update to XSPICE phase-locked loop example

examples/xspice/pll/README

@@ -1,11 +1,32 @@
 This directory contains a mixed mode pll, combining
 ngspice and XSPICE circuit blocks.
 The pll consists of the following blocks:
-voltage controlled oscillator: vco_sub.cir
-digital divider and frequency reference: pll-xspice.cir
-phase frequency detector: f-p-det-d-sub.cir
-loop filter: loop-filter.cir
-main simulation control: pll-xspice.cir
+
+** voltage controlled oscillator:
+vco_sub.cir
+   7 stage ring oscillator with gain cells, CMOS devices
+or
+vco_sub_new.cir
+   vco made from code model d_osc, cntl_array/freq_array data
+   are gained by running test-vco.cir with vco_sub.cir
+
+** digital divider and frequency reference:
+pll-xspice.cir
+
+** phase frequency detector:
+f-p-det-d-sub.cir
+
+** loop filter:
+loop-filter.cir
+   switched current sources as charge pump, 2nd order
+   passive RC filter
+or
+loop-filter-2.cir
+   transistors as switches for charge pump, 2nd or 3rd
+   order passive RC filters
+
+** main simulation control:
+pll-xspice.cir
 
 Two test files are included:
 test-vco.cir simulates vco frequency versus control voltage
@@ -15,3 +36,4 @@ The main building blocks are organised as subcircuits.
 
 main simulation control with three reference frequencies:
 pll-xspice-fstep.cir
+   simulates two steps of the reference in one simulation run

examples/xspice/pll/loop-filter-2.cir

@@ -0,0 +1,50 @@
+* loop filter for pll
+* in: d_up d_down digital data
+* out: vout, vco control voltage
+* using transistors to switch current
+* according to http://www.uwe-kerwien.de/pll/pll-schleifenfilter.htm
+* digital input d_Un d_D
+* anlog output vout
+
+
+.subckt loopf d_Un d_D vout
+
+.param initcond=2.5
+
+vdd dd 0 dc 'vcc'
+vss ss 0 dc 0
+
+* "driver" circuit, digital in, analog out
+abridge-f1 [d_Un d_D] [u1n d1] dac1
+.model dac1 dac_bridge(out_low = 0 out_high = 'vcc' out_undef = 'vcc/2'
++ input_load = 5.0e-12 t_rise = 1e-10
++ t_fall = 1e-10)
+
+* uses BSIM3 model parameters from pll-xspice_2.cir
+* transistors as switches
+mnd  dra d1  ss  ss  n1  w=12u  l=0.35u  AS=24p AD=24p PS=28u PD=28u
+mpd  dra u1n  dd  dd  p1  w=24u l=0.35u  AS=48p AD=48p PS=52u PD=52u
+
+*** passive filter elements ***
+*third order filter
+*parameters absolutely _not_ optimised
+*better check
+* http://www.national.com/assets/en/boards/deansbook4.pdf
+*to do so
+.ic v(vout)='initcond' v(c1)='initcond' v(dra)='initcond' v(int1)='initcond' v(u1n)='vcc' v(d1)=0
+R1 dra int1 300
+R2 int1 c1 200
+C1 c1 0 10n
+C2 int1 0 5n
+R3 int1 vout 50
+C3 vout 0 0.5n
+
+*second order filter
+*parameters not optimized
+*.ic v(vout)='initcond' v(c1)='initcond' v(dra)='initcond' v(u1n)='vcc' v(d1)=0
+*R1 dra vout 300
+*R2 vout c1 200
+*C1 c1 0 10n
+*C2 vout 0 5n
+
+.ends loopf

examples/xspice/pll/loop-filter.cir

@@ -3,7 +3,7 @@
 * out: vout, vco control voltage
 * according to http://www.uwe-kerwien.de/pll/pll-schleifenfilter.htm
 
-.subckt loopf d_U d_D vout
+.subckt loopfe d_U d_D vout
 
 .param loadcur=5m
 .param initcond=2.5

examples/xspice/pll/pll-xspice-fstep.cir

@@ -31,11 +31,13 @@ ainv1 d_d0 d_d1 invd1
 
 * vco
 .include vco_sub.cir
+.include vco_sub_new.cir
 * buf: analog out
 * d_digout: digital out
 * cont: analog control voltage
 * dd: analog supply voltage
-xvco buf d_digout cont dd ro_vco
+xvco buf d_digout cont dd d_osc_vco 
+*xvco buf d_digout cont dd ro_vco
 
 * digital divider
 adiv1 d_digout d_divout divider
@@ -48,17 +50,23 @@ adiv1 d_digout d_divout divider
 Xfpdet d_divout d_ref d_U d_Un d_D d_Dn  f-p-det
 
