SLUAAT8 December   2023 CSD13201W10 , CSD13202Q2 , CSD13302W , CSD13303W1015 , CSD13306W , CSD13380F3 , CSD13381F4 , CSD13383F4 , CSD13385F5 , CSD15380F3 , CSD15571Q2 , CSD16301Q2 , CSD16321Q5 , CSD16322Q5 , CSD16323Q3 , CSD16325Q5 , CSD16327Q3 , CSD16340Q3 , CSD16342Q5A , CSD16401Q5 , CSD16403Q5A , CSD16404Q5A , CSD16406Q3 , CSD16407Q5 , CSD16408Q5 , CSD16409Q3 , CSD16410Q5A , CSD16411Q3 , CSD16412Q5A , CSD16413Q5A , CSD16414Q5 , CSD16415Q5 , CSD16556Q5B , CSD16570Q5B , CSD17301Q5A , CSD17302Q5A , CSD17303Q5 , CSD17304Q3 , CSD17305Q5A , CSD17306Q5A , CSD17307Q5A , CSD17308Q3 , CSD17309Q3 , CSD17310Q5A , CSD17311Q5 , CSD17312Q5 , CSD17313Q2 , CSD17318Q2 , CSD17322Q5A , CSD17327Q5A , CSD17381F4 , CSD17382F4 , CSD17483F4 , CSD17484F4 , CSD17501Q5A , CSD17505Q5A , CSD17506Q5A , CSD17507Q5A , CSD17510Q5A , CSD17522Q5A , CSD17527Q5A , CSD17551Q3A , CSD17551Q5A , CSD17552Q3A , CSD17552Q5A , CSD17553Q5A , CSD17555Q5A , CSD17556Q5B , CSD17559Q5 , CSD17570Q5B , CSD17571Q2 , CSD17573Q5B , CSD17575Q3 , CSD17576Q5B , CSD17577Q3A , CSD17577Q5A , CSD17578Q3A , CSD17578Q5A , CSD17579Q3A , CSD17579Q5A , CSD17581Q3A , CSD17581Q5A , CSD17585F5 , CSD18501Q5A , CSD18502KCS , CSD18502Q5B , CSD18503KCS , CSD18503Q5A , CSD18504KCS , CSD18504Q5A , CSD18509Q5B , CSD18510KCS , CSD18510KTT , CSD18510Q5B , CSD18511KCS , CSD18511KTT , CSD18511Q5A , CSD18512Q5B , CSD18513Q5A , CSD18514Q5A , CSD18531Q5A , CSD18532KCS , CSD18532NQ5B , CSD18532Q5B , CSD18533KCS , CSD18533Q5A , CSD18534KCS , CSD18534Q5A , CSD18535KCS , CSD18535KTT , CSD18536KCS , CSD18536KTT , CSD18537NKCS , CSD18537NQ5A , CSD18540Q5B , CSD18541F5 , CSD18542KCS , CSD18542KTT , CSD18543Q3A , CSD18563Q5A , CSD19501KCS , CSD19502Q5B , CSD19503KCS , CSD19505KCS , CSD19505KTT , CSD19506KCS , CSD19506KTT , CSD19531KCS , CSD19531Q5A , CSD19532KTT , CSD19532Q5B , CSD19533KCS , CSD19533Q5A , CSD19534KCS , CSD19534Q5A , CSD19535KCS , CSD19535KTT , CSD19536KCS , CSD19536KTT , CSD19537Q3 , CSD19538Q2 , CSD19538Q3A , CSD22202W15 , CSD22204W , CSD22205L , CSD22206W , CSD23202W10 , CSD23203W , CSD23280F3 , CSD23285F5 , CSD23381F4 , CSD23382F4 , CSD25202W15 , CSD25211W1015 , CSD25213W10 , CSD25304W1015 , CSD25310Q2 , CSD25402Q3A , CSD25404Q3 , CSD25480F3 , CSD25481F4 , CSD25483F4 , CSD25484F4 , CSD25485F5 , CSD25501F3 , CSD75207W15 , CSD75208W1015 , CSD83325L , CSD85301Q2 , CSD85302L , CSD85312Q3E , CSD86311W1723 , CSD87312Q3E , CSD87313DMS , CSD87501L , CSD87502Q2 , CSD87503Q3E , CSD88537ND , CSD88539ND

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
  5. 2Review the ZθJC Graph
  6. 3Using the ZθJC Graph to Estimate Junction Temperature Rise
  7. 4Application Example
  8. 5Using the ZθJC Graph to Estimate MOSFET Peak Current Capability
  9. 6Application Example
  10. 7Summary
  11. 8References

4 Application Example

Power MOSFETs are found in a wide variety of applications but typically fall into one of two categories: switch-mode and linear-mode. Some examples of switch-mode applications are DC-DC converters, class-D audio amplifiers and motor drives. Inrush control for hot-swap, load switching and as a pass element in a linear regulator are common linear-mode applications.

In most switch-mode applications, the MOSFET is selected and evaluated for a continuous output power level - thermal design power (TDP) - under steady state operating conditions. In this case, the power loss in the FET is constant and the junction temperature can be estimated using the thermal resistance, RθJC, specified in the data sheet. However, during fault conditions such as an output short circuit, a DC-DC converter can go into hiccup mode current limiting. In this mode of operation, the controller stops the FET switching for a predefined time period before trying to restart. If the fault condition persists, the controller again stops switching and attempts to restart. This continues periodically until the fault condition is removed. An example for the TPS53819A in a synchronous buck converter is shown in Figure 4-1.

GUID-F573A31B-87C5-4833-B072-505039869037-low.gif Figure 4-1 TPS53819A Hiccup Mode Short Circuit Protection

In this example, the pulse width, t1, is approximately 2 ms and the period, t2, is about 18 ms giving a duty cycle of 11%. Going back to the CSD17579Q5A ZθJC graph, draw a vertical line from the x-axis at 2 ms up to the (closest) 10% duty cycle curve. From that intersection, draw a horizontal line to the y-axis which results in a ZθJC value of approximately 0.52.

In linear mode applications, such as hot swap, the FET can be exposed to both single pulse events, such as inrush and overcurrent and periodic events such as retry mode which is similar to hiccup mode operation shown in the previous example.