SkyWater Foundry Provided Standard Cell Libraries¶
There are seven standard cell libraries provided directly by the SkyWater Technology foundry available for use on SKY130 designs, which differ in intended applications and come in three separate cell heights.
Libraries sky130_fd_sc_hs (high speed), sky130_fd_sc_ms (medium speed), sky130_fd_sc_ls (low speed), and sky130_fd_sc_lp (low power) are compatible in size, with a 0.48 x 3.33um site, equivalent to about 11 met1 tracks.
Libraries sky130_fd_sc_hd (high density) and sky130_fd_sc_hdll (high density, low leakage) contain standard cells that are smaller, utilizing a 0.46 x 2.72um site, equivalent to 9 met1 tracks.
The sky130_fd_sc_hvl (high voltage) library contains 5V devices and utilizes a 0.48 x 4.07um site, or 14 met1 tracks.
Supply voltage, FETs, and approximate cell counts for these libraries appear in the table below:
sky130_fd_sc_lp |
sky130_fd_sc_ls |
sky130_fd_sc_ms |
sky130_fd_sc_hs |
sky130_fd_sc_hd |
sky130_fd_sc_hdll |
sky130_fd_sc_hvl |
|
|---|---|---|---|---|---|---|---|
VDD |
1.8 |
1.8 |
1.8 |
1.8 |
1.8 |
1.8 |
5 |
NMOS devices used |
sky130_fd_pr__nfet_01v8 |
sky130_fd_pr__nfet_01v8 |
sky130_fd_pr__nfet_01v8_lvt |
sky130_fd_pr__nfet_01v8_lvt |
sky130_fd_pr__nfet_01v8 |
sky130_fd_pr__nfet_01v8 |
sky130_fd_pr__nfet_g5v0d10v5 |
PMOS devices used |
sky130_fd_pr__pfet_01v8_hvt |
sky130_fd_pr__pfet_01v8_hvt |
sky130_fd_pr__pfet_01v8 |
sky130_fd_pr__pfet_01v8_lvt |
sky130_fd_pr__pfet_01v8 |
sky130_fd_pr__pfet_01v8_hvt |
sky130_fd_pr__pfet_g5v0d10v5 |
inverters, buffers |
108 |
48 |
48 |
48 |
56 |
62 |
19 |
AND, OR, NAND, NOR |
159 |
66 |
86 |
86 |
153 |
170 |
8 |
XOR, XNOR |
16 |
12 |
12 |
12 |
8 |
10 |
2 |
AND-OR-INV, OR-AND-INV |
138 |
71 |
71 |
71 |
115 |
125 |
4 |
AND-OR, OR-AND |
132 |
68 |
68 |
68 |
132 |
134 |
4 |
Adders, Comparators, Multiplexors |
59 |
37 |
33 |
33 |
31 |
44 |
11 |
Latches and Flip-Flops |
92 |
68 |
68 |
68 |
60 |
60 |
17 |
Custom power gating, bus cells |
43 |
66 |
42 |
42 |
51 |
42 |
|
Macro cells |
5 |
||||||
UDB custom cells |
21 |
17 |
The libraries uses 4 terminal transistors throughout. Individual cells do not have tap in them for the most part (there are a few exceptions). Instead, there are tap cells provided that allow for a staggered tap grid to be placed and connected to allow for body biasing, sleep mode support, and latchup protection.
The following sections will review the libraries in more detail, in terms of performance.
