DAC8501_13 Datasheet, PDF (15/22 Pages) Texas Instruments – Low-Power, Rail-to-Rail Output, 16-Bit Serial Input DIGITAL-TO-ANALOG CONVERTER

The output voltage for any input code can be calculated as
follows:
V_O
=

^V_REF

• ^{} _65D536^{}
•


R₁ + R₂
R₁


–
V_REF
•


R₂
R₁





(3)
where D represents the input code in decimal (0 to 65535).
With V_REF = 5V, R₁ = R₂ = 10kΩ:
V_O
=

10 • D
65536

–
5V
(4)
This is an output voltage range of ±5V with 0000_H corre-
sponding to a –5V output and FFFF_H corresponding to a +5V
output. Similarly, using V_REF = 2.5V, a ±2.5V output voltage
range can be achieved.
LAYOUT
A precision analog component requires careful layout, ad-
equate bypassing, and clean, well-regulated power supplies.
As the DAC8501 offers single-supply operation, it will often
be 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 switch-
ing speed, the more difficult it will be to keep digital noise
from appearing at the output.
Due to the single ground pin of the DAC8501, all return
currents, including digital and analog return currents, must
flow through the GND pin, which would, ideally, be con-
nected directly to an analog ground plane. This plane would
be separate from the ground connection for the digital com-
ponents until they were connected at the power-entry point of
the system.
The power applied to V_DD should be well regulated and low
noise. Switching power supplies and DC/DC converters will
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 connec-
tions and analog output.
As with the GND connection, V_DD should be connected to a
power-supply plane or trace that is separate from the con-
nection for digital logic until they are connected at the power-
entry point. In addition, the 1µF to 10µF and 0.1µF bypass
capacitors are strongly recommended. In some situations,
additional bypassing may be required, such as a 100µF
electrolytic capacitor or even a Pi filter made up of inductors
and capacitors—all designed to essentially low-pass filter the
+5V supply, removing the high-frequency noise.
DAC8501
15
SBAS212A
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