DAC8552 Datasheet, PDF (19/22 Pages) Burr-Brown (TI) – 16-BIT, DUAL CHANNEL, ULTRA-LOW GLITCH VOLTAGE OUTPUT DIGITAL-TO-ANALOG CONVERTER

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used, the current it needs to supply to the DAC8552
is 340µA typical and 500µA max for V_DD = 5V. When
a DAC output is loaded, the REF02 also needs to
supply the current to the load. The typical current
required (with a 5kΩ load on a given DAC output) is:
340µA + (5V/5kΩ) = 1.34mA
+15
+5V
REF02
1.34mA
3−Wire
Serial
Interface
SYNC
SCLK
D_IN
V_DD, V_REF
DAC8552
V_OUT = 0V to 5V
Figure 50. REF02 as a Power Supply to the
DAC8552
BIPOLAR OPERATION USING THE DAC8552
The DAC8552 has been designed for single-supply
operation but a bipolar output range is also possible
using the circuit in Figure 51. The circuit shown will
give an output voltage range of ±V_REF. Rail-to-rail
operation at the amplifier output is achievable using
an amplifier such as the OPA703, seeFigure 51.
+5V
R₁
10kΩ
10µF
0.1µF
V_DD, V_REF
V_OUTA,B
DAC8552
R₂
10kΩ
+6V
OPA703
±5V
−6V
NOTE: Other pins omitted for clarity.
Figure 51. Bipolar Operation with the DAC8552
The output voltage for any input code can be
calculated as follows:
ƪ VOUTA, B + VREF
ǒ Ǔ D
65536
DAC8552
SLAS430 – JULY 2006
ǒ Ǔ ǒ Ǔƫ R1 ) R2
R1
* VREF
R2
R1
where D represents the input code in decimal
(0–65535).
With V_REF = 5 V, R1 – R2 = 10kΩ.
ǒ Ǔ VOUTA, B +
10 D
65536
*5V
(3)
This is an output voltage range of ±5V with 0000_H
corresponding 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, adequate bypassing, and clean,
well-regulated power supplies.
The DAC8552 offers single-supply operation, and 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 switching speed, the more
difficult it will be to keep digital noise from appearing
at the output.
Due to the single ground pin of the DAC8552, 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 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 connections and
analog output.
As with the GND connection, V_DD should be
connected to a positive 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 1µF to 10µF capacitor in parallel with a
0.1µF bypass capacitor is 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 supply, removing the high-frequency noise.
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