The ADL5902 provides a solution in a variety of high frequency systems requiring an accurate measurement of signal power. Requiring only a single supply of 5 V and a few capacitors, it is easy to use and capable of being driven single-ended or with a balun for differential input drive. The ADL5902 can operate from 50 MHz to 9 GHz and can accept inputs from −62 dBm to at least +3 dBm with large crest factors, such as GSM, CDMA, W-CDMA, TD-SCDMA, WiMAX, and LTE modulated signals.

The ADL5902 can determine the true power of a high frequency signal having a complex low frequency modulation envelope or can be used as a simple low frequency rms voltmeter. Used as a power measurement device, VOUT is connected to VSET. The output is then proportional to thelogarithm of the rms value of the input. In other words, the reading is presented directly in decibels and is scaled 1.06 V per decade, or 53 mV/dB; other slopes are easily arranged. In controller mode, the voltage applied to VSET determines the power level required at the input to null the deviation from the set point. The output buffer can provide high load currents.

The ADL5902 has 1.5 mW power consumption when powered down by a logic high applied to the PWDN pin. It powers up within approximately 5 μs to its nominal operating current of 73 mA at 25°C. The ADL5902 is supplied in a 4 mm × 4 mm, 16-lead LFCSP for operation over the wide temperature range of −40°C to +125°C.

The ADL5902 is also pin-compatible with the AD8363, 50 dB dynamic range TruPwr™ detector. This feature allows the designer to create one circuit layout for projects requiring different dynamic ranges. A fully populated RoHS-compliant evaluation board is available.

Applications

• Power amplifier linearization/control loops
• Transmitter power controls
• Transmitter signal strength indication (TSSI)
• RF instrumentation