AD6459

a FEATURES Fully Compliant with Standard and Enhanced GSM Specification –11 dBm Input 1 dB Compression Point 0 dBm Input Third Order Intercept 10 dB SSB Noise Figure (50 ) DC-500 MHz RF and LO Bandwidths Linear IF Amplifier Linear-in-dB and Stable over Temperature Voltage Gain Control Quadrature Demodulator On-Board Phase-Locked Quadrature Oscillator Demodulates IFs from 5 MHz to 50 MHz Low Power 8 mA at Midgain 2 A Sleep Mode Operation 2.7 V to 5.5 V Operation Interfaces to AD7013, AD7015 and AD6421 Baseband Converters 20-Lead SSOP GSM 3 V Receiver IF Subsystem AD6459 FUNCTIONAL BLOCK DIAGRAM LO I RF BPF PLL Q GAIN CONTROL FREF AD6459 GENERAL DESCRIPTION The AD6459 is a 3 V, low power receiver IF subsystem for operation at input frequencies as high as 500 MHz and IFs from 5 MHz up to 50 MHz. It is optimized for operation in GSM, DCS1800 and PCS1900 receivers. It consists of a mixer, an IF amplifier, I and Q demodulators, a phase-locked quadrature oscillator, a precise AGC subsystem, and a biasing system with external power-down. The AD6459’s low noise, high intercept mixer is a doublybalanced Gilbert-Cell type. It has a nominal –11 dBm inputreferred 1 dB compression point and a 0 dBm input-referred third-order intercept. The mixer section of the AD6459 also includes a local oscillator (LO) preamplifier, which lowers the required LO drive to –16 dBm. The gain control input accepts an external gain-control voltage input from an external AGC detector or a DAC. It provides an 80 dB gain range with 27 mV/dB gain scaling. The I and Q demodulators provide in-phase and quadrature baseband outputs to interface with Analog Devices’ AD7013 (IS54, TETRA, MSAT) AD7015 and AD6421 (GSM, DCS1800, PCS1900) baseband converters. An on-board quadrature VCO that is externally phase-locked to the IF signal drives the I and Q demodulators. This locked reference signal is normally provided by an external VCTCXO under the control of the radio’s digital processor. The AD6459 can also provide demodulation of N-PSK and N-QAM in many non-TDMA systems when used with external analog carrier recovery systems such as the Costas Loop. Finally, the VCO can be phase-locked to a frequency that is deliberately offset from the IF as in the case of a Beat-Frequency oscillator (BFO) resulting in the product detection of CW or SSB. The AD6459 uses supply voltages from 2.7 V to 5.5 V over the temperature range of –40°C to +85°C. Operation is enabled by a CMOS logical level; response time is typically < 80 µs. When disabled, the standby current is reduced to 2 µA. The AD6459 comes in a 20-pin shrink small outline (SSOP) surface mount package. R EV. 0 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. One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Tel: 617/329-4700 World Wide Web Site: http://www.analog.com Fax: 617/326-8703 © Analog Devices, Inc., 1996 AD6459–SPECIFICATIONS (@ T = +25 C, V = 3.0 V, GREF = 1.2 V, unless otherwise noted) A P Model Parameter DYNAMIC PERFORMANCE MIXER Maximum RF and LO Frequency AGC Conversion Gain Variation Input 1 dB Compression Point Input Third-Order Intercept SSB Noise Figure1 Mixer Output Bandwidth at MXOP IF AMPLIFIERS AGC Gain Variation Input Referred Noise Input Resistance Bandwidth I AND Q DEMODULATORS Demodulation Gain Output Voltage Range Output Voltage Common-Mode Level Output Offset Voltage Error in Quadrature Amplitude Match I/Q Output Bandwidth Output Resistance GAIN CONTROL Total Gain Control Range Control Voltage Range at GAIN Gain Scaling Gain Law Conformance Bias Current at GREF Input Resistance at GAIN PLL Frequency Range Phase Noise Acquisition Time Input Drive Level (FREF) POWER-DOWN INTERFACE Logical Threshold Input Current for Logical High Turn-On Response Time Turn-Off Response time Standby Current POWER SUPPLY Supply Range Supply Current OPERATING TEMPERATURE TMIN to TMAX Conditions Min AD6459ARS Typ Max Units 0.2 V < VGAIN < 2.25 V @ VGAIN = 0.2 V @ VGAIN = 0.2 V @ ZS = 50 Ω, FRF = 240 MHz, FLO = 229.3 MHz at –16 dBm @ –3 dB 0.2 V < VGAIN