+ Low Power Mixer/Limiter/RSSI 3 V Receiver IF Subsystem AD608 The RF and local oscillator (LO) bandwidths both exceed FEATURES 500 MHz. In a typical IF application, the AD608 can accept the Mixer output of a 240 MHz surface acoustic wave (SAW) filter and down- 15 dBm, 1 dB compression point convert it to a nominal 10.7 MHz IF with a conversion gain of 5 dBm IP3 24 dB (Z = 165 ). The AD608 logarithmic/limiting amplifier IF 24 dB conversion gain section handles any IF from low frequency (LF) up to 30 MHz. >500 MHz input bandwidth Logarithmic/limiting amplifier The mixer is a doubly balanced gilbert-cell mixer and operates 80 dB RSSI range linearly for RF inputs spanning 95 dBm to 15 dBm. It has a 3 phase stability over 80 dB range nominal 5 dBm third-order intercept. An on-board LO pre- Low power amplifier requires only 16 dBm of LO drive. The current output 21 mW at 3 V power consumption of the mixer drives a reverse-terminated, industry-standard CMOS-compatible power-down to 300 W typical 10.7 MHz, 330 filter. 200 ns enable/disable time The nominal logarithmic scaling is such that the output is +0.2 V for a sinusoidal input to the IF amplifier of 75 dBm and +1.8 V APPLICATIONS at an input of +5 dBm over this range, the logarithmic confor- PHS, GSM, TDMA, FM, or PM receivers mance is typically 1 dB. The logarithmic slope is proportional Battery-powered instrumentation to the supply voltage. A feedback loop automatically nulls the Base station RSSI measurements input offset of the first stage down to the submicrovolt level. The AD608 limiter output provides a hard-limited signal output GENERAL DESCRIPTION at 400 mV p-p. The voltage gain of the limiting amplifier to this The AD608 provides a low power, low distortion, low noise mixer output is more than 100 dB. Transition times are 11 ns and the as well as a complete, monolithic logarithmic/limiting amplifier phase is stable to within 3 at 10.7 MHz for signals from 75 dBm that uses a successive-detection technique. In addition, the AD608 to +5 dBm. provides both a high speed received signal strength indicator The AD608 is enabled by a CMOS logic-level voltage input, (RSSI) output with 80 dB dynamic range and a hard-limited with a response time of 200 ns. When disabled, the standby output. The RSSI output is from a two-pole postdemodulation power is reduced to 300 W within 400 ns. low-pass filter and provides a loadable output voltage of 0.2 V to The AD608 is specified for the industrial temperature range of 1.8 V. The AD608 operates from a single 2.7 V to 5.5 V supply 25C to +85C for 2.7 V to 5.5 V supplies and 40C to +85C for at a typical power level of 21 mW at 3 V. 3.0 V to 5.5 V supplies. This device comes in a 16-lead plastic SOIC. FUNCTIONAL BLOCK DIAGRAM 3dB NOMINAL 110dB LIMITER GAIN 24dB MIXER GAIN INSERTION LOSS 90dB RSSI RSSI OUTPUT RSSI IF INPUT 7 FULL-WAVE 11 6mA MAX OUTPUT 20mV/dB RECTIFIER CELLS 75dBm TO (890mV INTO 165) 0.2V TO 1.8V 2 +15dBm 2MHz 5 RFHI LPF 12 COM3 MIXER 10.7MHz RF INPUT IFHI MXOP BAND-PASS VPS2 95dBm TO 7 9 14 +2.7V TO 5.5V FILTER 1 15dBm BPF LMOP 5-STAGE IF AMPLIFIER DRIVER 330 15 LIMITER 330 RFLO 6 (16dB PER STAGE) OUTPUT 10nF LO VMID 400mV p-p FINAL PREAMP 8 10 LIMITER + IFLO 100nF 100 MIDSUPPLY IF BIAS 13 FDBK 18nF 50A BIAS AD608 VPS1 COM1 LOHI COM2 PRUP 1 2 3 4 16 2.7V TO LO INPUT CMOS LOGIC 5.5V 16dBm INPUT 1 15dBm = 56mV MAXIMUM FOR LINEAR OPERATION. 2 39.76V RMS TO 397.6mV RMS FOR 1dB RSSI ACCURACY. Figure 1. Rev. C 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 One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. rights of third parties that may result from its use. Specifications subject to change without notice. No Tel: 781.329.4700 www.analog.com license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Fax: 781.461.3113 19962009 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. + 07886-001AD608 TABLE OF CONTENTS Features .............................................................................................. 1 Mixer ...............................................................................................9 Applications ....................................................................................... 1 Mixer Gain .....................................................................................9 General Description ......................................................................... 1 IF Filter Terminations ................................................................ 10 Functional Block Diagram .............................................................. 1 The Logarithmic IF Amplifier .................................................. 10 Revision History ............................................................................... 2 Offset Feedback Loop ................................................................ 10 Specif icat ions ..................................................................................... 3 RSSI Output ................................................................................ 11 Absolute Maximum Ratings ............................................................ 4 Digitizing the RSSI ..................................................................... 11 Thermal Resistance ...................................................................... 4 Power Consumption .................................................................. 11 ESD Caution .................................................................................. 4 Troublesho ot ing .......................................................................... 11 Pin Configuration and Function Descriptions ............................. 5 Applications Information .............................................................. 12 Typical Performance Characteristics ............................................. 6 Outline Dimensions ....................................................................... 13 Test Circuits ....................................................................................... 8 Ordering Guide .......................................................................... 13 Theory of Operation ........................................................................ 9 REVISION HISTORY 2/09Rev. B to Rev. C Updated Format .................................................................. Universal Reorganized Layout ............................................................ Universal Change to General Description Section ........................................ 1 Changes to DC Level Parameter, Operating Range Parameter, and TMIN to TMAX Parameter, Table 1 .......................................... 3 Added Typical Performance Characteristics Heading ................ 6 Added Test Circuits Heading .......................................................... 8 Changes to Figure 17 and Figure 19 ............................................... 8 Change to Figure 22 ......................................................................... 9 Changes to Table 5 ............................................................................ 9 Updated Outline Dimensions ....................................................... 13 Changes to Ordering Guide .......................................................... 13 Rev. C Page 2 of 16