Datasheet AD8318 (Analog Devices)

1 MHz to 8 GHz, 70 dB Logarithmic Detector/Control er Data Sheet AD8318 FEATURES FUNCTIONAL BLOCK DIAGRAM Wide bandwidth: 1 MHz to 8 GHz VPSI ENBL TADJ VPSO High accuracy: ±1.0 dB over 55 dB range (f < 5.8 GHz) TEMP GAIN Stability over temperature: ±0.5 dB TEMP SLOPE SENSOR BIAS I V VSET Low noise measurement/controller output (VOUT) Pulse response time: 10 ns/12 ns (fall/rise) I V VOUT Integrated temperature sensor DET DET DET DET Small footprint LFCSP CLPF INHI Power-down feature: <1.5 mW at 5 V INLO Single-supply operation: 5 V at 68 mA
001
Fabricated using high speed SiGe process CMIP CMOP
04853- Figure 1.
APPLICATIONS RF transmitter PA setpoint control and level monitoring RSSI measurement in base stations, WLAN, WiMAX, and radars GENERAL DESCRIPTION
The AD8318 is a demodulating logarithmic amplifier, capable a decreasing linear-in-dB function of the RF input signal of accurately converting an RF input signal to a corresponding amplitude. decibel-scaled output voltage. It employs the progressive The logarithmic slope is nominally −25 mV/dB but can be compression technique over a cascaded amplifier chain, each adjusted by scaling the feedback voltage from VOUT to the stage of which is equipped with a detector cell. The device is VSET interface. The intercept is 20 dBm (referenced to 50 Ω, used in measurement or control er mode. The AD8318 maintains CW input) using the INHI input. These parameters are very accurate log conformance for signals of 1 MHz to 6 GHz and stable against supply and temperature variations. provides useful operation to 8 GHz. The input range is typically 60 dB (referenced to 50 Ω) with error less than ±1 dB. The The AD8318 is fabricated on a SiGe bipolar IC process and is AD8318 has a 10 ns response time that enables RF burst available in a 4 mm × 4 mm, 16-lead LFCSP for the operating detection to beyond 45 MHz. The device provides unprecedented temperature range of –40oC to +85oC. logarithmic intercept stability vs. ambient temperature conditions.
2.4 6
A 2 mV/°C slope temperature sensor output is also provided for
2.2 5
additional system monitoring. A single supply of 5 V is required.
2.0 4
Current consumption is typically 68 mA. Power consumption
1.8 3
decreases to <1.5 mW when the device is disabled.
1.6 2 B) 1.4 1 d
The AD8318 can be configured to provide a control voltage
(V) R ( UT 1.2 0
to a VGA, such as a power amplifier or a measurement output,
OV 1.0 –1 RRO E
from Pin VOUT. Because the output can be used for controller
0.8 –2
applications, wideband noise is minimal.
0.6 –3
In this mode, the setpoint control voltage is applied to VSET.
0.4 –4 0.2 –5
The feedback loop through an RF amplifier is closed via VOUT,
0 –6
the output of which regulates the amplifier output to a magnitude
–65 –60 –55 –50 –45 –40 –35 –30 –25 –20 –15 –10 –5 0 5 10
052 corresponding to VSET. The AD8318 provides 0 V to 4.9 V
PIN (dBm)
04853- output capability at the VOUT pin, suitable for controller Figure 2. Typical Logarithmic Response and Error vs. Input Amplitude at 5.8 GHz applications. As a measurement device, Pin VOUT is externally connected to VSET to produce an output voltage, VOUT, which is
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Document Outline Features Applications Functional Block Diagram General Description Revision History Specifications Absolute Maximum Ratings ESD Caution Pin Configuration and Function Descriptions Typical Performance Characteristics Theory of Operation Using the AD8318 Basic Connections Enable Interface Input Signal Coupling Output Interface Setpoint Interface Temperature Compensation of Output Voltage Temperature Sensor Measurement Mode Device Calibration and Error Calculation Selecting Calibration Points to Improve Accuracy over a Reduced Range Variation in Temperature Drift from Device to Device Temperature Drift at Different Temperatures Setting the Output Slope in Measurement Mode Response Time Capability Output Filtering Controller Mode Characterization Setup and Methods Evaluation Board Outline Dimensions Ordering Guide