IC Controls Power For Cell Phone PAs

Intended for closed-loop bias control of GSM power amplifiers, the MAX4473 PA power control IC facilitates power ramp-up and ramp-down control required by GSM and other TDMA cell phone PAs. The device simplifies cell phone layout and design by replacing three discrete op amps and a handful of passive components, thus virtually eliminating various RF noise and stability design issues. Optimized to meet strict enable/disable times and low 1.2 mA supply current, the chip reduces power consumption without compromising dynamic response. In addition, three external gain resistors offer maximum versatility. A rail-to-rail output capable of driving 500 ohms and/or 300pF of capacitance enables the device to drive low-impedance PA gain control inputs. Supply voltage range is 2.7V to 6.5V and, in shutdown, the device draws less than 1µA of supply current.