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Buck converter suits W-CDMA/N-CDMA PAs

Posted: 01 May 2007 ?? ?Print Version ?Bookmark and Share

Keywords:W-CDMA power amplifiers? buck converter? step-down converter?

Maxim Integrated Products introduced the MAX8805Y/MAX8805Z 600mA, PWM step-down converters in 2-by-2mm wafer-level packages (WLPs) for W-CDMA/N-CDMA power amplifiers (PAs). These devices enhance battery efficiency by integrating a step-down converter for medium- and low-power transmission, as well as a 60-milliohm, bypass FET which provides 1.5A of peak current. The MAX8805Y/MAX8805Z is suitable for multiband W-CDMA/N-CDMA applications, including cellular handsets, wireless PDAs and smartphones.

Supporting 1.5A of peak current, the integrated 60-milliohm bypass FET provides maximum power with minimum dropout under low-battery conditions. Each device automatically enters bypass mode if the required output voltage is within 92 percent of the input voltage; or, the user can force the IC into bypass mode using a simple logic input. The output voltage is controlled using an external analog input signal, which has a gain of 2V/V. Additionally, the 7.5?s (typical) slew rate of the output voltage ensures plenty of margin to the CDMA-required maximum time of 50?s.

The MAX8805Y/MAX8805Z also integrates two low-noise (35?VRMS), high-PSRR (70dB at 1kHz, typ) LDOs, making them suitable for PA biasing or applications that require a clean power source. Each LDO features a separate ON/OFF control, provides 3 percent (max) output accuracy and requires 10nF of output capacitance for loads of 10mA or less. Output voltage options include combinations of 1.80-, 2.5-, 2.7-, 2.8-, 2.85- and 3.0 V. Other MAX8805Y/MAX8805Z features include overcurrent protection for the buck regulator and LDOs, overtemperature protection, and operation over the extended temperature range of -40C to 85C.

These devices are already available with pricing beginning at $1.75 each in 2,500-piece quantities.

- Emily Gleason

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