STW81102 datasheet(29/43 Pages) STMICROELECTRONICS

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STW81102

I2C bus interface

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5.4

VCO calibration procedure

The calibration of the VCO center frequency is activated by a '0' to '1' transition of the

SERCAL bit (CALIBRATION Register bit[6]).

In order to program properly the device, ensuring the VCO calibration, the following

procedure is required before every channel change:

Reset the "CALIBRATION" Register using a single-byte write sequence (sub-

address 05H) with all the bits set to '0'

Program all the Registers using a multi-byte write sequence with the desired

settings (Functional Mode, B and A counters, R counter, VCO amplitude, Charge

Pump, Prescaler Modulus) and the SERCAL bit of the "CALIBRATION" Register

(05H) set to '1'

The maximum allowed PFD frequency (fPFD) to perform the calibration process is 1 MHz; if

the desired fPFD is higher than 1MHz the following steps are needed:

–

Perform all the steps of the calibration procedure programming the desired VCO

frequency with a proper setting of R, B and A counter so that fPFD is ≤ 1MHz.

–

Program the device with the proper setting for the desired VCO and PFD

frequencies according to the above step b) only.

STW81102 데이터시트(PDF) 29 Page - STMicroelectronics