Datasheet

ADC108S052

SNAS337G –SEPTEMBER 2005–REVISED MARCH 2013

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LAYOUT AND GROUNDING

Capacitive coupling between the noisy digital circuitry and the sensitive analog circuitry can lead to poor

performance. The solution is to keep the analog circuitry separated from the digital circuitry and the clock line as

short as possible.

Digital circuits create substantial supply and ground current transients. The logic noise generated could have

significant impact upon system noise performance. To avoid performance degradation of the ADC108S052 due

to supply noise, do not use the same supply for the ADC108S052 that is used for digital logic.

Generally, analog and digital lines should cross each other at 90° to avoid crosstalk. However, to maximize

accuracy in high resolution systems, avoid crossing analog and digital lines altogether. It is important to keep

clock lines as short as possible and isolated from ALL other lines, including other digital lines. In addition, the

clock line should also be treated as a transmission line and be properly terminated.

The analog input should be isolated from noisy signal traces to avoid coupling of spurious signals into the input.

Any external component (e.g., a filter capacitor) connected between the converter's input pins and ground or to

the reference input pin and ground should be connected to a very clean point in the ground plane.

We recommend the use of a single, uniform ground plane and the use of split power planes. The power planes

should be located within the same board layer. All analog circuitry (input amplifiers, filters, reference

components, etc.) should be placed over the analog power plane. All digital circuitry and I/O lines should be

placed over the digital power plane. Furthermore, all components in the reference circuitry and the input signal

chain that are connected to ground should be connected together with short traces and enter the analog ground

plane at a single, quiet point.

Product Folder Links: ADC108S052