SN55189A: Does the Dissipation Rating Table in the datasheet talks about the maximum power dissipation that the device can withstand or the maximum power consumed by the device?

Hi Komal,

It is the max power the device can dissipate without taking damage, but there is a large caveat with that table. 

From that table you can derive the thermal impedance from Ambient - R_Theta_JA.

Just as example use the "D" package row from the table. 

Using the following equation:

TJ = TA + R_theta_JA * P_dissipated 

Where TJ max is 150C (its not directly listed in datasheet - but the max storage is and that is 150C - the max storage is typically equal to max junction temperature) 

So plugging in the 25C values for row 1:

150C = 25C + R_theta_JA * 0.95W

R_theta_JA(D-Package) = (150C - 25C)/0.95W ~ 131.6 C/W 

You can use this process on the other packages - depending on what package you are using. 

The issue is that R_theta_JA is extremely system dependent and variable and the table included in datasheet assumes a static and ideal R_theta_JA which is not what you will see in reality. 

There is a process to find the effective R_theta_JA mentioned in this app note: https://www.ti.com/lit/an/spra953c/spra953c.pdf?ts=1709826375232&ref_url=https%253A%252F%252Fwww.google.com%252F 

It also includes a lot of information on thermal metrics. Since this is an older device we didn't directly specify the thermal parameters on this device. 

To fine tune the system and find the actual break point of the system - a thermal analysis of the "real" system itself needs to be done. 

So essentially this gives an idea of what the max power could be in our specific setup - but for system specific max power dissipation the effective R_theta_JA must be found. 

Best,

Parker Dodson