Analog Devices EVAL-ADAQ23875FMCZ, User Manual

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UG-1896 EVAL-ADAQ23875FMCZ User Guide
Rev. 0 | Page 4 of 26
ANALOG INPUTS
The SMA connectors on the EVAL-ADAQ23875FMCZ (VIN+
and VIN−) provide analog inputs from a low noise, audio
precision signal source (such as the SYS-2700 or the SYS-x555
series). There are three options available to feed analog inputs
directly to the
ADG774 , the ADA4899-1 , and the ADAQ23875,
as shown in Figure 20. To test the multiplexed functionality
using the
ADG774 (U2) CMOS multiplexer in front of the
ADAQ23875 (U1), the positive and negative differential inputs
of the
ADG774 are switched continuously to generate a full-
scale step. The optional amplifiers, ADA4899-1 (A2, A3), can
be set up in a unity-gain configuration driving the ADAQ23875 .
In a default configuration of board, an input signal via VIN+
and VIN− can be fed directly to the
ADAQ23875 by bypassing
U2, A2, and A3.
The EVAL-ADAQ23875FMCZ is factory configured to provide
the appropriate input signal type, single-ended or fully
differential, and different gain/attenuation or input range
scaling. Table 2 lists the necessary jumper positions and link
options for different configurations. The default board
configuration presents 4.096 V on the REFBUF pin. The default
board configuration also presents a buffered 2.048 V (midscale)
at the VCMO pin of the FDA on the
ADAQ23875 .
To evaluate dynamic performance, a fast Fourier transform
(FFT), integral nonlinearity (INL), differential nonlinearity
(DNL), or time domain (waveform, histogram) test can be
performed by applying a very low distortion ac source (see
Figure 13 to Figure 17). For low input frequency testing below
100 kHz, it is recommended to use a low noise, audio precision
signal source (such as the SYS-2700 series) with the outputs set
to balanced floating. A different precision signal source can be
used alternatively with additional band-pass filtering. The filter
bandwidth depends on input bandwidth of interest.
LINK CONFIGURATION OPTIONS
Multiple link options must be set correctly for the appropriate
operating setup before applying the power and signal to the
EVAL-ADAQ23875FMCZ. Table 2 shows the default link
positions for the EVAL-ADAQ23875FMCZ.
Table 2. Link Options for the EVAL-ADAQ23875FMCZ
Link Default Function Comment
JP3 Center to B FPGA CNV+ Change center to A when using ADC_.
JP4 Center to B FPGA CNV− Change center to A when using ADC_PLL_CNV−.
JP5 Center to A AMP+ Change center to B when using an external supply.
JP6 Center to A AMP− Change center to B when using an external supply. If configured
to single supply VS− to GND, remove both jumpers (JP6) and
install R49 (0 Ω).
JP9 Center to A 3.3 V Change center to B when using an external 3.3 V supply.
P1
Tie Pin 2 and Pin 3
(connected to GND)
Two-lane digital output modes
Digital input that enables two-lane output mode. Use this jumper
to select either single-lane or two-lane data output mode. The
default setting is Pin 2 and Pin 3. The Pin 2 and Pin 3 setting
clocks out all data on the DA± pin. The Pin 1 and Pin 2 setting
clocks out data alternately on the DA± and DB± pins.
P2 No connect ADCIN− Negative input of an internal ADC. Extra capacitance can be
added on this pin to reduce the RC filter bandwidth. Optional for
the
ADAQ23875 .
P3 No connect ADCIN+ Positive input of an internal ADC. Additional capacitance can be
added on this pin to reduce the RC filter bandwidth. Optional for
the
ADAQ23875
P4 Tie Pin 1 and Pin 2 PDB_AMP Active low. Connect this pin to GND to power-down the fully
differential ADC driver. Otherwise, connect it to VS+.
P5 Not applicable SDP-H1 FMC connector
The EVAL-ADAQ23875FMCz board interfaces to the SDP-H1
board via a 160-pin connector.
P6 Tie Pin 1 and Pin 2 PDB_ADC Digital input that enables the power-down mode. When
PDB_ADC is low, an internal ADC core enters power-down mode,
and all circuitry (including the LVDS interface) is shut down. When
PDB_ADC is high, the device operates normally. Logic levels are
determined by VIO.
P7 0 Ω installed −VS for the ADA4899-1 (A2, A3) Remove 0 Ω to use the external supply for the ADA4899-1 (A2, A3).
P8 0 Ω installed +VS for the ADA4899-1 (A2, A3) Remove 0 Ω to use the external supply for the ADA4899-1 (A2, A3).
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