The AD8315 is a complete low cost subsystem for the precisecontrol of RF power amplifiers operating in the frequency range0.1 GHz to 2.5 GHz and over a typical dynamic range of 50 dB.It is intended for use in cellular handsets and other batteryoperatedwireless devices. The log amp technique provides a muchwider measurement range and better accuracy than controllersusing diode detectors. In particular, the temperature stability isexcellent over a specified range of −30°C to +85°C.

Its high sensitivity allows control at low signal levels, thusreducing the amount of power that must be coupled tothe detector.

For convenience, the signal is internally ac-coupled. Thishigh-pass coupling, with a corner at approximately 0.016 GHz,determines the lowest operating frequency. Therefore, thesource can be dc grounded.

The AD8315 provides a voltage output, VAPC, that has thevoltage range and current drive to directly connect to mosthandset power amplifiers’ gain control pin. VAPC can swingfrom 250 mV above ground to within 200 mV below the supplyvoltage. Load currents of up to 6 mA can be supported.

The setpoint control input is applied to the VSET pin and hasan operating range of 0.25 V to 1.4 V. The associated circuitdetermines the slope and intercept of the linear-in-dBmeasurement system; these are nominally 23 mV/dB and−60 dBm for a 50 Ω termination (−73 dBV) at 0.9 GHz.Further simplifying the application of the AD8315, the inputresistance of the setpoint interface is over 100 MΩ, and the biascurrent is typically 0.5 μA.

The AD8315 is available in MSOP and LFCSP packages andconsumes 8.5 mA from a 2.7 V to 5.5 V supply. When powereddown, the sleep current is 4 μA.

Applications

• Single, dual, and triple band mobile handset (GSM, DCS, EDGE)
• Transmitter power control

At least one model within this product family is in production and available for purchase. The product is appropriate for new designs but newer alternatives may exist.