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https://designers-guide.org/forum/YaBB.pl Design >> Mixed-Signal Design >> Analog MUX for high-speed ADC https://designers-guide.org/forum/YaBB.pl?num=1156754418 Message started by ywguo on Aug 28th, 2006, 1:40am |
Title: Analog MUX for high-speed ADC Post by ywguo on Aug 28th, 2006, 1:40am Hi Guys, I am designing a high-speed ADC, which requires an analog MUX put at the front-end. For eg., a 2:1 MUX preceding the ADC. Many SAR ADCs have analog MUX at the front-end, like 5:1 MUX or 8:1 MUX. They are usually complemetary MOS switch, because SAR ADCs have low conversion rate. However, I need an analog MUX for a pipleined ADC with >100MS/s sampling rate, which . Should I use a bootstrapped switch? Or simply use a very large complementary MOS switch? Any comments are very appreciated. Thanks Yawei |
Title: Re: Analog MUX for high-speed ADC Post by vivkr on Aug 28th, 2006, 6:57am Hi Yawei, Does your ADC have a sampling switch (no buffer) upfront? If so, then you can simply create the MUX functionality by placing multiple switches in parallel, all tied to different input channels, and use some digital logic to allow only 1 channel to be sampled at a time. This is easily done. I would use a bootstrapped switch as the performance is much superior although reliability is atleast of some concern even with the best designs if you are working in short-channel regime. CMOS transmission gates will get really big and will not be linear enough. By the way, be careful that the logic implementing your MUX function does not ruin the analog performance of your switch. What are you using the MUX for? Regards Vivek |
Title: Re: Analog MUX for high-speed ADC Post by ywguo on Aug 28th, 2006, 9:52pm Hi Vivek, I am designing a display interface composed of 2:1 MUX, clamp, PGA and 10-bit ADC. It is used to sample video signals like YPbPr, RGB, etc. I think the linearity must be important. The sampling rate must be more than 100MS/s. Thanks Yawei |
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