A USB wireless modem, USB dongle, or USB data card can be used along with notebook and tablet PCs to access the Internet as needed. Recently, LTE (Long Term Evolution) supportive modems have been introduced to make a step towards the 4G generation of mobile telephony.
This article focuses on power management solutions for GSM/GPRS mobile systems. It has been a challenging task for designers to cope with 2A peak current pulsed load during data transmission mode, which enables the output power to easily exceed the USB power specification of 5V/500mA. The design study in this article is classified into two different topologies depending on the place of a current limit switch and a step-down converter. The article also determines which topology is better in diversified demand. The FAN5353, a 3A rated monolithic synchronous buck converter operating at 3MHz frequency and FPF2165R, an integrated load switch, limit the USB input current and are applied for the design consideration of both topologies.
Figure 1. System Block Diagram of Multi-band Network USB Wireless Modem
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