Rohm LAPIS Semiconductor ML7404 Series, Hardware Design Manual

Page: 15 / 26

ML7404 Family LSIs
Hardware Design Manual
FEXL7404DG-03
9
4.1. Adjusting component values for VCO tank
Adjustment procedure of the VCO tank component
ｓ
is as below:
1. Execute the VCO calibration with the following condition.

Set the frequency to the center of usingfrequency range.

In the idle state with the room temperature.
2. Adjust the L1 and C1 values so that the calibration value obtained by [VCO_CAL] register (B0 0x6E)
becomes close to “64”(Decimal).

Reducing one or both L1 and C1 values if decreasing the VCO_CAL value.

Increasing one or both L1 and C1 values if increasing the VCO_CAL value.
[Note] In order to lock the PLL, the VCO_CAL value is required to be in the range from 1 to 126 (decimal) under
all conditions.
The frequency range that PLL can lock, VCO phase noise and the temperature feature depend on the L1, C1
values. It is recommended to evaluate these characteristics when L1 and C1 values is fixed.
Table 4.1.1 Representative component values for operating frequency
Target RF frequency
PLL
（
VCO
）
divider
setting
VCO
oscillation
frequency
VCO tank value
L1 C1
ML7404
426MHz divide by 2 852MHz 4.7nH 3.9pF
494.998MHz divide by 2 980MHz 3.6nH 3.3pF
868MHz no divide 868MHz 4.7nH 3.9pF
920MHz no divide 920MHz 3.9nH 3.3pF
[Note] These component values appropriate for use on the LAPIS Semiconductor’s RF board. It is not guaranteed
to obtain same result on your specific board.