EVAL-AD7983SDZ View Datasheet(PDF) - Analog Devices
Part Name
Description
MFG CO.
'EVAL-AD7983SDZ' PDF : 24 Pages View PDF
AD7983
VOLTAGE REFERENCE INPUT
The AD7983 voltage reference input, REF, has a dynamic input
impedance and should therefore be driven by a low impedance
source with efficient decoupling between the REF and GND
pins, as explained in the Layout section.
When REF is driven by a very low impedance source, for example,
a reference buffer using the AD8031, ADA4805-1, or
ADA4807-1, a ceramic chip capacitor is appropriate for
optimum performance.
If an unbuffered reference voltage is used, the decoupling value
depends on the reference used. For instance, a 22 µF (X5R,
1206 size) ceramic chip capacitor is appropriate for optimum
performance using a low temperature drift reference, such as
the ADR435, ADR445, LTC6655, or ADR4550.
If desired, a reference-decoupling capacitor value as small as
2.2 µF can be used with a minimal impact on performance,
especially DNL.
Regardless, there is no need for an additional lower value ceramic
decoupling capacitor (for example, 100 nF) between the REF
and GND pins.
Data Sheet
POWER SUPPLY
The AD7983 uses two power supply pins: a core supply (VDD)
and a digital input/output interface supply (VIO). VIO allows
direct interface with any logic between 1.8 V and 5.0 V. To
reduce the number of supplies needed, VIO and VDD can be
tied together. When VIO is greater than or equal to VDD, the
AD7983 is insensitive to power supply sequencing. In normal
operation, if the magnitude of VIO is less than the magnitude
of VDD, VIO must be applied before VDD. Additionally, it is
very insensitive to power supply variations over a wide frequency
range, as shown in Figure 24.
80
75
70
65
60
55
1
10
100
1000
FREQUENCY (kHz)
Figure 24. PSRR vs. Frequency
Rev. C | Page 16 of 25
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