DAC8811 Datasheet, PDF (18/29 Pages) Texas Instruments – 16-Bit, Serial Input Multiplying Digital-to-Analog Converter

DAC8811
SLAS411D – NOVEMBER 2004 – REVISED FEBRUARY 2016
11 Layout
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11.1 Layout Guidelines
A precision analog component requires careful layout, adequate bypassing, and clean, well-regulated power
supplies. The DAC8811devices offer single-supply operation, and are often 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. As a result of the single ground pin of the DAC8811, 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. The power applied to AVDD should be well-
regulated and low noise. Switching power supplies and dc-dc converters often have high-frequency glitches or
spikes riding on the output voltage. In addition, digital components can create similar high-frequency spikes as
their internal logic switches states. This noise can easily couple into the DAC output voltage through various
paths between the power connections and analog output. As with the GND connection, AVDD should be
connected to a power-supply plane or trace that is separate from the connection for digital logic until they are
connected at the power-entry point. In addition, a pair of 100-pF to 1-nF capacitors and a 0.1-μF to 1-μF bypass
capacitor are strongly recommended. 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 essentially to
provide low-pass filtering for the supply and remove the high-frequency noise.
While all the other recommendations apply to most DACs, multiplying DACs also require that the transimpedance
amplifier be placed in close proximity in order to minimize non-linearity errors introduced by any resistance
between the I_OUT pin and V- pin of the amplifier.
11.2 Layout Example
Figure 29. DAC8811 Layout Example
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