Datasheet

DriftError=
´ 10 (ppm/ C)°
6
V V-
REF_MAX REF_MIN
V T´
REF RANGE
5
6
7
8
12
11
10
9
IOV
DD
D
IN
SCLK
SYNC
V L
REF
GND
V C
OUT
V D
OUT
AV
DD
DAC7565
1
2
3
4
16
15
14
13
LDAC
ENABLE
RSTSEL
RST
V A
OUT
V B
OUT
V H/V OUT
REF REF
AV
DD
0.1 Fm
150nF
DAC7565
SBAS412B –FEBRUARY 2008–REVISED MARCH 2011 www.ti.com
APPLICATION INFORMATION
INTERNAL REFERENCE
Temperature Drift
The internal reference of the DAC7565 does not
The internal reference is designed to exhibit minimal
require an external load capacitor for stability
drift error, defined as the change in reference output
because it is stable with any capacitive load.
voltage over varying temperature. The drift is
However, for improved noise performance, an
calculated using the box method described by
external load capacitor of 150nF or larger connected
Equation 2:
to the V
REF
H/V
REF
OUT output is recommended.
Figure 97 shows the typical connections required for
operation of the DAC7565 internal reference. A
supply bypass capacitor at the AV
DD
input is also
(2)
recommended.
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 (grade C only) 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
(grade C only) is observed. Temperature drift results
are summarized in the Typical Characteristics.
Noise Performance
Figure 97. Typical Connections for Operating the
Typical 0.1Hz to 10Hz voltage noise can be seen in
DAC7565 Internal Reference
Figure 8, Internal Reference Noise. Additional filtering
can be used to improve output noise levels, although
Supply Voltage
care should be taken to ensure the output impedance
does not degrade the ac performance. The output
The internal reference features an extremely low
noise spectrum at V
REF
H/V
REF
OUT without any
dropout voltage. It can be operated with a supply of
external components is depicted in Figure 7, Internal
only 5mV above the reference output voltage in an
Reference Noise Density vs Frequency. Another
unloaded condition. For loaded conditions, refer to
noise density spectrum is also shown in Figure 7.
the Load Regulation section. The stability of the
This spectrum was obtained using a 4.8μF load
internal reference with variations in supply voltage
capacitor at V
REF
H/V
REF
OUT for noise filtering.
(line regulation, dc PSRR) is also exceptional. Within
Internal reference noise impacts the DAC output
the specified supply voltage range of 2.7V to 5.5V,
noise; see the DAC Noise Performance section for
the variation at V
REF
H/V
REF
OUT is less than 10μV/V;
more details.
see the Typical Characteristics.
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