STW81100 Datasheet, PDF(19/23 Page) STMicroelectronics – MULTI-BAND RF FREQUENCY SYNTHESIZER WITH INTEGRATED VCOS

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STW81100 Datasheet, PDF (19/23 Pages) STMicroelectronics – MULTI-BAND RF FREQUENCY SYNTHESIZER WITH INTEGRATED VCOS

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STW81100

Table 20. A_COUNTER

MSB

LSB

Bit B0 for B Counter, A Counter value and bit R8 for Reference divider.

Table 21. REF_DIVIDER

MSB

LSB

Reference Clock divider ratio R[7:0] (bit R8 in the previous register).

The LO output frequency is programmed by setting the proper value for A,B and R according to the fol-

lowing formula:

FOUT

F----R----E----F---_---C---L---K--

where DR equals

0.5

0.25

for Direct Output

for Output Divided by 2

for Output Divided by 4

Table 22. Calibration

MSB

INIT CAL

SER CAL

SEL EXT CAL

CAL 0

CAL 1

CAL 2

CAL 3

LSB

CAL 4

This register controls VCO calibrator.

INITCAL: resets the auto-calibrator State Machine (writing to â1â and back to â0â)

SERCAL: at â1â starts the VCO auto-calibration (should be reset to â0â at the end of calibration)

SELEXTCAL: at â1â selects control word EXTCAL[4:0] for the VCO

EXTCAL[4:0]: control word for the VCO

Table 23. CONTROL

PLL_A0

PLL_A1

CP SEL 0

CP SEL 1 CP SEL 2

The CONTROL register is used to set the VCO output voltage amplitude and the Charge Pump Current.

PLL_A[1:0]: VCO amplitude

CPSEL[2:0]: Charge Pump output current

19/23

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