GENERAL DESCRIPTION

The AD8317ACPZ-R7 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 AD8317ACPZ-R7 maintains accurate log conformance for signals of 1 MHz to 8 GHz and provides useful operation to 10 GHz. The input dynamic range is typically 55 dB (referenced to 50 Ω) with less than ±3 dB error. The AD8317ACPZ-R7 has 6 ns/10 ns response time (fall time/rise 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 of 3.0 V to 5.5 V is required to power the device. Current consumption is typically 22 mA, and it decreases to 200 μA when the device is disabled.  

The AD8317ACPZ-R7 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 output of the amplifier to a magnitude corresponding to VSET. The AD8317ACPZ-R7 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 is a decreasing linear-in-dB function of the RF input signal amplitude. 

The logarithmic slope is 22 mV/dB, determined by the VSET interface. The intercept is 15 dBm (referenced to 50 Ω, CW input) using the INHI input. These parameters are very stable against supply and temperature variations. 

The AD8317ACPZ-R7 is fabricated on a SiGe bipolar IC process and is available in a 2 mm × 3 mm, 8-lead LFCSP with an operating temperature range of −40°C to +85°C. 

FEATURES
Wide bandwidth: 1 MHz to 10 GHz
High accuracy: ±1.0 dB over temperature
55 dB dynamic range up to 8 GHz ± 3 dB error
Stability over temperature: ±0.5 dB
Low noise measurement/controller output, VOUT
Pulse response time: 6 ns/10 ns (fall/rise)
Small footprint, 2 mm × 3 mm LFCSP
Supply operation: 3.0 V to 5.5 V at 22 mA
Fabricated using high speed SiGe process
APPLICATIONS
RF transmitter PA setpoint control and level monitoring
Power monitoring in radio link transmitters
RSSI measurement in base stations, WLANs, WiMAX, and radars 

Feature

Applications