ZHCSFB6D April 2016 – June 2021 THS4551
PRODUCTION DATA
The very low internal quiescent power dissipation for the THS4551, combined with the excellent thermal impedance of the 16-pin VQFN package (RGT), limits the possibility of excessively high internal junction temperatures. A more detailed analysis may be warranted because the 10-pin WQFN (RUN) package has a much higher junction-to-ambient thermal impedance (θJA = 163°C/W).
To estimate the internal TJ, an estimate of the maximum internal power dissipation is first required. There are two pieces to the internal power dissipation: quiescent current power and the power used in the output stage to deliver load current. To simplify the latter, the worst-case output stage power drives a dc differential voltage across a load using half the total supply voltage. Also assume a maximum ambient temperature of 125°C, giving the maximum quiescent current as shown in Figure 11-1. As an example:
Even for this extreme condition and the maximum-rated ambient of 125°C, the junction temperature is a maximum of 127°C, which is less than the rated absolute maximum of 150°C. Follow this same calculation sequence for the exact application and package selected to predict the maximum TJ.