DAC8560 Datasheet, PDF (22/29 Pages) Burr-Brown (TI) – 16-Bit, Ultra-Low Glitch, Voltage Output DIGITAL-TO-ANALOG CONVERTER with 2.5V, 2ppm/°C Internal Reference

DAC8560
SLAS464 – DECEMBER 2006
www.ti.com
APPLICATION INFORMATION
INTERNAL REFERENCE
The DAC8560 internal reference does not require an
external load capacitor for stability because it is
stable with any capacitive load. However, for
improved noise performance, an external load
capacitor of 150nF or larger connected to the V_REF
output is recommended. Figure 67 shows the typical
connections required for operation of the DAC8560
internal reference. A supply bypass capacitor at the
V_DD input is also recommended.
DAC8560
V_DD
V_REF
1mF
1 V_DD
2 V_REF
3
150nF
4
V_FB
V_OUT
GND 8
D_IN 7
SCLK 6
SYNC 5
Figure 67. Typical Connections for Operating the
DAC8560 Internal Reference
The DAC8560 internal reference (grades C and D)
features an exceptional typical drift coefficient of
2ppm/°C from –40°C to +120°C. Characterizing a
large number of units, a maximum drift coefficient of
5ppm/°C (grades C and D) is observed. Temperature
drift results are summarized in the Typical
Characteristics.
Noise Performance
Typical 0.1Hz to 10Hz voltage noise can be seen in
Figure 8, Internal Reference Noise. Additional
filtering can be used to improve output noise levels,
although care should be taken to ensure the output
impedance does not degrade the AC performance.
The output noise spectrum at V_REF without any
external components is depicted in Figure 7, Internal
Reference Noise Density vs Frequency. Another
noise density spectrum is also shown in Figure 7,
which was obtained using a 4µF load capacitor at
V_REF for noise filtering. Internal reference noise
impacts the DAC output noise; see the DAC Noise
Performance section for more details.
Supply Voltage
The DAC8560 internal reference features an
extremely low dropout voltage. It can be operated
with a supply of only 5mV above the reference
output voltage in an unloaded condition. For loaded
conditions, refer to the Load Regulation section. The
stability of the DAC8560 internal reference with
variations in supply voltage (line regulation, DC
PSRR) is also exceptional. Within the specified
supply voltage range of 2.7V to 5.5V, the variation at
V_REF is smaller than 10µV/V; see the Typical
Characteristics.
Temperature Drift
The DAC8560 internal reference is designed to
exhibit minimal drift error, defined as the change in
reference output voltage over varying temperature.
The drift is calculated using the box method, which is
described by Equation 2:
ǒ Ǔ Drift Error +
V_{REF_MAX} * V_{REF_MIN}
V_REF T_RANGE
10⁶ (ppmń°C)
Where:
V_{REF_MAX} = maximum reference voltage
observed within temperature range T_RANGE.
V_{REF_MIN} = minimum reference voltage observed
within temperature range T_RANGE.
V_REF = 2.5V, target value for reference output
voltage.
Load Regulation
Load regulation is defined as the change in
reference output voltage as a result of changes in
load current. The load regulation of the DAC8560
internal reference is measured using force and sense
contacts as pictured in Figure 68. The force and
sense lines reduce the impact of contact and trace
resistance, resulting in accurate measurement of the
load regulation contributed solely by the DAC8560
internal reference. Measurement results are
summarized in the Typical Characteristics. Force and
sense lines should be used for applications requiring
improved load regulation.
Sense Line
Output Pin
Contact and
Trace Resistance
V_OUT
Force Line
I_L
Meter
Load
Figure 68. Accurate Load Regulation of the
DAC8560 Internal Reference
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