ADL5513S:  Aerospace 1 MHz to 4 GHz, 80 dB Logarithmic Detector/Controller

The ADL5513 is a demodulating logarithmic amplifier, capable of accurately converting an RF input signal to a corresponding decibel-scaled output. It employs the progressive compression technique over a cascaded amplifier chain, each stage of which is equipped with a detector cell. The device can be used in either measurement or controller modes. The ADL5513 maintains accurate log conformance for signals up to 4 GHz. The input dynamic range is typically 80 dB (referred to 50 Ω) with error less than ±3 dB and 74 dB with error less than ±1 dB. That dynamic range is held nearly constant over the entire 4 GHz frequency range. The ADL5513 has a 20 ns response time that enables RF burst detection to a pulse rate of beyond 50 MHz. The device provides unprecedented logarithmic intercept stability vs. ambient temperature conditions. A supply voltage of 2.7 V to 5.5 V is required to power the device. Current consumption is 31 mA, and it decreases to 200 μA when the device is disabled.

The ADL5513 can be configured to provide a control voltage to a power amplifier or a measurement output from the VOUT pin. Because the output can be used for controller applications, special attention has been paid to minimize wideband noise. In this mode, the setpoint control voltage is applied to the VSET pin. The feedback loop through an RF amplifier is closed via VOUT, the output of which regulates the amplifier output to a magnitude corresponding to VSET. The ADL5513 provides 0 V to (VPOS − 0.1 V) output capability at the VOUT pin, suitable for controller applications. As a measurement device, VOUT is externally connected to VSET to produce an output voltage, VOUT, that increases linear-in-dB with RF input signal amplitude.

The logarithmic slope is 21 mV/dB, determined by the VSET interface. The intercept is -88 dBm (referred to 50 Ω, continuous wave input, 900 MHz) using the INHI input. These parameters are very stable against supply and temperature variations.

The ADL5513 is fabricated on a SiGe bipolar IC process.