AD8318

1 MHz TO 8 GHz, 70 dB Logarithmic Detector / Controller
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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

Product Lifecycle

checked Recommended for New Designs

This product has been released to the market. The data sheet contains all final specifications and operating conditions. For new designs, ADI recommends utilization of these products.

Evaluation Kits

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Product Details

AD8318-EVALZ is a fully populated, 4-layer evaluation board powered by a single supply in the 4.5 V to 5.5 V range. The board can be operated in the Controller or Measurement mode by configuring the feedback resistor as an open or short. Performance in each mode can be optimized using resistive and filtering networks provided on the board. The inputs are configured for single-ended operation and provide a broadband input impedance of 50 Ω. The board also provides options for the user to optimize the output filtering and temperature compensation interface.


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ADI has always placed the highest emphasis on delivering products that meet the maximum levels of quality and reliability. We achieve this by incorporating quality and reliability checks in every scope of product and process design, and in the manufacturing process as well.  "Zero defects" for shipped products is always our goal.

AD8318 Material Declaration
PCN-PDN Information Quality And Reliability Symbols and Footprints

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Overview

4 Reviews
3 out of 4 (75%) customers recommend this product.
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Most Helpful Review

by Anonymous
we found the AD8318's VSWR more than 2:1 at 2~8GHz ,I think it is cause by our 52.3ohm resistor.

Most Recent Review

by Anonymous
I'm going to use this product in few prototypes. On the first board it's performance was convincing.

All Reviews

by Anonymous, 6 Nov 13
Excellent product
I'm going to use this product in few prototypes. On the first board it's performance was convincing.
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by Anonymous, 14 Mar 13
Verry good product.
The application schematic gived in the datasheet Rev B page 18, figure 39 (AD8318 + ADCMP563) did not work. No signal at the output pins of the ADCMP563 !? I had to change the two 100 ohm resistors connected from the output of the ADCMP563 to the -5,2V with resistors of 10K....100Kohms ! and with this new configuration, your schematics worked. This two resistors seems to act as feedback for the ADCMP563 comparator. But on the same page under(figure 40), i never could reach the sensitivity of -50dBm gived in the graph !! I couldn't get under -30dBm.
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by Anonymous, 6 Jan 13
Very good RF GHz power meter
It should be nice when the output of this chip acts the same as the AD8307. I mean the output voltage is reversed. What is the meaning of that?
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by Anonymous, 26 Sep 12
we fail to reasch the parameter in datasheet
we found the AD8318's VSWR more than 2:1 at 2~8GHz ,I think it is cause by our 52.3ohm resistor.
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The USA list pricing shown is for BUDGETARY USE ONLY, shown in United States dollars (FOB USA per unit for the stated volume), and is subject to change. International prices may differ due to local duties, taxes, fees and exchange rates. For volume-specific price or delivery quotes, please contact your local Analog Devices, Inc. sales office or authorized distributor. Pricing displayed for Evaluation Boards and Kits is based on 1-piece pricing.


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Evaluation Boards Pricing displayed is based on 1-piece.
Pricing displayed is based on 1-piece. The USA list pricing shown is for budgetary use only, shown in United States dollars (FOB USA per unit), and is subject to change. International prices may vary due to local duties, taxes, fees and exchange rates.