AD8306 Analog Devices, AD8306 Datasheet

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AD8306

Manufacturer Part Number
AD8306
Description
5 - 400 Mhz, 100 DB High Precision Limiting - Logarithmic Amplifier
Manufacturer
Analog Devices
Datasheet

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a
PRODUCT DESCRIPTION
The AD8306 is a complete IF limiting amplifier, providing both
an accurate logarithmic (decibel) measure of the input signal
(the RSSI function) over a dynamic range of 100 dB, and a
programmable limiter output, useful from 5 MHz to 400 MHz.
It is easy to use, requiring few external components. A single
supply voltage of +2.7 V to +6.5 V at 16 mA is needed, corre-
sponding to a power consumption of under 50 mW at 3 V, plus
the limiter bias current, determined by the application and typi-
cally 2 mA, providing a limiter gain of 90 dB when using 200
loads. A CMOS-compatible control interface can enable the
AD8306 within about 500 ns and disable it to a standby current
of under 1 A.
The six cascaded amplifier/limiter cells in the main path have a
small signal gain of 12.04 dB ( 4), with a –3 dB bandwidth of
850 MHz, providing a total gain of 72 dB. The programmable
output stage provides a further 18 dB of gain. The input is fully
differential and presents a moderately high impedance (1 k in
parallel with 2.5 pF). The input-referred noise-spectral-density,
when driven from a terminated 50 , source is 1.28 nV/ Hz,
equivalent to a noise figure of 3 dB. The sensitivity of the
AD8306 can be raised by using an input matching network.
Each of the main gain cells includes a full-wave detector. An
additional four detectors, driven by a broadband attenuator, are
used to extend the top end of the dynamic range by over 48 dB.
Information furnished by Analog Devices is believed to be accurate and
reliable. However, no responsibility is assumed by Analog Devices for its
use, nor for any infringements of patents or other rights of third parties
which may result from its use. No license is granted by implication or
otherwise under any patent or patent rights of Analog Devices.
REV. A
FEATURES
Complete, Fully Calibrated Log-Limiting IF Amplifier
100 dB Dynamic Range: –91 dBV to +9 dBV
Stable RSSI Scaling Over Temperature and Supplies:
Programmable Limiter Gain and Output Current
Single Supply of +2.7 V to +6.5 V at 16 mA Typical
Fully Differential Inputs, R
500 ns Power-Up Time, <1 A Sleep Current
APPLICATIONS
Receivers for Frequency and Phase Modulation
Very Wide Range IF and RF Power Measurement
Receiver Signal Strength Indication (RSSI)
Low Cost Radar and Sonar Signal Processing
Instrumentation: Network and Spectrum Analyzers
20 mV/dB Slope, –95 dBm Intercept
Differential Outputs to 10 mA, 2.4 V p-p
Overall Gain 90 dB, Bandwidth 400 MHz
Constant Phase (Typical
0.4 dB RSSI Linearity up to 200 MHz
IN
= 1 k , C
56 ps Delay Skew)
IN
= 2.5 pF
5 MHz–400 MHz 100 dB High Precision
INLO
INHI
The overall dynamic range for this combination extends from
–91 dBV (–78 dBm at the 50
value of +9 dBV, using a balanced drive of antiphase inputs each of
2 V in amplitude, which would correspond to a sine wave power
of +22 dBm if the differential input were terminated in 50 .
Through laser trimming, the slope of the RSSI output is closely
controlled to 20 mV/dB, while the intercept is set to –108 dBV
(–95 dBm re 50 ). These scaling parameters are determined
by a band-gap voltage reference and are substantially indepen-
dent of temperature and supply. The logarithmic law conform-
ance is typically within 0.4 dB over the central 80 dB of this
range at any frequency between 10 MHz and 200 MHz, and is
degraded only slightly at 400 MHz.
The RSSI response time is nominally 73 ns (10%–90%). The
averaging time may be increased without limit by the addition of
an external capacitor. The full output of 2.34 V at the maximum
input of +9 dBV can drive any resistive load down to 50
this interface remains stable with any value of capacitance on
the output.
The AD8306 is fabricated on an advanced complementary
bipolar process using silicon-on-insulator isolation techniques
and is available in the industrial temperature range of –40 C to
+85 C, in a 16-lead narrow body SO package. The AD8306 is
also available for the full military temperature range of –55 C to
+125 C, in a 16-lead side-brazed ceramic DIP.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781/329-4700
Fax: 781/326-8703
ENBL
Limiting-Logarithmic Amplifier
LADR ATTEN
4
DET
GAIN
BIAS
FUNCTIONAL BLOCK DIAGRAM
12dB
TEN DETECTORS SPACED 12dB
SIX STAGES TOTAL GAIN 72dB
DET
World Wide Web Site: http://www.analog.com
REFERENCE
BAND-GAP
12dB
DET
level) to a maximum permissible
SLOPE
BIAS
© Analog Devices, Inc., 1999
12dB
AD8306
DET
TYP GAIN 18dB
TEMP COMP
INTERCEPT
LIM
I–V
CTRL
BIAS
and
LMHI
LMLO
LMDR
VLOG
FLTR

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AD8306 Summary of contents

Page 1

... A CMOS-compatible control interface can enable the AD8306 within about 500 ns and disable standby current of under 1 A. The six cascaded amplifier/limiter cells in the main path have a small signal gain of 12. 4), with a – ...

