3.6V, 1W Autoramping Power Amplifier for 900MHz Applications

The MAX2235 low-voltage, silicon RF power amplifier (PA) is designed for use in the 900MHz frequency band. It operates directly from a single +2.7V to +5.5V supply, making it suitable for use with 3-cell NiCd or 1-cell Li-Ion batteries. The device delivers +30dBm (1W) typical output power from a +3.6V supply or +28dBm from a +2.7V supply.

The MAX2235's gain is adjustable over a 37dB range. A power-control pin controls gain and bias to maintain optimum efficiency, even at lower output power levels, thus extending the operating life of the battery. At +30dBm output power, efficiency is typically 47%. An additional power-saving feature is a shutdown mode that typically reduces supply current below 1µA.

A key feature of this PA is its autoramping capability. During turn-on and turn-off periods, the RF envelope is controlled to approximate a raised cosine on the rising and falling edge, thereby minimizing transient noise and spectral splatter. The ramp time is set by selecting the value of an external capacitor.

The MAX2235 is intended for use in constant envelope applications such as AMPS, two-way paging, or FSK-based communications in the 900MHz ISM band. The device is available in a thermally enhanced 20-pin TSSOP package with a heat slug.

Applications

* 900MHz ISM-Band Applications * Analog Cellular Phones * Microcellular GSM (Power Class 5) * Two-Way Paging * Wireless Data Networks

* 800MHz to 1000MHz Operation

* High Output Power at 836MHz

* +32.5dBm at +5.0V

* +30dBm at +3.6V

* +29dBm at +3.0V

* +28dBm at +2.7V

* +2.7V to +5.5V Single-Supply Operation

* Automatic Power-Up/Power-Down Ramp

* Direct On/Off Keying (OOK) without Intersymbol Interference or VCO Pulling

* 37dB Power-Control Range

* 47% Efficiency

* < 1µA Supply Current in Shutdown Mode

* Small 20-Pin TSSOP Package with Heat Slug