Architecture Comparison |
Low Speed |
High Density |
High Density Low Leakage |
High Voltage |
|---|---|---|---|---|
TAP BAR |
NO |
NO |
NO |
YES |
X-GRID |
0.480 |
0.460 |
0.460 |
0.480 |
Y-GRID |
0.370 |
0.340 |
0.340 |
0.370 |
CELL HEIGHT |
9 GRIDS |
8 GRIDS |
8 GRIDS |
11 GRIDS |
CELL HEIGHT |
3.330 |
2.720 |
2.720 |
4.07 |
NAND2 WIDTH |
3 GRIDS |
3 GRIDS |
4 GRIDS |
5 GRIDS |
NAND2 WIDTH |
1.440 |
1.380 |
1.840 |
2.400 |
NAND2 AREA |
4.7952 |
3.7536 |
5.0048 |
9.770 |
WPMAX |
1.120 |
1.000 |
1.000 |
1.500 |
WNMAX |
0.740 |
0.650 |
0.650 |
0.75 |
sky130_fd_sc_hd - High Density Standard Cell Library¶
The sky130_fd_sc_hd library is designed for high density.
Compared to sky130_fd_sc_ls, this library enables higher routed gated density, lower dynamic power consumption, and comparable timing and leakage power. As a trade-off it has lower drive strength and does not support any drop in replacement medium or high speed library.
sky130_fd_sc_hd includes clock-gating cells to reduce active power during non-sleep modes.
Latches and flip-flops have scan equivalents to enable scan chain creation.
Multi-voltage domain library cells are provided.
Routed Gate Density is 160 kGates/mm^2 or better.
leakage @ttleak_1.80v_25C (no body bias) is 0.86 nA / kGate
sky130_fd_sc_XX__buf_16 max cap (ss_1.60v_-40C, in/out tran=1.5ns) is 0.746 pF
Body Bias-able
sky130_fd_sc_hdll - High Density, Low Leakage Standard Cell Library¶
The sky130_fd_sc_hdll library is a low leakage high density standard cell library.
Compared to sky130_fd_sc_hd, this library enables 5-10X lower leakage power, but the same X, Y pin grids, routing layer pitches, and cell height.
Blocks should be DRC clean when intermingled with sky130_fd_sc_hd cells.
Raw gate density (number of sky130_fd_sc_hdll__nand2_1 gates able to fit in 1mm2) for sky130_fd_sc_hd is 266kGates/mm2 and 200kGates/mm2 for sky130_fd_sc_hdll.
Includes integrating clock-gating cells to reduce active power during non-sleep modes
Latches and flip-flops in the library have a scan equivalent implementation to enable scan chain creation and testing supported by the synthesis tools
Multi-voltage domain library cells are provided
Routed Gate Density is 120 kGates/mm^2
leakage @ttleak_1.80v_25C (no body bias) is 0.08 nA / kGate
sky130_fd_sc_XX__buf_16 max cap (ss_1.60v_-40C, in/out tran=1.5ns) < 1 pF
Multi-Voltage Design Support
Body Bias-able
sky130_fd_sc_hs - Low Voltage (<2.0V), High Speed, Standard Cell Library¶
sky130_fd_sc_hs library enables the implementation of low voltage high speed logic blocks in the SKY130 technology.
sky130_fd_sc_hs cells are drop-in compatible with sky130_fd_sc_ms`a for the same function and drive strength. sky130_fd_sc_hs has the highest speed and the highest leakage of these.
All logic cells are implemented with low voltage transistors and should be powered within the limits of those transistors. Specifically, the timing and power models are valid from 1.60V up to 1.95V, with timing data included for 10% and 20% dynamic IR drop analysis.
All cells are functional at 1.2v. The low to high level shifter cells are capable of shifting from 1.2v to 1.95v.
sky130_fd_sc_ms - Low Voltage (<2.0V), Medium Speed, Standard Cell Library¶
sky130_fd_sc_ms is drop-in compatible with sky130_fd_sc_ls or sky130_fd_sc_hs libraries for cells of the same function and drive strength. sky130_fd_sc_ms cells have medium speed and leakage.
sky130_fd_sc_ms is implemented with low voltage transistors; timing and power models are valid from 1.60V up to 1.95V. All cells are functional at 1.2v.
The low to high level shifter cells are capable of shifting from 1.2v to 1.95v.
