DAC8565ICPWG4 Datasheet, PDF (34/49 Pages) Texas Instruments – 16-Bit, Quad Channel, Ultra-Low Glitch, Voltage Output

DAC8565
SBAS411C – JUNE 2007 – REVISED MARCH 2011
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APPLICATION INFORMATION
INTERNAL REFERENCE
The internal reference of the DAC8565 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_REFH/V_REFOUT output is recommended.
Figure 97 shows the typical connections required for
operation of the DAC8565 internal reference. A
supply bypass capacitor at the AV_DD input is also
recommended.
Temperature Drift
The 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 described by
Equation 2:
Drift Error =
V_{REF_MAX} - V_{REF_MIN}
V_REF ´ T_RANGE
´ 10⁶ (ppm/°C)
(2)
AV_DD
DAC8565
150nF
0.1mF
1 V_OUTA
2 V_OUTB
3 V_REFH/V_REFOUT
4 AV_DD
5 V_REFL
6 GND
7 V_OUTC
8 V_OUTD
LDAC 16
ENABLE 15
RSTSEL 14
RST 13
IOV_DD 12
D_IN 11
SCLK 10
SYNC 9
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.
The 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.
Figure 97. Typical Connections for Operating the
DAC8565 Internal Reference
Supply Voltage
The 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
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_REFH/V_REFOUT is less than 10μV/V;
see 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_REFH/V_REFOUT 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.
This spectrum was obtained using a 4.8μF load
capacitor at V_REFH/V_REFOUT for noise filtering.
Internal reference noise impacts the DAC output
noise; see the DAC Noise Performance section for
more details.
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