STW82102B datasheet(29/67 Pages) STMICROELECTRONICS

29 / 67 page

STW82102B

General description

Doc ID 018516 Rev 2

29/67

VCO calibration auto-restart feature

The VCO Calibration Auto-Restart feature, once activated, allows the calibration procedure

to be restarted when the Lock Detector reports that the PLL has moved to an unlock

condition (trigger on ‘1’ to ‘0’ transition of Lock Detector signal).

This situation could happen if the device experiences a significant temperature variation and

the CALTYPE bit is set for optimum PLL phase noise performance (CALTYPE [0]).

By enabling the VCO Calibration Auto-Restart feature (through the AUTO_CAL bit), the

device re-selects the proper VCO frequency sub-range, without any external user

command.

This feature can be enabled only when the FPFD is lower than 1 MHz.

VCO voltage amplitude control

The voltage swing of the VCOs can be adjusted over 4 levels by means of two dedicated

programming bits (PLL_A1 and PLL_A0). This setting trades current consumption with

phase noise performances of the VCO. Higher amplitudes provide best phase noise while

lower ones save power.

STW82102B 数据表(PDF) 29 Page - STMicroelectronics