DC/DCs for CDMA power amps include bypass FET

The MAX8581 and MAX8582 devices from Maxim Integrated Products are touted as the first 2.5MHz DC/DC converters for dynamic CDMA/WCDMA power amplifiers (PAs), integrate a low-RDS bypass FET to minimize PCB area and extend battery lifetimes. Both devices, in a 3-by-3mm TDFN package, are optimized for use with a tiny, low-cost inductor and small ceramic capacitors.

Both the MAX8581 and MAX8582 can deliver a continuous 600mA and are capable of switching at 2.5MHz, while the MAX8582 also runs at 1.5MHz for minimizing switching losses. The devices' bypass FET for directly connecting the power amp to the battery during high power operation, with an RDS of just 65 milliohms, has a dropout of just 33mV at 500mA. To maximize PA efficiency, the output can be dynamically varied from 0.4V to V_in, as per distance requirements to the base station and the transmission mode (voice or data). This flexibility improves efficiency by 47 percent at 10dBm, according to the company. Consequently, handset designers can almost double the talk-time.

The MAX8581/MAX8582, rated for operation over -40°C to 85°C, is priced starting at $1.48 each (2,500-up, FOB USA). An evaluation kit is available to speed designs.

- Vince Biancomano
eeProductCenter