Okay, here's a summary of the provided transcript in the requested bullet-list format, focusing on timestamps, details, and key takeaways:

Open Source Silicon Stream #6: Exploring Low-Voltage Operation and Level Shifters

• 0:00:05 Introduction: Matt Venn introduces the stream, highlighting its regularity (Mondays at 5 PM CET) and resources for viewers (YouTube channel, mailing list, Tiny Tapeout Discord, courses).

• 0:01:26 News and Updates:

  • Venn recounts a successful workshop in Copenhagen.
  • Tiny Tapeout 8 demo scene entries are compiled into a single video.
  • Tiny Tapeout 10 closes in 14 days, with a free-to-enter demo competition.
  • New chip scans from Tiny Tapeout 7 are available.
  • Efabless Chip Chat #5 is scheduled for February 25th (9 AM PST).
  • Latchup 2025 registration and call for speakers are open (May 2nd-4th, Santa Barbara).
  • Yosys Users Group 10 featured a presentation on ASIC synthesis with Yosys.
  • Anton's mixed-signal design with an interposer board and Kasten Wolf's SAR ADC bring-up video are highlighted.

• 0:06:50 Topic Introduction: MUX Experiment and Level Shifters: The main topic is an experiment to test a Tiny Tapeout design at reduced voltages and the challenges that emerge with the output multiplexer.

• 0:07:53 Problem Definition: The original idea of lowering the device-under-test (DUT) voltage directly affects the 3.3V transmission gates in the output analog multiplexer, compromising the output signal.

• 0:08:40 Level Shifter Introduction: A level shifter is needed to boost the low-voltage output of the DUT to a level compatible with the multiplexer, which still operates at higher voltages.

• 0:08:52 Input Buffer Requirement: An input buffer is also required, as directly connecting a 1.8V input to a DUT operating at, for example, 0.8V would improperly bias the N-wells and cause current leakage.

• 0:09:03 Live Experiment: Venn performs a live experiment, removing a resistor from a Tiny Tapeout board and supplying a variable voltage to the DUT.

• 0:10:52 Experiment Result: The factory design continues to work remarkably well down to approximately 0.78V, but the output signal becomes increasingly slow and distorted at lower voltages.

• 0:27:11 Level Shifter Solution: The revised plan involves using the multiplexer normally, level-shifting the DUT output, and then supplying a controlled 1.8V to the core.

• 0:28:34 N-well Biasing, Input Buffer Use: The reason for using a input buffer is explained further. Connecting a high-voltage input to the lower-voltage DUT creates biasing problems.

• 0:30:59 Initial Level Shifter Design: A classic level shifter design (suggested by Sam Elliot) is presented and simulated.

• 0:33:52 Initial Level Shifter Limitation: The initial level shifter design stops working reliably around 1.1V input, which is insufficient for the experiment's goals.

• 0:35:37 Improved Level Shifter (Silvan's Design): Silvan introduces an improved level shifter design based on an analog comparator, using a voltage divider and a CMOS buffer for a full-swing output.

• 0:36:13 Silvan's Level Shifter Biasing Silvan did not want to use a large poly resistor, and instead, m3 is used as a resistor, with minimum width and length to lower current to a few microamps.

• 0:37:13 Silvan's Level Shifter Posos: Posos are used for the differential input pair due to the low voltage of the inputs.

• 0:37:57 Silvan's Error: int() argument must be a string, a bytes-like object or a real number, not 'NoneType' Voltage Divider: Transistor pair on the far left is a voltage divider, generating voltage intermediate between both, comparing the input signal to half the rail, then transitioning its output.

• 0:40:08 Level Shifter Sizing Discussion: Discussion of transistor sizing (W/L ratio) and potential sharing of components for multiple level shifter channels.

• 0:41:57 Simulation of Improved Design: The improved level shifter is successfully simulated, demonstrating operation down to 0.2V input.

• 0:44:27 Layout Preparation: The improved level shifter design is prepared for layout in Magic, importing the Spice netlist.

• 0:46:55 Alternative Shifter Ideas: Native VT transistors are briefly discussed as another level-shifter possibility but not pursued.

• 0:53:29 Connecting Port Issue: A reminder about the naming requirement for the port.

• 0:57:39 Magic Import: Silvan's design is imported into Magic.

• 1:01:07 Conclusion and Future Plans: The successful simulation of the improved level shifter is summarized. Venn plans to lay out the design and share the process.

• 1:01:34 Closing Remarks: Viewers are encouraged to subscribe, join the mailing list, etc., and the stream concludes.

Key Takeaways:

• Directly lowering the supply voltage of a Tiny Tapeout design within the multiplexer framework affects the output analog multiplexer, necessitating a level shifter.
• An input buffer is needed between the input and DUT to protect the n-wells.
• A basic level shifter design has limitations, failing at lower voltages.
• An improved, comparator-based level shifter (Silvan's design) provides reliable operation down to very low input voltages (0.2V).
• Live experiments and simulations are valuable for validating design choices.
• The use of a variable voltage supply to a chip and monitoring its output is confirmed.