P-channel FETs in low power DC-DC converters

AN4391

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hence, the driver is also cooler. At high-currents, a better R

DS(on)

allows higher efficiency

and lower temperature.

3.2

2.5 V - 5 V, 1 A, 600 kHz synchronous boost converter

Low power synchronous boost converters are widely used: in fact, their input voltage range

(typically, from 2.5 V to 4.2 V) allows operation from a 3.3 V source or directly from a Li-ion

battery. In this converter (

Figure 11), P-channel FET (Q2) can be used as synchronous

element, replacing a low-V

F

diode with lower voltage drop increasing the efficiency of the

entire system.

Figure 11. Synchronous boost converter schematic

The STL30P3LLH6 and planar device’s switching and efficiency behavior (see

Table 1) are

compared. Due to low input voltage level, there are not D-S voltage stress issues, with

maximum values well lower than the device breakdown rating (

Figure 12 and Figure 13).

So, waveforms are quite regular for both devices.

GIPG131120131330FSR