AD8318

Wide bandwidth: 1 MHz to 8 GHz
High accuracy: ±1.0dB over 55 dB range (f < 5.8 GHz)
Stability over temperature: 0.5 dB
Low noise measurement/controller output VOUT
Pulse response time 10/12 ns (fall/rise)
Integrated temperature sensor
Small footprint CSP package
Power-down feature: <1.5 mW at 5 V
Single-supply operation: 5V @ 68 mA
Fabricated using high speed SiGe process

RF transmitter PA setpoint control and level monitoring
RSSI measurement in base stations, WLAN, radar

The AD8318 is a demodulating logarithmic amplifier, capable of accurately converting an RF input signal to a corresponding decibel-scaled output voltage. 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 measurement or controller mode. The AD8318 maintains accurate log conformance for signals of 1 MHz to 6 GHz and provides useful operation to 8 GHz. The input range is typically 60 dB (re: 50 ) with error less than ±1 dB. The AD8318 has a 10 ns response time that enables RF burst detection to beyond 60 MHz. The device provides unprecedented logarithmic intercept stability versus ambient temperature conditions. A 2 mV/K slope temperature sensor output is also provided for additional system monitoring. A single supply of +5 V is required. Current consumption is typically 68 mA. Power consumption decreases to <1.5 mW when the device is disabled.

The AD8318 can be configured to provide a control voltage to a VGA, such as a power amplifier or a measurement output, from pin VOUT. Since 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 VSET. The feedback loop through an RF amplifier is closed via VOUT; the output of which regulates . the amplifiers output to a magnitude corresponding to VSET The AD8318 provides 0 V to 4.9 V output capability at the VOUT pin, suitable for controller applications. As a measurement device, VOUT is externally connected to that is a decreasing VSET to produce an output voltage VOUT linear-in-dB function of the RF input signal amplitude.

The AD8318 is fabricated on a SiGe bipolar IC process and is available in a 4 mm 4 mm 16-pin LFCSP package, for the operating temperature range of -40to+85