Analog IC Note – Non-overlap Circuit
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When utilizing big size of MOS, we often avoid the huge shoothrough current from supply to GND happening. This problem usually occurs at IO circuit, charge pump and others which need big MOS. To solve this strategy, non-overlap mechanism is commonly added to these kinds of circuits. Today, I wanna keep some notes for design non-overlap circuit.
1.Find the switches pairs that might create a path from supply to GND. (or between two different voltages)
2.Make each gate signal of switches pair separated. It means we don’t let the switches pair turn on at the same time.
3.Define “turn-on”: It’s a better way to use threshold voltage of the MOS(switch) as check. AVOID USING 0.9XVDD OR 0.1XVDD.
4.Remember to consider the worst case when designing the non-overlap time. Concern the process variation, supply voltage value and temperature.
5.You can do a final check for double confirming the shoothrough current not happened. It’s to probe the channel currents of switches pair at simulation. As long as there is no any channel current occurring at the same time, you can assure the non-overlap circuit working well.
I'm Peter, an analog IC R&D in Taiwan.
Nice to meet u.
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REF:
1. Sedra Smith,"Microelectronic Circuits",Edition 6
2. Charles K. Alexander and Matthew N.O. Sadiku, “Fundamentals of Electric Circuits”, Seventh Edition, McGraw Hill, 2021.
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