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