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Maxim > Design Support > Technical Documents > Application Notes > Power-Supply Circuits > APP 1782
Keywords: step-down regulator, high-frequency seitching, micro-second response time, µs response
time, ceramic capacitors
APPLICATION NOTE 1782
All-Ceramic Capacitors Enable the Smallest
Footprint for a 1MHz, 6A Step-Down Regulator
Nov 11, 2002
Abstract: This application note explains how the use of all-ceramic capacitors reduces footprint of 1MHz,
6A step-up converter. The MAX1945R step-down regulator achieves 10µs response time and 1%
accuracy, and uses ceramic capacitors to reduce overall size.
One benefit of high-frequency switching is the fast loop response. This translates to smaller footprint and
lower cost, because the ceramic capacitors can be used. The MAX1945 internal switch step-down
regulator is designed for high-frequency switching. It can be switched at 1MHz. Its peak current mode
control architecture allows simple Type II compensation (R2 and C2) to achieve high bandwidth, further
reducing the external component count.
As shown in Figure 1, for 6A output, only two 1210 footprint ceramic capacitors are needed to meet the
50% step load change, thus greatly reducing the output capacitor size when compared to switching at
500kHz or less. A second benefit is due to the low ESR of the ceramic capacitors. Large inductor ripple
current is allowed to achieve the 1% ripple voltage requirement.The value of the output inductor is
0.68µH, resulting in a footprint of 8.2mm x 8.2mm for 6A output current, further reducing buck converter
size.
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