The MAX4473 PA power control IC is intended for closed-loop bias control of GSM power amplifiers. The device facilitates accurate control of the current delivered to the power amplifier (PA) through a control voltage. The error amplifier senses the voltage drop across an external current-sense resistor placed between the supply and the PA. The output of the error amplifier adjusts the PA gain until the current is proportional to the power control voltage applied to the MAX4473. This unique topology is useful in time-division-multiple-access (TDMA) systems, such as GSM, where accurate transmit burst shaping and power control is required. User-selectable current sensing and gain setting resistors maximize flexibility.
The MAX4473 operates from a single 2.7V to 6.5V supply and typically draws 1.2mA of supply current. The error amplifier has a common-mode range that extends from 1V to VCC. The power control input and error amplifier outputs swing rail-to-rail. A low-power shutdown mode reduces supply current to less than 1µA and activates an on-board active pull-down at the error amplifier output. Fast enable/disable times of 0.9µs reduce average power consumption without compromising dynamic performance. The MAX4473 is available in a space-saving 8-pin QFN package.
Key Features
Applications/Uses
Optimized for GSM Timing Requirements
2.7V to 6.5V Single-Supply Operation
1.2mA Supply Current
<1µA Supply Current in Shutdown Mode
Guaranteed 1.5µs Enable/Disable Times
Active Output Pull-Down in Shutdown Mode
Rail-to-Rail Error Amplifier Output
Rail-to-Rail Power Control Input
Output Drive Capability—500Ω and 300pF Loads
1V to VCC Current Sense Input Common-Mode Voltage Range
No Phase-Reversal for Common-Mode Voltage from 0 to VCC
External Current Sensing and Gain Setting Resistors Maximize Flexibility
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