ywguo
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Hello,
As well known, substrate noise is a very severe problem in mixed signal circuit design.
Basically, the digital supply and analog supply are seperated on chip. Some papers has presented that guard ring is not effective for low-ohmic substrate. Somebody recommends that analog ground should not connect to substrate because the low-ohmic substrate is polluted by digital circuits.
But I am confused by a practical configuration. It is shown in the following. vdda 3.3V DAC supply vssa clean vssa (not connected to substrate), connect to board analog ground gnda Ground input (connected to substrate), connect to vssa if using high-ohmic substrate, connect to digital gnd! if using low-ohmic substrate. gnd! substrate ground, keep minimal resistance to gnd! bondpad vdd! digital supply
Who could explain the configuratoin for me? Thanks very much in advance.
Best Regards,
Yawei Guo
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