●Product Details
●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 is 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 Ω) with error less than ±1 dB. The AD8318 has a 10 ns response time that enables RF burst detection to beyond 45 MHz. The device provides unprecedented logarithmic intercept stability vs. ambient temperature conditions. A 2 mV/°C 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. Because the output can be used for controller applications, wideband noise is minimal.
●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 amplifier 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, Pin VOUT is externally connected to VSET to produce an output voltage, VOUT, which is a decreasing linear-in-dB function of the RF input signal amplitude.
●The logarithmic slope is nominally −25 mV/dB but can be adjusted by scaling the feedback voltage from VOUT to the VSET interface. The intercept is 20 dBm (re: 50 Ω, CW input) using the INHI input. These parameters are very stable against supply and temperature variations.
●The AD8318 is fabricated on a SiGe bipolar IC process and is available in a 4 mm × 4 mm, 16-lead LFCSP for the operating temperature range of –40°C to +85°C.
●Applications
● RF transmitter PA setpoint control and level monitoring
● RSSI measurement in base stations, WLAN, WiMAX, and radars
●### Features and Benefits
● Wide bandwidth: 1 MHz to 8 GHz
● High accuracy: ±1.0 dB over 55 dB range (f < 5.8 GHz)
● Stability over temperature: ±0.5 dB
● Low noise measurement/controller output (VOUT)
● Pulse response time: 10 ns/12 ns (fall/rise)
● Integrated temperature sensor
● Small footprint LFCSP
● Power-down feature: <1.5 mW at 5 V
● Single-supply operation: 5 V @ 68 mA
● Fabricated using high speed SiGe process
●AD8138-EP supports defense and aerospace applications (AQEC standard)
● Download AD8318-EP data sheet (pdf)
● V62/12665 DSCC Drawing Number
