Datasheet

V =
HYST
´ 10 (ppm/ C)°
6
|V V |-
REF_PRE REF_POST
V
REF_NOM
OutputPin
Meter
Load
ForceLine
SenseLine
Contactand
TraceResistance
I
L
V
OUT
DAC7568
DAC8168
DAC8568
www.ti.com SBAS430D –JANUARY 2009–REVISED MAY 2012
Load Regulation Thermal Hysteresis
Load regulation is defined as the change in reference Thermal hysteresis for a reference is defined as the
output voltage as a result of changes in load current. change in output voltage after operating the device at
The load regulation of the internal reference is +25°C, cycling the device through the operating
measured using force and sense contacts as shown temperature range, and returning to +25°C.
in Figure 126. The force and sense lines reduce the Hysteresis is expressed by Equation 3:
impact of contact and trace resistance, resulting in
accurate measurement of the load regulation
contributed solely by the internal reference.
Measurement results are summarized in the Typical
(3)
Characteristics. Force and sense lines should be
Where:
used for applications that require improved load
V
HYST
= thermal hysteresis.
regulation.
V
REF_PRE
= output voltage measured at +25°C
pre-temperature cycling.
V
REF_POST
= output voltage measured after the
device cycles through the temperature range of
–40°C to +125°C, and returns to +25°C.
DAC NOISE PERFORMANCE
Typical noise performance for the DAC7568,
DAC8168, and DAC8568 with the internal reference
enabled is shown in Figure 66 to Figure 67. Output
noise spectral density at the V
OUT
pin versus
frequency is depicted in Figure 66 for full-scale,
Figure 126. Accurate Load Regulation of the
midscale, and zero-scale input codes. The typical
DAC7568/DAC8168/DAC8568 Internal Reference
noise density for midscale code is 120nV/√Hz at
1kHz and 100nV/√Hz at 1MHz. High-frequency noise
can be improved by filtering the reference noise.
Long-Term Stability
Integrated output noise between 0.1Hz and 10Hz is
Long-term stability/aging refers to the change of the
close to 6μV
PP
(midscale), as shown in Figure 67.
output voltage of a reference over a period of months
or years. This effect lessens as time progresses (see
Figure 7, the typical long-term stability curve). The
typical drift value for the internal reference is 50ppm
from 0 hours to 1900 hours. This parameter is
characterized by powering-up 20 units and measuring
them at regular intervals for a period of 1900 hours.
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