EVAL-AD7922_15 Datasheet, PDF (3/16 Pages) Analog Devices – Evaluation Board for 1 MSPS, 2-Channel, 12-/10-Bit ADCs

EVAL-AD7912/AD7922
EVALUATION BOARD HARDWARE
POWER SUPPLIES
When using this evaluation board with EVAL-CONTROL-
BRD2, all supplies are provided from the controller board
through the 96-way connector. When using the board as a
standalone unit, external supplies must be provided.
This evaluation board has seven power supply inputs: EXT_VDD,
AGND, +12 V, −12 V, AGND, DVDD, and DGND. The VDD for
the AD7912/AD7922 can be supplied either from the EXT_VDD
external supply or from the selected reference chip. The +12 V
and −12 V inputs are used to supply the AD780, the ADR435, and
the AD8022 dual op amps. One or both of the AGND inputs is
connected to 0 V. The DVDD input can be used to supply a separate
5 V for the 7S04 DVDD pin. The DGND input must be tied to 0 V.
The supplies are decoupled to the relevant ground plane with 10 μF
tantalum and 0.1 μF multilayer ceramic capacitors at the pin where
they enter the board. The supply pins of the dual op amps and
the references are also decoupled to AGND with 10 μF tantalum
and 0.1 μF ceramic capacitors. The AD7912/AD7922 VDD supply
pin is decoupled to AGND with 10 μF tantalum, 1 μF ceramic,
and 0.1 μF multilayer ceramic capacitors.
Extensive ground planes are used on this board to minimize the
effect of high frequency noise interference. There are two ground
planes, AGND and DGND. These are connected at one location
close to the AD7912/AD7922.
LINK OPTIONS
There are 18 link options, which must be set for the required
operating setup before using the evaluation board. The
functions of these options are outlined in Table 1.
If the user is interested in testing only one of the input channels,
the nonselected channel should not be left floating. Therefore,
that analog input should be connected to ground by means of
LK1 or LK2. LK1 and LK2 need to be in Position B if the
nonselected input is VIN0 or VIN1, respectively.
SETUP CONDITIONS
Care should be taken before applying power and signals to the
evaluation board to ensure that all link positions are as per the
required operating mode. Table 2 shows the position in which all
the links are set when the evaluation board is shipped. The board is
compatible with the EVAL-CONTROL-BRD2 when shipped.
Table 1.
Link No.
LK1, LK2
LK3, LK4
LK5
LK6
LK7
LK8
LK9
Function
These link options allow the user to connect the input of the AD8022 analog buffer to the VIN input sockets or to AGND.
• When this link is in Position A, the VIN socket is tied to the input of the AD8022 buffer. In this configuration, an analog
signal applied to the VIN input socket is buffered and presented at the AD7912/AD7922 analog input.
• When this link is in Position B, the AD8022 buffer input is tied to AGND.
These link options set the DC bias voltage that is applied to the optional bias-up circuit.
• When this link is in Position A, the bias voltage is set to the same level as the voltage that is applied to the AD7912/
AD7922 VDD pin. In this configuration, a bipolar analog input applied to the AIN SMB socket is biased up by the bias circuit
and is presented at the VBIASED SMB as a unipolar signal biased around VDD/2.
• When this link is in Position B, the bias voltage is set to AGND. In this configuration the bias-up circuit is not used.
This link option is used to connect the output of either the ADR435 or the AD780 to the VDD pin of the AD7912/AD7922 (if LK12
is in Position C).
• When this link is in Position A, the ADR435 supplies the VDD voltage for the AD7912/AD7922.
• When this link is in Position B, the AD780 supplies the VDD voltage for the AD7912/AD7922.
This link option is used to select a 50 Ω termination on the analog input buffer circuit, the AIN1 socket.
• When this link is inserted, the 50 Ω termination is applied.
• When this link is removed, the 50 Ω termination is removed.
This link option is used to select the source of the CS signal for the AD7912/AD7922.
• When this link is in Position A, the CS signal is generated by the EVAL-CONTROL-BRD2 via the 96-way connector.
• When this link is in Position B, the CS signal is applied from an external source via the CS MB socket.
This link option allows the user to connect the data output pin, DOUT, of the AD7912/AD7922 to the EVAL-CONTROL-BRD2 or
to an external SMB socket.
• When this link is in Position A, the DOUT pin of the AD7912/AD7922 is connected to the EVAL-CONTROL-BRD2.
• When this link is in Position B, the DOUT pin of the AD7912/AD7922 is connected to the external DOUT SMB socket.
This link option selects the source of the data to be applied to the DIN pin of the AD7912/AD7922.
• When this link is in Position A, the data being applied to the DIN pin of the AD7912/AD7922 comes from the EVAL-
CONTROL-BRD2.
• When this link is in Position B, the data being applied to the DIN pin of the AD7912/AD7922 is from an external source
applied via the DIN SMB socket.
Rev. 0 | Page 3 of 16