Description

The AD8312 is a complete, low cost subsystem for the measurement of RF signals in the frequency range of 50 MHz to 3.5 GHz. It has a typical dynamic range of 45 dB and is intended for use in a wide variety of cellular handsets and other wireless devices. It provides a wider dynamic range and better accuracy than possible using discrete diode detectors. In particular, its temperature stability is excellent over the full operating range of −40°C to +85°C.Its high sensitivity allows measurement at low power levels, thus reducing the amount of power that needs to be coupled to the detector. It is essentially a voltage-responding device, with a typical signal range of 1.25 mV to 224 mV rms or −45 dBm to 0 dBm, referencing 50 Ω.For convenience, the signal is internally ac-coupled, using a 5 pF capacitor to a load of 3 kΩ in shunt with 1.3 pF. This high-pass coupling, with a corner at approximately 16 MHz, determines the lowest operating frequency. Therefore, the source may be dc grounded.The AD8312 output, VOUT, increases from close to ground to about 1.2 V because the input signal level increases from 1.25 mV to 224 mV. A capacitor may be connected between the VOUT and CFLT pins when it is desirable to increase the time interval over which averaging of the input waveform occurs.The AD8312 is available in a 6-ball, 1.0 mm × 1.5 mm, wafer-level chip scale package and consumes 4.2 mA from a 2.7 V to 5.5 V supply.Applications Cellular handsets (GSM, CDMA, WCDMA) RSSI and TSSI for wireless terminal devices Transmitter power measurement