INTRODUCTION

The S1M8831A/33 is a Fractional-N frequency synthesizer with integrated prescalers, designed for RF operation up to 1.2GHz/K-PCS and for IF operation up to 520MHz. The fractional-N synthesizer allows fast-locking, low phase noise phase-locked loops to be built easily, thus having rapid channel switching and reducing standby time for extended battery life. The S1M8831A/33 based on å - D fractional-N techniques solves the fractional spur problems in other fractional-N synthesizers based on charge pump compensation. The synthesizer also has an additional feature that the PCS/CDMA channel frequency in steps of 10kHz can be accurately programmed.

FEATURES

• High operating frequency dual synthesizer

— S1M8831A: 0.71 to 1.2GHz(RF)/ 45 to 520MHz(IF)

— S1M8833: 1.6 to 1.65GHz(RF)/ 45 to 520MHz(IF)

• Operating voltage range: 2.7 to 4.0V

• Low current consumption (S1M8831A: 5.0mA, S1M8833: 7.0mA)

• Selectable power saving mode (ICC = 1uA typical @ 3V)

• Dual-modulus prescaler and Fractional-N/Integer-N:

— S1M8831A (RF) 8/9 Fractional-N

— S1M8833 (RF) 16/17 Fractional-N

— S1M8831A/33 (IF) 8/9 Integer-N

• Excellent in-band phase noise ( – 85dBc/Hz @ PCS, -90dBc/Hz @CDMA) Improved fractional spurious performance ( < 80dBc)

• Frequency resolution (= 10kHz/64 @ fref = 9.84MHz)

• Fast channel switching time: < 500us

• Programmable charge pump output current: from 50uA to 800uA in 50uA steps

• Programmability via on-chip serial bus interface

APPLICATIONS

• High-rate data-service cellular telephones (for CDMA): S1M8831A, S1M8833

• High-rate data-service portable wireless communications (for Korean-PCS): S1M8833

• Other wireless communications systems