in the part 2) The resistance of the FET varies greatly over temps, Vcc, and process, but the resistance of the Rled does not. That will mean a more consistent current through the LED which means consistent brightness.
The power dissipation due to ICC (=ICCP+ICCI) is generally speaking very low compared to this application. Here is how to calculate it worst case assuming Vcc and Vcci are the same voltage.
2) As an general approximation use the Max Operating free-air temp as the max junction temp. We do not guarantee it this way, but is a good way to approximate it.
3) See 1) for answers
Let me know if you have any more questions.
-Francis Houde
