-------------------------------------------------------------------------------
-- Copyright (c) 2001 Mentor Graphics Corporation
--
-- This model is a component of the Mentor Graphics VHDL-AMS educational open 
-- source model library, and is covered by this license agreement. This model,
-- including any updates, modifications, revisions, copies, and documentation 
-- are copyrighted works of Mentor Graphics. USE OF THIS MODEL INDICATES YOUR 
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-- notice that this model has been modified and the date of modification; and 
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-- conspicuous notice that this model is available from Mentor Graphics in its
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--
-- THIS MODEL IS LICENSED TO YOU "AS IS" AND WITH NO WARRANTIES, EXPRESS OR 
-- IMPLIED.  MENTOR GRAPHICS SPECIFICALLY DISCLAIMS ALL IMPLIED WARRANTIES OF 
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-------------------------------------------------------------------------------
-- File       : VCOAnalog.vhd
-- Author     : Mentor Graphics
-- Created    : 2001/07/11
-- Last update: 2003-05-13
-------------------------------------------------------------------------------
-- Description: Analog Voltage Controlled Oscillator
-------------------------------------------------------------------------------
-- Revisions  :
-- Date        Version     Author              Description
-- 2001/07/11  1.0         Mentor Graphics     Created
-- 2003-04-29  1.1         Mentor Graphics     Added differential output
-------------------------------------------------------------------------------
library IEEE;
use IEEE.math_real.all;
use IEEE.electrical_systems.all;

entity VCOAnalog is
  generic (
    Kv          : real := 100.0e3;   -- VCO Gain [Hz/Volt]
    Fc          : real := 1.0e6;     -- center freq [Hz]
    Vc          : voltage := 2.5;    -- input voltage that gives fc [Volts] 
    Vcmin       : voltage := 0.0;    -- control voltage mininum [Volts]
    Vcmax       : voltage := 5.0;    -- control voltage maximum [Volts]
    Vout_ampl   : voltage := 1.0;    -- amplitude of output [Volts]
    Vout_offset : voltage := 0.0     -- offset voltage of output [Volts]
    );
  port (
    terminal v_inp, v_inm, v_outp, v_outm : electrical);
end entity VCOAnalog;

-------------------------------------------------------------------------------
-- VCO Equation:
-- Fout = Fc + Kv*Vin
-------------------------------------------------------------------------------
architecture behavioral of VCOAnalog is
  quantity vout across iout through v_outp to v_outm;
  quantity vctrl across v_inp to v_inm;
  quantity phi : real;
  quantity vtmp : real;
  constant Kv_w : real := math_2_pi*Kv;    -- convert gain to (Rad/s)/Volt
  constant wc : real := math_2_pi*Fc;        -- convert freq to Rad/s

begin

  if vctrl > Vcmax use                  -- test control voltage for limits
    vtmp == Vcmax;
  elsif vctrl < Vcmin use
    vtmp == Vcmin;
  else
    vtmp == vctrl;
  end use;
  									       
  if domain = quiescent_domain use
    phi     == 0.0;
  else
  -- use one of the following equations depending on preference
    phi'dot == Fc + Kv*(vtmp-Vc);     -- Calculate output Freq in Rad/s
  --  phi'dot == wc + Kv_w*(vtmp-Vc);     -- Calculate output Freq in Hz
  end use;

-- Use one of the following equations depending on phi'dot equation above
vout == Vout_offset + Vout_ampl*cos(math_2_pi*phi);
--vout == Vout_offset + Vout_ampl*cos(phi);

end architecture behavioral;

-------------------------------------------------------------------------------
-- Copyright (c) 2001 Mentor Graphics Corporation
-------------------------------------------------------------------------------