DAC8564 datasheet(35/46 Pages) TI

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Load Regulation

Thermal Hysteresis

HYST

´ 10 (ppm/ C)

REF_PRE

REF_POST

REF_NOM

(3)

DAC NOISE PERFORMANCE

OutputPin

Meter

Load

ForceLine

SenseLine

Contactand

TraceResistance

OUT

Long-Term Stability

DAC7565

www.ti.com ............................................................................................................................................... SBAS412A – FEBRUARY 2008 – REVISED MARCH 2008

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

+25

°C.

in Figure 98. The force and sense lines reduce the

Hysteresis is expressed by Equation 3:

impact of contact and trace resistance, resulting in

accurate

measurement

the

load

regulation

contributed

solely

the

internal

reference.

Measurement results are summarized in the Typical

Characteristics. Force and sense lines should be

Where:

used for applications that require improved load

VHYST = thermal hysteresis.

regulation.

VREF_PRE = output voltage measured at +25°C

pre-temperature cycling.

VREF_POST = output voltage measured after the

device cycles through the temperature range of

–40

°C to +120°C, and returns to +25°C.

Typical noise performance for the DAC7565 with the

internal reference enabled is shown in Figure 54 to

Figure 56. Output noise spectral density at the VOUT

pin versus frequency is depicted in Figure 54 for

full-scale, midscale, and zero-scale input codes. The

Figure 98. Accurate Load Regulation of the

typical noise density for midscale code is 120nV/

√Hz

DAC7565 Internal Reference

at 1kHz and 100nV/

√Hz at 1MHz. High-frequency

noise can be improved by filtering the reference noise

as shown in Figure 55, where a 4.8

µF load capacitor

connected

the

VREFH/VREFOUT pin and

Long-term stability/aging refers to the change of the

compared to the no-load condition. Integrated output

output voltage of a reference over a period of months

noise between 0.1Hz and 10Hz is close to 6

µV

or years. This effect lessens as time progresses (see

(midscale), as shown in Figure 56.

Figure 6, 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 and measuring 20 units

at regular intervals for a period of 1900 hours.

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