The library supports low leakage sleep mode via state retention flops
Includes integrating clock-gating cells to reduce active power during non-sleep modes
Latches and flip-flops in the library have a scan equivalent implementation to enable scan chain creation and testing supported by the synthesis tools
Library details:
Inverters and buffers: 48
AND, OR, NAND, NOR gates: 86
Exclusive-OR and Exclusive-NOR: 12
Inverted And-Or and Inverted Or-And: 71
And-Or and Or-And: 68
Adders, Comparators and Multiplexers: 33
Latches and filp-flops: 68
Low Power Flow Cells: 42
UDB custom cells: 17
sky130_fd_sc_ls - Low Voltage (<2.0V), Low Speed, Standard Cell Library¶
sky130_fd_sc_ls cells are drop-in compatible with sky130_fd_sc_ms`a for the same function and drive strength. sky130_fd_sc_ls has the lowest speed and the lowest leakage of these.
sky130_fd_sc_ls is implemented with low voltage transistors; timing and power models are valid from 1.60V up to 1.95V. All cells are functional at 1.2v.
The low to high level shifter cells are capable of shifting from 1.2v to 1.95v.
The library supports low leakage sleep mode via sleep transistors
Includes integrating clock-gating cells to reduce active power during non-sleep modes
Latches and flip-flops in the library have a scan equivalent implementation to enable scan chain creation and testing supported by the synthesis tools
Drop-in compatible with sky130_fd_sc_ms and sky130_fd_sc_hs libraries
Only the high to low level-shifters are functional at 1v (sky130_fd_sc_ls__lpflow_lsbuf_hl_*). The low to high level-shifters (sky130_fd_sc_ls__lpflow_lsbuf_lh_*) are not functional at 1v as the threshold voltages of the FETs are not enough to flip the state.
Library details:
Inverters and buffers: 48
AND, OR, NAND, NOR gates: 86
Exclusive-OR and Exclusive-NOR: 12
Inverted And-Or and Inverted Or-And: 71
And-Or and Or-And: 68
Adders, Comparators and Multiplexers: 37
Latches and filp-flops: 68
Low Power Flow Cells: 66
Macro Cells: 5
UDB Custom Cells: 21
sky130_fd_sc_lp - Low Voltage (<2.0V), Low Power, Standard Cell Library¶
sky130_fd_sc_lp is the largest of the SKY130 standard cell libraries at nearly 750 cells. All logic cells are implemented with low voltage transistors and should be powered within the limits of those transistors. Specifically, the timing and power models are valid from 1.55V up to 2.0V.
sky130_fd_sc_lp supports low leakage sleep mode via sleep transistors
Includes integrating clock-gating cells to reduce active power during non-sleep modes
Latches and flip-flops have scan equivalents to enable scan chain creation
Larger Library size:
Inverters, Buffers: 108
AND, OR, NAND, NOR gates: 159
Exclusive-OR, Exclusive-NOR: 16
AND-OR-Inverted, OR-AND-Inverted: 138
AND-OR, OR-AND: 132
Adders, Comparators, Multiplexors: 59
Custom Power gating, bus cells: 43
Latches and flip-flops: 92
sky130_fd_sc_hvl - High Voltage (5V), Standard Cell Library¶
The sky130_fd_sc_hvl library has the smallest cell count of the SKY130 standard cell libraries, but is the only one that enables 5V tolerant logic blocks. All logic cells are implemented with 5v tolerant transistors; timing and power models are valid from 1.65v to 5.5v. The low voltage to high voltage level shifter is functional shifting from 1.2v to 5.5v.
Raw gate density (number of sky130_fd_sc_hvl__nand2_1 gates able to fit in 1mm2) should be 170kGates/mm2.
Routed should be >= 100kGates/mm2. Due to the gate length for these high voltage transistors, the actual gate density is lower than 170kGates/mm2. The size of a 2-input NAND gate in this library is actually 5 grids wide, whereas the 170k calculation is based on a gate that is 3 grids wide. With a 5 grid wide gate, the raw gate density is 102kGates/mm2.