STW81103 View Datasheet(PDF) - STMicroelectronics
Part Name
Description
MFG CO.
'STW81103' PDF : 53 Pages View PDF
SPI digital interface
STW81103
The LO output frequency is programmed by setting the proper value for A, B and R
according to the following formula:
FOUT = DR × (B × P + A) × -F----R----E-----F--R---–----C-----L----K--
7.3.1
where DR equals
{
1
0.5
for direct output
for output divided by 2
0.25 for output divided by 4
and P is the selected prescaler modulus.
Default configuration
At power on, all the bits are set to '0'. Consequently the part starts in power down mode.
7.4
7.4.1
VCO calibration procedure
Calibration of the VCO center frequency is activated when the SERCAL bit (ST1 register
bit[6]) is set to 1.
To program the device properly while ensuring VCO calibration, perform the following steps
before every channel change:
1. Program the ST2 register with the desired settings (functional mode, B and A
counters).
2. Program the ST1 register with the desired settings (R counter, VCO amplitude, charge
pump, prescaler modulus) and 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 (step 1 and 2 above) of the calibration procedure, making sure to
program the desired VCO frequency with proper settings of the R, B and A counters so
that FPFD is ≤1 MHz.
● Program the device with the desired VCO and PFD frequency settings as per steps 1
and 2 above with SERCAL bit set to 0.
VCO calibration auto-restart feature
The VCO calibration auto-restart feature can be enabled in two steps:
1. Set the desired frequency ensuring VCO calibration as described above (Section 7.4)
2. Program the ST2 register with the CAL_AUTOSTART_EN bit set to '1' while keeping
unchanged the others.
40/53
Share Link: 
