DAC8564 Datasheet, PDF (34/46 Pages) Texas Instruments – 16-Bit, Quad Channel, Ultra-Low Glitch, Voltage Output DIGITAL-TO-ANALOG CONVERTER with 2.5V, 2ppm/°C Internal Reference

DAC8564
SBAS403A – JUNE 2007 – REVISED NOVEMBER 2007
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APPLICATION INFORMATION
INTERNAL REFERENCE
The internal reference of the DAC8564 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 DAC8564 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)
Where:
DAC8564
1 V_OUTA
2 V_OUTB
LDAC 16
ENABLE 15
V_{REF_MAX} = maximum reference voltage observed
within temperature range T_RANGE.
V_{REF_MIN} = minimum reference voltage observed
within temperature range T_RANGE.
3 V_REFH/V_REFOUT
A1 14
V_REF = 2.5V, target value for reference output
voltage.
AV_DD
4 AV_DD
A0 13
The internal reference (grades C and D) features an
5 V_REFL
IOV_DD 12
exceptional typical drift coefficient of 2ppm/°C from
6 GND
D_IN 11
–40°C to +120°C. Characterizing a large number of
7 V_OUTC
SCLK 10
units, a maximum drift coefficient of 5ppm/°C (grades
C and D) is observed. Temperature drift results are
8 V_OUTD
SYNC 9
summarized in the Typical Characteristics.
Figure 97. Typical Connections for Operating the
DAC8564 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.
34
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