Page 2

... Due to the extremely high Gain Bandwidth Product of the AD8306, the output of either LMHI or LMLO will be unstable for levels below –78 dBV (–65 dBm Standard deviation remains essentially constant over frequency. See Figures 13, 14, 16 and 17. ...

Page 3

... ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily accumulate on the human body and test equipment and can discharge without detection. Although the AD8306 features proprietary ESD protection circuitry, permanent damage may occur on devices subjected to high energy electrostatic discharges. Therefore, proper ESD precautions are recommended to avoid performance degradation or loss of functionality ...

Page 4

... AD8306 –Typical Performance Characteristics 100 + 0 + 0.01 0.001 0.0001 0.00001 0.5 0.7 0.9 1.1 1.3 1.5 ENABLE VOLTAGE – V Figure 1. Supply Current vs. Enable Voltage @ T = –40 C, +25 C and + ADDITIONAL SUPPLY CURRENT LIMITER OUTPUT 2 CURRENT 100 150 200 250 R – LIM Figure 2 ...

Page 5

... C, for Figure 12. Log Linearity of RSSI Output vs. Input Level +25 C, for Frequencies of 200 MHz, 300 MHz and A 400 MHz –5– AD8306 – –100 –80 –60 –40 –20 0 (– ...

Page 6

... AD8306 100 200 FREQUENCY – MHz Figure 13. RSSI Slope vs. Frequency Using Termination of 52.3 0.4 0.375 0.35 0.325 0.3 0.275 0. 100 150 200 250 FREQUENCY – MHz Figure 14. RSSI Slope Standard Deviation vs. Frequency LMLO LMHI LIMITER OUTPUTS: 50mV PER VERTICAL DIVISION INPUT: 1mV PER VERTICAL DIVISION 12 ...

Page 7

... It follows well-developed foundations proven over a period of some fifteen years, with constant refine- ment. The backbone of the AD8306 (Figure 19) comprises a chain of six main amplifier/limiter stages, each having a gain of 12. and small-signal –3 dB bandwidth of 850 MHz. ...

Page 8

... E mended, even when only one output pin is used, and these should always be returned to the same well decoupled node on the PC board. When the AD8306 is used only to generate an RSSI output, the limiter should be completely disabled by omitting R TO STAGES 1 THRU 5 ...

Page 9

... V level will be as long for load. This may be reduced by adding a grounded load resistance. USING THE AD8306 The AD8306 exhibits very high gain from 1 MHz to over 1 GHz, at which frequency the gain of the main path is still over 65 dB. Consequently susceptible to all signals, within this very broad frequency range, that find their way to the input termi- nals ...

Page 10

... Slope and Intercept. The logarithmic slope is defined as the change in the RSSI output voltage for change at the input. For the AD8306 the slope is calibrated mV/dB. The intercept is the point at which the extrapolated linear re- sponse would intersect the horizontal axis. For the AD8306 the intercept is calibrated to be – ...

Page 11

... The very high frequency attenuation is relatively small, however, since in the limiting = 50 , the limiter output case it is determined simply by the ratio of the AD8306’s input capacitance to the coupling capacitors. Table I provides solu- tions for a variety of center frequencies f ...

Page 12

... Simple schemes can be used to increase and decrease the loga- = 100 MHz rithmic slope as shown in Figure 30. For the AD8306, only IN power, ground and logarithmic output connections are shown; refer to Figure 24 for complete circuitry. In Figure 30(a), the op amp’s gain of +2 increases the slope to 40 mV/dB. In Figure ...

Page 13

... Even higher output powers can be ob- tained using emitter-followers. In Figure 31, the supply voltage to the AD8306 is dropped from about 4 the diode. This increases the available swing at each output to about 2 V. Taking both outputs differentially, a square wave output p-p can be generated ...

Page 14

... Component Function SW1 Device Enable. When in Position A, the ENBL pin is connected to +V AD8306 is in normal operating mode. In Position B, the ENBL pin is connected to an SMA connector labeled Ext Enable. A signal can be applied to this connector to enable/disable the AD8306. R1 This pad is used to ac-couple INLO to ground for single-ended input drive. To drive the AD8306 differentially, R1 should be removed ...

Page 15

... Figure 34. Layout of Signal Layer Figure 35. Layout of Power Layer REV. A Figure 36. Signal Layer Silkscreen Figure 37. Power Layer Silkscreen –15– AD8306 ...

Page 16

... AD8306 0.1574 (4.00) 0.1497 (3.80) OUTLINE DIMENSIONS Dimensions shown in inches and (mm). 16-Lead Narrow Body SO (SO-16) 0.3937 (10.00) 0.3859 (9.80 0.2440 (6.20) 0.2284 (5.80 PIN 1 0.0688 (1.75) 0.050 (1.27) BSC 0.0532 (1.35) 0.0098 (0.25) 0.0192 (0.49) SEATING 0.0099 (0.25) PLANE 0.0040 (0.10) 0.0138 (0.35) 0.0075 (0.19) –16– 0.0196 (0.50) 45 0.0099 (0.25 0.0500 (1.27) 0.0160 (0.41) REV. A ...

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