AD8318:  1 MHz to 8 GHz, 70 dB Logarithmic Detector/Controller

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 ...More

AD8318:  1 MHz to 8 GHz, 70 dB Logarithmic Detector/Controller

Product Description

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

    • Data Sheet, Rev. B, 4/07

    Features

    • 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

    Verified Circuits Using This Part

    Verified Circuits are designed for ease of use and proven to work by ADI applications engineers. To learn more about Verified Circuits from ADI, please visit Verified Circuits Home.

    Circuit Diagram

    Diagrams

    AD8318 Diagram
    Functional Block Diagram for AD8318

    Specifications

    RF Frequency (MHz) 1 to 8000
    Dynamic Range (dB) 70dB
    Temp Stability (dB) ±0.5dB
    Response Time (ns typ) 10ns
    Voltage Supply (V) 4.5 to 5.5
    Supply Current (max) 68mA
    Power Consumption (mW) 340mW
    Package 16-Lead CSP

    ADL5513 - 1 MHz to 4 GHz, 80 dB Logarithmic Detector/Controller

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    Part# Product Description RF Frequency (MHz) Dynamic Range (dB) Temp Stability (dB) Response Time (ns typ) Voltage Supply (V) Supply Current (max) Package Price* (1000-4999)
    AD606 Limiter Output - 80 - 400 4.5 to 5.5 13 16-Lead DIP, 16-Lead SOIC $22.00
    AD640 Military Specified Part Available - 50 ±1 10 +/- 4.5 to +/- 7.5 44 20-Lead DIP, 20-Lead LCC, 20-Lead PLCC $36.48
    AD641 Military Specified Part Available - 44 ±1 10 +/- 4.5 to +/- 7.5 44 20-Lead DIP, 20-Lead LCC, 20-Lead PLCC $32.82
    AD8302 Dual-Channel Gain and Phase Outputs 2,700 60 ±1 60 2.7 to 5.5 19 14-Lead TSSOP $12.14
    AD8306 Military Specified Part Available 5 to 400 100 ±1 73 2.7 to 5.5 16 16-Lead SOP $14.67
    AD8307 High Dynamic Range dc to 500 92 ±1 400 2.7 to 5.5 8 8-Lead SOIC/DIP $6.07
    AD8309 Limiter Output 5 to 500 100 ±1 67 2.7 to 5.5 16 16-Lead TSSOP $7.84
    AD8310 High Dynamic Range dc to 440 100 ±1 15 2.7 to 5.5 8 8-Lead SOIC $4.00
    AD8311 Low Power for Battery Operation 100 to 2500 50 ±0.5 150 2.7 to 5.5 8.5 WLCSP $1.27
    AD8312 Low Power for Battery Operation 50 to 3500 45 ±0.5 70 2.7 to 5.5 4.2 WLCSP $1.27
    AD8313 Industry Standard 100 to 2500 70 ±1.25 40 2.7 to 5.5 14 8-Lead uSOIC $7.99
    AD8314 Industry Standard 100 to 2700 45 ±1 70 2.7 to 5.5 4.5 8-Lead uSOIC/CSP $1.10
    AD8315 Low Power for Battery Operation 100 to 2500 50 ±1 150 2.7 to 5.5 8.5 8-Lead uSOIC $4.00
    AD8317 Available in Die 1 to 10000 55 ±0.5 6 3 to 5.5 20 8-Lead CSP $3.98
    AD8318 Integrated Temp Sensor 1 to 8000 70 ±0.5 10 4.5 to 5.5 68