Example Circuits (Continued)
20049404
FIGURE 3. 5V to 1.2V, 10A, 300kHz
This circuit design, detailed in the Design Considerations
section, uses inexpensive aluminum capacitors and off-the-
shelf inductors. It can deliver 10A at better than 85% effi-
ciency. Large bulk capacitance on input and output ensure
stable operation.
20049405
FIGURE 4. 5V to 1.8V, 3A, 600kHz
The example circuit of Figure 4 has been designed for
minimum component count and overall solution size. A
switching frequency of 600kHz allows the use of small input/
output capacitors and a small inductor. The availability of
separate 5V and 12V supplies (such as those available from
desk-top computer supplies) and the low current further
reduce component count. Using the 12V supply to power the
MOSFET drivers eliminates the bootstrap diode, D1. At low
currents, smaller FETs or dual FETs are often the most
efficient solutions. Here, the Si4826DY, an asymmetric dual
FET in an SO-8 package, yields 92% efficiency at a load of
2A.
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