STW81103 datasheet(35/53 Pages) STMICROELECTRONICS

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STW81103

I2C bus interface

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6.4

VCO calibration procedure

Calibration of the VCO center frequency is activated when the SERCAL bit (CALIBRATION

To program the device properly while ensuring VCO calibration, perform the following steps

before every channel change:

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 all the bits of the CALIBRATION register (05H) set to 0.

Program the CALIBRATION register using a single-byte write sequence (subaddress

05H) with the SERCAL bit set to 1.

The maximum allowed PFD frequency (FPFD) during calibration is 1 MHz; if you want a FPFD

higher than 1 MHz, perform the following additional steps:

●

Perform all the steps of the calibration procedure, making sure to program the desired

VCO frequency with proper settings for the R, B and A counters so that FPFD is ≤1 MHz.

●

Program the device with the desired VCO and PFD frequency settings according to

step 1) above.

6.4.1

VCO calibration auto-restart feature

The VCO calibration auto-restart feature can be enabled in two steps:

set the desired frequency ensuring VCO calibration as described above (section 6.4)

program the FUNCTIONAL_MODE register (sub-address 00H) using a single-byte

write sequence with the CAL_AUTOSTART_EN bit set to '1' while keeping unchanged

the others.

STW81103 데이터시트(PDF) 35 Page - STMicroelectronics