Communications: Step-Down Regulator Rings In For CDMA Cell Phones

The variable low voltage and high current required by CDMA or 3G wideband CDMA (WCDMA) cell-phone power amplifiers can be achieved with the LTC3408 switching regulator. This synchronous buck regulator operates at 1.5 MHz and contains an internal p-channel MOSFET with an on-resistance of only 0.08 Ω. A constant-frequency current-mode architecture operates with an input voltage range of 2.5 to 5 V. The output can be dynamically programmed from 0.3 to 3.5 V to optimize the efficiency of CDMA power amplifiers. Maximum current rating is 800 mA, and efficiency stands at 96%. The LTC3408 comes in a 3- by 3-mm, eight-lead DFN package and is optimized for low-power cell-phone applications. Price is $2.15 in 1000-unit quantities.