UG-1042
Easy to Use AD4000 Series 16-/18-/20-Bit Precision SAR ADCs User Guide
Rev. E | Page 4 of 25
EVALUATION BOARD HARDWARE
EASY TO USE AD4000 SERIES 16-BIT/18-BIT/20-BIT
PRECISION SAR ADCs EVALUATION BOARD
VIN+
VIN–
IN+
IN–
AD4000/
AD4001/
AD4002/
AD4003/
AD4020
+V
S
–V
S
GND
SCK
SDO
CNV
VIO
SDI
REF
+7V
VDD
ADA4807-1
ADA4807-1
A B
–2.5V
–2.5V
+7V
GND
VCM
ADA4807-1
POWER SUPPLY CIRCUITRY
ADP7118, ADP2370, ADM660, ADP7182
VDD
VREF
GND
(OPTIONAL)
(OPTIONAL)
+7V/+5V/–2.5
+1.8V
+7V
+3.3V
ADR4550
5V
ADA4807-1
EVAL-SDP-CH1Z
SPI
INTERFACE
120-PIN
CONNECTOR
12V
12V
12V
WALL WART
USB PORT
POWER
SUPPLY
CIRCUITRY
ADSP-BF527
SPARTAN-6
FPGA
XC6SLX25
14
981-
0
01
Figure 2. Simplified Evaluation Board Block Diagram
SETTING UP THE EVALUATION BOARD
Figure 2 shows the simplified evaluation board block diagram.
Figure 25 shows the evaluation board schematic. The board
consists of the ADC, U1, with a reference, U6 (
ADR4550
), and
ADC drivers, U12 and U14, the
ADA4807-1
for the
AD4001
/
AD4002
/
AD4003
/
AD4020
and the
ADA4805-1
for the
AD4000
(see Table 5). The user also has an option to populate U2 with a
low power, fully differential ADC driver such as the ADA4940-1
when evaluating the
AD4001
/
AD4003
/
AD4020
. The evaluation
board is a flexible design that enables the user to select components
in addition to operating from an adjustable bench top power
supply.
POWER SUPPLIES
The system demonstration platform (
SDP-H1
) board supplies
12 V to power the necessary rails for the
AD4000
/
AD4001
/
AD4002
/
AD4003
/
AD4020
evaluation board.
Table 1. Power Supplies Provided on the Board
Power Supply (V)
Function
Components Used
5, 7 (default)
1
Positive
rail
ADP7118
−5, −2.5 (default)
1
Negative
rail
ADP2370
,
ADM660
,
ADP7182
1.8 ADC
power
ADP7118
,
ADP5300
3.3 V
DRIVE
(digital power)
ADP7118
1
See Table 2.
The 7 V amplifier positive rail (+V
S
) is generated from U17 (the
ADP7118
). The −2.5 V negative amplifier rail (−V
S
) is generated
by a combination of U3 (the
ADP2370
), U7 (the
ADM660
), and
U21 (the
ADP7182
).
Each supply is decoupled where it enters the board and again at
each device. A single ground plane is used on this board to
minimize the effect of high frequency noise interference.
In addition, there is also the ability to power the board from a
bench top power supply. The screw terminals, J2 and J3, are
provided for this function. When bench power is used, the on-
board power supplies are no longer required. The solder links also
must be changed: SL1 = SL2 = SL5 = SL6 = SL7 = SL8 = SL9 = B.
REFERENCE, REFERENCE BUFFER, AND COMMON-
MODE BUFFER
An external 5 V reference (U6,
ADR4550
) is used by default to
supply the ADCs directly. However, the user can also use one of
the 2.5 V, 3.3 V, and 4.096 V references by changing the reference
device on the board (U6,
ADR4525
/
ADR4533
/
ADR4540
). There is
also an option to use a lower power reference (U22,
ADR3450
).
Note that the
ADR3450
cannot accept input voltages beyond 5.5 V.
The
ADA4807-1
is used as a reference buffer (U16) and common-
mode buffer (U18) by default. However, it can also be replaced by
the
AD8031
if needed without compromising the performance.
