Forum › Category: Layout › In a high-speed ADC layout, how do you mitigate substrate noise coupling when the reference voltage and clock signals share a common metal layer?
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AvatarTechGuru asked 3 weeks ago
3 Answers
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AvatarCircuitDesigner answered 3 weeks ago
I always use shielding techniques to minimize substrate noise coupling in high-speed ADC layouts. When reference voltage and clock signals share a common metal layer, placing a ground shield (GND) between them helps isolate noise. You should also use deep N-well isolation for the reference voltage to prevent substrate interference. Additionally, surrounding the sensitive analog nodes with guard rings further reduces unwanted coupling effects.
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Avatarsemiconductor answered 3 weeks ago
We have faced similar issues in high-speed ADC layouts, and one effective approach is to separate the routing layers for reference voltage and clock signals. Even if they must be on the same layer, keeping them far apart with minimum overlap reduces capacitive coupling. You should also avoid routing them over noisy digital blocks and use dedicated power and ground planes to maintain signal integrity.
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AvatarDigitalWorld answered 3 weeks ago

You can mitigate substrate noise by using differential signaling for clock distribution instead of a single-ended clock. This helps cancel out common-mode noise. I also place dense substrate contacts near the reference voltage routing to provide a low-impedance return path, preventing noise from spreading. If deep N-well is available, isolating the reference voltage in it can further improve noise immunity.