EVAL-AD7902SDZ Datasheet, PDF (8/32 Pages) Analog Devices – On-board reference

UG-608
EVALUATION BOARD HARDWARE
DEVICE DESCRIPTION
The AD7902 is a 16-bit, 1 MSPS, precision, power efficient, dual
pseudo differential PulSAR ADC that uses SAR-based
architecture and does not exhibit any pipeline delay or latency.
The AD7902 is specified for use with a single supply of 2.5 V
(VDD1, VDD2). The interface from the digital host to the
AD7902 uses 1.8 V/2.5 V/3.3 V/5.5 V logic. The AD7902 is
compatible with the SPI/QSPI/MICROWIRE/DSP serial
interface to transfer data conversions. Complete AD7902
specifications are provided in the AD7902 data sheet and
should be consulted in conjunction with this user guide when
using the evaluation board. Full details on the EVAL-SDP-
CB1Z are available on the Analog Devices website, at
www.analog.com.
Figure 26 to Figure 31 show the evaluation board schematics.
The board consists of an AD7902 ADC (U1) with a reference
(U6—ADR435), and two ADC drivers (U12 and U17—
ADA4841-1YRZ). The evaluation board is a flexible design that
enables you to adjust compensation components and operate
the evaluation board from an adjustable bench top power supply.
POWER SUPPLIES
The evaluation board can be powered from a wall adapter or
from a bench top power supply. By default, the board is set up
to operate from a 9 V wall adapter using the on-board power
supplies described in Table 1.
Table 1. Power Supplies Provided on the Board
Power Supply (V) Function
Components Used
+5
SDP power
ADP2301
+7.5
Positive rail
ADP7104
−2.5
Negative rail
ADP2301
+2.5
ADC VDD rail
ADP7104
+3.3
VDRIVE (digital power) ADP7104
EVAL-AD7902SDZ User Guide
Each on-board power supply is decoupled where it enters the
board as well as where it connects to each device. A single ground
plane is used on this board to minimize the effect of high frequency
noise interference.
Alternatively, the board can be powered from a bench top power
supply by using the J2 and J3 screw terminals and changing the
SL1 to SL4 and LK3 to LK5 solder link settings to Position B (see
Table 2). When bench top power is used, use of the wall adapter
and the on-board power supplies are no longer required.
Table 2. Solder Links—Settings for Bench Top Power Supply¹
Link
Setting
Function
SL1
B
+VS
SL2
B
−VS
SL3
B
−VS
SL4
B
+VS
LK3
B
V_SDP
LK4
B
VREF
LK5
B
VDD for ADC
1 _{All other solder link settings are as described in Table 3.}
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