10.1 Layout Guidelines

A precision analog component requires careful layout, adequate bypassing, and clean, well-regulated power supplies.

The DAC8551 offers single-supply operation, and it often is used in close proximity with digital logic, microcontrollers, microprocessors, and digital signal processors. The more digital logic present in the design and the higher the switching speed, the more difficult it is to keep digital noise from appearing at the output.

Due to the single ground pin of the DAC8551, all return currents, including digital and analog return currents for the DAC, must flow through a single point. Ideally, GND would be connected directly to an analog ground plane. This plane would be separate from the ground connection for the digital components until they were connected at the power-entry point of the system.

As with the GND connection, V_DD should be connected to a 5-V power-supply plane or trace that is separate from the connection for digital logic until they are connected at the power-entry point. TI recommends an additional 1-μF to 10-μF capacitor and 0.1-μF bypass capacitor. In some situations, additional bypassing may be required, such as a 100-μF electrolytic capacitor or even a Pi filter made up of inductors and capacitors—all designed to essentially low-pass filter the 5-V supply, removing the high-frequency noise.

10.2 Layout Example

Figure 59. Layout Diagram