Datasheet

DAC121C081, DAC121C085

SNAS395D –DECEMBER 2007–REVISED MARCH 2013

www.ti.com

LAYOUT, GROUNDING, AND BYPASSING

For best accuracy and minimum noise, the printed circuit board containing the DAC121C081 should have

separate analog and digital areas. The areas are defined by the locations of the analog and digital power planes.

Both of these planes should be located on the same board layer. There should be a single ground plane. A

single ground plane is preferred if digital return current does not flow through the analog ground area. Frequently

a single ground plane design will utilize a "fencing" technique to prevent the mixing of analog and digital ground

current. Separate ground planes should only be utilized when the fencing technique is inadequate. The separate

ground planes must be connected in one place, preferably near the DAC121C081. Special care is required to

ensure that digital signals with fast edge rates do not pass over split ground planes. They must always have a

continuous return path below their traces.

The DAC121C081 power supply should be bypassed with a 4.7µF and a 0.1µF capacitor as close as possible to

the device with the 0.1µF right at the device supply pin. The 4.7µF capacitor should be a tantalum type and the

0.1µF capacitor should be a low ESL, low ESR type. The power supply for the DAC121C081 should only be

used for analog circuits.

Avoid crossover of analog and digital signals and keep the clock and data lines on the component side of the

board. These clock and data lines should have controlled impedances.

Product Folder Links: DAC121C081 DAC121C085