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Evaluation Board User
Guide
POWER SUPPLIES
Care should be taken before applying power and signals to the
evaluation board to ensure that all link positions are as required
by the operating mode.
When using the EVAL-AD7656-1/57-1/58-1SDZ in
conjunction with the EVAL-SDP-CB1Z board, connect the 9V
DC supply to connector J702. VDD, VDRIVE and op amp
supplies are generated on-board.
Each supply is decoupled on the EVAL-AD7656-1/57-1/58-
1SDZ . A single ground plane is used on this board to minimize
the effect of high frequency noise interference.
Table 3. External Power Supply Required
POWER
VOLTAGE
PURPOSE
SUPPLY
RANGE
1
VIN
7V to 9V
Supplies all onboard power supplies
which generate all required voltages
J702
to run the evaluation board
VDD
+12V to
Amplifier positive rail
+16.5V
J100
VSS
-12V to
Amplifier negative rail
J100
-16.5V
AVCC
2.7V to
ADC analog supply.
5.25V
J703
DVCC
2.7V to
ADC digital supply.
5.25V
J701
1.
When this is supplied all other power supplies are available onboard.
If this supply is not used then all other supplies must be sourced from
an external source.
PARALLEL INTERFACE
The AD7656-1/57-1/58-1 uses a high-speed parallel interface,
which allows sampling rates up to 250kSPS. For details on the
operation of the serial bus, refer to the AD7656-1/57-1/58-1
datasheet.
The EVAL-AD7656-1/57-1/58-1SDZ uses the parallel interface
to transfer data to the EVAL-SDP-CB1Z.
SERIAL INTERFACE
Connection to the serial interface is also possible in standalone
mode via socket J7. For details on the operation of the serial
bus, refer to the AD7656-1/57-1/58-1 datasheet.
DIGITAL INTERFACE
The EVAL-AD7656-1/57-1/58-1SDZ communicates with the
EVAL-SDP-CB1Z board using level shifters. The EVAL-SDP-
CB1Z operates at a 3.3V logic level. This allows VDRIVE
voltages to exceed 3.3V to be used without damaging the
EVAL-SDP-CB1Z interface.
ANALOG INPUTS
Inputs V1 to V6 allow signals to be connected to the board via
SMB connectors.
The analog inputs on the EVAL-AD7656-1/57-1/58-1SDZ are
filtered and buffered by AD8597: Ultralow Distortion, Ultralow
Noise (single) Op Amps. Further filtering is provided by an R-
C filter directly before the AD7656-1/57-1/58-1 inputs.
Alternatively, the op amps may be bypassed and the inputs fed
directly to the AD7656-1/57-1/58-1 via the R-C filter.
REFERENCE OPTIONS
2 on board reference supplies are available. ADR431: Ultralow
Noise XFET® Voltage References with Current Sink and Source
Capability, AD780: 2.5 V/3.0 V Ultrahigh Precision Bandgap
Voltage Reference. Alternatively, the AD7656-1/57-1/58-1 can
supply an internal reference voltage.
Rev. PrA | Page 11 of 32
UG-AD7656-1/57-1/58-1
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