DESCRIPTION
The SA1620 is a combined receive (Rx) and transmit (Tx) front-end for GSM cellular telephones. The receive path contains two low noise amplifiers (LNA1 and LNA2) with four switchable attenuation steps. A Gilbert Cell mixer in the receive path down-converts the RF signal to a first IF of 70 to 500 MHz. A second Gilbert Cell in the transmit path transposes a GMSK or phase modulated IF to RF by image reject mixing and has a fixed IF of 400 MHz. A buffered LO signal is fed to Rx and Tx mixers. Rx or Tx path or the entire circuit may be powered-down.

FEATURES
•Excellent noise figure: <2dB for the LNAs at 950MHz
•LNAs matched to 50Ωwith external matching components
•LNAs with gain control, 59dB dynamic range in four discrete step
•LNA gain stability ±0.5dB within -40 to 85°C
•Feedthrough attenuation LNA1 to Rx mixer ≥35dB
•Tx power adjustable from -3 to +12dBm by external resistor
•Direct supply: 2.7V to 5.5V
•Battery supply voltage VBATT= 3.3V to 7.5V or direct supply
•Two DC regulators programmable for 3.0V, 3.4V, 3.7V or 5.1V
•Low current consumption: 28mA for Rx or 59mA for Tx
•Fully compatible with SA1638 GSM IF Digital I/Q circuit

APPLICATIONS
•900MHz front end for GSM hand-held units
•Portable radio, TDMA systems