Optimization With HSpice

1
Optimization With HSpice
2
Before you start optimizing

• What are you optimizing for?
• Linearity (as in an amplifier)
• Gain
• Frequency response
• Drive ability
• Transition point
• Speed

3
Before you start optimizing

• How are you going to test the designs quality?
• Simulated loading
• Resistive
• Capacitive
• Both
• In circuit testing

4
Optimization syntax

• The HSpice manual is located in
  cg477/tools/hspice/98/98.4/docs
• The syntax is described in detail in chapter 12
• This is a brief introduction
• I will show examples afterwards

5
Optimization statements

• .MODEL modelname OPT optimization parameters
• .PARAM parameterOPTxxx(optimization range
  specification)
• .DC, .AC, or .TRANS statement with
  MODELmodelname, OPTOPTxxx, and
  RESULTSmeasurename(s)
• .MEASURE statement with GOAL specified

6
Limitations

• You can optimize transistor sizes to shift
  transition points, gain, linearity, etc.
• Transistor optimization is difficult even for
  HSpice. My experience has been that it is mostly
  useful for aiding in sizing.
• HSpice is very useful for bias voltage
  determination.
• If you are close to the best choice for an
  optimization parameter, HSpice will have
  difficulty finding that best choice. It can get
  you close, however.

7
Example buffer

• .MODEL model1 OPT ITROPT30
• .PARAM TransPOPT1 (16, 4, 50, 1)
• .PARAM TransNOPT1 (27, 4, 50, 1)
• .DC Va 0V 3.3V 0.0001 SWEEP OPTIMIZEOPT1
  RESULTStranspt MODELmodel1
• .DC Va 0 3.3 0.001
• .MEASURE DC transpt WHEN v(q0)v(a) CROSSLAST
  goal1.2
• other hspice commands
• m1000 vdd a q0 vdd pch wTransP l2
• ad96 pd44 as80 ps42
• m1001 q1 q0 vdd vdd pch wTransP l2
• ad80 pd42 as0 ps0
• m1002 gnd a q0 gnd nch wTransN l2
• ad138 pd150 as115 ps102
• m1003 q1 q0 gnd gnd nch wTransN l2
• ad115 pd102 as0 ps0

8
Examples gain 2 amplifier

• .MODEL model1 OPT ITROPT30
• .PARAM Pbv1OPT1 (3.233, 0.00, 3.30) Pbv2OPT1
  (0.932, 0.00, 3.30)
• .PARAM Tbv1OPT1 (28, 3, 50, 1) Tbv2OPT1 (29,
  3, 50, 1)
• .PARAM Tbv125
• .PARAM Tbv244
• .PARAM Tain58
• .param trans_pttrans_pt_low
• .DC Vain 0.5V 2.50V 0.001 SWEEP OPTIMIZEOPT1
  RESULTSslope_mid,curve_area MODELmodel1
• .param slope_cur"-sqrt(2)"
• .param trans_pt_low1.150
• .param trans_pt_high1.250
• .param interval_low"trans_pt-(trans_pt_high-trans
  _pt_low)/2"
• .param interval_high"trans_pt(trans_pt_high-tran
  s_pt_low)/2"
• .param interval_low_mid"(trans_ptinterval_low)/2
  "
• .param interval_high_mid"(trans_ptinterval_high)
  /2"
• .param interval_center"trans_pt-sign((trans_pt_hi
  gh-trans_pt_low)/2,trans_pt-(trans_pt_hightrans_p
  t_low)/2)"
• .meas DC slope_mid deriv v(t1) attrans_pt
  goalslope_cur weight200