INTRODUCTION

The S1M8836/37 is a Fractional-N frequency synthesizer with integrated prescalers, designed for RF operation up to 1.0GHz/2.5GHz 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 S1M8836/37 based on S - 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

• Operating voltage range : 2.7 to 4.0V

• Low current consumption(S1M8836: 5.5mA, S1M8837: 7.5mA)

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

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

- S1M8836 (RF) 8/9/12/13 Fractional-N

- S1M8837 (RF) 16/17/20/21 Fractional-N

- S1M8836/37 (IF) 8/9 Integer-N

• S1M8836: 250MHz to 1.0GHz(RF) / 45MHz to 520MHz(IF)

• S1M8837: 500MHz to 2.5GHz(RF) / 45MHz to 520MHz(IF)

• 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 50mA to 800mA in 50mA steps

• Programmability via on-chip serial bus interface

APPLICATIONS

• High-rate data-service cellular telephones (for CDMA) : S1M8836, S1M8837

• High-rate data-service portable wireless communications : S1M8837

• Other wireless communications systems