摘要 :Design note shows a step-up DC-DC converter for USB that delivers 5V at 200mA with > 90% efficiency. Use of all-ceramic capacitors enables lowest profile and highest availability. The MAX1790 step-up converter is featured.
A USB-powered device is constrained to draw no more than 0.5A from the input supply. The input-supply voltage must be re-regulated to provide +5V ± 5%. Efficiency is paramount in order to maximize the power available from the port. In addition, this application can be implemented with all-ceramic capacitors for lowest profile and high availability. This MAX1790 circuit delivers +5V at 200mA from +4.35V input with > 90% efficiency.