 * loop filter
-.include loop-filter.cir
-Xlf d_U d_D cont loopf
+*2nd or 3rd order, transistors as switches
+.include loop-filter-2.cir
+Xlf d_Un d_D cont loopf
+* 2nd order, Exxxx voltage controlled current sources as 'switches'
+* loop filter current sources as charge pump
+*.include loop-filter.cir
+*Xlf d_U d_D cont loopfe
 
 * d to a for plotting
-abridge-w1 [d_divout d_ref d_U d_D] [s1 s2 u1 d1] dac1
+abridge-w1 [d_divout d_ref d_Un d_D] [s1 s2 u1 d1] dac1 ; change to d_u or d_Un
 .model dac1 dac_bridge(out_low = 0 out_high = 1 out_undef = 0.5
 + input_load = 5.0e-12 t_rise = 1e-10
 + t_fall = 1e-10)
 
 .control
 save cont s1 s2 u1 d1
+iplot cont
 * calculate breakpoint for switching frequency
 let t1_3 = simtime/3
 set ti1_3 ="$&t1_3"
@@ -82,7 +90,7 @@ alter @vref[pulse] = [ 0 3.3 10n 1n 1n  $&pw3 $&per3 ]
 resume
 rusage
 plot cont s1 s2+1.2 u1+2.4 d1+3.6 xlimit 15u 16u
-plot cont
+*plot cont
 .endc
 
 *model = bsim3v3

examples/xspice/pll/pll-xspice.cir

@@ -1,9 +1,11 @@
 * pll circuit using xspice code models
+* output frequency 400 MHz
+* locked to a 1 or 10 MHz reference
 
 .param vcc=3.3
 .param divisor=40
 .param fref=10e6
-.csparam simtime=20u
+.csparam simtime=25u
 
 .global d_d0 d_d1
 
@@ -11,7 +13,7 @@ vdd dd 0 dc 'vcc'
 *vco cont 0 dc 1.9
 
 *PULSE(V1 V2 TD TR TF PW PER)
-* 10 MHz reference frequency
+* reference frequency selected by param fref
 * PULSE(V1 V2 TD TR TF PW PER)
 vref ref 0 dc 0 pulse(0 'vcc' 10n 1n 1n  '1/fref/2' '1/fref')
 abridgeref [ref] [d_ref] adc_vbuf
@@ -27,11 +29,13 @@ ainv1 d_d0 d_d1 invd1
 
 * vco
 .include vco_sub.cir
+.include vco_sub_new.cir
 * buf: analog out
 * d_digout: digital out
 * cont: analog control voltage
 * dd: analog supply voltage
-xvco buf d_digout cont dd ro_vco
+xvco buf d_digout cont dd d_osc_vco 
+*xvco buf d_digout cont dd ro_vco
 
 * digital divider
 adiv1 d_digout d_divout divider
@@ -43,22 +47,29 @@ adiv1 d_digout d_divout divider
 .include f-p-det-d-sub.cir
 Xfpdet d_divout d_ref d_U d_Un d_D d_Dn  f-p-det
 
-* loop filter
-.include loop-filter.cir
-Xlf d_U d_D cont loopf
+* loop filters
+*2nd or 3rd order, transistors as switches
+.include loop-filter-2.cir
+Xlf d_Un d_D cont loopf
+* 2nd order, Exxxx voltage controlled current sources as 'switches'
+* loop filter current sources as charge pump
+*.include loop-filter.cir
+*Xlf d_U d_D cont loopfe
 
 * d to a for plotting
-abridge-w1 [d_divout d_ref d_U d_D] [s1 s2 u1 d1] dac1
+abridge-w1 [d_divout d_ref d_Un d_D] [s1 s2 u1n d1] dac1 ; change to d_u or d_Un
 .model dac1 dac_bridge(out_low = 0 out_high = 1 out_undef = 0.5
 + input_load = 5.0e-12 t_rise = 1e-10
 + t_fall = 1e-10)
 
 .control
-save cont s1 s2 u1 d1 ; to save memory
+save cont s1 s2 u1n d1 v.xlf.vdd#branch; to save memory
+iplot cont
 tran 0.1n $&simtime uic
 rusage
-plot cont s1 s2+1.2 u1+2.4 d1+3.6
-plot cont
+plot cont s1 s2+1.2 u1n+2.4 d1+3.6 xlimit 4u 5u
+plot v.xlf.vdd#branch xlimit 4u 5u ylimit -8m 2m
+*plot cont
 .endc
 
