              DESCRIPTION OF "VCO4046A.WK1 and VCO9046A.WK1"
              ==============================================
Introduction
------------

VCO4046A.WK1 and VCO9046A.WK1 are worksheet files who calculate the output
frequency of the VCO part of the HC/HCT4046 and 9046 as a function of input
voltage and RC components of the VCO. The files work with Lotus 1-2-3 (R),
versions 2.01 and higher, and similar spreadsheet programs.
The formulas used are identical to the ones in the PLL design program. The
difference is that the PLL Design Program calculates the VCO circuit
components from certain conditions (required output centre frequency,
frequency range) where this spreadsheet calculates output frequency data
using VCO RC values as an input: R1 (connected to pin 11), R2 (pin 12) and
C1 (pin 6-7).

Using the worksheet
-------------------

From Lotus 1-2-3 load the file in the normal way.
You are automatically placed in the "INPUT AREA" where you may enter values
for R1, R2, C1, and d, the part-to-part spread in these components and
internal VCO parameters. You should not change any of the other values.

 For the entered values, the VCO output frequency is calculated for some
values of VCO input control voltage (Vvcoin). The frequencies for a typical
device are shown in the lower box, C17..C19, at Vvcoin = 1.1, 2.5 and 3.9V.
 The part-to-part spread may result in a different output frequency. For a
deviation of + d % and - d % the output frequency is calculated as well,
enabling you to check worst-case behaviour. The results are shown next to
the lower box (cells E17..G19).

When you have an appropriate graphics screen, you will see a graphic curve
by pressing ESC and then F10. The graph shows the output frequency range as
function of Vvcoin for a typical device and for the worst case minimum and
maximum conditions.  Some other interesting output data are:

 - FO     (Cell C12) : Typical centre freq. at Vvcoin = 2.5 Volt.
 - 2Fr    (Cell C13) : Typical frequency range (from Vvcoin = 1.1 to 3.9 V)
 - FOav   (Cell C14) : Mid frequency between Vvcoin = 1.1 and 3.9 Volt.
 - 2Freff (Cell G13) : Effective frequency range for the entered d, being
   the frequency range taking the part-to-part spread into account
   (G13=E19-G17). This value should be positive and larger than the
   variation in PLL input signal frequency. If not, then the frequency
   range should be increased by decreasing R1 and increasing R2.(smaller
   offset, larger range) or a lower spread should be realized.
 - FOeffav (Cell G14): Effective average centre frequency. Mid frequency of
   the effective frequency range ((+E19+G17)/2).

Background information
-----------------------

Some constants and variables are to be found in the CONSTANTS section.
These take into account the entered data and internal parameters of the
HC/HCT4046A and HCT9046A VCO section such as current mirror factor,
propagation delay and stray capacitance.
In rows 7 to 10 of the worksheet, the VCO output frequency is calculated
for a typical device with VCO input voltages of 1.1, 2.5 and 3.9 Volt and
Vcc = 5 V.
The formulas used are the same as the ones used in the PLL Design program.

Comment on the use of this disk are highly appreciated.


                                                          Wim Rosink.



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