AD6600(Dual Channel, Gain-Ranging ADC with RSSI)IntroductionThe AD6600 mixed-signal receiver chip directly samples signals at analog input frequencies up to 250 MHz. The device includes two input channels, each with 1 GHz input amplifiers and 30dB of automatic gain-ranging circuitry. Both channels are sampled with a 450 MHz track-and-hold followed by an 11-bit,20 MSPS analog-to-digital converter. Digital RSSI outputs, an AB channel indicator, a 2x Clock output, references, and control circuitry are all on-chip. Digital output signals are two’s complement, CMOS-compatible and interface directly to 3.3 V or 5 V digital processing chips.The primary use for the dual analog input structure is sampling both antennas in a two-antenna diversity receiver.However, users may also use Channels A and B to sample two independent IF signals. Diversity, or dual channel mode, limits each channel to 10 MSPS. In single-channel mode, users can apply the full clock rate of 20 MSPS to a single carrier.The AD6600 may be used as a stand-alone sampling chip, or it may be combined with the AD6620 Digital Receive Signal Processor. The AD6620 provides 10dB—25dB of additional processing gain before passing data to a fixed- or floating point DSP.Driving the AD6600 is simplified by using the AD6630 differential IF amplifier. The AD6630 is easily matched to inexpensive SAW filters from 70MHz to 250MHz.Designed specifically for cellular/PCS receivers, the AD6600 supports GSM, IS-136, CDMA and Wireless I ANs, as well as proprietary air interfaces used in WLI /fixed-access systems.Units are available in plastic, surface-mount packages (44-lead LQFP) and specified over the industrial temperature range(-40°C to 85°C).FeatureDual IF Inputs, 70 MHz- -250 MHzDiversity or Two Independent IF SignalsSeparate Attenuation PathsOversample RF Channels20 MSPS on a Single Carrier10 MSPS/Channel in Diversity ModeTotal Signal Range 90 dB30dB from Automatic Gain-Ranging (AGC)60dB from A/D ConverterRange >100dB After Processing GainDigital Outputs11-Bit ADC Word3-Bit RSSI Word2x Clock, A/B IndicatorSingle 5 V Power SupplyOutput DVCC 3.3 V or 5 V775 mW Power DissipationAppearance
