Coverage for klayout_pex/klayout/netlist_expander.py: 97%
71 statements
« prev ^ index » next coverage.py v7.11.0, created at 2025-10-31 20:14 +0000
1#
2# --------------------------------------------------------------------------------
3# SPDX-FileCopyrightText: 2024-2025 Martin Jan Köhler and Harald Pretl
4# Johannes Kepler University, Institute for Integrated Circuits.
5#
6# This file is part of KPEX
7# (see https://github.com/iic-jku/klayout-pex).
8#
9# This program is free software: you can redistribute it and/or modify
10# it under the terms of the GNU General Public License as published by
11# the Free Software Foundation, either version 3 of the License, or
12# (at your option) any later version.
13#
14# This program is distributed in the hope that it will be useful,
15# but WITHOUT ANY WARRANTY; without even the implied warranty of
16# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
17# GNU General Public License for more details.
18#
19# You should have received a copy of the GNU General Public License
20# along with this program. If not, see <http://www.gnu.org/licenses/>.
21# SPDX-License-Identifier: GPL-3.0-or-later
22# --------------------------------------------------------------------------------
23#
24from __future__ import annotations
26import re
27from typing import *
29import klayout.db as kdb
31from ..log import (
32 info,
33 warning,
34)
35from ..common.capacitance_matrix import CapacitanceMatrix
36from ..util.unit_formatter import format_spice_number
39class NetlistExpander:
40 @staticmethod
41 def expand(extracted_netlist: kdb.Netlist,
42 top_cell_name: str,
43 cap_matrix: CapacitanceMatrix,
44 blackbox_devices: bool) -> kdb.Netlist:
45 expanded_netlist: kdb.Netlist = extracted_netlist.dup()
46 top_circuit: kdb.Circuit = expanded_netlist.circuit_by_name(top_cell_name)
48 if not blackbox_devices:
49 for d in top_circuit.each_device():
50 name = d.name or d.expanded_name()
51 info(f"Removing whiteboxed device {name}")
52 top_circuit.remove_device(d)
54 # create capacitor class
55 cap = kdb.DeviceClassCapacitor()
56 cap.name = 'PEX_CAP'
57 cap.description = "Extracted by kpex/FasterCap PEX"
58 expanded_netlist.add(cap)
60 fc_gnd_net = top_circuit.create_net('FC_GND') # create GROUND net
61 vsubs_net = top_circuit.create_net("VSUBS")
62 nets: List[kdb.Net] = []
64 # build table: name -> net
65 name2net: Dict[str, kdb.Net] = {n.expanded_name(): n for n in top_circuit.each_net()}
67 # find nets for the matrix axes
68 pattern = re.compile(r'^g\d+_(.*)$')
69 for idx, nn in enumerate(cap_matrix.conductor_names):
70 m = pattern.match(nn)
71 nn = m.group(1)
72 if nn not in name2net:
73 raise Exception(f"No net found with name {nn}, net names are: {list(name2net.keys())}")
74 n = name2net[nn]
75 nets.append(n)
77 cap_threshold = 0.0
79 def add_parasitic_cap(i: int,
80 j: int,
81 net1: kdb.Net,
82 net2: kdb.Net,
83 cap_value: float):
84 if cap_value > cap_threshold:
85 c: kdb.Device = top_circuit.create_device(cap, f"Cext_{i}_{j}")
86 c.connect_terminal('A', net1)
87 c.connect_terminal('B', net2)
88 c.set_parameter('C', cap_value) # Farad
89 if net1 == net2:
90 raise Exception(f"Invalid attempt to create cap {c.name} between "
91 f"same net {net1} with value format_capacitance(cap_value)")
92 else:
93 warning(f"Ignoring capacitance matrix cell [{i},{j}], "
94 f"{format_spice_number(cap_value)} is below threshold {format_spice_number(cap_threshold)}")
96 # -------------------------------------------------------------
97 # Example capacitance matrix:
98 # [C11+C12+C13 -C12 -C13]
99 # [-C21 C21+C22+C23 -C23]
100 # [-C31 -C32 C31+C32+C33]
101 # -------------------------------------------------------------
102 #
103 # - Diagonal elements m[i][i] contain the capacitance over GND (Cii),
104 # but in a sum including all the other values of the row
105 #
106 # https://www.fastfieldsolvers.com/Papers/The_Maxwell_Capacitance_Matrix_WP110301_R03.pdf
107 #
108 for i in range(0, cap_matrix.dimension):
109 row = cap_matrix[i]
110 cap_ii = row[i]
111 for j in range(0, cap_matrix.dimension):
112 if i == j:
113 continue
114 cap_value = -row[j] # off-diagonals are always stored as negative values
115 cap_ii -= cap_value # subtract summands to filter out Cii
116 if j > i:
117 add_parasitic_cap(i=i, j=j,
118 net1=nets[i], net2=nets[j],
119 cap_value=cap_value)
120 if i > 0:
121 add_parasitic_cap(i=i, j=i,
122 net1=nets[i], net2=nets[0],
123 cap_value=cap_ii)
125 # Short VSUBS and FC_GND together
126 # VSUBS ... substrate block
127 # FC_GND ... FasterCap's GND, i.e. the diagonal Cii elements
128 # create capacitor class
130 res = kdb.DeviceClassResistor()
131 res.name = 'PEX_RES'
132 res.description = "Extracted by kpex/FasterCap PEX"
133 expanded_netlist.add(res)
135 gnd_net = name2net.get('GND', None)
136 if not gnd_net:
137 gnd_net = top_circuit.create_net('GND') # create GROUND net
139 c: kdb.Device = top_circuit.create_device(res, f"Rext_FC_GND_GND")
140 c.connect_terminal('A', fc_gnd_net)
141 c.connect_terminal('B', gnd_net)
142 c.set_parameter('R', 0)
144 c: kdb.Device = top_circuit.create_device(res, f"Rext_VSUBS_GND")
145 c.connect_terminal('A', vsubs_net)
146 c.connect_terminal('B', gnd_net)
147 c.set_parameter('R', 0)
149 return expanded_netlist