Voltage dropout is the difference between the input voltage and output voltage that is required to maintain output voltage regulation while providing the rated output current.

To ensure the TPSM53603 maintains output voltage regulation over the operating temperature range, the minimum V_IN is 3.8 V or (V_OUT + 1 V), whichever is greater.

The TPSM53603 operates in a frequency foldback mode when the dropout voltage is less than the recommendation above. Frequency foldback reduces the switching frequency to allow the output voltage to maintain regulation as input voltage decreases. At light load, the TPSM53603 operates in PFM mode, which is a reduced frequency operation. See Section 7.4.2 for more information on PFM mode. Figure 7-7 through Figure 7-12 show typical dropout voltage and frequency foldback curves for 3.3 V, 5 V, and 7 V outputs at T_A = 25°C.

VOUT = 3.3 V

Figure 7-7 Voltage Dropout

VOUT = 5 V

Figure 7-9 Voltage Dropout

VOUT = 7 V

Figure 7-11 Voltage Dropout

VOUT = 3.3 V

Figure 7-8 Frequency Foldback

VOUT = 5 V

Figure 7-10 Frequency Foldback

VOUT = 7 V

Figure 7-12 Frequency Foldback