The safe operating area (SOA) of a typical design is shown in Figure 8-2, through Figure 8-5 for 3.3-V, 5-V and 12-V outputs and varying amounts of forced air flow. The temperature derating curves represent the conditions at which the internal components and external components are at or below the manufacturer’s maximum operating temperatures. Derating limits apply to devices soldered directly to a double-sided PCB with 2 oz. copper, similar to the EVM. Careful attention must be paid to the other components chosen for the design, especially the catch diode. In most applications the thermal performance will be limited by the catch diode. When operating with high duty cycles, higher input voltage or at higher switching frequency the TPS54561's thermal performance can become the limiting factor.

Figure 8-2 3.3-V Output with 400-kHz Switching Frequency

Figure 8-4 12-V Output with 800-kHz Switching Frequency

Figure 8-3 5-V Output with 400-kHz Switching Frequency

VIN = 36 V

VO = 12 V

fsw = 800 kHz

Figure 8-5 Air Flow Conditions