Automating Analog Layout
Keith Sabine 5/8/2019 Post a comment
There has been vast progress over the last 30 years or so in digital layout automation, which has made it possible to develop complex digital ICs relatively quickly. However, for analog layout, techniques are still much the same as they were years ago.
Constraint-driven Analog Placement and Routing
Keith Sabine 10/19/2015 Post a comment
Although digital design productivity has improved massively since the introduction of synthesis, advanced place and route and timing-driven design, analog design still relies on circuit simulation, manual layout and verification.
Using Deep N Wells in Analog Design
Keith Sabine 5/7/2015 2 comments
On a conventional CMOS process, NMOS devices are formed in a P well or substrate connected to ground (or the most negative supply in the circuit). PMOS devices are formed in an N well connected to the most positive supply
Latchup and its prevention in CMOS
Keith Sabine 1/14/2015 5 comments
Early CMOS processes suffered a reliability concern that became known as latchup. It resulted in circuits either malfunctioning or consuming excessive power, and could be either inherent in the design or triggered by voltage spikes on IO pads that could forward bias PN junctions they were connected to.
Improving Analog Design Time
Keith Sabine 7/9/2014 10 comments
Designers can estimate parasitics early in the design flow, at the RTL level, to see if they meet timing and power criteria. Thus design changes can be iterated relatively quickly until the design goals are met, with detailed layout following.
Matching in Analog Layout
Keith Sabine 5/20/2014 Post a comment
Analog circuits often use structures like differential pairs and current mirrors, where matching of device characteristics such as the threshold voltage Vt is important.
There’s a further cool thing you can do with a spreadsheet that most SPICEs can’t. That’s to use the spreadsheet ‘solver’ functionality to adjust component values in the search for a better-fitting circuit – or even to find a set of component values for a circuit you can’t otherwise design.
Infineon MOSFETs have been embedded into PC boards by Schweizer Electronic AG
You now need to adjust component values to achieve some system goal, such as predefined frequency response or time behaviour, and there’s no closed method for working out those values.
As a member of the electronics design community, I am angry and disappointed with the recent deaths of 346 people due to the Boeing MAX 8 design