 *model = bsim3v3

examples/xspice/pll/test-f-p-det.cir

@@ -26,14 +26,19 @@ abridge-w1 [d_sig1 d_sig2 d_U d_D] [s1 s2 u1 d1] dac1
 + input_load = 5.0e-12 t_rise = 1e-10
 + t_fall = 1e-10)
 
-* loop filter
-.include loop-filter.cir
-Xlf d_u d_D vco loopf
+* loop filters
+*2nd or 3rd order, transistors as switches
+.include loop-filter-2.cir
+Xlf d_Un d_D cont loopf
+* 2nd order, Exxxx voltage controlled current sources as 'switches'
+* loop filter current sources as charge pump
+*.include loop-filter.cir
+*Xlf d_U d_D cont loopfe
 
 .control
 set xtrtol=2
 tran 0.1n 1000n
-plot s1 s2+1.2 u1+2.4 d1+3.6 xlimit 100n 200n
+plot s1 s2+1.2 u1+2.4 d1+3.6 xlimit 140n 200n
 plot v(vco)
 .endc
 

examples/xspice/pll/test_vco.cir

@@ -1,16 +1,19 @@
-VCO: 7 stage Ring-Osc. made of gain cells BSIM3
+* Test of VCO: frequency versus control voltage
+* 7 stage Ring-Osc. made of gain cells BSIM3
 * P.-H. Hsieh, J. Maxey, C.-K. K. Yang, IEEE JSSC, Sept. 2009, pp. 2488 - 2495
-* get frequency versus control voltage
+* alternatively use d_osc code model
 * measure frequency of R.O. by fft 
 
 .param vcc=3.3
 .csparam simtime=500n
 
 .include vco_sub.cir
+.include vco_sub_new.cir
 
 vdd dd 0 dc 'vcc'
 vco cont 0 dc 2.5
-xvco buf digout cont dd ro_vco
+*xvco buf digout cont dd ro_vco ; ring oscillator vco
+xvco buf digout cont dd d_osc_vco ; code model d_osc vco
 
 .option noacct
 
@@ -75,6 +78,7 @@ setplot $freq_volt
 settype frequency foscvec
 settype voltage vcovec
 plot foscvec vs vcovec
+print vcovec foscvec
 rusage
 .endc
 

examples/xspice/pll/vco_sub.cir

@@ -1,7 +1,7 @@
 * VCO: 7 stage Ring-Osc. made of gain cells BSIM3
 * P.-H. Hsieh, J. Maxey, C.-K. K. Yang, IEEE JSSC, Sept. 2009, pp. 2488 - 2495
-* automatically tune Vdd to achive a desired frequency of oscillation
-* measure frequency of R.O. either by delay measurement or by fft 
+* 150 MHz to 900 MHz with control voltage 2.5 to 0.5 V at 3.3 V supply
+* BSIM 3 model data for transistors in main file pll-xspice.cir
 
 ***** ring oscillator as voltage controlled oscillator *************** 
 * name: ro_vco
@@ -64,3 +64,4 @@ abridge1 [aout] [dout] adc_buff
 .model adc_buff adc_bridge(in_low = 'vcc*0.5' in_high = 'vcc*0.5')
 .ends ro_vco
 ******************************************************************
+

examples/xspice/pll/vco_sub_new.cir

@@ -0,0 +1,30 @@
+***** XSPICE digital controlled oscillator d_osc as vco *************** 
+* 150 MHz to 900 MHz
+* name: d_osc_vco
+* aout analog out
+* dout digital out 
+* cont control voltage
+* dd supply voltage
+
+.subckt d_osc_vco aout dout cont dd
+* curve fitting to ro_vco 'measured' data
+Bfit fitted 0 v = (-58256685.71*v(cont)*v(cont) - 186386142.9*v(cont) + 988722980)/10.
+
+*a5 fitted dout var_clock
+*.model var_clock d_osc(cntl_array = [1.0e7 5.0e7 9.0e7]
+*+ freq_array = [1.0e8 5.0e8 9.0e8]
+
+* linear interpolation, input data from measured ro vco
+a5 cont dout var_clock
+.model var_clock d_osc(cntl_array = [0.5 1 1.5 2 2.5]
++ freq_array = [8.790820e+008 7.472197e+008 5.799500e+008 3.772727e+008 1.611650e+008]
++ duty_cycle = 0.5 init_phase = 180.0
++ rise_delay = 1e-10 fall_delay=1e-10)
+
+*generate an analog output for plotting
+abridge-fit [dout] [aout] dac1
+.model dac1 dac_bridge(out_low = 0 out_high = 1 out_undef = 0.5
++ input_load = 5.0e-12 t_rise = 1e-10
++ t_fall = 1e-10)
+
+.ends d_osc_vco